Structure and Electrical Bistability of a New Class of Diphenyl-bithiophenes: A Combined Theoretical and Experimental Study

The more stable conformers of recently synthesized diphenyl.-bithiophene (DPBT) derivatives, a new class of relatively flexible conjugated molecules displaying electrical bistability, are investigated with the help of density functional theory calculations and by single crystal X-ray diffraction. The electronic structures of the neutral and positively charged species are computed for the most relevant isomeric forms along with intramolecular reorganization energies associated with charging. Two major mechanisms, charge injection at the interface and bulk charge transport, are considered to rationalize the observed electrical bistability and the efficiency of the electrical phenomenon for different DPBT species, in terms of computed molecular parameters. It is suggested that bistability is governed by an interplay of the two charge transport processes, with the OFF state being determined by activated hole injection.