Synthesis, structure and photophysical properties of ferrocenyl or mixed sandwich cobaltocenyl ester linked meso-tetratolylporphyrin dyads
We report here the design and synthesis of porphyrin–metallocene dyads consisting of a metallocene [either ferrocene or mixed sandwich η5‐[C5H4(COOH)]Co(η4‐C4Ph4) connected via an ester linkage at meso phenyl position of either free‐base or zinc porphyrin. All these dyad systems were characterized by various spectroscopic and electrochemical methods. A dimeric form of this molecule was observed in the X‐ray crystal structure of Zn‐TTPCo. The absorption spectra of all four dyads indicated the absence of electronic interactions between porphyrin macrocycle and metallocene in the ground state. However, interestingly, in all four dyads, fluorescence emission of the porphyrin was quenched (19–55%) as compared to their monomeric units. The quenching was more pronounced in ferrocene derivatives rather than cobaltocenyl derivatives. The emission quenching can be attributed to the excited‐state intramolecular photoinduced electron transfer from metallocene to singlet excited state of porphyrin and the electron‐transfer rates (kET) were established in the range 1.51 × 108 to 1.11 × 109 s−1. They were found to be solvent dependent.
Synthesis, characterization and photophysical properties of ferrocenyl and mixed sandwich cobaltocenyl ester linked meso-triaryl corrole dyads.
Shivaprasad Achary Balahoju, Ramya A. R., Trivedi Rajiv, Bangal P. R., Giribabu Lingamallu