Dissertations / Theses on the topic 'Heteroacenes'

2008/2009
In this thesis, different strategies for obtaining azaacenes suitable for solution-based processing techniques have been investigated and developed. The first synthetic approach involved the condensation of commercially available compounds which include the diamines 2,3-diaminobenzene, 2,3-diaminonaphtalene and 2,3-diaminophenazine and the bromoanilic acid and embelin. This synthetic route yielded a series of dihydroazaacenes with 5 and 7 fused aromatic rings. The low overall solubility of this azaacenes did not permit an extensive characterization of the compounds. A second synthetic approach was developed to investigate both C-N exchange and lateral expansion of the π-conjugation. Through this approach a tetraazaoctacene derivative was obtained and characterized. However it lacked of solubility necessary for being compatible with solution-processing techniques. A third strategy was based on the introduction of solubilizing groups on such extended tetraazaoctacene core. While the di-substitution did not render the azaoctacene soluble in neutral media, tetra-substitution yielded a derivative with enhanced solubility in neutral solvent.
1981

Inorganic materials have dominated electronic applications such as photovoltaic cells, thin film transistors (TFTs) and light emitting diodes (LEDs). However developments in the field of organic electronics over the past three decades have enabled the use of organic materials in these devices. While significant improvements have been made to improve their electronic properties there are several road blocks towards commercial application. One of the significant obstacles is the poor charge carrier mobility associated with organic semiconductors processed by well established printing methods. The goal of my research project is to improve the charge carrier mobility of solution cast films of acene semiconductors by partial halogenation and heteroatom substitution. Spin coated films of triisopropylsilylethynylated difluoropentacene exhibited higher hole mobility compared to TIPS pentacene due to contact induced nucleation of pentacene on perfluorobenzenethiol treated gold electrodes. The success of this project allowed me to further investigate the effect of degree of fluorination on the electronic properties of pentacene. A series of trialkylsilylethynylated tetrafluoro and octafluoropentacenes were synthesized and their performances in thin film transistors and solar cells were explored. Solar cells made from these materials using poly(3-hexylthiophene) as donor exhibited poor open circuit voltages (Voc) resulting in low power conversion efficiency (PCE). Better device performances were achieved using pentacenes having single halogen substituent. In order to improve the charge carrier mobility in TFTs soluble trialkylsilylethynylated hexacenes were explored. However these molecules exhibited a greater tendency to photo-dimerize in solution and solid state. Partial halogenation was used as a tool to improve the solution stability of reactive hexacene. The improved solution stability of partially halogenated hexacenes allowed me to successfully extend this approach to heptacene and nonacene. Finally a series of new trialkylsilylethynylated anthradiselenophenes were synthesized to improve molecular ordering in the solid state by increasing non-bonding Se – Se interaction. However single crystal x-ray diffraction studies revealed no such interaction between the acene chromophore resulting in poor device performance.

Our group has previously shown that small changes to molecular structure result in large changes to device properties and stability in organic electronic applications. By functionalizing aromatic heteroacenes with group 14 and group 16 elements, it is possible to control morphology and improve stability for a variety of applications such as thin film transistors and solar cells. Functionalization within the heteroacene core led to changes in electronic structure as observed by electrochemistry and light absorption. By substituting down the periodic table, the carbon heteroatom bond length increased, leading to subtle changes in crystal packing. Absorption maxima were red-­‐shifted and stability to light decreased. Substitution of group 14 elements to the solubilizing ethynyl groups attached to the heteroacene also had an effect on crystallization and stability. Substitution of silicon with carbon decreased solubility as well as stability to light. Substitution with germanium also decreased stability to light, but close contacts within the crystal structure and solubility in nonpolar organic solvents increased.

