Letteratura scientifica selezionata sul tema "Nitroaromatic molecules"

The standard heats of formation for 12 nitroaromatic molecules in gas at 298 K were calculated at B3P86/6-311G** levels using different isodesmic reactions. Comparison between the computational results and the experimental values reveals that using methane as reference compound to design isodesmic reaction is able to predict satisfactory results of heats of formation for ortho-substituted nitroaromatic molecules; however, using benzene as reference compound is able to give agreement with experimental data for meta-substituted and para-substituted nitroaromatic molecules.

Density functional theory (DFT) is used to calculate the C-NO2bond dissociation energies (BDEs) in nitrobenzene; 3-amino-nitrobenze; 4-amino-nitrobenze; 1,3-dinitrobenzene; 1,4-dinitrobenzene; 2-methyl-nitrobenzene; 4-methyl-nitrobenzene and 1,3,5-trinitrobenzene nitroaromatic molecular system. B3P86 and PBE0 methods in combination with 6-31G** and 6-311G** basis sets are employed. Comparison between the computational results and the experimental values reveals that the calculated C-NO2bond BDEs can be improved from B3P86 to PBE0 functional. Level of theory employing PBE0/6-311G** is found to be sufficiently reliable to compute BDEs of C-NO2bond for nitroaromatic molecules with an average absolute error of 0.98 kcal mol-1.

Acylhydrazone-based fluorescent conjugated microporous polymers (CMPs) with inter-and intra-hydrogen bonding-controlled emissive properties were prepared. The synthesized CMPs (BH-CMP and ABH-CMP) were characterized by Fourier-transform infrared spectroscopy, X-ray diffraction, solid-state 13C cross polarization/magic angle spinning nuclear magnetic resonance spectroscopy, and photoluminescence spectroscopy. Interestingly, BH-CMP exhibited emission enhancement via adsorption of water molecules, whereas the emission of ABH-CMP, which possesses free amine groups, decreased upon the addition of water molecules. The differences in the emission trends of BH-CMP and ABH-CMP in the presence of water molecules originate from the formation of different hydrogen-bonding networks in each CMP. The acylhydrazone-based CMPs were applied to the detection of nitroaromatic compounds. As a result, ABH-CMP in DMF exhibited high selectivity for 1,3,5-trinitrotoluene (TNT) over other nitroaromatic compounds nitrobenzene, 1-chloro-4-nitrobenzene, 2,3-dichloronitrobenzene, and 2,4-dinitrotoluene.

Three new Zn(ii)-based frameworks were fabricated and their fluorescence and sensing properties for specific anions and organic molecules such as benzaldehyde (BZH) and nitroaromatic compounds (NACs) were examined.

The photochemistry of bichromophoric species containing nitroaromatic and arylamino moieties has been studied in the presence and absence of an external magnetic field. Photolysis products are an unsubstituted arylamine, a nitrosoaromatic species (Product 1), and a nitroaromatic compound (Product 2). On application of the magnetic field, the formation yield for Product 1 decreases and that for Product 2 correspondingly increases, whereas the consumption of the starting material and the release of the unsubstituted arylamine are independent of the magnetic field. Analysis of the magnetic field effects shows that the hyperfine coupling mechanism predominates and that the photoreaction takes place in the triplet manifold of the nitroaromatic moiety. Application of the magnetic field may cause an appreciable change in the relative yield of cage and escape products, i.e., the branching ratio of competitive processes.

SUMMARY Nitroaromatic compounds are relatively rare in nature and have been introduced into the environment mainly by human activities. This important class of industrial chemicals is widely used in the synthesis of many diverse products, including dyes, polymers, pesticides, and explosives. Unfortunately, their extensive use has led to environmental contamination of soil and groundwater. The nitro group, which provides chemical and functional diversity in these molecules, also contributes to the recalcitrance of these compounds to biodegradation. The electron-withdrawing nature of the nitro group, in concert with the stability of the benzene ring, makes nitroaromatic compounds resistant to oxidative degradation. Recalcitrance is further compounded by their acute toxicity, mutagenicity, and easy reduction into carcinogenic aromatic amines. Nitroaromatic compounds are hazardous to human health and are registered on the U.S. Environmental Protection Agency's list of priority pollutants for environmental remediation. Although the majority of these compounds are synthetic in nature, microorganisms in contaminated environments have rapidly adapted to their presence by evolving new biodegradation pathways that take advantage of them as sources of carbon, nitrogen, and energy. This review provides an overview of the synthesis of both man-made and biogenic nitroaromatic compounds, the bacteria that have been identified to grow on and completely mineralize nitroaromatic compounds, and the pathways that are present in these strains. The possible evolutionary origins of the newly evolved pathways are also discussed.

The luminescence of azobenzene chromophore struts in a metal organic framework is quenched by nitroaromatic guests. X-ray photoelectron spectroscopic methods verify the emission changes are due to the surface adsorption of the guest molecules rather than encapsulation.

Nitroaromatic compounds—adducts of Morita–Baylis–Hillman (MBHA) reaction—have been applied in the treatment of malaria, leishmaniasis, and Chagas disease. The biological activity of these compounds is directly related to chemical reactivity in the environment, chemical structure of the compound, and reduction of the nitro group. Because of the last aspect, electrochemical methods are used to simulate the pharmacological activity of nitroaromatic compounds. In particular, previous studies have shown a correlation between the one-electron reduction potentials in aprotic medium (estimated by cyclic voltammetry) and antileishmanial activities (measured by the IC50) for a series of twelve MBHA. In the present work, two different computational protocols were calibrated to simulate the reduction potentials for this series of molecules with the aim of supporting the molecular modeling of new pharmacological compounds from the prediction of their reduction potentials. The results showed that it was possible to predict the experimental reduction potential for the calibration set with mean absolute errors of less than 25 mV (about 0.6 kcal·mol−1).

