Synthesis and Characterisation of Fused-Heterocyclic Molecular Rods: A Combined Experimental and Theoretical Study on Diethynyl-Dithienothiophenyl Derivatives

A structural and electronic diversity of symmetric diethynyl dithienothiophenyl (DTT) molecular rods were synthesised and their properties fully characterised using optical and thermal analysis and complemented with density functional theory (DFT) calculations. It was found that some structures are stable up to 381 °C. Due to the nature of both the derivative and the substituent, physical properties such as electron donating ability and thermal stability can be fine-tuned to generate rationally designed materials, all of which have excellent solubility in common organic solvents. The single-crystal x-ray structures revealed that both bulky silyl and linear alkyl derivatives generate regular lateral close packing between the adjacent molecules, suitable for charge-transfer in organic thin-film transistors (OTFTs), whereas the same ethynyl derivative without an alkyl chain gives a non-planar interlinking structure and thus unsuitable for OTFTs. These air-stable electron rich DTT-based molecular rods have strong potential as organic semiconductors for organic electronic applications.