The work presented in this thesis is primarily concerned with the synthesis and characterization of large, linear heteroacenes and their derivatives. We have been able to significantly expand on the types of materials available for application in organic electronic device architectures. In particular, the work focused on solution processible and novel derivatives of thiadiazoles, diazatetracenes, diazapentacenes, tetrazapentacences, and N,N-dihydrotetraazaheptacene. Extensive computational studies have been performed in order to better understand the optoelectronic properties of these materials. Although no devices have been fabricated that show appreciable hole or electron mobility, the properties of these materials are very promising. Besides our work on organic electronic materials for application in optoelectronic devices, we have also been able to develop, via the Click reaction, a series of aqueous metal sensors for copper (II), nickel (II), and silver (I) based upon fluorescence quenching. The use of a modified Stern-Volmer equation was necessary to fit the data in order to obtain binding constants. The exploration of new materials and their properties in the area of organic electronics is an exciting field for the synthetic organic chemist, as the goals associated with this work strive to impact humanity in a positive manner by reducing energy costs.

Polycyclic aromatic hydrocarbons composed of benzenoid rings fused in a linear fashion comprise the class of compounds known as acenes. The structures containing three to six ring fusions are brightly colored and possess band gaps and charge transport efficiencies sufficient for semiconductor applications. These molecules have been investigated throughout the past several decades to assess their optoelectronic properties. The absorption, emission and charge transport properties of this series of molecules has been studied extensively to elucidate structure-property relationships. A wide variety of analogous molecules, incorporating heterocycles in place of benzenoid rings, demonstrate similar properties to the parent compounds and have likewise been investigated. Functionalization of acene compounds by placement of groups around the molecule affects the way in which molecules interact in the solid state, in addition to the energetics of the molecule. The use of electron donating or electron withdrawing groups affects the frontier molecular orbitals and thus affects the optical and electronic gaps of the molecules. The use of bulky side groups such as alkylsilylethynyl groups allows for crystal engineering of molecular aggregates, and changing the volume and dimensions of the alkylsilyl groups affects the intermolecular interactions and thus changes the packing motif. In chapter 2, a series of tetracene and pentacene molecules with strongly electron withdrawing groups is described. The investigation focuses on the change in energetics of the frontier molecular orbitals between the base acene and the nitrile and dicyanovinyl derivatives as well as the differences between the pentacene and tetracene molecules. The differences in close packing motifs through use of bulky alkylsilylethynyl groups is also discussed in relation to electron acceptor material design and bulk heterojunction organic photovoltaic characteristics. Chapter 3 focuses on molecular acceptor and donor molecules for bulk heterojunction organic photovoltaics based on anthrathiophene and benzo[1,2-b:4,5-b’]dithiophene central units like literature molecules containing fluorene and dithieno[2,3-b:2’,3’-d]silole cores. The synthetic strategies of developing reduced symmetry benzo[1,2-b:4,5-b’]dithiophene to study the effect of substitution around the central unit is also described. The optical and electronic properties of the donors and acceptors are described along with the performance and characteristics of devices employing these molecules. The final two data chapters focus on new nitrogen containing polycyclic hydrocarbons containing indolizine and (2.2.2) cyclazine units. The optical, electronic and other physical properties of these molecules are explored, in addition to the synthetic strategies for incorporating the indolizine and cyclazine units. By use of alkylsilylethynyl groups, crystal engineering was investigated for the benzo[2,3-b:5,6-b’]diindolizine chromophore described in chapter 4 to target the 2-D “brick-work” packing motif for application in field effect transistor devices. Optical and electronic properties of the cyclazine end-capped acene molecules described in chapter 5 were investigated and described in relation to the base acene molecules. In both cases, density functional theory calculations were conducted to better understand unexpected optical properties of these molecules, which are like the linear acene series despite the non-linear attachment.

