π-conjugated poly(dithiafulvene)s and poly(diselenafulvene)s:: Effects of side alkyl chains on optical, electrochemical, and conducting properties

Electron-donating pi-conjugated polymers with dithiafulvene moiety (4) or with diselenafulvene moiety (5) were prepared by cycloaddition polymerization of chalcogenoketenes derived from aromatic diynes (3). The solubilities of the polymers strongly depended on the structures. The diselenafulvene polymers (5) showed lower solubilities than the corresponding dithiafulvene polymers (4). Attachment of long alkyl chains enhanced the solubilties in nonpolar solvents. The structures of the polymers were confirmed by IR and H-1 NMR spectra. UV-vis measurements indicated that pi-conjugations of the polymers were expanded; in particular, those of polymers containing the long alkoxy side chains were developed effectively. All the polymers showed electron-donating properties in cyclic voltammometry measurements and formed soluble charge-transfer complexes with 7,7,8,8-tetracyano-p-quinodimethane (TCNQ). After the complexation with TCNQ, the conductivities of the polymers increased.