Dissertations / Theses on the topic 'Electron donor-acceptor complexes'
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1
Cubberley, Mark Stull. "Investigation of solvent effects in aromatic electron donor-acceptor interactions /." Digital version accessible at:, 2000. http://wwwlib.umi.com/cr/utexas/main.
2
LEE, CHERYLYN. "PHOTO-INDUCED RADICAL COPOLYMERIZATIONS OF ELECTRON-RICH OLEFINS WITH ELECTRON-POOR OLEFINS." Diss., The University of Arizona, 1987. http://hdl.handle.net/10150/184135.
Abstract:
This study is a systematic investigation of the parameters and conditions necessary for photo-induced radical copolymerizations of donor olefins with acceptor olefins in the absence of an initiator. Very few cases have been previously reported and no mechanistic details of the initiation have been proposed in the literature. Our results show that the photoinitiation depends on the relative donor and acceptor strengths of the monomers, as well as the solvent. The highest occupied molecular orbital (HOMO) of the donor and the lowest unoccupied molecular orbital (LUMO) of the acceptor must be at the appropriate energy levels in order to produce a radical initiating species upon photoexcitation of the electron donor-acceptor (EDA) complex. If the donor-acceptor interaction is too weak, no copolymerization occurs. The excited complex (contact ion pair) presumably decays back to the ground state faster than producing an initiating species. If the donor-acceptor interaction is too strong, the excited complex dissociates to the free ions which could initiate ionic homopolymerization rather than radical copolymerization. The solvent may also determine the course of the reaction. In two cases, copolymerizations, which could be photo-induced in 1,2-dichloroethane, could not be photo-induced in acetonitrile. Dissociation of the excited complex (contact ion pair) is favored in polar solvents, such as acetonitrile, which are able to stabilize the ion radicals. This initiation method produces high molecular weight copolymers that may be cast into transparent films.
3
Caulfield, Jason M. "Magnetic quantum oscillations in organic metals based on the molecule bis(ethylenedithio)tetrathiafulvalene." Thesis, University of Oxford, 1994. http://ora.ox.ac.uk/objects/uuid:5fbf2599-96d8-4eac-b882-ac74213ac3a5.
Abstract:
ET charge transfer salts (where ET is
4
Xu, Yunhua. "Synthesis and Photoinduced Electron Transfer of Donor-Sensitizer-Acceptor Systems." Doctoral thesis, Stockholm : Department of Organic Chemistry, Stockholm University, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-411.
5
Holman, K. Travis. "The host-guest chemistry of new members in the cyclotriveratrylene family of cavitands /." free to MU campus, to others for purchase, 1998. http://wwwlib.umi.com/cr/mo/fullcit?p9924887.
6
Svarovsky, Serge A. "Structure, stability and reactivity of small organic sulfinic and sulfonic acids toxicological implications ; Role of charge transfer complexes in oxidation cleavage of benzpinacols by iron (III) trispenanthroline /." Morgantown, W. Va. : [West Virginia University Libraries], 2000. http://etd.wvu.edu/templates/showETD.cfm?recnum=1231.
7
Pui, Yung-lin. "Syntheses, luminescence studies and host-guest chemistry of d10 and d6 metal complexes containing diimine and/or chalcogenolate ligand." Click to view the E-thesis via HKUTO, 2000. http://sunzi.lib.hku.hk/hkuto/record/B43894367.
8
裴雍蓮 and Yung-lin Pui. "Syntheses, luminescence studies and host-guest chemistry of d10 and d6metal complexes containing diimine and/or chalcogenolate ligand." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2000. http://hub.hku.hk/bib/B43894367.
9
Furman, Gary S. "The contribution of charge-transfer complexes to the color of kraft lignin." Diss., Georgia Institute of Technology, 1986. http://hdl.handle.net/1853/5644.
10
Dornan, Thomas Joseph. "Calcium Transport Inhibition, Stimulation, and Light Dependent Modulation of the Skeletal Calcium Release Channel (RyR1) by the Prototropic Forms of Pelargonidin." PDXScholar, 2014. https://pdxscholar.library.pdx.edu/open_access_etds/1931.
Abstract:
The principle calcium regulator in the muscle cell is the calcium ion release channel (RyR). Improper calcium homeostasis in the muscle cell is the foundation of many pathological states and has been targeted as a contributing factor to ventricular tachycardia, which is known to precede sudden cardiac arrest.
Numerous endogenous and exogenous compounds can affect the way RyR regulates calcium. In this study the anthocyanidin Pelargonidin (Pg), an important natural colorant and dietary antioxidant, is evaluated for its effect on regulating the transport of calcium through the RyR1 of skeletal muscle sarcoplasmic reticulum. Pelargonidin undergoes time dependent structural changes in aqueous solutions at physiological pH and a mixture of up to seven forms of Pelargonidin are present in solution simultaneously. Pelargonidin is a unique RyR1 modulator. It can both stimulate and inhibit the RyR1 depending on the experimental conditions. In addition, when Pelargonidin is irradiated with white light, its inhibition properties on the RyR1 are essentially nullified. Proposed mechanisms include excited state charge shift within RyR1-Pg complexes.
11
Bhattacharyya, Anjan Kumar. "Intramolecular and intracomplex electron transfer in water soluble redox proteins." Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184339.
Abstract:
Electron transfer to and between the redox centers of milk xanthine oxidase was investigated by laser flash-photolysis. Evidence is presented for slow equilibration of electrons (k < 38 s⁻¹) between the various redox centers of the enzyme. The enzyme-bound flavin and the heme moieties of the flavoprotein and cytochrome subunits of p-cresol methyl hydroxylase from Pseudomonas putida are both reduced rapidly in a second order manner by 5-dRF generated by the laser flash, followed by slower first order intramolecular electron transfer (k = 220 s⁻¹) from the protein-bound neutral flavin radical to the oxidized cytochrome. Complex formation between spinach ferredoxin:NADP⁺-reductase (FNRₒᵪ), spinach ferredoxin (Fdₒᵪ), rubredoxin (Rdₒᵪ) from Clostridium pasteurianum, two homologous HIPIP's from Ectothiorhodospira halophila (iso-1 and iso-2) and two homologous cytochromes (cytochromes-c₂ from Paracoccus denitrificans and Rhodospirrilum rubrum) have been investigated. Evidence is presented supporting the formation of 1:1 complexes that are stabilized by attractive electrostatic interactions at low ionic strength. Kinetic studies of the above-mentioned complexes provide evidence for extremely rapid to relatively slower intracomplex electron transfer rates (k 7000 s⁻¹ to 4 s⁻¹). In addition the effect of complexation on the degree of accessibility of the various redox centers of the respective complexes to reduction by small reductants such as 5-dRF· and LfH· generated by the laser flash has been evaluated. The effect of both pH and ionic strength on the second order rate of reduction and the intracomplex rates in the respective complexes have also been investigated. The results have been interpreted in terms of redox potential differences, electrostatic and structural features that influence the electron transfer rates in these systems.
12
Farid, Ramy Samir Gray Harry B. Gray Harry B. "Electron transfer in rigid and semi-rigid iridium d [superscript 8]-d [superscript 8] donor-spacer-acceptor complexes /." Diss., Pasadena, Calif. : California Institute of Technology, 1991. http://resolver.caltech.edu/CaltechETD:etd-06212007-154303.
13
Zilic, Elvis. "Radiation curing and grafting of charge transfer complexes." Thesis, View thesis, 2008. http://handle.uws.edu.au:8081/1959.7/19385.
Abstract:
Charge transfer (CT) complexes have been used in a number of radiation polymerisation processes including grafting and curing. The complexes studied include donor (D) monomers like vinyl ethers and vinyl acetate (VA) with acceptor (A) monomers such as maleic anhydride (MA). Both UV and EB have been utilised as radiation sources. The complexes are directly grafted to these substrates in the presence of radiation. The complexes yield novel copolymers when radiation cured with concurrent grafting improving the properties of the finished product. The term cure grafting has been proposed for this concurrent grafting process. Studies in basic photografting work to complement the cure grafting have been proposed. The role of solvent in grafting is discussed, particularly the effect of aromatics in photografting to naturally occurring trunk polymers like wool and cellulose. The effect of the double bond molar ratio (DBMR) of the DA components in grafting is examined. The ultraviolet (UV) conditions for gel formation during photografting, hence the importance of homopolymer yields in these processes is reported. A plausible mechanism to explain the results from this photografting work is proposed. The significance of these photografting studies in the related field of curing, especially in UV and ionising radiation (EB) systems, is discussed. EB curing and cure grafting of charge transfer (CT) monomer complexes is investigated. The EB results are compared with UV curing and cure grafting of the same complexes. The work has been extended to include EB/UV curing and cure grafting of thiolene systems. The significance of these results in the potential commercial application of these complexes is discussed. Variables affecting the UV/EB curing and cure grafting of thiolenes on cellulose have been studied. These include effect of varying the type of olefin, increasing the functionality of the thiol, use of acrylate monomers and oligomers in hybrid systems, altering the surface structure of the cellulose and finally the role of air in these processes particularly with EB. Photopolymerisation of the thiol-enes in bulk has also been investigated. The thesis content is based on the published work of 14 research papers over the course of the project.