Les semiconducteurs organiques (OSC) tels que les composés organiques photovoltaïques (OPVs), les diodes électroluminescentes organiques (OLEDs) ou encore les transistors organiques à effet de champ (OFETs) constituent un domaine de recherche très attractif en raison de leur potentiel en tant que couches actives dans les dispositifs optoélectroniques. Les composés aromatiques polycycliques ainsi que les hétéroaromatiques sont considérés comme des matériaux prometteurs pour les OSC en raison de leurs conductivités électriques potentielles, de leurs propriétés optiques ainsi que de leurs assemblages géométriques. Ces deux systèmes et leurs propriétés photophysiques ont été étudiés dans les trois chapitres de cette thèse. Dans le premier chapitre, une étude sur un ensemble d'acènes linéaires, angulaires et condensés consistant en des liens hétéroatomes avec des agrégations uniques a été décrite et analysée. Les hétéroacènes N-fusionnés angulaires et π-étendus sont la classe principale étudiée dans le deuxième chapitre. Leurs synthèses sont basées sur la réaction de couplage de Suzuki-Miyaura et la réaction de Cadogan. Outre les acènes et les hétéroacènes N-fusionnés, les N-hétéroaromatiques ont fait l'objet d'une attention particulière dans le domaine de matériaux. L'un d'entre eux est la classe des quinazolines utilisées comme partie acceptrice d'électrons dans les structures push-pull pour le transfert de charge intramoléculaire (TCI). L'étude des relations entre les structures dérivées du motif quinazoline de type donneur d'électron-accepteur-donneur (D-A-D) et leurs propriétés de photoluminescence est le principal travail mentionné dans le troisième chapitre
Organic semiconductors (OSCs) are a highly attractive research field due to their potentials as active layers in optoelectronic devices such as organic field-effect transistors (OFETs), organic photovoltaic (OPVs) and organic light emitting diodes (OLEDs). Polycyclic aromatic compounds as well as heteroaromatics are considered as promising materials for OSCs due to their semi conductivity properties, optical properties and geometric structures. The mentioned systems and their photophysical properties were investigated in three chapters of my thesis. In the first chapter, a study on a set of linear, angular and condensed acenes consisting of heteroatom linkages with unique aggregations was described and analyzed. The angular and π-extended N-fused heteroacenes are the main class studied in the second chapter. Their synthesis is based on the Suzuki-Miyaura coupling and the Cadogan reactions. Besides acenes and N-fused heteroacenes, N-heteroaromatics have gained attention in material area. One of them is the quinazoline class that is known as an electron withdrawing unit in push-pull structures for intramolecular charge transfer (ICT). The investigation of the relationships between the electron donor-acceptor-donor (D-A-D) quinazoline-based structures and their photoluminescence properties is the main work mentioned in the third chapter

This thesis describes work towards a range of novel nitrogen containing polyaromatic heterocycles for use as organic semiconductors. A route to benzo[b]carbazole end-capped oligothiophenes has been developed; relying on two key steps; namely a connective-Pummerer cyclisation and a SmI2-mediated cleavage–cyclisation cascade. A route to extended dibenzoindolo[3,2-b]carbazole-based aza-heptacenes has also been developed, by employing the same key steps in a two-directional manner. The physical and electronic properties of the resulting materials has been assessed, and the utility of the materials in OFET devices has been demonstrated.

For organic electronic device applications materials are needed which display good charge carrier mobility, good processability, and stability towards oxygen and moisture. Alkynylated N-Heteroacenes fulfill many of these requirements. Substitution with alkyne groups as well as the introduction of the pyrazine subunit both inhibits oxidative degradation at sensitive position in the molecules. Additionally the trialkylsilylethynyl group aides in directing the packing motif as well as vastly increases the solubility over unsubstituted analogues. A requisite precursor in the synthesis of alkynylated N-heteroacenes is alkynylated acenothiadiazoles. These thiadiazoles display interesting photophysical properties and can be functionalized to produce a wide range of properties in closely related materials. The acenothiadiazoles themselves have potential applications as an N-type semiconductor. Optical gaps and calculated HOMO-LUMO gaps show that these molecules, when compared to known N-type materials, should be easily injected with electrons. Additionally the crystal packing of these compounds shows favorable π-orbital overlap which should provide excellent charge carrier mobilities.