Very large amplitude nitroaromatic sensing dynamics are observed upon a structural change within an alternating D–π–A chromophore initially configured to promote densely cofacial self-packing at a macromolecular scale.

Les kinétoplastidés sont des protozoaires flagellés responsables de maladies tropicales négligées, pouvant être potentiellement mortelles chez l’Homme, telles que la leishmaniose viscérale (L. donovani et L. infantum), la trypanosomiase humaine africaine (T. brucei) ou la maladie de Chagas (T. cruzi), et pour lesquelles les traitements actuellement disponibles présentent des limitations. Ces dernières années, un regain d’intérêt est porté aux molécules anti-infectieuses nitroaromatiques, à l’image du fexinidazole. L’activité anti-kinétoplastidés de ces composés résulte de leur bioactivation sélective par des nitroréductases parasitaires, conduisant à la formation d’espèces réactives toxiques pour le parasite. Deux hits antileishmaniens et deux hits anti-Trypanosoma, substrats des nitroréductases parasitaires de type 1, ont été précédemment décrits en série 3-nitroimidazo[1,2-a]pyridine. Ces travaux de thèse portent sur la synthèse et l’étude des relations structure-activité de cent-trois dérivés originaux, dont soixante-et-un dérivés sont fonctionnalisés en positions 2, 6 et 8 du pharmacophore 3-nitroimidazo[1,2-a]pyridine, et trente-cinq dérivés sont fonctionnalisés en positions 5 ou 7, via des réactions de SN2, SNAr, ou de couplages pallado-catalysés. Deux dérivés en série 3-nitroimidazo[1,2-b]pyridazine et cinq dérivés 5-nitroimidazoles sont obtenus par miodification structurale. Ainsi, deux nouveaux hits ont été identifiés en série 3-nitroimidazo[1,2-a]pyridine, un premier antileishmanien, et un second anti-Trypanosoma, possédant tous deux de meilleurs paramètres pharmacocinétiques et physicochimiques que les hits précédents
Kinetoplastids are flagellated protozoa responsible for life-threatening neglected tropical diseases in humans, such as visceral leishmaniasis (L. donovani and L. infantum), human African trypanosomiasis (T. brucei), or Chagas disease (T. cruzi), for which currently available treatments have limitations. The antikinetoplastid activity of these compounds results from their selective bioactivation by parasitic nitroreductases, leading to the formation of reactive species toxic to the parasite. Two antileishmanial and two anti-Trypanosoma hits, substrates of type 1 parasitic nitroreductases, have been previously described in 3-nitroimidazo[1,2-a]pyridine series. This thesis work focuses on the synthesis and structure-activity relationships of one hundred and three original derivatives, of which sixty-one derivatives are functionalized at positions 2, 6, and 8 of the 3-nitroimidazo[1,2-a]pyridine pharmacophore, and thirty-five derivatives are functionalized at positions 5 or 7, via SN2, SNAr, or pallado-catalyzed coupling reactions. Two 3-nitroimidazo[1,2-b]pyridazine series derivatives are also obtained from a scaffold-hopping strategy, and five 5-nitroimidazole derivatives are obtained by structural simplification. Thus, two new hits were identified in 3-nitroimidazo[1,2-a]pyridine series, a first one antileishmanial, and a second one anti-Trypanosoma, both showing better pharmacokinetic (microsomal stability, human albumin binding) and physicochemical (water solubility, PAMPA permeability tests) properties than the previous hits

