2-Thienyl-substituted 3a,6a-diaza-1,4-diphosphapentalene: Synthesis and complexation with 1,2,4,5-tetracyanobenzene

Synthesis of 2,5-dimethyl-3,6-di(2-thienyl)-3a,6a-diaza-1,4-diphosphapentalene was accomplished. Interaction of this compound with 1,2,4,5-tetracyanobenzene afforded black crystals of the 1 : 1 adduct containing π-stacks of D–A units with short interplanar spacing of 3.26 Å inside the unit and 3.47 Å between the D–A units, where tetracyanobenzene is an acceptor of 0.2 e. Estimation of the HOMO−LUMO gap from the onset of optical absorption gave value of 1.28 eV.