Synthesis, Properties, and Solid-State Structures of a Series of 6,13-Dicyanoheteropentacene Analogues: Towards New Liquid Crystalline Materials

The focus of this thesis is the synthesis of novel heterocyclic pentacene analogs and the investigation of their self-organization for the development of new materials for organic electronics. The thesis consists of two interrelated projects: the first being development of an improved synthesis of a series of liquid crystalline dicyanotetraoxapentacenes (DCTOPs) while the second entails the exploratory synthesis of several novel dicyanoheteropentacene analogues and a preliminary investigation of their photophysical properties and solid-state structures. Both of these projects centre around the use of nucleophilic aromatic substitution reactions on tetrafluoroterephthalonitrile. Soluble, tetrakis(bis(alkoxy)phenyl)-substituted DCTOPs were originally synthesised via a short synthesis complicated by a tedious purification required in the last step. Despite this, derivatives bearing long alkyl chains were prepared which displayed liquid crystalline properties in addition to aggregation-induced emission. Building upon this success, but with the goal of achieving DCTOPs in an efficient synthetic manner for this thesis, changes were made which eliminated the troublesome fourfold Suzuki coupling by changing the order of reactions, which in turn required a protection-deprotection sequence. Purification in the new synthesis was greatly simplified and the target tetraaryl-DCTOPs were accessed in good overall yields and purities. The synthesis and solid state structures of these DCTOPs are discussed in Chapter 2. Building on the methods developed in Chapter 2, several novel pentacene analogues containing combinations of nitrogen, oxygen, and sulfur atoms installed within the pentacene core were also synthesised. These compounds were prepared in good yields, and preliminary photophysical studies show that all the compounds displayed luminescence in solution and the solid state. It was also shown that replacement of O with N leads to a red shift in absorption and emission spectra. The X-ray crystal structures show that several of these compounds exhibit π−stacking in the solid state, which is an important design element for applications in organic electronics. The synthesis, photophysical properties, and solid-state organization of these novel 6,13-dicyanoheteropentacene analogues are discussed in Chapter 3

A New Pseudopolymorph of Hexakis-(4-cynaophenyl)benzene

The title compound (systematic name: benzene-4,4′,4′′,4′′′,-4′′′′,4′′′′′-hexaylhexabenzonitrile dichloromethane disolvate), C48H24N6•2CH2Cl2, crystallizes as an inclusion compound during the slow diffusion of methanol into a solution of hexakis(4-cyanophenyl)benzene in CH2Cl2. The hexakis(4- cyanophenyl)benzene molecule lies on an axis of twofold rotation in the space group Pbcn. Weak C—H•••N interactions between hexakis(4-cyanophenyl)benzene molecules define an open network with space for including guests. The resulting structure is a new pseudopolymorph of hexakis-(4-cyanophenyl)benzene. The eight known pseudopolymorphs have few shared architectural features, in part because none of the intermolecular interactions that are present plays a dominant role or forces neighboring molecules to assume particular relative orientations

Synthesis, Properties, and Solid-State Structures of a Series of 6,13-Dicyanoheteropentacene Analogues: Towards New Liquid Crystalline Materials