[ES] En este trabajo estudiamos dos reacciones catalíticas relevantes para la industria y la localización del anión fluoruro en la zeolita RTH, sintetizada en medio fluoruro. El capítulo 3 es el primer capítulo de resultados, donde se estudia la reducción quimioselectiva del nitroestireno en las superficies Ni(111), Co(111), Cu(111) y Pd(111). El mecanismo generalmente aceptado de esta reacción está basado en el esquema propuesto por Haber en 1898, en el que la reacción puede transcurrir por dos rutas, la directa y la de condensación. En este capítulo exploramos ambas rutas, y observamos que la ruptura de los enlaces N-O y la consecuente formación de enlaces metal-O está más favorecida que la formación de enlaces N-H en las superficies Ni(111) y Co(111), debido al carácter oxofílico de ambos metales. Las etapas más lentas involucran la formación de enlaces N-H. En las superficies de metales nobles como Pt(111) y Pd(111) se observa el comportamiento contrario. La superficie Cu(111) es un caso intermedio comparado con los metales nobles y no nobles. Además, el nitroestireno interactúa con los átomos de Cu de la superficie solo a través de grupo nitro, con lo cual es un candidato ideal para alcanzar selectividades cerca del 100%. Sin embargo, la superficie Cu(111) no es capaz de activar la molécula de H2. En este sentido, proponemos un catalizador bimetálico basado en Cu, dopado con otro metal capaz de activar al H2, tales como el Pd o el Ni. En los capítulos 4 y 5 se ha estudiado la reducción catalítica selectiva de los óxidos de nitrógeno (SCR, en inglés) con amoníaco. Usando métodos de DFT, hemos encontrado rutas para la oxidación de NO a NO2, nitritos y nitratos con energías de activación relativamente bajas. También, hemos encontrado que la reducción de Cu2+ a Cu+ requiere la participación simultánea de NO y NH3. Posteriormente, hemos estudiado la influencia del NH3 en este sistema con métodos de dinámica molecular. El NH3 interacciona fuertemente con el Cu+ de forma que dos moléculas de este gas son suficientes para romper la coordinación del catión Cu+ con los oxígenos del anillo 6r, y formar el complejo lineal [Cu(NH3)2]+. Además, los cationes Cu2+ pueden ser estabilizados fuera de la red mediante la formación del complejo tetraamincobre(II). Debido a la presencia de los cationes Cu+ y Cu2+ coordinados a la red de la zeolita, aparecen bandas en la región entre 800-1000 cm-1 del espectro infrarrojo. El análisis de las frecuencias IR de varios modelos con Cu+ y Cu2+ coordinados al anillo 6r, o formando complejos con amoniaco indica que cuando los cationes Cu+ y Cu2+ están coordinados a los oxígenos del anillo 6r aparecen vibraciones entre 830 y 960 cm-1. Frecuencias en esta zona también se obtienen en los casos en que NO, NO2, O2 y combinaciones de dos de ellos están adsorbidos en Cu+ y Cu2+. Sin embargo, cuando los cationes Cu+ y Cu2+ están fuera del anillo (no hay enlaces entre los cationes de cobre y los oxígenos del anillo 6r) no se obtienen vibraciones de IR en esta región del espectro. Estos resultados indican que con el seguimiento del espectro IR durante la reacción SCR es posible determinar si los cationes Cu+ y Cu2+ están coordinados o no al anillo de 6r en las etapas de oxidación y reducción. Por último, hemos simulado el desplazamiento químico de 19F, δiso,, en la zeolita sintetizada RTH. El análisis del δiso de los distintos modelos utilizados nos ha permitido reconocer la simetría del material sintetizado, el cual pertenece al grupo espacial P1 y la nueva celda unidad ha sido confirmada experimentalmente por difracción de rayos X. Finalmente, hemos asignado la señal experimental que aparece en el espectro de 19F a -67.2_ppm, al F- localizado en un sitio T2, el cual es a su vez la posición más estable. Además, la señal a -71.8 ppm se ha asignado al anión F- localizado en un sitio T4.
[CA] En aquest treball estudiem dues reaccions catalítiques rellevants per a la indústria i la localització de l'anió fluorur en la zeolita RTH, sintetitzada al mig fluorur. El capítol 3 és el primer capítol de resultats, on s'estudia la reducció quimioselectiva del nitroestireno en les superfícies Ni(111), Co(111), Cu(111) i Pd(111). El mecanisme generalment acceptat d'aquesta reacció està basat en l'esquema proposat per Haver-hi en 1898, en el qual la reacció pot transcórrer per dues rutes, la directa i la de condensació. En aquest capítol explorem totes dues rutes, i observem que la ruptura dels enllaços N-O i la conseqüent formació d'enllaços metall-O està més afavorida que la formació d'enllaços N-H en les superfícies Ni(111) i Co(111), a causa del caràcter oxofílico de tots dos metalls. Les etapes més lentes involucren la formació d'enllaços N-H. En les superfícies de metalls nobles com Pt(111) i Pd(111) s'observa el comportament contrari. La superfície Cu(111) és un cas intermedi comparat amb els metalls nobles i no nobles. A més, el nitroestireno interactua amb els àtoms de Cu de la superfície sol a través de grup nitre, amb la qual cosa és un candidat ideal per a aconseguir selectivitats prop del 100%. No obstant això, la superfície Cu(111) no és capaç d'activar la molècula d'H2. En aquest sentit, proposem un catalitzador bimetàl·lic basat en Cu, dopat amb un altre metall capaç d'activar a l'H2, com ara el Pd o el Ni. En els capítols 4 i 5 hem estudiat la reducció catalítica selectiva dels òxids de nitrogen (SCR, en anglés) amb amoníac. Usant mètodes de DFT, hem trobat rutes per a l'oxidació de NO a NO2, nitrits i nitrats amb energies d'activació relativament baixes. També, hem trobat que la reducció de Cu2+ a Cu+ requereix la participació simultània de NO i NH3. Posteriorment, hem estudiat la influència del NH3 en aquest sistema amb mètodes de dinàmica molecular. El NH3 interacciona fortament amb el Cu+ de manera que dues molècules d'aquest gas són suficients per a trencar la coordinació del catió Cu+ amb els oxígens de l'anell 6r, i formar el complex lineal [Cu(NH3)2]+. A més, els cations Cu2+ poden ser estabilitzats fora de la xarxa mitjançant la formació del complex tetraamincobre(II). A causa de la presència dels cations Cu+ i Cu2+ coordinats a la xarxa de la zeolita, apareixen bandes a la regió entre 800-1000 cm-1 de l'espectre infraroig. L'anàlisi de les freqüències IR de diversos models amb Cu+ i Cu2+ coordinats a l'anell 6r, o formant complexos amb amoníac indica que quan els cations Cu+ i Cu2+ estan coordinats als oxígens de l'anell 6r apareixen vibracions entre 830 i 960 cm-1. Freqüències en aquesta zona també s'obtenen en els casos en què NO, NO2, O2 i combinacions de dues d'ells estan adsorbidos en Cu+ i Cu2+. No obstant això, quan els cations Cu+ i Cu2+ estan fora de l'anell (no hi ha enllaços entre els cations de coure i els oxígens de l'anell 6r) no s'obtenen vibracions d'IR en aquesta regió de l'espectre. Aquests resultats indiquen que amb el seguiment de l'espectre IR durant la reacció SCR és possible determinar si els cations Cu+ i Cu2+ estan coordinats o no a l'anell de 6r en les etapes d'oxidació i reducció. Finalment, hem simulat el desplaçament químic de 19F, δiso, en la zeolita sintetitzada RTH. L'anàlisi del δiso dels diferents models utilitzats ens ha permés reconéixer la simetria del material sintetitzat, el qual pertany al grup espacial P1 i la nova cel·la unitat ha sigut confirmada experimentalment per difracció de raigs X. Finalment, hem assignat el senyal experimental que apareix en l'espectre de 19F a -67.2 ppm, al F- localitzat en un lloc T2, el qual és al seu torn la posició més estable. A més, el senyal a -71.8 ppm s'ha assignat a l'anió F- localitzat en un lloc T4.
[EN] In this work, we have studied two heterogeneous catalytic reactions and the localization of the fluoride anion in the as-made RTH framework, synthesized in fluoride medium. The first results, included in chapter 3, correspond to the chemoselective reduction of nitrostyrene on different metal surfaces, i.e, Ni(111), Co(111), Cu(111) and Pd(111). Until very recently, the reduction of the nitro group was explained on the basis of the general mechanism proposed by Haber in 1898 where the reaction can follow two routes, the direct and condensation route. We have explored the relevant elementary steps of both routes and found that because of the oxophilic nature of Ni and Co, the steps involving the dissociation of N-O bonds and formation of metal-O bonds are significantly favored compared with the other steps on both metal surfaces. In addition, the most demanding steps in terms of energy involve the formation of N-H bonds. These findings are in contrast to those of noble metals such as Pt and Pd, where the opposite behavior is observed. The behavior of Cu(111) lies in between the aforementioned cases, and also no chemical bonds between the carbon atoms of the aromatic ring of nitrostyrene and the Cu(111) surface is formed. For this reason, it might be an ideal candidate to achieve nearly 100 % selectivity. However, the Cu(111) surface does not seem to activate the H2 molecule. In this regard, we propose a bimetallic Cu-based catalyst whose surface is doped with atoms of a H2-activating metal, such as Ni or Pd. On another matter, we have also investigated the selective catalytic reduction of nitrogen oxides (SCR-NOx) and the main results are presented in the following two chapters, 4 and 5. By using static DFT methods, we found pathways for the oxidation of NO to NO2, nitrites and nitrates with relatively low activation energies. We also found, in agreement with experimental reports, that the reduction of Cu2+ to Cu+ requires the simultaneous participation of NO and NH3. Later, molecular dynamics simulations allowed us to assess the influence of NH3. The strong interaction of NH3 with the Cu+ cation is evidenced by its ability to detach Cu+ from the zeolite framework and form the mobile linear complex [Cu(NH3)2]+. Cu+ is no longer coordinated to the zeolite framework in the presence of two NH3 molecules. This observation and the fact that the T-O-T vibrations of the framework produce bands in the 800-1000 cm-1 region of the IR spectrum when perturbed by the coordination of Cu+ and Cu2+ cations, indicate that bands in the 800-1000 cm-1 regions should be observed when both copper cations are bonded to the framework oxygens. Finally, we have also studied NMR properties of the as-made pure silica RTH framework, aiming at locating the compensating fluoride anion. The calculation of the 19F chemical shift in different T sites and comparison with the experimental NMR spectra shows that the as-made RTH belongs to the P-1 space group with 16 Si, 32 O atoms, one fluoride anion and one OSDA cation. These results have been confirmed experimentally by XRD. In addition, we have assigned the experimental signal of 19F at -67.2 ppm to the fluoride anion in a T2 site, which in turn is the most stable location found, and the signal of -71.8 ppm to a fluoride anion sitting in a T4 site.
My acknowledgements to “La Caixa foundation” for the financial support through “La Caixa−Severo Ochoa” International PhD Fellowships (call 2015), to the Spanish Supercomputing Network (RES), to the Centre de Càlcul de la Universitat de València, to the Flemish Supercomputer Center (VSC) of Ghent University for the computational resources and technical support, and to the Spanish Government through the MAT2017-82288-C2-1-P programme
Millan Cabrera, R. (2021). Computational study of heterogeneous catalytic systems. Kinetic and structural insights from Density Functional Theory [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/161934
TESIS

