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Photophysical Properties of a Rhodium Tetraphenylporphyrin-tin Corrole Dyad. The First Example of a Through Metal–Metal Bond Energy Transfer

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  • This paper is part of a special issue dedicated to Professor J. C. (Tito) Scaiano on the occasion of his 60th birthday.

ABSTRACT

The luminescence spectroscopy study and the determination of the photophysical parameters for the M-M′-bonded rhodium meso-tetraphenylporphyrin-tin(2,3,7,13,17,18-hexamethyl-8,12-diethylcorrole) complex, (TPP)Rh-Sn(Me6Et2Cor) 1, was investigated. The emission bands as well as the lifetimes (τe) and the quantum yields (φe; at 77 K using 2MeTHF as solvent) were compared with those of (TPP)RhI 2 (TPP = tetraphenylporphyrin) and (Me6Et2Cor)SnCl 3 (Me6Et2Cor = 2,3,7,13,17,18-hexamethyl-8,12-diethylcorrole) which are the two chemical precursors of 1. The energy diagram has been established from the absorption, fluorescence and phosphorescence spectra. The Rh(TPP) and Sn(Me6Et2Cor) chromo-phores are the energy donor (D) and acceptor (A), respectively. The total absence of fluorescence in 1 (while fluorescence is observed in the tin derivative 3) indicates efficient excited state deactivation, presumably due to heavy atom effect and intramolecular energy transfer (ET). The large decreases in τp and φp of the Rh(TPP) chromophore going from 2 to 1 indicate a significant intramolecular ET in the triplet states of 1 with an estimated rate ranging between 106 and 108 s–1. Based on the comparison of transfer rates with other related dyads that exhibit similar D-A separations and no M-M′ bond, and for which slower through space ET processes (102–103 s–1) operate, a through M-M′ bond ET has been unambiguously assigned to 1.

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