In general, the nitrosyl complexes of Mn(II)−porphyrinate having the {Mn(NO)} 6 configuration are not considered as HNO or nitroxyl (NO − ) donors because of [Mn I −NO + ] nature. A nitrosyl complex of Mn(II)− porphyrin, [Mn(TMPP 2− )(NO)], 1 [TMPPH 2 = 5,10,15,20-tetrakis-4-methoxyphenylporphyrin], is shown to release HNO in the presence of HBF 4 . It is evidenced from the characteristic reaction of HNO with triphenylphosphine and isolation of the [(TMPP 2− )Mn III (H 2 O) 2 ](BF 4 ), 2. This is attributed to the fact that H + from HBF 4 polarizes the NO group whereas the BF 4 − interacts with metal ion to stabilize the Mn(III) form. These two effects cooperatively result in the release of HNO from complex 1. In addition, complex 1 behaves as a nitroxyl (NO − ) donor in the presence of [Fe(dtc) 3 ] (dtc = diethyldithiocarbamate anion) and [Fe(TPP)(Cl)] (TPP = 5,10,15,20-tetraphenylporphyrinate) to result in [Fe(dtc) 2 (NO)] and [Fe(TPP)(NO)], respectively.

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A five-coordinated {Mn(NO)}6 complex of Mn(II)-porphyrinate, [Mn(TMPP2-)(NO)], 1 {TMPPH2 = 5,10,15,20-tetrakis(4-methoxyphenyl)porphyrin}, upon reaction with two equivalents of superoxide (O2-) in THF at -40 °C results in the corresponding MnIII-OH...