The thesis entitled ‘Engaging Small Organic Molecules and Self-Assemblies for ‘Label-Free’ Recognition of Biologically Relevant Analytes’ mainly deals with design and synthesis of various types of small molecular probes or molecular assemblies for fluorometric recognition of a large number of biologically relevant analytes in water. The first chapter begins with the general overview of various types of biosensors and their working principles. Then we discussed about various small organic molecules or molecular assemblies based systems in optical biosensing. The strategies for designing these sensors have also been discussed in connection with frequently encountered photophysical interactions. Finally, the design principles of some biosensors were highlighted on the basis of the structural aspects of the concerned analytes. The second chapter describes the design and synthesis of various optical probes for selective detections of different warfare materials in water. Chapter 2A: Cyanide Mediated Facile Michael Addition Reaction: A Simple Protocol to Distinguish ‘Tabun Mimic’ DCNP in Solution as well as in Vapor Phase Figure 1. Structures of the molecular probes used in chapter 2A. This chapter discussed about involvement of a series of water soluble bis-indolyl compounds for selective detection of nerve gas mimicking agent, DCNP (Diethyl Cyanophosphonate) at pH 8.0 in water. The mechanism of interaction was proposed as the bis-indole assisted hydrolysis of phosphoester nerve gas agents through hydrogen bonding interaction. Then the Michael addition of the liberated CN- ion to the electron deficient C=C bond of the bisindolyl moiety. This led to a remarkable color change from red to colorless at ambient condition. Further the protocol was exploited in vapor phase detection of DCNP (Tabun mimic) below its toxic level. Chapter 2B: Selective and Efficient Detection of Nitro-Aromatic Explosives in Multiple Media including Water, Micelles, Organogel, and Solid Support Figure 2. Structures of the molecular probes used in chapter 2B. This chapter demonstrated development of phenylenevinylene based optical probes for the selective detection of both DNP (2,4-Dinitrophenol) and TNP (2,4,6-Trinitrophenol) in pure water as well as in micellar medium. The mechanistic investigation suggested that the initial proton transfer caused electrostatic association between the picrate anions and the protonated pyridine ends, which could further promote electron transfer from the electron-rich fluorophore moiety to the electron-deficient nitroaromatics (NACs). Thus the selectivity depends on the pKa of the probe molecules as well as the NACs under consideration. Further portable test strips were made successfully for rapid on-sight detection purpose. The third chapter describes identification of different enzymes in water as well as in biological fluids via disaggregation of template mediated molecular assemblies. Chapter 3A: Employment of ATP-Sensitive Lanthanide Ensemble for the Estimation of Creatine Kinase Level in Blood Serum and Live Cell Imaging Figure 3. Structures of the molecular probes used in chapter 3A. This chapter presents the use of in-situ generated luminescent lanthanide complexes in sensing of adenosine triphosphate (ATP) in water. The indicator tetracarboxylate salt showed rapid quenching in green molecular emission upon coordination with highly paramagnetic lanthanide ion (Gd3+). The addition of ATP could displace the lanthanide ion from the vicinity of the compound and retrieved its original emission. Further this selective ‘Turn-On’ response of the probe towards ATP was utilized to discriminate between the live and dead cells depending upon their ATP/ADP content. Moreover, excellent selectivity of the probe for ATP over ADP was utilized for the detection of Creatine Kinase in human blood serum samples. Chapter 3B: Estimation of Albumin Content in Different Biological Fluids and Monitoring Trypsin Mediated Digestion of HSA Figure 4. Structures of the molecular probes used in chapter 3B. This chapter describes design of several amphipathic carbazole dyes, which could form thermo sensitive, pH dependent fluorescent nano-aggregates in water. This facile nanoclustering behavior of the compounds was then utilized for detection of human serum albumin (HSA). The site-specific nature of the interaction was appeared to be the key reason for the unique selectivity of the probes towards HSA over other structurally resembled albumin proteins. Further the estimation of HSA was achieved in different biological fluids like human urine, blood serum and saliva etc. Finally the protease mediated digestion of protein template was applied as an alternative strategy for detection of trypsin. The fourth chapter describes fluorometric detection of different physiologically relevant monosaccharides by exploiting multi-point hydrogen bonding network. Chapter 4A: Analyte Induced Alteration in the Aggregation Property of Fluorescent Organic Nano-particles: A Simple Recognition Strategy for D-(-)-Ribose in Water Figure 5. Structures of the molecular probes used in chapter 4A. This chapter demonstrated selective detection of D(-)-ribose and ribose containing biomolecules (Adenosine, riboflavin etc.) in water via hydrogen bonding interactions from aceylhydrazone and pyridine units. The interaction with ribose was found to be responsible for dissociation of the preformed molecular assemblies, resulting drastic quenching in luminescent signal. Finally determination of ribose was also performed in presence of complex biological matrix like human urine. Chapter 4B: Restriction in Keto-Enol Tatumerization through Multipoint Hydrogen Bonding Network with D-(+)-Glucosamine Figure 6. Structures of the molecular probes used in chapter 4B. This chapter presents design and synthesis of different chromogenic probes by connecting nicotinic hydrazide with different -hydroxy aromatic aldehydes via carbonyl-nucleophile addition protocol. Addition of D-glucosamine was found to modulate the keto-enol tatumerization of the molecules via formation of multi-point hydrogen bonding network. The rapid change in color from bright yellow to colorless with prominent emission quenching led detection of up to 5.3 mg/L of glucosamine in water. Then monitoring of glucosamine level was also achieved in human blood serum as well as pharmaceutical formulations. Moreover, the probes were found to be competent in detection of glucosamine even in intracellular condition. The fifth chapter describes development of new fluorometric probes for identifying different inflammatory-response markers in water. Chapter 5A: Heparin Triggered Multicolor Emission Switching in Water: A Convenient Protocol for Heparinase I Assay Figure 7. Structures of the molecular probes used in chapter 5A. In this chapter, conjugated bis-pyridinium salts of phenylenevinylene (PPV) have been used for selective detection of heparin in water. The unique dose-dependent emission switching ability of the probes ensured quantitiative estimation of heparin without involving any sofisticated facilities. The higher negative charge density and preferential conformation of sugar dimers faciliated interaction between compounds and heparin. Finally, the heparin induced reversible aggregate formation was utilized to develop an alternative easy-to-operate heparinase I assay protocol. Chapter 5B: Application of Neurotransmitter Induced Emission Switching for Histamine Detection in Biological Fluids and Macrophage Cells Figure 8. Structures of the molecular probes used in chapter 5B. This chapter presents the involvement of well-known fluorescein aldehyde dyes in recognition of histamine below nanomolar concentration in water. Here, the dual mode of detection of histamine was achieved at pH 7.0 without involving any toxic metal ions. The selective response towards histamine was confirmed through secondary hydrogen bonding interaction followed by imine formation. Then the probes were also employed for detection of histamine in different biological fluid matrices (human urine and blood serum). Finally, the rise in endogenous histamine level in macrophage RAW 264.7 was identified under stimuli-responsive condition (treatement with thapsigargin). The sixth chapter describes fluorometric detection of purine alkaloids via their preferential stacking over the electron rich planer dye molecules. Chapter 6A: Hydrogen Bonding Triggered Crumbling of Pyrene Excimer: A Simple Method for Detection of Uric Acid in Human Serum and Infested Grain Extracts This chapter deals with design and synthesis of different amphipathic pyrene molecules for nanomolar detection of uric acid in water. Hydrogen bonding interaction of uric acid with amide functional groups found to push two adjacent pyrene units away from each other, resulting into quenching of blue excimer emission. The optimized liposomal formulation derived from the doping of probe molecules into soya lecithin vesicles was further utilized for estimating uric acid content in blood serum samples. Finally, the present protocol was used for identifying the rise in uric acid content in insect-infested grain samples. Figure 9. Structures of the molecular probes used in chapter 6A. Chapter 6B: Caffeine Modulated Dissociation of Carbazole Based FONs in Water: Excitation Triggered Alteration in Sensing Property Figure 10. Structures of the molecular probes used in chapter 6B. This chapter deals with self aggregation properties of a series of carbazole based ampiphilic dyes, which could be modulated by the micro polarity of the local environment and electronic influence from the functional groups attached to the core organic scaffold. In comparison to other structurally related purine analogs, caffeine exerted most prominent emission response due to its planar electron deficient structure. An optimal balance between selectivity and sensitivity was achieved by varying the excitation wavelengths or electron density over the carbazole core. In application, the sensor was successfully exploited to address diverse real-life problems ranging from applications in ‘dope-analysis in human urine’ to carbonated drinks.

