5-(3-Thienyl)-10,15,20-triethyl-21H,23H-porphine (H-2(ttep)) was synthesized and characterized. Oxidative polymerization of H-2(ttep) gave a novel oligomeric porphyrin linked at the 2,5-positions of the thienyl group. Electric conductivity of 4 x 10(-1) S/cm after I-2 doping indicated that the oligomer had a pi-conjugated. structure with a delocalization of pi electrons over the thienylene backbone. PM3 calculations revealed a low HOCO-LUCO gap, which was consistent with the relatively high electric conductivity. Regioregular (head-to-tail) structure was inferred from spectroscopic and calculational results. The pendant porphyrin groups formed a regular J-type array along the thienylene backbone, which was indicated by a significant red shift of the Soret, band maximum. (c) 2006 Wiley Periodicals, Inc.