Tang, Qin.
Thesis (Ph.D.)--Chinese University of Hong Kong, 2011.
Includes bibliographical references.
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Abstract also in Chinese.

He, Zikai.
Thesis (Ph.D.)--Chinese University of Hong Kong, 2013.
Includes bibliographical references.
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Abstract also in Chinese.

碩士
國立交通大學
應用化學系碩博士班
107
Solid-state structures of conjugated molecules play an important role in the field-effect transistor (FET) performances of the molecules. Penta-fused heteroacenes are useful building blocks for molecules used in optoelectronic devices. Here, a series of 5 heteroacene derivatives (Penta-fused heteroacenes: 4,5-Bis(2-ethylhexyl)-dithieno[2,3-d:2',3'-d']thieno[3,2-b:4,5-b']dipyrrole) were studied. The molecules were divided into three groups based on the chemical structures of their substituents. Crystal arrays of these derivatives were prepared by the PDMS-assisted crystallization (PAC) procedure. By analyzing the optical microscopy (OM) images, grazing incidence X-ray diffraction (GIXRD) patterns, Electron diffraction patterns (ED) and OFET performances of these derivatives, it was found that the different molecular symmetry and intermolecular interaction based on substituents can significantly affect the solid-state morphology and the OFET performances of the molecules.

Eines der zentralen elektronischen Bauelemente der gedruckten Elektronik ist der gedruckte Feldeffekttransistor. Um diese Bauteile herstellen zu können werden lösliche Halbleiter benötigt, die in Drucktinten eingesetzt werden können. Als n-halbleitende Materialien können beispielsweise ZnO-Nanopartikel eingesetzt werden, die als ZnO-Nanopartikel-Dispersionen verarbeitet werden. Die auf diesem Wege hergestellten halbleitenden Schichten, weisen jedoch Lücken zwischen den Partikeln auf, die in der Halbleiterschicht zu schlechten Ladungstransporteigenschaften führen. Deshalb beschäftigt sich die vorliegende Dissertation mit der Entwicklung von neuen halbleitenden organischen Bindermolekülen auf Basis von Stickstoffheteroacenen, die die Lücken zwischen den Nanopartikeln füllen und somit die Ladungstransporteigenschaften im Transistor verbessern können. Dazu wurden ZnO-Nanopartikel-Dispersionen hergestellt, charakterisiert und im Hinblick auf die Reinheit der Dispersionen optimiert. Weiterhin wurden als organische Binder verschiedene neue Naphtho[2,3-g]chinoxaline und Pyrazino[2,3-b]phenazine hergestellt und charakterisiert. Dabei wurden während des Entwicklungsprozesses die elektronischen Eigenschaften der organischen Binder gezielt auf die Eigenschaften der Nanopartikel abgestimmt. Außerdem wurden die entwickelten organischen Halbleiter auf ihre Stabilität und ihre Eignung als organische Binder untersucht. Als besonders vielversprechend kristallisierte sich hierbei die neu entwickelte Klasse der hochfluorierten Pyrazino[2,3-b]phenazine heraus. Das im Rahmen dieser Dissertation entwickelte hochfluorierte Pyrazino[2,3-b]phenazin konnte zur Infiltrierung von ZnO-Nanopartikel-Schichten verwendet werden. Mit Hilfe der Infiltrationsversuche wurde der positive Einfluss des hochfluorierten Pyrazino[2,3-b]phenazins auf die Transistoreigenschaften der ZnO-Nanopartikel-Schicht im Vergleich zur reinen ZnO-Nanopartikel-Schicht nachgewiesen.