14
Chan, Yiu Him. "Effect of dopants and gate dielectrics on charge transport and performance of organic thin film transistor." HKBU Institutional Repository, 2012. https://repository.hkbu.edu.hk/etd_ra/1450.
15
Zilic, Elvis. "Radiation curing and grafting of charge transfer complexes." View thesis, 2008. http://handle.uws.edu.au:8081/1959.7/19385.
Abstract:
Thesis (Ph.D.)--University of Western Sydney, 2008.Thesis submitted to the University of Western Sydney, College of Health and Science, School of Natural Sciences, in fulfilment of the requirements for admission to the Doctor of Philosophy. Includes bibliography.
16
Buker, Nicholas D. "Guanidine donors in nonlinear optical chromophores /." Thesis, Connect to this title online; UW restricted, 2006. http://hdl.handle.net/1773/8669.
17
Rattananakin, Pornpun. "Ab initio study of the rotation around the carbon-carbon double bond in push-pull systems." Diss., Mississippi State : Mississippi State University, 2006. http://sun.library.msstate.edu/ETD-db/ETD-browse/browse.
18
Khajehpour, Mazdak. "Solvent effects upon the charge-transfer reaction of the ADMA molecule in the excited state /." free to MU campus, to others for purchase, 2001. http://wwwlib.umi.com/cr/mo/fullcit?p3025621.
19
Mecker, Christoph J. Chemistry Faculty of Science UNSW. "The synthesis of advanced " special pair " models for the photosynthetic reaction centre." Awarded by:University of New South Wales. School of Chemistry, 2000. http://handle.unsw.edu.au/1959.4/17835.
Abstract:
Multi-step photoinduced electron transfer takes place over a large distance in the photosynthetic reaction centres (PRCs). Electron donor in this life-spending event is the photo-excited 'special pair', a unit of two electronically coupled porphyrinoid chromophores. Bacteriopheophytin and two quinone molecules function as electron acceptors and contribute to the charge separation with almost unit quantum efficiency. The natural photosynthetic reaction centre is the most sophisticated molecular electronic device to date and interest is high in increasing our understanding of the basic quantum mechanical principles behind efficient electron transfer and ultimately copying Nature and construct similar efficient devices. Two main approaches towards a better understanding of the mechanisms involved have been taken. The more biological disciplines isolate, cultivate and alternate reaction centres whereas synthetic chemists prefer to construct well-defined models that mimic certain aspects of the reaction centres. Such a synthetic approach is described in the 'Synthesis of Advanced 'Special Pair' Models for the Photosynthetic Reaction Centre'. The aspect to be mimicked is the 'special pair'. One or two porphyrins in a well-defined spatial disposition (kinked or non-kinked in respect to each other) were to act as electron donor in rigid bichromophoric and trichromophoric systems. A tetracyanonaphthoquinodimethane (TCNQ) unit was employed as the electron acceptor in the series of dyads synthesised. The TCNQ acceptor was replaced by a naphthoquinone (NQ) primary acceptor covalently linked to a TCNQ secondary electron acceptor in the series of triads. Rigid norbornylogous bridges held the chromophores in place and Diels-Alder methodology as well as condensation reactions were applied to link donor, bridge and acceptor components. Despite larger interchromophoric separation than in the natural 'special pair', the two porphyrin chromophores of the series of 'special pair' dyads show some interaction and thereby prove the success of our approach towards 'special pair' mimics. Strong fluorescence quenching in the porphyrin-TCNQ dyads indicates the sought after electron transfer process. A number of synthetic problems experienced and overcome in the synthesis of the series of triads led to discovery of a one-step 'bis-ketonisation' from an olefin under Sharpless bis-hydroxylation conditions with N-methylmorpholine-N-oxide. High pressure was applied to circumvent a lack of reactivity in the condensation reaction used to attach the porphyrin moieties (one or two) to the donor backbone. For the linkage of donor, bridge and acceptor component, a procedure was developed and successfully applied to give the giant mono-porphyrin-NQ-TCNQ trichromophore. In a similar manner 'special pair' trichromophoric systems should be available as part of future work.
20
Kinayyigit, Solen. "Platinum (II) charge transfer chromophores electrochemistry, photophysics, and vapochromic sensing applications /." Bowling Green, Ohio : Bowling Green State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=bgsu1182802954.
21
Soper, Jake D. "Reactions at nitrogenous ligands on oxidizing group 8 metal centers /." Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/8589.
22
Arias, Olivares David. "Relation Among Localization, Delocalization and Physicochemical Properties. From Electron Density Databases to Magnetic Properties Effects of the acceptor unit in dyes with acceptor–bridge–donor architecture on the electron photo-injection mechanism and aggregation in DSSCs The role of Cr, Mo and W in the electronic delocalization and the metal–ring interaction in metallocene complexes." Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS015.
Abstract:
Tout d'abord, nous évoquerons un aperçu général de l'analyse topologique basée sur la densité d'électronique, le trou d'échange-corrélation et la densité de paires. Une fois la densité électronique rappelée, l'analyse topologique de la densité électronique est expliquée, ainsi que la procédure de calcul des points critiques de la densité électronique, le calcul de la matrice hessienne de la densité électronique et la définition des points critiques à la surface. Tous ces outils topologiques permettent de caractériser la nature des liaisons chimiques parallèlement à l'indice basé sur la délocalisation. Afin de comprendre la nature des énergies et des interactions dans les systèmes, l'analyse d'interaction non covalente est expliquée et combinée à l'analyse de décomposition d?énergie. De plus, les états de transition seront étudiés en appliquant les orbitales naturelles pour la valence chimique (ETS-NOCV). Les concepts clés du magnétisme moléculaire sont abordés. Nous nous concentrons sur l'aimantation et la susceptibilité magnétique, les composants diamagnétiques et paramagnétiques provenant de toute réponse magnétique dans les systèmes. Les propriétés de champs magnétiques induits sont étudiés dans le but de comprendre l'aromaticité à travers de deux descripteurs, les déplacements chimiques indépendants du noyau et les densités de courant induit. En annexe à la théorie, l'interaction isotrope dans les composés dinucléaires est introduite pour expliquer et mesurer certaines erreurs trouvées dans la théorie de la fonctionnelle de densité (TFD). [...]The first property here analysed and related with electronic localization/delocalization is the aromaticity. Aromaticity is an important concept introduced by Kekulé; since then, theoreticians and experimentalist have tried to understand it in different groups of molecules analogues to benzene. The importance of this concept and how the aromaticity is affected by the chemical environment is important to understand and link some physicochemical properties. i.e., reactivity, stability, magnetic response. The physicochemical properties of interest are the electronic structure, the nature of bonds and organometallic interactions(differentiation between metallocenes and metallabencenes). Furthermore, the magnetic response and the study of building blocks as possible candidates to make nano-wires or new low-dimension magnetic materials. Finally, we try to understand the interaction and the errors involved in some properties theoretically computed like, the isotropic coupling between metals through aromatic (or organic) units that have become important benchmark molecules to study magnetic properties in inorganic as well as metal-organic systems [...]
23
D'Acchioli, Jason S. "On the nature of the electronics structure of metal-metal quadruply bonded complexes." Connect to resource, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1126621699.
Abstract:
Thesis (Ph. D.)--Ohio State University, 2005.Title from first page of PDF file. Document formatted into pages; contains xii, 286 p.; also includes graphics (some col.). Includes bibliographical references (p. 273-286). Available online via OhioLINK's ETD Center
24
Rabah, Jad. "Assemblages donneur-accepteur à base de BODIPY-[60]Fullerène pour l’électronique organique : Synthèse, caractérisation, et modification de surface Photoinduced Electron Transfer and Energy Transfer Processes in a Flexible BODIPY‑C60 Dyad Synthesis of a Dual Clickable Fullerene Platform and Construction of a Dissymmetric BODIPY-[60]Fullerene DistyrylBODIPY Triad A fullerene helical peptide: synthesis, characterization and formation of self-assembled monolayers on gold surfaces." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASF036.
