Synthesis and Properties of Head-to-head, Head-to-tail, and Tail-to-tail Orientational Isomers of Extended Dihexylbithiophene–Octaethylporphyrin System [OEP–(DHBT)n–OEP] Connected with 1,3-Butadiyne Linkages

An extended π-electronic conjugation system of dihexylbithiophene–octaethylporphyrin [OEP–(DHBT)n–OEP; n = 1–5], all the chromophores in which are connected with the linkage of 1,3-butadiyne (diacetylene), was synthesized by an oxidative cross-coupling reaction of the corresponding terminal acetylenes. Absorption spectral and electrochemical properties of the OEP–(DHBT)n–OEP system were examined. The results proved that the orientation of two 3-hexylthiophene (3HTh) rings of DHBT plays an important role in electronic communications between the two terminal OEP rings.