The mpz+/mpz.bul. pair as organic analog of the NO+/NO.bul. ligand redox system (mpz = N-methylpyrazinium). A combined electrochemical and spectroscopic study (UV/Vis/NIR, IR, EPR) of complexes (mpz)M(CN)52-/3- (M = Fe, Ru, Os). Inorganic Chemistry, (36)14:2969--2974, 1997. [PUMA: IR analog;near complex complex;EPR complex;IR complex;iron complex;osmium complex;visible cyano electrochem metal methylpyrazinium nitrosyl pentacyano redn spectra spectroscopy;UV spectroscopy;electrochem spectroscopy;methylpyrazinium spectroscopy;ruthenium]