Abstract:
Ce manuscrit de thèse porte sur la synthèse de nouveaux assemblages covalents Donneur(s)-Accepteur(s) [BODIPY(s)-C60(s), BDP-C60] qui pourraient conduire à des applications potentielles en électronique organique et en photo-catalyse. Pour atteindre ces objectifs, nous avons dans un premier temps mis au point une nouvelle stratégie de synthèse permettant la double fonctionnalisation d’un dérivé du C60, par différents BDP(s), via des réactions de chimie clic. Cette nouvelle stratégie a permis la synthèse d’assemblages BPD(s)-C60(s) complexes conduisant à des processus photo-induits multiples liés à l’arrangement des différents partenaires (transfert d’électron et/ou transfert d’énergie). La seconde partie de cette thèse a porté sur la synthèse et la caractérisation de dérivés du BDP étendus fonctionnalisés par une ou deux unités ferrocène(s) (Fc) ou tetrathiafulvalène(s) (TTF). Ces assemblages présentent des propriétés d’absorption étendues dans le domaine du visible voire dans le proche IR dans certains cas. En outre, une bonne communication électronique entre les unités redox (Fc-BDP ou TTF-BDP) à l’état fondamental et excité a été mise en évidence. La modulation de l’émission de fluorescence du BDP dans certains de ces assemblages a également été mise en évidence par modification de l’état redox (du TTF ou du Fc) ouvrant la voie à des applications en électro-fluorochromisme.Ces assemblages ont été par la suite greffés sur la nouvelle plateforme C60 d’une manière simple et efficace. Les premières études réalisées sur les assemblages (Fc(s))-BDP-C60 ont révélé l’existence de processus de transfert d’électron en cascade, suite à la photo-excitation du BDP, avec une augmentation considérable des temps de vie des états de charges séparées. La dernière partie de ce manuscrit expose les résultats obtenus lors de l’immobilisation des systèmes BDP-C60 sur des surfaces d’or sous la forme de monocouches auto-assemblées. L’objectif est ici de développer des cellules photo-électrochimiques organiques (PEC) pour la génération de photo-courant. Pour réaliser cet objectif, ces assemblages BDP-C60 ont été modifiés par un hexa-peptide adoptant une conformation hélicoïdale, ce dernier permettant une meilleure structuration de la surface et un meilleur transport des électrons vers la surface métallique comparativement à une chaîne alkyle. Lors de cette partie, nous avons montré que l’association du peptide au C60 conduisait à une meilleure structuration de la surface par comparaison à une chaîne alkyle. Enfin, l’incorporation de monocouches auto-assemblées à base de (BDP)-C60-peptide dans des cellules photo-électrochimiques a montré une meilleure efficacité en termes de génération de photo-courant comparativement aux analogues fonctionnalisés par une chaîne alkyleThis manuscript describes the synthesis and characterization of novel BODIPY-[60]Fullerene –based Donor-Acceptor conjugates for applications in organic electronics and photocatalysis.In the first part of this dissertation, we report the elaboration of a novel dual clickable methanofullerene building block that can be functionalized, on both sides of the C60, by different BDP light-harvester/electron donor appendages. This strategy allowed the efficient and straightforward construction of complex BDP-C60 –based arrays exhibiting multiple photoinduced events (electron or /and energy transfer) brought by the closely-spaced arrangement between the redox counterparts. In the second part of this thesis, we report the synthesis and characterization of extended-BDP derivatives containing one or two units of Ferrocene (Fc) or tetrathiafulvalene (TTF) donors. The resulting conjugates displayed remarkable light-harvesting properties with wide absorption in the visible region that can be extended to the NIR in some cases. In addition, a good electronic communication between the redox centers (Fc-BDP or TTF-BDP) at the fundamental or/and excited states was demonstrated in these conjugates. The modulation of the BDP emission within these assemblies was also investigated by switching the redox properties of the TTF and Fc moieties. Moreover, these TTF-BDP and Fc-BDP systems were consecutively connected to the newly-described methanofullerene platform using our described synthetic strategy in the previous part, which resulted in the formation of TTF-BDP-C60 and Fc-BDP-C60 assemblies in an efficient manner. These derivatives exhibited interesting photophysical and photodynamic properties thanks to the occurrence of efficient cascade PET processes, resulting in the formation of relatively-long charge-separated state lifetimes. Finally, in the last part of this dissertation, we report the immobilization of the BDP-C60 and extended-BDP-C60 –based assemblies on gold surfaces through the formation of self-assembled monolayers (SAMs) for the design of photoelectrochemical cells (PEC). For this, we appended a helical peptide, playing a dual role as structuring agent and good electron mediator, between the metallic surface and the redox centers. The association of the (BDP)-C60 derivatives with the peptide spacer appeared as a successful strategy for the formation of more dense and vertically-oriented monolayers, when compared to their alkyl chains analogs. The incorporation of the SAM-based BDP-C60-peptide assemblies in a PEC device revealed interesting photocurrent generation properties, which makes these assemblies potential candidates for organic electronics applications
25
Hudson, Joshua M. "Photophysical studies of silver(I), platinum(II), palladium(II), and nickel(II) complexes and their use in electronic devices." Thesis, University of North Texas, 2007. https://digital.library.unt.edu/ark:/67531/metadc5165/.
Abstract:
This dissertation deals with two major topics that involve spectroscopic studies of (a) divalent group 10 metals and (b) silver(I)-phosphine complexes. The scope of the work involved the delineation of the electronic structure of these complexes in different environments and their use in electronic devices. The first topic is a look at the luminescence of tetrahedral silver(I)-phosphine complexes. Broad unstructured emissions with large Stokes shifts were found for these complexes. Computational analysis of the singlet and triplet state geometries suggests that this emission is due to a Jahn-Teller type distortion. The second topic represents the major thrust of this research, which is an investigation into the electronic structure of M(diimine)X2 (M= Pt(II), Pd(II), or Ni(II); X = dichloro, or dithiolate ligands) complexes and their interactions with an electron acceptor or Lewis acid. Chapter 3 assesses the use of some of these complexes in dye sensitized solar cells (DSSCs); it is shown that these complexes may lead to a viable alternative to the more expensive ruthenium-based dyes that are being implemented now. Chapter 4 is an investigation into donor/acceptor pairs involving this class of complexes, which serves as a feasibility test for the use of these complexes in organic photo-voltaics (OPVs) and thin-film field-effect transistors (OTFTs). The mixing of a donor Pt molecule with an electron deficient nitrofluorenone gives rise to new absorption bands in the NIR region. Computational studies of one of the solids suggest that these complexes may have metallic behavior. Chapter 5 demonstrates association in solution, previously unobserved, for Pt(diimine)Cl2 complexes. This chapter is an investigation into the effects of the association mode for this class of complexes on the absorption and emission properties. One of the complexes was used as the emitter in organic light emitting diodes (OLEDs). The results of this study show that these complexes have tunable absorption and emission energies that are concentration dependant. The concentration dependence of the absorption and emission energies is utilized in the OLED device where association enhances the performance.
26
Bachrach, Max. "Electron-Transfer in Covalently Coupled Donor-Acceptor Complexes." Thesis, 1996. https://thesis.library.caltech.edu/14028/2/bachrach-m_1996.pdf.
Abstract:
A picosecond transient absorption experiment has been constructed and used for the study of intramolecular electron-transfer (ET) in three molecular systems. The first of these is a donor-bridge-acceptor (D(br)A) complex composed of a d⁸-d⁸ iridium core covalently coupled to two pyridinium acceptors with flexible phosphonite spacers. Varying the pyridiniums' substituents allows control of the driving-forces (ΔG°) of the photoinduced ET reactions from the core's singlet and triplet states. The rates of these reactions have been determined from steady-state and time-resolved emission experiments. Picosecond transient absorption has been used to measure the rates of subsequent charge-recombination, and determine their dependencies on ΔG°. The reorganization energy accompanying intramolecular electron-transfer within this system (λ ≈ 0.86 eV) has been determined by fitting the rates of photoinduced and thermal reactions to a single-mode quantum-mechanical ET model.
The rates of all the photoinduced and thermal ET reactions have been measured as a function of temperature (200° K - 280° K). These data show that the charge-recombination reactions, which lie within the Marcus inverted region (ΔG° > λ), have rates (kBET) that are strongly dependent on temperature. Deuteration of the pyridinium acceptor has a temperature independent effect (kH/kD = 1.2) on kBET, indicating that, although the inverted region reactions within these complexes exhibit behavior that is remarkably classical, quantum-mechanical effects do need to be considered. Both temperature and isotope effects suggest that the molecules' low internal reorganization energies (λin = 0.006 eV) account for their ET behavior.
Less comprehensive studies of two other electron-transfer systems are also reported. Unlike the iridium system, in which the donor-acceptor electronic coupling HAB is less than 100 cm-1, the couplings within these are over 2000 cm-1. It has been found that despite the large amount of coupling between the metals of [(bpy)(tpy)RuIICNRuII(NH3)5]2+ (bpy = 2,2'-bipyridine; tpy = 2,2',2"-terpyridine), our transient absorption experiment is able to detect formation of a charge-separated state following excitation into the Ru → immine charge-transfer band. It is proposed that this species can be described as [(bpy)(tpy•-)RuIICNRuIII(NH3)5]2+ and that unusually low coupling between the tpy ligand and the oxidized ruthenium leads to slow (1 x 1010 s-1) charge-recombination.
