Bisporphyrins with bischlorin features obtained by direct anodic coupling of porphyrins

The proximity of two or more porphyrin or chlorin-like structures has been shown to be crucial in numerous biological processes, such as electron transfers. The one-pot electrochemical synthesis of a dimeric tetraphenylporphyrin with one 1,2-(diphenylphosphonium)benzene as a spacer and of its porphyrin-monomer precursor are reported. These new compounds have been characterized by (1)H and (31)P NMR, ESR, and UV-visible spectroscopy and microanalysis. Electrochemical data are reported, and the redox behavior is analyzed for the monomers and the dimers. Important interactions between the two chromophores and a phosphonium-phosphonium interaction have been observed. UV-visible and (1)H NMR data along with electrochemical behavior suggest that the positive charge carried by the two phosphonium units is in part delocalized onto the pi system of the porphyrins, this gives an unexpected bis-porphyrin with bischlorin spectroscopic features.