Photo-induced nitroxyl anion/HNO release from a nitrosyl complex of Mn(II)-porphyrinate

Abstract

MnII-nitrosyls having {MnNO}6 configuration are generally considered to have electronic character of low spin [MnI-NO+] owing to which HNO/ NO¯ release from MnII-nitrosyls is not favourable. Although only a handful of {MnNO}6 are known to release NO under specific conditions, till date a MnII-nitrosyl in meso-tetrakis(4-methoxyphenyl)porphyrin framework is the only reported to release NO¯ in the presence of a neutral or anionic sixth ligand. A nitrosyl complex of Mn(II)-porphyrinate, 1, [Mn(TTMPP2-)(NO)] {H2TTMPP = 5,10,15,20-tetrakis(3,4,5-trimethoxyphenyl)porphyrin}has been synthesized and characterized. Complex 1, in dichloromethane solution at -40 C, in the presence of visible light was found to donate nitroxyl anion (NO-) to [FeIII(TPP)Cl] and [FeIII(dtc)3] {H2TPP = tetra-phenylporphyrin and dtc = diethyldithiocarbamate}to result in the corresponding Fe(II)-nitrosyls. Further, when complex 1 was stirred with equivalent amount of HBF4 under visible light, the presence of N2O in the headspace gas was observed. This, in turn, suggests that the complex 1 donates HNO in the presence of H+ under visible light. All these studies suggest that complex 1 acts as a NO-/HNO donor in the presence of visible light.