The focus of this thesis is the synthesis of novel heterocyclic pentacene analogs and the investigation of their self-organization for the development of new materials for organic electronics. The thesis consists of two interrelated projects: the first being development of an improved synthesis of a series of liquid crystalline dicyanotetraoxapentacenes (DCTOPs) while the second entails the exploratory synthesis of several novel dicyanoheteropentacene analogues and a preliminary investigation of their photophysical properties and solid-state structures. Both of these projects centre around the use of nucleophilic aromatic substitution reactions on tetrafluoroterephthalonitrile. Soluble, tetrakis(bis(alkoxy)phenyl)-substituted DCTOPs were originally synthesised via a short synthesis complicated by a tedious purification required in the last step. Despite this, derivatives bearing long alkyl chains were prepared which displayed liquid crystalline properties in addition to aggregation-induced emission. Building upon this success, but with the goal of achieving DCTOPs in an efficient synthetic manner for this thesis, changes were made which eliminated the troublesome fourfold Suzuki coupling by changing the order of reactions, which in turn required a protection-deprotection sequence. Purification in the new synthesis was greatly simplified and the target tetraaryl-DCTOPs were accessed in good overall yields and purities. The synthesis and solid state structures of these DCTOPs are discussed in Chapter 2. Building on the methods developed in Chapter 2, several novel pentacene analogues containing combinations of nitrogen, oxygen, and sulfur atoms installed within the pentacene core were also synthesised. These compounds were prepared in good yields, and preliminary photophysical studies show that all the compounds displayed luminescence in solution and the solid state. It was also shown that replacement of O with N leads to a red shift in absorption and emission spectra. The X-ray crystal structures show that several of these compounds exhibit π−stacking in the solid state, which is an important design element for applications in organic electronics. The synthesis, photophysical properties, and solid-state organization of these novel 6,13-dicyanoheteropentacene analogues are discussed in Chapter 3

Synthesis and Mesomorphic Properties of Novel Dibenz­[<i>a</i>,<i>c</i>]­anthra­cene­dicar­box­imides

The synthesis and characterization of a novel series of dibenz­[<i>a</i>,<i>c</i>]­anthracene­dicarbox­imides is reported. Incorporating electron-withdrawing imides bearing flexible alkyl chains allowed for the production of materials that self-assemble into hexagonal columnar mesophases featuring broad temperature ranges. Furthermore, longer <i>N</i>-alkyl chains or branched <i>N</i>-alkyl chains broaden the mesophase temperature range by lowering the melting transition without greatly influencing the clearing point

Unusual Structures, Phase Behavior, and Fluorescent Properties of 3-phenyl-1-(pyridin-2-yl)-1H-pyrazol-5-amine and Its’ ZnCl2 Complex

The synthesis and single crystal structures of 3-phenyl-1-(pyridin-2-yl)-1H-pyrazol-5-amine (L1) and its complex with ZnCl2 are reported. L1 exhibits supercooling, with a difference in melting and solidification points of over 100 oC. The complex [L1ZnCl2] has a room-to-low temperature single crystal-to-crystal phase transition in the solid state, while a birefringent fluid phase mixed with crystalline domains is observed at high temperatures. Significant fluorescence enhancement is observed upon formation of the ZnCl2 complex

Solid-State 11B and 13C NMR, IR, and X-ray Crystallographic Characterization of Selected Arylboronic Acids and their Catechol Cyclic Ester

Nine arylboronic acids, seven arylboronic catechol cyclic esters, and two trimeric arylboronic anhydrides (boroxines) are investigated using 11B solid-state NMR spectroscopy at three different magnetic field strengths (9.4, 11.7, and 21.1 T). Through the analysis of spectra of static and magic-angle spinning samples, the 11B electric field gradient and chemical shift tensors are determined. The effects of relaxation anisotropy and nutation field strength on the 11B NMR line shapes are investigated. Infrared spectroscopy was also used to help identify peaks in the NMR spectra as being due to the anhydride form in some of the arylboronic acid samples. Seven new X-ray crystallographic structures are reported. Calculations of the 11B NMR parameters are performed using cluster model and periodic gauge-including projector-augmented wave (GIPAW) density functional theory (DFT) approaches, and the results are compared with the experimental values. Carbon-13 solid-state NMR experiments and spectral simulations are applied to determine the chemical shifts of the ipso carbons of the samples. One bond indirect 13C-11B spin-spin (J) coupling constants are also measured experimentally and compared with calculated values. The 11B/10B isotope effect on the 13C chemical shift of the ipso carbons of arylboronic acids and their catechol esters, as well as residual dipolar coupling, is discussed. Overall, this combined X-ray, NMR, IR, and computational study provides valuable new insights into the relationship between NMR parameters and the structure of boronic acids and esters