Synthesis and properties of alternating acceptor-donor π-conjugated copolymers of cyclodiborazane with dithiafulvene

Alternating acceptor-donor pi-conjugated copolymers of cyclodiborazane with dithiafulvene were prepared by hydroboration polymerization of 2,6-bis(p-cyanophenyl)-1,4-dithiafulvene (1) with tripylborane (2a) or mesitylborane (2b). The structures of the polymers 3 were supported by H-1 NMR, B-11 NMR, and IR spectra. The obtained polymers were soluble in common organic solvents such as tetrahydrofuran, chloroform, and benzene. The peak due to the pi-pi* transition of 3a was observed at 415 nm, which was bathochromic shifted in comparison with that of the monomer 1 and the corresponding homopolymers. The emission peaks of 3a was observed at 531 nm (excitation wavelength at 415 nm). The cyclic voltammogram showed that 3a was electroactive either in the cathodic or in the anodic region. A soluble charge-transfer (CT) complex of 3a with 7,7,8,8-tetracyanoquinodimethane (TCNQ) was formed when TCNQ was added to a DMSO solution of 3a. Before doping, 3a exhibited an electrical conductivity of 2 x 10(-5) S cm(-1) as measured on a cast film from DMSO. The cast film of the CT complex of 3a with TCNQ had a conductivity of 1 x 10(-4) S cm(-1).