Synthesis and electronic properties of hexylthiophene-octaethylporphyrin derivatives (HTh-OEP) connected with diacetylene linkage: substituent effect on the electronic structure of the extended HTh-OEP conjugation system

Octaethylporphyrin (OEP) was combined with 2-substituted 3-hexylthiophenes (HTh) by diacetylene linkage to afford the highly extended conjugation system (HTh-OEP). Their absorption spectral properties were examined, proving that the electronic structure of OEP is affected by the more electron-withdrawing substituents through the diacetylene linkage more dramatically. The substituent effect on the HTh-OEP conjugation system is much outstanding, as compared with that on the corresponding benzene system (Bzn-OEP).