The ground-state absorption features and excited-state decay kinetics of a series of ferrocene-based D(br)A complexes have also been measured. It is proposed that HAB is much larger than 2000 cm-1 for these complexes, and plays an important role in determining their nonlinear optical properties.
27
Reczek, Joseph James. "Aromatic electron donor-acceptor interactions in novel supramolecular assemblies." Thesis, 2006. http://hdl.handle.net/2152/2906.
28
Bradford, Valerie Jean 1980. "Aromatic donor-acceptor interactions : bridging abiotic and peptide folding." Thesis, 2008. http://hdl.handle.net/2152/3842.
Abstract:
Aromatic donor-acceptor interactions have been utilized by the Iverson group in the development of abiotic molecules, called aedamers, that achieve new folding motifs, intermolecular association in heteroduplexes, and new material properties. These molecules exploit the interaction between the electron-rich 1,5-dialkoxynapthalene (DAN) and electron-deficient 1,4,5,8-naphthalenetetracarboxylic diimide (NDI) units in a face-centered stacking geometry in aqueous solution. This dissertation describes the use of DAN-NDI interactions in the realm of peptides and proteins to expand the scope for applications of this interaction. This work specifically focuses on three areas of aromatic donor-acceptor interactions: achieving protein behavior with abiotic molecules, introducing the interaction into natural peptides, and utilizing the interaction in the intermolecular association of an abiotic molecule and a natural peptide. Chapter 2 refines the model of aggregation of an amphiphilic aedamer, which forms a hydrogel upon heating. The aedamer behaves similarly to proteins called amlyoids, which form fibrils and plaques in vivo which have been implicated in a variety of diseases, including Alzheimer's. Chapter 3 describes the synthesis of [alpha]-amino acids with DAN- and NDI-containing side chains. These amino acids can be used in a peptide model of [beta]-hairpin secondary structure. The model system can determine whether aromatic donor-acceptor interactions are useful in stabilizing peptide and protein structure. Chapter 4 describes the study of the Anchored Periplasmic Expression System (APEx) for use in screening random peptide libraries. A random peptide library is used to determine the sequence of a natural peptide, potentially containing electron-rich aromatic residues, which could bind an NDI oligomer with high affinity for use as a protein expression tag. Chapter 5 describes work toward the use of cyclic NDI bisintercalators for binding both the major and minor grooves of a specific sequence of DNA simultaneously, in addition to the use of cyclic NDI and DAN molecules for the further study of NDI-DAN interactions in abiotic intermolecular assembiles. Overall, this work has advanced the application of aromatic donor-acceptor interactions in peptides and should serve as a foundation for the future study of this interaction in protein folding and behavior in biological systems.text
29
Ghosh, Sampa. "Quadratic Optical Nonlinearity And Geometry Of 1:1 Electron Donor Acceptor Complexes In Solution." Thesis, 2008. https://etd.iisc.ac.in/handle/2005/711.
Abstract:
The knowledge of geometry of molecular complexes formed via molecular association in solution through weak interactions is always important to understand the origin of stability and function of an array of molecules, supramolecular assemblies, and macromolecular networks. Simple 1:1 molecular complexes are very useful in this regard as they provide a model to understand both the nature of these interactions and their structural implications. Several weak noncovalent forces from long range (van der Waal’s, electrostatic, induction, dispersion) to short range (charge transfer) govern the geometry, that is, relative orientation of the two molecules in such a complex. On one hand, we find 1:1 electron donor acceptor (EDA) complexes such as naphthalene-tetracyanobenzene, hexamethylbenzene-chloranil etc. which stack parallel or in slipped parallel geometry in their crystals. On the other, benzene dimer has been found to stabilize in T shaped geometry in all its three physical states. In this thesis, I focus on 1:1 EDA complexes in solution. A good volume of literature is available which deals with the optical studies on the formation of such complexes. It has been suggested that the nature of the intermolecular interactions stabilizing these complexes in the gas phase or in their crystals is modified by the presence of solvent-solute interactions in solution thus bringing in difference in the solution geometry. However, the existing experimental techniques, both optical and magnetic, are unable to determine the exact geometries of 1:1 EDA complexes in solution. This opens an opportunity to probe their geometry in solution.
The quadratic nonlinearity or first hyperpolarizability (β) of a molecule is a measure of the change in dipole moment (or polarization) in the second order of the applied electrical field and thus has a purely electronic origin. It is a tensorial property and can be resolved in components along the three dimensions. The number of β components and the nonlinear optical anisotropies in a typical donor-acceptor type dipolar molecule, defined as (equation) (where1, 2, 3 axes define the molecular frame, 1 being the direction along the principal axis of symmetry and pointing from the acceptor toward the donor), are determined by the symmetry /structure of the molecule. It has been shown theoretically that the 1:1 EDA complexes possess large hyperpolarizabilities. In the case of pNA dimers calculation revealed that the geometry of the dimer and its symmetry is important for obtaining the correct estimate of β from its tensorial components. Therefore, it should be possible to use the values of tensorial β components to construct the unknown geometry of such complexes. Experimentally macroscopic depolarization ratios (D and D′) in the laboratory fixed frame (XYZ, X being the direction of polarization and Z the direction of propagation of the incident light), are measured from the polarization resolved intensities of second harmonic scattering from molecules in solution using the hyper-Rayleigh scattering technique. The depolarization ratios are correlated to the anisotropy parameters, u and v through a co-ordinate transformation. In this thesis I, have first, characterized the quadratic nonlinear optical property of a variety of 1:1 electron donor acceptor complexes and used the values of u and v obtained from depolarized hyper-Rayleigh scattering to deduce their geometry in solution.
Chapter 1 provides an introduction to the 1:1 electron donor acceptor complexes, their relevance to chemistry and biology. It also contains an introduction to nonlinear optical processes in molecules. The objective of the present work and scope of the investigation carried out in this thesis is presented in this chapter.
Chapter 2 describes the details of the experimental polarization resolved HRS technique. The geometrical model adopted for the analysis of the HRS data has also been introduced and the method of analysis has been described in detail in this chapter.
Chapter 3 presents the measurement of β values of two series of 1:1 EDA complexes of variously substituted methylbenzenes donors with tetrachloro-p-benzoquinone (CHL) and dicyanodichloro-p-benzoquinone (DDQ) acceptors at 1064 nm. In agreement with recent theoretical results we find large first hyperpolarizabilities for these complexes. The β values are greater than that of the typical push-pull molecule p-nitroaniline (pNA). We also find that in general β decreases with decrease in the donor strength.
Chapter 4 presents the β values for the two series of EDA complexes of CHL and DDQ acceptors at 1907 nm. The values of β are less in magnitude at 1907 nm than that at 1064 nm which is due to the dispersion effect in β.
In Chapter 5 and 6, it is described how depolarized hyper-Rayleigh scattering can be utilized to probe geometries of 1:1 complexes in solution. Chapter 5 concentrates mainly on 1:1 EDA complexes of CHL and DDQ and TCNB (tetracyanobenzene), while chapter 6 contains examples of other 1:1 molecular complexes where the noncovalent interactions are much weaker, such as in benzene-naphthalene, benzene-methoxybenzene, benzene-hexafluorobenzene and benzene-chlorobenzene pairs. We find the geometry of 1:1 EDA complexes in solution in terms of tilt angle (θ) and twist angle (ϕ) between the donor and acceptor pairs. The angle θ varies from 29°-47° for different pairs of EDA complexes, while ϕ varies within 34° and 38°. We find that the geometry of 1:1 EDA complexes in solution is different (twisted and tilted cofacial and twisted ‘V’) from those in the crystalline or gaseous states (cofacial), if known. We find that both benzene-naphthalene and benzene-chlorobenzene pairs assume twisted ‘T’ shape geometry with θ = 82° and 85°, respectively, and φ = 38°, while benzene-hexafluorobenzene assumes a twisted ‘V’ shape. A strong solvent effect is seen in the geometry of the benzene- methoxybenzene complex. The tilt angle is 55° when chloroform is used as a solvent and it is 82° without chloroform.
Chapter 7 is the concluding chapter where the main work done in this thesis is summarized and future directions are presented.
30
Ghosh, Sampa. "Quadratic Optical Nonlinearity And Geometry Of 1:1 Electron Donor Acceptor Complexes In Solution." Thesis, 2008. http://hdl.handle.net/2005/711.
