Hydrogen-Bonding Trends in a Bithiophene with 3-and/or 4-Pyridyl Substituents

To improve the charge-carriertransport capabilities of thin-filmorganic materials, the intermolecular electronic couplings in thematerial should be maximized. Decreasing intermolecular distance whilemaintaining proper orbital overlap in highly conjugated aromatic moleculeshas so far been a successful way to increase electronic coupling.We attempted to decrease the intermolecular distance in this studyby synthesizing cocrystals of simple benzoic acid coformers and dipyridyl-2,2 & PRIME;-bithiophenemolecules to understand how the coformer identity and pyridine N atomplacement affected solid-state properties. We found that with the5-(3-pyridyl)-5 & PRIME;-(4-pyridyl)-isomer, the 4-pyridyl ring interactedwith electrophiles and protons more strongly. Synthesized cocrystalpowders were found to have reduced average crystallite size in referenceto the parent compounds. The opposite was found for the intermolecularelectronic couplings, as determined via density functional theory(DFT) calculations, which were relatively large in some of the cocrystals.