Synthesis and characterization of "face-to-face" porphyrins (bimetallic ligands/metal-metal interaction/electron spin resonance/dioxygen reduction/dinitrogen reduction)

The syntheses of four binary porphyrins, two of which are constrained to a "face-to-face" conformation, and their Co2+ and Cu2+ derivatives are described. Electron spin resonance indicates that the intermetallic separation in the binuclear "face-to-face" porphyrins is about 6.5-6.8 A. Elec- tronic spectra and proton magnetic resonance spectra support the postulated "face-to-face" conformations. A hypothesis that related compounds may serve as multielectron redox catalysts for 02 and N2 is presented.