Abstract:
The knowledge of geometry of molecular complexes formed via molecular association in solution through weak interactions is always important to understand the origin of stability and function of an array of molecules, supramolecular assemblies, and macromolecular networks. Simple 1:1 molecular complexes are very useful in this regard as they provide a model to understand both the nature of these interactions and their structural implications. Several weak noncovalent forces from long range (van der Waal’s, electrostatic, induction, dispersion) to short range (charge transfer) govern the geometry, that is, relative orientation of the two molecules in such a complex. On one hand, we find 1:1 electron donor acceptor (EDA) complexes such as naphthalene-tetracyanobenzene, hexamethylbenzene-chloranil etc. which stack parallel or in slipped parallel geometry in their crystals. On the other, benzene dimer has been found to stabilize in T shaped geometry in all its three physical states. In this thesis, I focus on 1:1 EDA complexes in solution. A good volume of literature is available which deals with the optical studies on the formation of such complexes. It has been suggested that the nature of the intermolecular interactions stabilizing these complexes in the gas phase or in their crystals is modified by the presence of solvent-solute interactions in solution thus bringing in difference in the solution geometry. However, the existing experimental techniques, both optical and magnetic, are unable to determine the exact geometries of 1:1 EDA complexes in solution. This opens an opportunity to probe their geometry in solution.
The quadratic nonlinearity or first hyperpolarizability (β) of a molecule is a measure of the change in dipole moment (or polarization) in the second order of the applied electrical field and thus has a purely electronic origin. It is a tensorial property and can be resolved in components along the three dimensions. The number of β components and the nonlinear optical anisotropies in a typical donor-acceptor type dipolar molecule, defined as (equation) (where1, 2, 3 axes define the molecular frame, 1 being the direction along the principal axis of symmetry and pointing from the acceptor toward the donor), are determined by the symmetry /structure of the molecule. It has been shown theoretically that the 1:1 EDA complexes possess large hyperpolarizabilities. In the case of pNA dimers calculation revealed that the geometry of the dimer and its symmetry is important for obtaining the correct estimate of β from its tensorial components. Therefore, it should be possible to use the values of tensorial β components to construct the unknown geometry of such complexes. Experimentally macroscopic depolarization ratios (D and D′) in the laboratory fixed frame (XYZ, X being the direction of polarization and Z the direction of propagation of the incident light), are measured from the polarization resolved intensities of second harmonic scattering from molecules in solution using the hyper-Rayleigh scattering technique. The depolarization ratios are correlated to the anisotropy parameters, u and v through a co-ordinate transformation. In this thesis I, have first, characterized the quadratic nonlinear optical property of a variety of 1:1 electron donor acceptor complexes and used the values of u and v obtained from depolarized hyper-Rayleigh scattering to deduce their geometry in solution.
Chapter 1 provides an introduction to the 1:1 electron donor acceptor complexes, their relevance to chemistry and biology. It also contains an introduction to nonlinear optical processes in molecules. The objective of the present work and scope of the investigation carried out in this thesis is presented in this chapter.
Chapter 2 describes the details of the experimental polarization resolved HRS technique. The geometrical model adopted for the analysis of the HRS data has also been introduced and the method of analysis has been described in detail in this chapter.
Chapter 3 presents the measurement of β values of two series of 1:1 EDA complexes of variously substituted methylbenzenes donors with tetrachloro-p-benzoquinone (CHL) and dicyanodichloro-p-benzoquinone (DDQ) acceptors at 1064 nm. In agreement with recent theoretical results we find large first hyperpolarizabilities for these complexes. The β values are greater than that of the typical push-pull molecule p-nitroaniline (pNA). We also find that in general β decreases with decrease in the donor strength.
Chapter 4 presents the β values for the two series of EDA complexes of CHL and DDQ acceptors at 1907 nm. The values of β are less in magnitude at 1907 nm than that at 1064 nm which is due to the dispersion effect in β.
In Chapter 5 and 6, it is described how depolarized hyper-Rayleigh scattering can be utilized to probe geometries of 1:1 complexes in solution. Chapter 5 concentrates mainly on 1:1 EDA complexes of CHL and DDQ and TCNB (tetracyanobenzene), while chapter 6 contains examples of other 1:1 molecular complexes where the noncovalent interactions are much weaker, such as in benzene-naphthalene, benzene-methoxybenzene, benzene-hexafluorobenzene and benzene-chlorobenzene pairs. We find the geometry of 1:1 EDA complexes in solution in terms of tilt angle (θ) and twist angle (ϕ) between the donor and acceptor pairs. The angle θ varies from 29°-47° for different pairs of EDA complexes, while ϕ varies within 34° and 38°. We find that the geometry of 1:1 EDA complexes in solution is different (twisted and tilted cofacial and twisted ‘V’) from those in the crystalline or gaseous states (cofacial), if known. We find that both benzene-naphthalene and benzene-chlorobenzene pairs assume twisted ‘T’ shape geometry with θ = 82° and 85°, respectively, and φ = 38°, while benzene-hexafluorobenzene assumes a twisted ‘V’ shape. A strong solvent effect is seen in the geometry of the benzene- methoxybenzene complex. The tilt angle is 55° when chloroform is used as a solvent and it is 82° without chloroform.
Chapter 7 is the concluding chapter where the main work done in this thesis is summarized and future directions are presented.
31
Farid, Ramy Samir. "Electron transfer in rigid and semi-rigid iridium d8-d8 donor-spacer-acceptor complexes." Thesis, 1991. https://thesis.library.caltech.edu/2680/1/Farid_rs_1991.pdf.
Abstract:
A series of rigid and semi-rigid donor-spacer-acceptor complexes, [Ir(µ-pz*)(CO)(Ph2P-O-C6H4-(CH2)n-py[superscript +]-R)]2(pz* = 3,5-dimethylpyrazolyl; C6H4 = phenylene; py[superscript +] = pyridinium; R = H, 4-tert-butyl, and 4-amide; and n = 0,1,2, and 3, has been synthesized for the purpose of studying photoinduced electron-transfer (ET) reactions. The spacers separating the iridium center (electron donor, Ir2) and pyridinium cation (electron acceptor, py[superscript +]) are based on terminal phosphinite ligands, consisting of a phenylene group and a number of methylene groups ranging from 0 to 3. Three distinct ET reactions can be studied in each complex: singles excited-state electron transfer ([superscript 1]ET), triplet excited-state electron transfer ([superscript 3]ET), and thermal back electron transfer (ET[superscript b]).
Atomic positions, obtained from the X-ray crystal structure of [Ir(µ-pz*)(CO)(Ph2P-O-C6H4-CH3]2 were used as a basis for molecular mechanics calculations, furnishing solution structures for the series of Ir2-py[superscript +] donor-acceptor complexes. These results revealed that the spacers in complexes where n = 0 and n =1 are rigid, and that in complexes where n = 2 and n = 3, the spacers are semi-rigid, taking on either folded or stretched conformations in fluid solution.
Steady-state and time-resolved emission and absorption experiments were employed to determine [superscript 1]ET, [superscript 3]ET, and ET[superscript b] rates in these complexes. The [superscript 1]ET and [superscript 3]ET rates for the n = 2 and n = 3 complexes exhibit Gaussian free-energy dependence, in excellent agreement with classical ET theory (n = 2: [lambda] = 1.10 eV, H[subscript DA] = 26 cm[superscript -1]; n = 3: [lambda] = 1.05 eV and H[subscript DA] = 7 cm[superscript -1]). However, the [superscript 1]ET and [superscript 3]ET rates in n = 0 and n = 1 complexes exhibit dramatically different behavior: the [superscript 3]ET rates in these rigid complexes are on the order of 10,000 times slower than the corresponding [superscript 1]ET rates. H[subscript DA]s for the ET[superscript b] reactions (n = 1,2) are similar to those of the corresponding [superscript 1]ET reactions. These results are discussed in terms of the solution structure parameters obtained for the series of donor-acceptor complexes. Evidence that through-bond and through-space couplings play different roles in singles and triplet electron transfer is presented for the first time.
32
D'Alessandro, Deanna Michelle. "Stereochemical effects on intervalence charge transfer /." 2005. http://eprints.jcu.edu.au/1289.
33
CHEN, SHENG-GONG, and 陳勝恭. "Semiempirical method study on two conformational isomers of para-substituted benzene/TCNE electron-donor-acceptor complexes." Thesis, 1992. http://ndltd.ncl.edu.tw/handle/25610710452912666544.
34
Bheemaraju, Amarnath. "Effect of side chains on organic donor (D) and acceptor (A) complexes and photophysical properties of D-A dyads." 2011. https://scholarworks.umass.edu/dissertations/AAI3482586.
Abstract:
This dissertation aims to understand the effect of incompatible side chains on the complexes of π-conjugated electron-rich donors and electron-deficient acceptors in solution. The role of incompatible side chains were studied in simple mixtures of organic donor and acceptor molecules that form donor-acceptor complexes. The incompatible branched and linear alkane side chains on the acceptor and donor respectively prevented complex formation between naphthalene diimide acceptor and naphthalene ether donor. However, the incompatible hydrocarbon-fluorocarbon and polar-non polar side chain pairs did not affect complex formation between the donor and acceptor. In quaterthiophene-naphthalene diimide dyads, the incompatibility of the side chain on the acceptor with respect to the side chain on the donor do not have any influence on the donor-acceptor complex formation. Irrespective of the attached side chains, all the dyads show charge transfer absorption bands and have similar electron transfer rates. The effect of point of attachment of the acceptor to the donor in the quaterthiophene-flavin dyad is also studied.
