Tuning of the electronic and optical properties of oligothiophenes via cyano substitution: A joint experimental and theoretical study

Cyano-substituted bi- and terthiophene derivatives have been synthesized and characterized both electrochemically and optically. The experimental data are compared to the results of quantum-chemical calculations in order to rationalize the evolution of the frontier levels of the thiophene oligomers as a function of the number and position of the cyano substituents. This issue is of particular relevance in the context of organic light-emitting diodes and field-effect transistors to determine the substitution pattern required for the design of efficient electron-transporting (n-type) oligothiophene derivatives. The experimental and theoretical results demonstrate that the cyano functionalization allows for a fine-tuning of the electronic and optical properties of the thiophene compounds.