Direct C-H arylation of dithiophene-tetrathiafulvalene: tuneable electronic structure and 2D self-assembled molecular networks at the solid/liquid interface

Abstract

Tetrathiafulvalene is among the most well-known building block in molecular electronics due to its outstanding electron-donating and redox properties. Among its derivatives, dithiophene-tetrathiafulvalene (DT-TTF) received a lot of interest for organic electronics due to its high charge mobility. Herein we report the direct C-H arylation of DT-TTF (1) to synthesise mono- (2, 3) and tetraarylated (4, 5) derivatives bearing different functional groups. The incorporation of electron-donor or electron-withdrawing groups into the DT-TTF core allows the fine-tuning of its electronic structure as demonstrated by cyclic voltammetry, UV-vis spectroscopy and DFT calculations. The self-assembly of DT-TTF-tetrabenzoic acid (5) derivative was studied using scanning tunneling microscopy which revealed the formation of ordered, densely packed 2D hydrogen-bonded networks at the graphite/liquid interface. Importantly, molecule 5 can reach a planar geometry on the graphite surface due to van der Waals interactions with the surface and H-bonding with neighbouring molecules. This work demonstrates a simple method for synthesising arylated DT-TTF derivatives with tuneable molecular orbital energy levels and the formation of 2D networks on the surface, allowing the construction of extended electroactive frameworks based on DT-TTF building blocks.