35
Hung, Chih-Chang, and 洪志昌. "Electron-Transfer Dynamics of Tetracyanoethylene-Methylbenzene Electron Donor-Acceptor Complexes Studied by Ultrafast Time-resolved Optical Kerr Gating Fluorescence Spectroscopy." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/07195938509400445029.
36
Renison, Carina Alicia. "Substituent effects in triarylphosphines." Thesis, 2012. http://hdl.handle.net/10210/6353.
Abstract:
M.Sc.The main objective of the work presented in this dissertation was to investigate the application of the phosphorus atom as a probe to evaluate stereo-electronic effects in arylphosphines. Traditionally, electronic effects are described as having inductive or resonance origins. In addition to the aforementioned mechanisms, the possibility of an additional field effect pathway was also investigated. For this purpose, a series of ortho, meta and para mono-substituted triaryl phosphines, i.e. Ph2(C6H4-X), were synthesised using a lithium-halogen exchange pathway. This series included a selection of electron-withdrawing and electron-donating substituents (X = F, CN, COOtBu, Me, OMe, NMe2) as well as combinations of these. Most of these ligands are crystalline which allowed analysis of their electronic nature by means of X-ray crystallography. From these ligands a representative range of electron-donating and electron-withdrawing aryl substituted phosphines was chosen to collect high-resolution (d=0.5 Å) data. An aspherical multipole refinement was carried out on each of the high-resolution data sets by employing the Hansen Coppens multipole formalism. This was followed by an experimental charge density analysis of each phosphine by employing the principles of QTAIM employed in WinXD. From topological analysis of the Laplacian of the electron density, properties at the (3,-3) lone pair critical points were evaluated. Similarly, the density properties at the (3,-1) bond critical points of the P-Cipso bond were evaluated by analysis of the topology of the electron density. In addition, several integrated properties including the volume, charge and electron population of the phosphorus atom were evaluated. All of the above properties showed very good linear correlations with the infrared CO stretching frequencies of the Rh-Vaska-type complexes corresponding to these phosphines. Furthermore, computational chemistry was employed as a complementary investigation tool to the X-ray crystallographic study. A theoretical charge density study was conducted for the complete range of phosphines described above in paragraph 1 of this Synopsis by employing the principles of QTAIM employed in AIMAll. All of the properties mentioned in the above paragraph were also calculated. In addition, the calculated molecular electrostatic potential properties of the phosphorus lone pair (Vmin and dcp), the integrated substituent bond dipole and NBO (Natural bond orbital) analysis was used to evaluate substituent electronic effects. All of the calculated properties (with the exception of the charge and electron population of the phosphorus atom calculated from NBO analysis) showed good linear correlations with the infrared CO stretching frequencies of the Vaska-type complexes corresponding to these phosphines within a particular electron-withdrawing/electron-donating or ortho/meta and para series. In addition, very ii good linear correlations were obtained between the experimental and theoretical properties within a particular electron-withdrawing/electron-donating or ortho/meta and para series. As additional investigation tools, the ligands were characterised by several techniques including infrared CO stretching frequency measurements performed on Rh Vaska-type compounds derived from the synthesised ligands, 31P NMR chemical shift measurements as well as 103Rh-31P coupling constant measurements to evaluate the effect of various substituents on the electron density at the phosphorus lone pair. In conclusion, it was found that the phosphorus atom is a sensitive probe of substituent electronic effects. Furthermore, it was found that high-resolution X-ray crystallography, computational chemistry, 31P NMR and infrared spectroscopy are all excellent techniques that can be employed to obtain a better understanding of the nature and transmission of substituent effects. From this study, it appeared that the electronic effects in phosphine ligands could not be rationalised by an inductive mechanism alone, but seemingly more correctly by an additional field effect mechanism.
37
Zilic, Elvis, University of Western Sydney, College of Health and Science, and School of Natural Sciences. "Radiation curing and grafting of charge transfer complexes." 2008. http://handle.uws.edu.au:8081/1959.7/19385.
Abstract:
Charge transfer (CT) complexes have been used in a number of radiation polymerisation processes including grafting and curing. The complexes studied include donor (D) monomers like vinyl ethers and vinyl acetate (VA) with acceptor (A) monomers such as maleic anhydride (MA). Both UV and EB have been utilised as radiation sources. The complexes are directly grafted to these substrates in the presence of radiation. The complexes yield novel copolymers when radiation cured with concurrent grafting improving the properties of the finished product. The term cure grafting has been proposed for this concurrent grafting process. Studies in basic photografting work to complement the cure grafting have been proposed. The role of solvent in grafting is discussed, particularly the effect of aromatics in photografting to naturally occurring trunk polymers like wool and cellulose. The effect of the double bond molar ratio (DBMR) of the DA components in grafting is examined. The ultraviolet (UV) conditions for gel formation during photografting, hence the importance of homopolymer yields in these processes is reported. A plausible mechanism to explain the results from this photografting work is proposed. The significance of these photografting studies in the related field of curing, especially in UV and ionising radiation (EB) systems, is discussed. EB curing and cure grafting of charge transfer (CT) monomer complexes is investigated. The EB results are compared with UV curing and cure grafting of the same complexes. The work has been extended to include EB/UV curing and cure grafting of thiolene systems. The significance of these results in the potential commercial application of these complexes is discussed. Variables affecting the UV/EB curing and cure grafting of thiolenes on cellulose have been studied. These include effect of varying the type of olefin, increasing the functionality of the thiol, use of acrylate monomers and oligomers in hybrid systems, altering the surface structure of the cellulose and finally the role of air in these processes particularly with EB. Photopolymerisation of the thiol-enes in bulk has also been investigated. The thesis content is based on the published work of 14 research papers over the course of the project.Doctor of Philosophy (PhD)
38
Msane, Gugu. "The synthesis of modified chlorophyll carbon nanotube photoactive dyad systems." Thesis, 2012. http://hdl.handle.net/10210/6361.
Abstract:
M.Sc.Donor-acceptor (D-A) systems consist of a donor covalently or non-covalently linked to an acceptor. The simplest D–A system consists of a donor linked to an acceptor and is called a dyad system. Photoactive dyad systems are molecular devices designed to perform through the separation of charge separation states and the conversion of solar energy to chemical energy in analogy to photosynthesis.1 These dyad systems consist of a donor which is usually a chromophore and an acceptor. The design of these systems is guided to mimic photo-induced electron transfer (PET) and charge separation (CS), which are fundamental processes of photosynthesis. In nature, photosynthetic units are often built from dyads consisting of pigments like chlorophyll (donors), non–covalently linked to quinones, (acceptors). The donor harvests light energy and transfers the energy to the nearby pigment molecules until it eventually reaches a special region of the chlorophyll macrocycle called the reaction centre where this light energy is then converted to electrochemical energy. Photoactive dyad systems act as artificial photosynthetic models as they reproduce photo–induced electron transfer and charge separation of natural photosynthesis. In this project, dyad systems were made by covalently linking zinc pheophorbide, a modified chlorophyll derivative to double–walled carbon nanotubes (DWCNTs). Zinc pheophorbide acts as the donor and DWCNTs as the acceptors. Chlorophyll was modified by cutting the phytol chain and inserting zinc as the central metal to yield zinc pheophorbide. This derivative is stable against irradiation, has a good range of acceptor wavelength and is also a good light harvester. DWCNTs are one dimensional nanowires with two concentric tubes. They readily accept electrons because they have an extended π electron system. These electrons are then transported efficiently under ballistic conditions. DWCNTs were synthesised by catalytic chemical vapour deposition (CCVD) of methane over Mg0.99Co0.075Mo0.025O catalyst. In dyad system 1, amidated zinc pheophorbide molecules were covalently attached to oxidised DWCNTs in the presence of N–ethyl–N’–(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) \ and N–hydroxysuccinnimide (NHS) as a catalysts. Dyad system 2 was synthesized by attaching zinc pheophorbide molecules to amidated DWCNTs using the same catalysts.
39
Mecker, Christoph J. "The synthesis of advanced "special pair" models for the photosynthetic reaction centre /." 2000. http://www.library.unsw.edu.au/~thesis/adt-NUN/public/adt-NUN20011128.150754/index.html.
40
Pandey, Ravindra. "Probing The Equilibrium Geometry Of Weakly Interacting Systems In Solution By Hyper-Rayleigh Scattering." Thesis, 2011. https://etd.iisc.ac.in/handle/2005/2365.
