Palladium(II) and platinum(II) tetramethyltetrapyridinoporphyrazine complexes: Redox properties and interactions with cysteine and histidine

Cyclic voltammetry and spectroelectrochemistry studies are reported for the tetramethyl-tetrapyridinoporphyrazine complexes N,N',N",N"'-tetramethyltet ra-2,3-pyridinoporphyrazine palladium(II) (1a), N, N', N'', N'''-tetramethy ltetra-3,4-pyridinoporphyrazine palladium(II) (1b), N, N', N", N"'-tetramet hyltetra-2,3-pyridinoporphyrazine platinum(II) (2a) and N, N', N'', N"'-tet ramethyltetra-3,4-pyridinoporphyrazine platinum(II) (2b). Cyclic voltammetr y on Pt disc electrodes showed two reductions. The first reduction was assi gned to one-electron transfer to the ring with the formation of a monoanion species. All the tetramethyltetrapyridinoporphyrazine complexes are readil y reduced to the monoanion species in the presence of histidine or cysteine . The rate constants for the interaction of complexes la, Ib, 2a and 2b wit h histidine and cysteine range from similar to 2 x 10(-3) to 0.26 dm(3) mol (-1) s-(1). Copyright (C) 1999 John Wiley & Sons, Ltd.