Bei organischen Halbleitern zur Anwendung als Ladungstransportschicht in Feldeffekt-Transistoren werden zwei Molekülklassen unterschieden: Erstens sogenannte „kleine Moleküle“, die durch ihre Kristallinität und damit hohe Ordnung im Material sehr hohe Ladungsträgermobilitäten aufweisen, aber häufig nur aus dem Vakuum verarbeitet werden können. Zweitens die Polymere, die aufgrund ihrer guten Materialeigenschaften kostengünstig aus Lösung verarbeitet werden können, aber schlechteren Ladungstransport aufweisen. Das Ziel dieser Dissertation war also die Entwicklung eines halbleitenden Materials, das die Vorteile der „kleinen Moleküle“ mit denen der Polymere kombiniert. Als Zielmolekül wurde ein Polystyrol-basiertes Polymer angestrebt, das in der Seitenkette eine auf einem N-Heteroacen-basierte Ladungstransport-Einheit trägt, welche über einen flexiblen Spacer mit der Hauptkette verbunden ist. Dieser Spacer soll die vorteilhafte Anordnung der Ladungstransport-Einheiten zueinander trotz der Anbindung an ein Polymerknäuel gewähr leisten. Eine Strategie zur Synthese solcher Polymere wurde etabliert und durchgeführt, wobei dieses durch radikalische Polymerisation eines Chinoxalin-Monomers mit Styrol hergestellt wurde. Eine zweite Route, basierend auf einer polymeranalogen Umsetzung eines Chinoxalin-Ethers an einem bestehenden Copolymer, wurde ebenfalls erfolgreich durchgeführt. Durch die elektronische Charakterisierung des Polymers konnte der Erhalt der Ladungstransporteigenschaften bewiesen werden. Des Weiteren wurden in dieser Arbeit Synthesewege hin zu unterschiedlichen, asymmetrisch funktionalisierten N-Heteroacenen erarbeitet und die erhaltenen Moleküle charakterisiert.

