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).