In the last few years, considerable efforts have been given to develop sensitive and effective sensors for explosive materials and to generate systems which exhibit high luminescence in both solution and solid-state. The increasing number of terrorist activities around the world have prompted scientists to design effective ways to detect and disarm even the trace amount of explosives. The nitroaromatics (NACs) are the common constituents of most of the explosives due to high explosive velocity and ease of availability. The NACs were extensively used as the main constituents in landmines until World War II. Apart from their explosive behavior, the NACs are well-known environmental pollutants. The industrial waste and the leakages from unexploded landmines are the major contributors towards the soil and ground water contamination. Presently for effective detection of trace amount of explosives, skilled canines and metal based detectors are commonly used. The canines are trained for a specific type of explosives which limit their ability to detect different types of substrates. The chemical sensors that work on the principle of colorimetric and/or fluorimetric detection techniques have emerged as suitable alternative due to cheap production cost, portability and sensitivity. Different types of materials including conjugated polymers, metal-organic frameworks (MOFs), and quantum-dots have been reported as efficient chemosensors for NACs. However, poor solubility in the common organic solvents, low solid-state fluorescence, very high molecular weight and lack of signal amplification have restricted the application of these material for in-field testing. Renewed interests have been invested in small molecule based systems; and metal-organic discrete molecular architectures due to precise control over their photophysical properties and the supramolecular interaction among neighboring molecules that facilitates energy migration among the molecular backbone. On the other hand, recently post-synthetic modification of different molecular systems including MOFs and polymers has emerged as a potential technique to incorporate desired functional groups into the system and to tune their properties with the retention of basic structures. Reports on the post-synthetic modification of discrete metal-organic architectures are rare due to the delicate nature of the metal-organic bonds that ruptures on mild environmental changes. Therefore, post-synthetic functionalization of discrete molecular systems using mild reaction conditions will open up a myriad of possibilities to generate new systems with desired characteristics. Chapter 1 of the thesis will briefly discuss the history of different explosive materials including different detection methodologies that are widely used. It will also include a brief discussion on different small molecular systems with high solid-state luminescence. In Chapter 2, design and synthesis of triphenylamine-based two Platinum(Pt)(II) molecules functionalized with carboxylic acid and ester groups including their organic analogues have been discussed. The triphenylamine core was chosen due its unique non-planarity and luminescence. On the other hand, Pt(II) center was incorporated to increase intermolecular spacing in solid-state that can induce high luminescence. Scheme 1. Schematic representation of fluorescence quenching using small molecules. All the four molecules were found to be highly sensitive towards NACs including picric acid and dinitrophenol. Although the molecules exhibited similar sensitivity in solution, the carboxylic acid analogues demonstrated superior sensitivity in solid-state. Careful observation of the crystal structures of the systems revealed the acid analogues were oriented in a 2-D grid-like pattern that facilitated energy migration among neighboring molecules (Scheme 1.). Chapter 3 describes design, synthesis, and NACs sensing behavior of anthracene-based four purely organic small molecules. The molecules exhibited high selectivity towards picric acid only. All the molecules were found to be highly emissive in both solution and solid-state due to the vinylanthracene backbone (Scheme 2.). Scheme 2. Schematic representation of fluorescence quenching and solid-state sensing behavior. Chapter 4 discusses the strategy to develop mechano-fluorochromic and AIE active triphenylamine-based Pt(II) complex and its organic analogue. The twisted triphenylamine backbone restricted molecular close packing in solid-state; and weak C-H-- interactions were utilized to hinder the motion of the phenyl rings. As a result, the molecules were highly emissive in solid-state. Grinding disrupted the intermolecular interactions and thus mechano-fluorochromic behavior was observed. Due to twisted backbone, the molecules were also found to be AIE active. Both the systems containing terminal aldehyde groups were finally utilized for selective detection of biomolecule cysteine (Scheme 3.). Scheme 3. Mechano-fluorochromic and AIE behavior of the triphenylamine based Pt(II) complex. In Chapter 5 vinylanthracene-based linear donor was used in combination with carbazole-based 90° and triphenylamine-based 120° Pt(II) acceptors to generate (4+4) and (6+6) molecular squares and hexagons, respectively. The vinylanthracene backbone imparts high solution and solid-state luminescence to the system as well as made them AIE active. The molecules were further investigated for the solution and solid-state sensing for NACs and found to be effective for trinitrotoluene (TNT) and dinitrotoluene (DNT) (Scheme 4.). Scheme 4. Schematic representation of AIE active molecular square and its NACs sensing. Chapter 6 describes the formation of Pd3 self-assembled molecular trinuclear barrels containing triphenylamine imidazole donors and Pd(II) acceptors. Using Knoevenagel condensation the aldehyde group present in the barrel was post-synthetically functionalized with Meldrum’s acid. From spectroscopic characterization, it was proved that the structural integrity remained intact after the post-modification treatment (Scheme 6.). Surprisingly, pre-synthetic modification of the donor alone with Meldrum’s acid followed by self-assembly treatment with the Pd(II) ion did not yield trigonal barrel 6.8. Scheme 6. Post-synthetic functionalization of trinuclear barrels using Knoevenagel condensation.(For colour pictures pl see the abstract pdf file)