Die vorliegende Arbeit befasst sich mit der Darstellung und Untersuchung cyclischer konjugierter Systeme des Bors. Hierbei wurden die zentralen Ringeinheiten der organischen Analoga mit zwei Boratomen in 1,4-Position substituiert. 1 Darstellung und Eigenschaften des CyCAAC-stabilisierten 1,4 Diborabenzols (87) Die Darstellung eines weiteren Vertreters des basenstabilisierten 1,4-Diborabenzols orientierte sich an vorangegangen Arbeiten der Gruppe um Braunschweig auf diesem Gebiet. Das Cyclohexyl-CAAC koordinierte Diboracumulen (85) wurde unter einer gereinigten Acetylen-atmosphäre mit einem Druck von etwa 1 bar gerührt. Quantenchemische Rechnungen ergaben einen NICS(0)-Wert von –2.6483 des [B2C4]-Rings (vgl. NICS(0)Benzol: –8.1723; B3LYP/Def2SVP Niveau) und bestätigten zusätzlich die Bildung eines Ringstroms bzw. eines aromatischen Systems. Umsetzungen des Diborabenzols 87 mit den Alkalimetallen Lithium und Natrium wurden durchgeführt und die entsprechenden dianionischen Verbindungen 88 und 89 erhalten. Unter gleichen Reaktionsbedingungen wurden im Falle des Kaliums Einkristalle erhalten deren röntgenkristallographische Untersuchung den Konnektivitätsbeweis für das Monoanion 90 liefern. 2 Synthese und Umsetzungen CAAC-stabilisierter 9,10 Diboraanthracene Die Darstellung des 9,10-(Dibromo)diboraanthracens 63 entlehnt sich der Literatur und findet durch eine Abfolge von Salzmetathesereaktionen zwischen o(Bistrimethylsilyl)benzol (65) und Bortribromid statt. Nach der Koordination der CAAC-Liganden an 63 wurde die schrittweise reduktive Abstraktion der Bromatome möglich. Die Einelektronreduktionen von 92 und 93 lieferten nicht, wie erwartet, neutrale gemischtvalente Systeme. Röntgenkristallographische Untersuchungen an geeigneten Einkristallen der Verbindung 99 zeigten, dass sich eine salzartige Struktur bildete. Bei der Reduktion von 93 wurden beide Bromidreste abgespalten und das Diboraanthracenfragment liegt als Radikalkation vor. Die zweifache Reduktion der Verbindungen 92 und 93 liefert ebenfalls Produkte, die keine 11B-NMR-Resonanz zeigen. Dieser Umstand spricht erneut für die Generierung offenschaliger Systeme. Die Röntgenstrukturanalyse geeigneter Einkristalle der beiden erhaltenen Produkte 103 und 104 zeigte, dass die neutrale Diboraanthracenspezies gebildet wurde (Schema 58). ESR-Experimente bei tiefen Temperaturen lieferten Einsicht über den elektronischen Grundzustand der beiden Verbindungen 103 und 104. Die beiden Verbindungen liegen, unter den gewählten Bedingungen, im open shell-Singulett-grundzustand vor. Es ergeben sich Singulett-Triplett-Abstände ΔES→T = 0.43 kJ/mol (4.46 meV) für 103 bzw. ΔES→T = 2.3 kJ/mol (23.8 meV) für 104. Die Reduktion von 92 mit einem Überschuss von Lithium lässt die Darstellung des dianionischen Diborataanthracens 110 zu. Unter photochemischen Bedingungen bildet 103 eine zwitterionische Spiroverbindung 113, durch die Insertion eines Boratoms in den Pyrrolidinring des koordinierten CAAC-Liganden. Weiterhin sind 103 und 104 geeignete Ausgangsmaterialien zur Aktivierung kleiner Moleküle unter milden Bedingungen. Die Umsetzung der MeCAAC-Spezies 103 mit elementarem Schwefel liefert Verbindung 128, bei der eine S3-Brücke zwischen den Boratomen insertiert wird. Im Falle des CyCAAC-Diboraanthracens 104 konnte die Koordination eines CO-Moleküls an die Boratome (140) nachgewiesen werden. Zusätzlich konnten, durch die Darstellung des Halbsandwichkomplexes 149, erste Einsichten in die Verwendung des Diboraanthracens (104) als Ligand in der Übergangsmetallchemie gewonnen werden (Schema 60). Der Halbsandwichkomplex [η6-(9,10-(CyCAAC)2DBA)Cr(CO)3] (149) wurde durch die Zugabe von 104 zu [(MeCN)3Cr(CO)3] dargestellt und das zugehörige IR-Spektrum der Verbindung 149 identifiziert 104 als starken Elektronendonorliganden
This thesis deals with the synthesis and examination of cyclic conjugated systems of boron. The central ring-moiety of the organic analogues were substituted with two boron centres in 1,4-position. 1 Synthesis and properties of a CAAC-stabilized 1,4 diborabenzene (87) The synthesis of an additional example of base-stabilized 1,4-diborabenzene follows preceding studies of the Braunschweig´s research group on this topic. The cyclohexyl-CAAC coordinated diboracumulene (84) was stirred under an atmosphere of purified acetylene with a pressure of approximately 1 bar. Quantum chemical calculations, conducted on 87 established a NICS(0) value of –2.6483 at the [B2C4]-ring (cf. NICS(0)benzene: –8.1723; B3LYP/Def2SVP-level of theory) confirming the existence of a ring current and thus aromaticity of this system. Reaction of the diborabenzene 87 with the alkali metals lithium and sodium were performed and the corresponding dianionic compounds (88) and (89) were generated. Instead, for the reduction with potassium, under similar reaction conditions, single crystals were obtained that provided the evidence for the connectivity of the monoanionic species (90) by X-ray diffraction. 2 Synthesis and reactivity of CAAC stabilised 9,10 diboraanthracenes The synthesis of 9,10‐(dibromo)diboraanthracene 63 was performed according to a published procedure that follows a series of salt‐metathesis reactions of o‐bis(trimethylsilyl)benzene (65) and borontribomide. After the coordination of the CAAC ligands to compound 90 the stepwise reductive abstraction of the bromides was performed (Scheme 3). A single electron reduction of 92 and 93 did not result in the expected neutral mixed valence systems but instead provided products that did not show an 11B NMR-spectroscopic signal. X Ray crystallographic examination of suitable single crystals of the compound 93 showed a salt-like structure. Both bromides of 93 had been abstracted, leaving the diboraanthracene fragment as a radical cation. The double reduction of 92 and 93 also yielded 11B-NMR silent products, again suggesting the presence of open-shell systems. X-Ray diffraction of suitable single crystals of the obtained compounds 103 und 104 indicate the formation of the desired neutral diboraanthracene species In the solid state. Low temperature EPR-experiments gave insights into the electronic ground state of the compounds 103 und 104. Singlet-triplet gaps were deduced to be ΔES→T = 0.43 kJ/mol (4.46 meV) for 103 and ΔES→T = 2.3 kJ/mol (23.8 meV) for 104. Both compounds are present in open shell singlet ground state. The reduction of 92 with an excess of elemental lithium permitted the synthesis of the dianionic diborataanthracene 110. Under photochemical conditions by insertion of a boron atom into the pyrrolidine moiety of the coordinated CAAC ligand 103 forms a zwitterionic spiro-compound 113. Furthermore, 103 und 104 were found to be suitable reagents for the activation of small molecules under mild conditions. The reaction of MeCAAC-species 103 with elemental sulfur yields compound 128 with an S3 bridge between the boron atoms. For the CyCAAC-stabilized diboraanthracene 104 the coordination of a CO molecule to the boron atoms was observed (140). Additionally, initial insights were obtained into the ability of the diboraanthracene 104 to act as a ligand in transition metal chemistry by the synthesis of the halfsandwich-compound 149. The half sandwich complex [η6-(9,10-(CyCAAC)2DBA)Cr(CO)3] (149) was prepared by the addition of 104 to [(MeCN)3Cr(CO)3] and the IR-spectrum of 149 indicated that compound 104 is a strongly electron donating ligand

