Effects of meso-substituents and core-modification on photophysical and electrochemical properties of porphyrin–ferrocene conjugates

The effects of meso-substituents and porphyrin core-modification on electronic communication between ferrocene and porphyrin in covalently linked porphyrin–ferrocene conjugates are described. The electrochemical and photophysical studies indicated that the electronic communication between porphyrin and ferrocene is strong when meso-substituents are five membered aryl groups than six membered aryl groups. This may be traced to the near orthogonal arrangement of porphyrin ring with six membered meso-aryl groups leading to weaker interaction between the porphyrin and ferrocenyl groups in conjugates, while the five membered furyl and thienyl groups are closer to the porphyrin plane than being orthogonal. Molecular orbital studies are performed at semiempirical PM3 and BLYP levels to rationalize the results.