Unusual band-gap migration of N-alkylcarbazole-thiophene derivative

The 9-heptyl-3,6-di(thiophen-2-yl)-9H-carbazole (BTC-C7) monomer shows unusual electronic properties during electropolymerization process, we describe the possibility of electrosynthesis of oligomers of different chain length. What is extraordinary about these systems is that their band-gap size is the same, irrespective of the number of repeat units in the oligomer. We compared band-gap width for different oligomers using absorption spectroscopy, cyclic voltammperometry. Analysis of this data suggests that the observed constant band-gap width feature is due to simultaneous, and equipollent change of the energy of HOMO and LUMO orbitals across the series of oligomers being considered.