Spectroelectrochemistry, supramolecular

The porphyrin reduction potential is also sensitive to the coordinated metal ion and its oxidation state. For example, the reduction of the Co 4-TRPyP) species is cathodically shifted due to the previous formation of Co (4-TRPyP), while the ring oxidation potentials remain almost invariant at 1.5 V. Although the existence of the M P state was already reported for Ni, Co, and Fe porphyrins, the only case detected in supramolecular porphyrins is for Co (4-TRPyP) and Co (4-TCPyP), occurring around — I.IV, as observed in the spectroelectrochemistry measurements (122, 170). Its formation usually shifts the porphyrin and bpy reduction processes to more negative potentials (Table III). In all cases, the spectroelectrochemistry technique has proved essential for the proper assignment of the redox processes (a typical set is shown in Fig. 18) (38, 118, 119, 170). 

Brewer and Elvington used spectroelectrochemistry to investigate a photochemical problem involving a transition metal complex. Spectroelectrochemistry was used to help elucidate a complex sequence of excited state reductions in the supramolecular complex [ (bpy)2Ru(dpp) 2RhCl2] + (dpp = 2,3-bis-2-pyridylpyrazine). The spectroelectrochemical experiment involved the bulk reduction of the complex at —0.4V vs. Ag/AgCl, just after the two-electron irreversible... 

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