Abstract:
Under the electric dipole approximation, second harmonic of the incident light is scattered by a collection of randomly oriented molecular dipoles in solution due to instantaneous orientational fluctuation which is directional. If two such dipoles are correlated in space through intermolecular or other interactions, the intensity of the second harmonic scattered light (SHSL) will be related to the extent of such interactions. If two dipoles are arranged in a particular geometry by design, the geometry will determine the intensity of the SHSL. If a molecule has no dipole moment, the intensity of the SHSL will be less and is only allowed by higher order electric multipoles. If two such zero-dipole molecules interact with each other and transfer some amount of electronic charge from one to the other, the induced dipole moment will give rise to an enhanced SHSL. However, along with the direction of the dipole moment from the donor to the acceptor, the actual geometry of such molecular dimer/complex should also play an important role to determine the nature of the SHSL response. If all the isotropic nonzero components of first hyperpolarizability (β) are taken into account, from the measurement of β and related quantities such as depolarization ratios, in solution it should be possible to derive information about the geometry of the dimer/complex. This is precisely the motivation behind this thesis.
Chapter 1 gives a brief introduction of 1:1 charge transfer (CT) complexes between a donor and an acceptor and their importance in chemistry. It also contains an introduction to nonlinear optics, various spectroscopic techniques to characterize CT complexes, etc. The motivation of extracting the geometry of such complexes from hyper-Rayleigh scattering (HRS) measurements in solution is presented in this chapter.
In Chapter 2, all the experimental details of the unpolarized and polarization resolved HRS measurements at various excitation wavelengths have been described. Generation of infrared wavelengths (1543 nm and 1907 nm) using stimulated Raman scattering in gases have also been discussed.
In Chapter 3, the first hyperpolarizability (βHRS) for two series of 1:1 molecular complexes between methyl substituted benzene donors with tetrachloro-p-benzoquinone (CHL) and dicyanodichloro-p-benzoquinone (DDQ) acceptors in solution at 1543 nm have been presented. Enhancement of βHRS due to charge transfer from the donor to the acceptor molecule which was predicted theoretically has been verified. Using linearly (electric field vector along X direction) and circularly polarized incident light, respectively, two macroscopic depolarization ratios D = I2ω,X,X/I2ω,Z,X and D' = I2ω,X,C/I2ω,Z,C in the laboratory fixed XYZ frame by detecting the SHSL in a polarization resolved fashion have been measured. The experimentally obtained first hyperpolarizability (βHRS), D and D' values, are then matched with the theoretically calculated values from single and double configuration interaction calculations using the Zerner’s intermediate neglect of differential overlap and the self-consistent reaction field (ZINDO–SDCI– SCRF) approach by adjusting the geometrical parameters. It has been found that in most of the CT complexes studied here, there exists a significant twist in the equilibrium geometry at room temperature which is not a simple slipped parallel geometry as was believed.
In chapter 4, the βHRS, D and D' values of 1:1 pyridine (PY)-chloranil (CHL) complex at 1064 nm have been described. Previous theoretical studies have shown that there is a tilt angle of 77.9 degree in the gas phase PY-CHL complex. In this chapter, this prediction about the geometry of
1:1 PY-CHL complex has been probed. The experimentally found βHRS, D and D' are matched well with theoretically calculated values, using ZINDO–SDCI–SCRF, for a cofacial geometry of PY-CHL complex in solution indicating that the solution geometry is different from the gas phase geometry.
In Chapter 5, the βHRS, D and D' for a series of 1:1 complexes of tropyliumtetrafluoroborate and methyl-substituted benzenes in solution at 1064 nm have been reported. The measured D and D' values vary from 1.36 to 1.46 and 1.62 to 1.72, respectively and are much lower than the values expected from a typical sandwich or a T-shaped geometry. The lowering in D and D' indicates that these complexes have higher symmetry than C2v. The value of D close to 1.5 indicates there is a significant octupolar contribution in such complexes. In order to probe it further, βHRS, D and D' were computed using the ZINDO-SDCI-SCRF technique in the presence of BF4-anion. By arranging the three BF4-ions in a C3 symmetry around the complex in such a way that electrical neutrality is maintained, the computed values are brought to agreement with experiments. This unprecedented influence of the anion on the HRS, D and D' values of these complexes are discussed in this chapter.
In Chapter 6, the effect of dipolar interactions, within a multichromophoric system, on the second order nonlinear optical properties have been studied. It has been found that the βHRS response of the multichromophoric system is always larger than expected for uncorrelated chromophores demonstrating that the dipole moment of individual chromophores are not merely additive within the multichromophoric system but contribute cooperatively to the SHSL signal. Also the relative orientation and nature of the chromophores and the angle of interaction between them alter the HRS values.
Chapter 7 is the concluding chapter in which all the work done in the thesis has been summarized and future direction has been proposed.
41
Pandey, Ravindra. "Probing The Equilibrium Geometry Of Weakly Interacting Systems In Solution By Hyper-Rayleigh Scattering." Thesis, 2011. http://hdl.handle.net/2005/2365.
Abstract:
Under the electric dipole approximation, second harmonic of the incident light is scattered by a collection of randomly oriented molecular dipoles in solution due to instantaneous orientational fluctuation which is directional. If two such dipoles are correlated in space through intermolecular or other interactions, the intensity of the second harmonic scattered light (SHSL) will be related to the extent of such interactions. If two dipoles are arranged in a particular geometry by design, the geometry will determine the intensity of the SHSL. If a molecule has no dipole moment, the intensity of the SHSL will be less and is only allowed by higher order electric multipoles. If two such zero-dipole molecules interact with each other and transfer some amount of electronic charge from one to the other, the induced dipole moment will give rise to an enhanced SHSL. However, along with the direction of the dipole moment from the donor to the acceptor, the actual geometry of such molecular dimer/complex should also play an important role to determine the nature of the SHSL response. If all the isotropic nonzero components of first hyperpolarizability (β) are taken into account, from the measurement of β and related quantities such as depolarization ratios, in solution it should be possible to derive information about the geometry of the dimer/complex. This is precisely the motivation behind this thesis.
Chapter 1 gives a brief introduction of 1:1 charge transfer (CT) complexes between a donor and an acceptor and their importance in chemistry. It also contains an introduction to nonlinear optics, various spectroscopic techniques to characterize CT complexes, etc. The motivation of extracting the geometry of such complexes from hyper-Rayleigh scattering (HRS) measurements in solution is presented in this chapter.
In Chapter 2, all the experimental details of the unpolarized and polarization resolved HRS measurements at various excitation wavelengths have been described. Generation of infrared wavelengths (1543 nm and 1907 nm) using stimulated Raman scattering in gases have also been discussed.
In Chapter 3, the first hyperpolarizability (βHRS) for two series of 1:1 molecular complexes between methyl substituted benzene donors with tetrachloro-p-benzoquinone (CHL) and dicyanodichloro-p-benzoquinone (DDQ) acceptors in solution at 1543 nm have been presented. Enhancement of βHRS due to charge transfer from the donor to the acceptor molecule which was predicted theoretically has been verified. Using linearly (electric field vector along X direction) and circularly polarized incident light, respectively, two macroscopic depolarization ratios D = I2ω,X,X/I2ω,Z,X and D' = I2ω,X,C/I2ω,Z,C in the laboratory fixed XYZ frame by detecting the SHSL in a polarization resolved fashion have been measured. The experimentally obtained first hyperpolarizability (βHRS), D and D' values, are then matched with the theoretically calculated values from single and double configuration interaction calculations using the Zerner’s intermediate neglect of differential overlap and the self-consistent reaction field (ZINDO–SDCI– SCRF) approach by adjusting the geometrical parameters. It has been found that in most of the CT complexes studied here, there exists a significant twist in the equilibrium geometry at room temperature which is not a simple slipped parallel geometry as was believed.
In chapter 4, the βHRS, D and D' values of 1:1 pyridine (PY)-chloranil (CHL) complex at 1064 nm have been described. Previous theoretical studies have shown that there is a tilt angle of 77.9 degree in the gas phase PY-CHL complex. In this chapter, this prediction about the geometry of
1:1 PY-CHL complex has been probed. The experimentally found βHRS, D and D' are matched well with theoretically calculated values, using ZINDO–SDCI–SCRF, for a cofacial geometry of PY-CHL complex in solution indicating that the solution geometry is different from the gas phase geometry.
In Chapter 5, the βHRS, D and D' for a series of 1:1 complexes of tropyliumtetrafluoroborate and methyl-substituted benzenes in solution at 1064 nm have been reported. The measured D and D' values vary from 1.36 to 1.46 and 1.62 to 1.72, respectively and are much lower than the values expected from a typical sandwich or a T-shaped geometry. The lowering in D and D' indicates that these complexes have higher symmetry than C2v. The value of D close to 1.5 indicates there is a significant octupolar contribution in such complexes. In order to probe it further, βHRS, D and D' were computed using the ZINDO-SDCI-SCRF technique in the presence of BF4-anion. By arranging the three BF4-ions in a C3 symmetry around the complex in such a way that electrical neutrality is maintained, the computed values are brought to agreement with experiments. This unprecedented influence of the anion on the HRS, D and D' values of these complexes are discussed in this chapter.