In the last few years, considerable efforts have been given to develop sensitive and effective sensors for explosive materials and to generate systems which exhibit high luminescence in both solution and solid-state. The increasing number of terrorist activities around the world have prompted scientists to design effective ways to detect and disarm even the trace amount of explosives. The nitroaromatics (NACs) are the common constituents of most of the explosives due to high explosive velocity and ease of availability. The NACs were extensively used as the main constituents in landmines until World War II. Apart from their explosive behavior, the NACs are well-known environmental pollutants. The industrial waste and the leakages from unexploded landmines are the major contributors towards the soil and ground water contamination. Presently for effective detection of trace amount of explosives, skilled canines and metal based detectors are commonly used. The canines are trained for a specific type of explosives which limit their ability to detect different types of substrates. The chemical sensors that work on the principle of colorimetric and/or fluorimetric detection techniques have emerged as suitable alternative due to cheap production cost, portability and sensitivity. Different types of materials including conjugated polymers, metal-organic frameworks (MOFs), and quantum-dots have been reported as efficient chemosensors for NACs. However, poor solubility in the common organic solvents, low solid-state fluorescence, very high molecular weight and lack of signal amplification have restricted the application of these material for in-field testing. Renewed interests have been invested in small molecule based systems; and metal-organic discrete molecular architectures due to precise control over their photophysical properties and the supramolecular interaction among neighboring molecules that facilitates energy migration among the molecular backbone. On the other hand, recently post-synthetic modification of different molecular systems including MOFs and polymers has emerged as a potential technique to incorporate desired functional groups into the system and to tune their properties with the retention of basic structures. Reports on the post-synthetic modification of discrete metal-organic architectures are rare due to the delicate nature of the metal-organic bonds that ruptures on mild environmental changes. Therefore, post-synthetic functionalization of discrete molecular systems using mild reaction conditions will open up a myriad of possibilities to generate new systems with desired characteristics. Chapter 1 of the thesis will briefly discuss the history of different explosive materials including different detection methodologies that are widely used. It will also include a brief discussion on different small molecular systems with high solid-state luminescence. In Chapter 2, design and synthesis of triphenylamine-based two Platinum(Pt)(II) molecules functionalized with carboxylic acid and ester groups including their organic analogues have been discussed. The triphenylamine core was chosen due its unique non-planarity and luminescence. On the other hand, Pt(II) center was incorporated to increase intermolecular spacing in solid-state that can induce high luminescence. Scheme 1. Schematic representation of fluorescence quenching using small molecules. All the four molecules were found to be highly sensitive towards NACs including picric acid and dinitrophenol. Although the molecules exhibited similar sensitivity in solution, the carboxylic acid analogues demonstrated superior sensitivity in solid-state. Careful observation of the crystal structures of the systems revealed the acid analogues were oriented in a 2-D grid-like pattern that facilitated energy migration among neighboring molecules (Scheme 1.). Chapter 3 describes design, synthesis, and NACs sensing behavior of anthracene-based four purely organic small molecules. The molecules exhibited high selectivity towards picric acid only. All the molecules were found to be highly emissive in both solution and solid-state due to the vinylanthracene backbone (Scheme 2.). Scheme 2. Schematic representation of fluorescence quenching and solid-state sensing behavior. Chapter 4 discusses the strategy to develop mechano-fluorochromic and AIE active triphenylamine-based Pt(II) complex and its organic analogue. The twisted triphenylamine backbone restricted molecular close packing in solid-state; and weak C-H-- interactions were utilized to hinder the motion of the phenyl rings. As a result, the molecules were highly emissive in solid-state. Grinding disrupted the intermolecular interactions and thus mechano-fluorochromic behavior was observed. Due to twisted backbone, the molecules were also found to be AIE active. Both the systems containing terminal aldehyde groups were finally utilized for selective detection of biomolecule cysteine (Scheme 3.). Scheme 3. Mechano-fluorochromic and AIE behavior of the triphenylamine based Pt(II) complex. In Chapter 5 vinylanthracene-based linear donor was used in combination with carbazole-based 90° and triphenylamine-based 120° Pt(II) acceptors to generate (4+4) and (6+6) molecular squares and hexagons, respectively. The vinylanthracene backbone imparts high solution and solid-state luminescence to the system as well as made them AIE active. The molecules were further investigated for the solution and solid-state sensing for NACs and found to be effective for trinitrotoluene (TNT) and dinitrotoluene (DNT) (Scheme 4.). Scheme 4. Schematic representation of AIE active molecular square and its NACs sensing. Chapter 6 describes the formation of Pd3 self-assembled molecular trinuclear barrels containing triphenylamine imidazole donors and Pd(II) acceptors. Using Knoevenagel condensation the aldehyde group present in the barrel was post-synthetically functionalized with Meldrum’s acid. From spectroscopic characterization, it was proved that the structural integrity remained intact after the post-modification treatment (Scheme 6.). Surprisingly, pre-synthetic modification of the donor alone with Meldrum’s acid followed by self-assembly treatment with the Pd(II) ion did not yield trigonal barrel 6.8. Scheme 6. Post-synthetic functionalization of trinuclear barrels using Knoevenagel condensation.(For colour pictures pl see the abstract pdf file)

