Microwave accelerated synthesis and evaluation of conjugated oligomers based on 2,5-di-thiophene-[1,3,4]thiadiazole

Abstract

A series of p-conjugated 2,5-di-thiophene- [1,3,4]thiadiazole based pentamers have been synthesised by microwave promoted palladium catalysed cross-coupling reactions. The aromatic groups that terminate each pentamer have a profound effect on the observed optical, electrochemical and liquid crystalline properties. Substitution of progressively less electron rich aromatic groups at the periphery of the pentamers decreased the energy gap between the ground state and the first excited state and also lowered the energy of the frontier orbitals sufficiently to impede oxidation and facilitate reduction. The thermotropic calamitic mesogen, 2,5-bis-[5-(4-hexyl-phenyl)-thiophen-2-yl]-[1,3,4]thiadiazole, 7 showed non-dispersive ambipolar charge transport in the nematic, smectic and crystalline phases. The charge mobility increased concomitantly with increasing molecular order of the mesophase to a maximum in the highest ordered smectic phase (m hole z 4 Â 10 À3 cm 2 V À1 s À1 , m electron z 8 Â 10 À3 cm 2 V À1 s À1 ).

Board‐like Fused‐Thiophene Liquid Crystals and their Benzene Analogs: Facile Synthesis, Self‐Assembly, p‐Type Semiconductivity, and Photoluminescence

“…Polythiophenes as polymeric semiconductors becomee lectrical conductors when doped: poly(3,4-ethylenedioxythiophene)( PEDOT)d oped with polystyrene sulfuric acid becomes ac onjugated conducting polymer and plays ak ey role in plastic electronics, [5] whereas poly-3-hexylthiophene (P3HT), as ap -type organic semiconductor when paired with the n-type C 60 fullerened erivative, exhibits superiorp erformance in organic photovoltaic solar cells. [6] Oligothiophene derivatives end-capped with alkyl chains, show liquid crystalline properties, [7][8][9][10][11][12][13][14][15][16][17][18][19][20] and prefer to self-organize into supramolecular ordered layered structures:t hey display two-dimensional charge transport mobility comparable to inorganic semiconductors of amorphous and polycrystalline silicon, and have been investigated as active materials in organic field-effect transistors (OFET). [21][22][23][24][25] Discoticl iquid crystals (DLCs) [26][27][28][29] that contain afused-thiophene unit [30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46] are also ...…”

Self-assembly and charge transport properties of a benzobisthiazole end-capped with dihexyl thienothiophene units

“…17 This strategy avoids trap states 18 that are often seen with pentacene and related materials, leading to instability in air. There has been interest lately in conjugated materials incorporating electron-deficient heterocycles, such as [1,3,4]thiadiazoles [19][20][21][22][23] and dibromobenzo[1,2-d;4,5-d 0 ]bisthiazole, [24][25][26][27] particularly due to their relevance to n-type materials. 28 Recently, we reported a novel material (1) based on a benzobisthiazole core with hexylthiophene end units.…”

“…17 This strategy avoids trap states 18 that are often seen with pentacene and related materials, leading to instability in air. There has been interest lately in conjugated materials incorporating electron-deficient heterocycles, such as [1,3,4]thiadiazoles [19][20][21][22][23] and dibromobenzo [1,2-…”

Symmetrically Disubstituted Bithiophene Derivatives of 1,3,4-Oxadiazole, 1,3,4-Thiadiazole, and 1,2,4-Triazole – Spectroscopic, Electrochemical, and Spectroelectrochemical Properties

“…1,16,17 The above outlined strategy can also be applied to the synthesis of molecules showing IP significantly higher than that of oligothiophenes. In such compounds a central strongly electron accepting unit of tetrazine- [18][19][20][21] , thiadiazole- 22,23 or oxadiazole-type bridges two bi-or terthiophene segments. 24 In this report we describe new five-ring donor-acceptor-donor Electrochemical determination of the redox properties of these new semiconductors is of crucial importance in view of the fact that some of them show strong electroluminescence and can be used as components of light emitting diodes with tunable colors .…”