In Chapter 6, the effect of dipolar interactions, within a multichromophoric system, on the second order nonlinear optical properties have been studied. It has been found that the βHRS response of the multichromophoric system is always larger than expected for uncorrelated chromophores demonstrating that the dipole moment of individual chromophores are not merely additive within the multichromophoric system but contribute cooperatively to the SHSL signal. Also the relative orientation and nature of the chromophores and the angle of interaction between them alter the HRS values.
Chapter 7 is the concluding chapter in which all the work done in the thesis has been summarized and future direction has been proposed.
42
HSING-FANG, CHIANG, and 江幸芳. "(a)Synthesis, Characterization, Structure and Studies of metal complexes with short Fluoro-ponytailed Bipyridine Ligands Possessing Halogen (Halogen Bonding) (b)Studies of The Non-Covalent Bonds of Flourous Compounds as Electron Acceptor or Donor." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/qsxrh7.
Abstract:
碩士國立臺北科技大學
有機高分子研究所
105
(a) Our Lab has been started to synthesize polyfluorinated compounds and promoted their recognition considerably. On continuation of our prior studies, I synthesized Bipyridine ligands having terminal Halogen and its palladium / platinum metal complexes in the research to study their structural properties. The reaction of bipyridine ligands with Palladium and Platinum Metals to generate their corresponding Metal complexes. The synthesized ligands and their metal complexes have been characterized using IR, NMR, Single Crystal X-ray diffraction, and Melting point techniques. We have attempted to prepare crystals with various structures, using dual solvent and change of temperature during recrystallization. With calculation, compared experimental value and theoretical value, to study their structural properties and non-colvalent bond (Halogen Bond). (b) Flourous compounds can be electron donor or electron acceptor. Our Lab has been successfully synthesized a series of fluorine-containing pyridine. Because pyridine ligands are liquid, we used ligands to react with hydrogen halide or saccharin to generate the pyridium salts and pyridium saccharinate salts. We have attempted to prepare crystals with various structures. Because the structure contains many weak interactions, so we focus on the discussion of non-covalent bonding, and fluorine-containing pyridium salts as an acceptor of the halogen bonding. Furthermore, we also found that IPFB and 1,4-DITFB could be used as the donor of the halogen bonding. The Raman spectra and theoretical calculations were used to analyze the vibrational spectra of these weak interactions, and a series of non-covalent bonds to explore.
43
Mukhopadhyay, Sukrit. "Theoretical Studies Of Electronic Properties And Electronic Processes In Conjugated Molecules." Thesis, 2010. https://etd.iisc.ac.in/handle/2005/1265.
Abstract:
This thesis deals with theoretical studies of electronic properties of organic conjugated molecules. The first chapter introduces different classes of organic conjugated molecules which possess high hole mobility, large quadratic non-linear response and low band gap. In this chapter, we further describe different photo-physical processes and the basic principles of various opto-electronic devices. The second chapter provides an introduction to various many-body techniques, which are employed in studying ground and excited state properties of organic conjugated systems. First, we describe the Hartree-Fock theory and the Density Functional (DFT) method. These are followed by full Configuration-Interaction (CI) methods and various semi-empirical methods (CNDO, INDO and NDDO). The INDO method is used in subsequent chapters to obtain the ground and excited state properties of organic conjugated molecules. In addition, we describe the restricted CI (SCI and SDCI) and the Density Matrix Renormalization Group (DMRG) methods. The third chapter of this thesis deals with a time evolution study to ascertain the role of the triplet state in the green emission of the ethyl-hexyl substituted poly-fluorene (PF2/6) films. To understand this phenomenon, we have modeled various non-radiative processes like (i) Inter-System Crossing (ISC), (ii) electron-hole Recombination (e-hR) and (iii) Triplet Quenching (TQ). These studies conclusively prove the contribution of triplet states to the 500 nm EL peak. In chapter four, we describe the origin of the unusual EL in tri-p-tolylamine (TTA) based hole conductors. In order to model this phenomenon, we have performed SCI calculations on TTA, its radical ions and allied hole conductors (TAPC and TPD). These calculations indicate that the unusual EL is due to low-lying charge-transfer (CT) state, which is stabilized by charge-dipole and charge-induced-dipole interactions. In chapter five, we turn our attention to the calculation of ground and excited state properties of a class of donor-acceptor (DA) system using ab-initio DFT and INDO methods. In these systems, DFT calculations along with INDO-SCI calculation, show strong intramolecular charge transfer interaction between the D and the A units. We have further calculated various properties like permanent dipole moments, oscillator strengths, Stoke’s shifts in various solvents etc. In chapter six, we focus on studying linear and non-linear optical properties of first generation nitrogen based dendrimers, using DMRG method. A novel scheme which includes the weights of the dipole allowed states in the computation of the density matrix is developed to obtain accurate dipole allowed excited states as well as the linear and nonlinear optical responses. Chapter seven deals with non-linear optical properties of weak donor-acceptor (DA) complexes formed between methyl substituted phenylenes (donor) and Chloranil or DDQ (acceptors). We have calculated the ground and the low-lying excited states of these DA complexes using INDO-SDCI method. The first hyperpolarizability (β) response coefficients are calculated using the Correction Vector (CV) technique, which are further used to obtain macroscopic depolarization ratios. By comparing the theoretical results with experimental findings, it can be shown that the slipped parallel configuration with a slight twist is the most preferred geometry of these weak DA complexes in solution.
44
Mukhopadhyay, Sukrit. "Theoretical Studies Of Electronic Properties And Electronic Processes In Conjugated Molecules." Thesis, 2010. http://etd.iisc.ernet.in/handle/2005/1265.
Abstract:
This thesis deals with theoretical studies of electronic properties of organic conjugated molecules. The first chapter introduces different classes of organic conjugated molecules which possess high hole mobility, large quadratic non-linear response and low band gap. In this chapter, we further describe different photo-physical processes and the basic principles of various opto-electronic devices. The second chapter provides an introduction to various many-body techniques, which are employed in studying ground and excited state properties of organic conjugated systems. First, we describe the Hartree-Fock theory and the Density Functional (DFT) method. These are followed by full Configuration-Interaction (CI) methods and various semi-empirical methods (CNDO, INDO and NDDO). The INDO method is used in subsequent chapters to obtain the ground and excited state properties of organic conjugated molecules. In addition, we describe the restricted CI (SCI and SDCI) and the Density Matrix Renormalization Group (DMRG) methods. The third chapter of this thesis deals with a time evolution study to ascertain the role of the triplet state in the green emission of the ethyl-hexyl substituted poly-fluorene (PF2/6) films. To understand this phenomenon, we have modeled various non-radiative processes like (i) Inter-System Crossing (ISC), (ii) electron-hole Recombination (e-hR) and (iii) Triplet Quenching (TQ). These studies conclusively prove the contribution of triplet states to the 500 nm EL peak. In chapter four, we describe the origin of the unusual EL in tri-p-tolylamine (TTA) based hole conductors. In order to model this phenomenon, we have performed SCI calculations on TTA, its radical ions and allied hole conductors (TAPC and TPD). These calculations indicate that the unusual EL is due to low-lying charge-transfer (CT) state, which is stabilized by charge-dipole and charge-induced-dipole interactions. In chapter five, we turn our attention to the calculation of ground and excited state properties of a class of donor-acceptor (DA) system using ab-initio DFT and INDO methods. In these systems, DFT calculations along with INDO-SCI calculation, show strong intramolecular charge transfer interaction between the D and the A units. We have further calculated various properties like permanent dipole moments, oscillator strengths, Stoke’s shifts in various solvents etc. In chapter six, we focus on studying linear and non-linear optical properties of first generation nitrogen based dendrimers, using DMRG method. A novel scheme which includes the weights of the dipole allowed states in the computation of the density matrix is developed to obtain accurate dipole allowed excited states as well as the linear and nonlinear optical responses. Chapter seven deals with non-linear optical properties of weak donor-acceptor (DA) complexes formed between methyl substituted phenylenes (donor) and Chloranil or DDQ (acceptors). We have calculated the ground and the low-lying excited states of these DA complexes using INDO-SDCI method. The first hyperpolarizability (β) response coefficients are calculated using the Correction Vector (CV) technique, which are further used to obtain macroscopic depolarization ratios. By comparing the theoretical results with experimental findings, it can be shown that the slipped parallel configuration with a slight twist is the most preferred geometry of these weak DA complexes in solution.