Two new energetic nitroaromatic compounds, 1,4-bis(1H-pyrazol-4'-yl)-2,5-dinitrobenzene (H2dpzb(NO2)2) and 1,4-bis(1H-3',5'-dinitropyrazol-4'-yl)-2,5-dinitrobenzene (H2dpzb(NO2)6), were prepared by nitration of 1,4-bis(1H-pyrazol-4'-yl)benzene (H2dpzb) with mixed acid. H2dpzb(NO2)x were isolated as yellow powders in moderate yields. They are stable under ambient conditions, soluble in dimethylformamide and dimethylsulfoxide, but poorly soluble in weakly coordinating solvents, and deflagrate in the heat. Both compounds have been characterised by 1H, 13C NMR and IR spectroscopies as well as by X-ray crystallography. H2dpzb(NO2)x crystallise readily as impact-insensitive dmso or thf solvates. Due to steric crowding at the (pyrazolyl group)–(benzene) bonds, H2dpzb(NO2)x adopt a twisted molecular geometry with extended (x = 2) or localised intermolecular hydrogen-bonding (x = 6) that involve the pyrazolyl H atoms and solvent of crystallisation. H2dpzb(NO2)6 reacts with base to form crystalline [B-H]2[dpzb(NO2)6], B = NEt3, which possesses remarkably high density ([B-H]2[dpzb(NO2)6]), or a powder consisting of Na2dpzb(NO2)6 (B = NaHCO3, crystallised as the coordination polymer Na(dmso)(dpzb(NO2)6). A mixture of H2dpzb(NO2)6, Zn(NO3)2, NEt3, dmso and water afforded the coordination compound [Zn(κ(O)-dmso)6]2[dpzb(NO2)6.

