Thiazole-induced rigidification in substituted dithieno-tetrathiafulvalene: the effect of planarisation on charge transport properties

Abstract

SummaryTwo novel tetrathiafulvalene (TTF) containing compounds 1 and 2 have been synthesised via a four-fold Stille coupling between a tetrabromo-dithienoTTF 5 and stannylated thiophene 6 or thiazole 4. The optical and electrochemical properties of compounds 1 and 2 have been measured by UV–vis spectroscopy and cyclic voltammetry and the results compared with density functional theory (DFT) calculations to confirm the observed properties. Organic field effect transistor (OFET) devices fabricated from 1 and 2 demonstrated that the substitution of thiophene units for thiazoles was found to increase the observed charge transport, which is attributed to induced planarity through S–N interactions of adjacent thiazole nitrogen atoms and TTF sulfur atoms and better packing in the bulk.

To bend or not to bend – are heteroatom interactions within conjugated molecules effective in dictating conformation and planarity?

“…In the case of attractive interactions the electronic structure of the compound might be affected not only by an improvement of the conjugation upon planarisation, but by the direct influence of the heteroatom on the electroactive unit it is interacting with in the planar molecular conformation. In a recent paper, 24 we have shown that substitution of peripheral thiophene units by more electron deficient thiazole moieties in an H-shaped hybrid TTF-terthiophene compound (20 and 21, respectively), in fact destabilises the HOMO, which is located on the central TTF unit. Such direct control over frontier orbital energy levels through non-covalent interactions opens up a new strategy of tailoring the electronic structure of organic semiconductors.…”

Divergent Synthesis and Semiconductor Properties of Dithienobenzothiazoles with S•••N and S•••S Interactions Controlling Molecular Arrangement in Crystal

“…In the past two decades, many polycyclic aromatic compounds have been developed as high-performance OSC materials. [12] In addition, the results of several studies show that the performance of these materials is controlled by solid state molecular orientation governed by intermolecular interactions, exemplified by p•••p interaction, [12] CH•••p interaction, [13] S•••S contact, [14] and S•••N contact [15] to construct brickwork, [16] herringbone, [1], [17] [18][19] [20] [21] and slipped-p-stacked crystal structure. [22] Actually, some linearly-fused p-electronic systems exhibit high charge-carrier mobilities as a result of their closepacked crystalline structures.…”

Tetrathiafulvalene–oligofluorene star-shaped systems: new semiconductor materials for fluorescent moisture indicators

“…9,10 TTF-based materials have been developed for potential use within various applications including organic photovoltaic cells, 11,12 cation sensors 13,14 and organic field effect transistors. [15][16][17] Increasing the conjugation in TTF-based systems contributes to forming an increasingly polarisable species which is more likely to be involved in intermolecular interactions. Increasing the conjugation is also utilised in the stabilisation of the radical cation and dication which facilitates charge transport in the material.…”