Synthesis, optical properties and charge transport characteristics of a series of novel thiophene-fused phenazine derivatives

A series of tetrathienophenazine derivatives (t-TTP, l-TTP, m-TTP and their alkyl-substituted derivatives) have been synthesized via a simple condensation reaction between diketones and diamines. The redox potentials, UV-vis absorption spectra and fluorescence spectra of these derivatives are significantly affected by the positions of the sulfur atoms and the alkyl groups. The observed electronic properties were well reproduced by theoretical calculations based on density functional theory. X-ray analyses of these derivatives reveal extensive pi-pi interactions and short S center dot center dot center dot S contacts. The alkyl-substituted derivatives afford highly crystalline thin films by vapor deposition, and show reasonable field effect transistor performance. The conductivity of doped single crystals of these materials was also investigated, and showed an increase by several orders of magnitude upon I-2 vapor doping. The pi-pi stacked structures of these crystals and conductive properties indicate that these thiophene-fused phenazines are useful materials for application in organic electronics.