Two new energetic nitroaromatic compounds, 1,4-bis(1H-pyrazol-4'-yl)-2,5-dinitrobenzene (H2dpzb(NO2)2) and 1,4-bis(1H-3',5'-dinitropyrazol-4'-yl)-2,5-dinitrobenzene (H2dpzb(NO2)6), were prepared by nitration of 1,4-bis(1H-pyrazol-4'-yl)benzene (H2dpzb) with mixed acid. H2dpzb(NO2)x were isolated as yellow powders in moderate yields. They are stable under ambient conditions, soluble in dimethylformamide and dimethylsulfoxide, but poorly soluble in weakly coordinating solvents, and deflagrate in the heat. Both compounds have been characterised by 1H, 13C NMR and IR spectroscopies as well as by X-ray crystallography. H2dpzb(NO2)x crystallise readily as impact-insensitive dmso or thf solvates. Due to steric crowding at the (pyrazolyl group)–(benzene) bonds, H2dpzb(NO2)x adopt a twisted molecular geometry with extended (x = 2) or localised intermolecular hydrogen-bonding (x = 6) that involve the pyrazolyl H atoms and solvent of crystallisation. H2dpzb(NO2)6 reacts with base to form crystalline [B-H]2[dpzb(NO2)6], B = NEt3, which possesses remarkably high density ([B-H]2[dpzb(NO2)6]), or a powder consisting of Na2dpzb(NO2)6 (B = NaHCO3, crystallised as the coordination polymer Na(dmso)(dpzb(NO2)6). A mixture of H2dpzb(NO2)6, Zn(NO3)2, NEt3, dmso and water afforded the coordination compound [Zn(κ(O)-dmso)6]2[dpzb(NO2)6.