碩士
國立交通大學
應用化學系碩博士班
105
Solid-state structures of conjugated molecules play an important role in the field-effect transistor (FET) performances of the molecules. Multi-fused heteroacenes (HA) are useful building blocks for molecules used in optoelectronic devices. Although the influences of the constituent aromatic units on the chemical properties of HAs have been known, their influences on the physical structures of the HA derivatives have not been systematically studied. Here, a series of 8 heteroacene (HA) derivatives provided by Professor Ken-Tsung Wong’s laboratory at National Taiwan University were studied. The molecules were divided into three groups based on the chemical structures of their HA cores (HA1: 4,9-Bis(2-ethylhexyl)-thieno[3,2-b]thieno[2''',3''':4'',5'']pyrrolo[2'',3'':4',5']thieno[2',3':4,5]-thieno[2,3-d]pyrrole, HA2: 6,12-Bis(2-ethylhexyl)-Indolo[2'',3'':4',5']thieno[2',3':4,5]thieno[3,2-b]indole, HA3: 4,5-Bis(2-ethylhexyl)-dithieno[2,3-d:2',3'-d']thieno[3,2-b:4,5-b']dipyrrole). Crystal arrays of the HA derivatives were prepared by the PDMS-assisted crystallization (PAC) procedure. By analyzing the polarized optical microscopy (POM) images, grazing incidence X-ray diffraction (GIXRD) patterns, and OFET performances of the HA derivatives, it was found that the lateral alkyl substituents and the end-capping groups can significantly affect the solid-state morphology and the OFET performances of the molecules.