Manganese nitrosyl porphyrin

Manganese nitrosyl porphyrins [215] are considered good models for the iron-nitric oxide analogs, which are relatively unstable but very vital to many biological operations. A six-coordinate manganese nitrosyl porphyrin of the form (por)Mn(NO)(L), where por can be TTP (TTP = tetra(4-methylphenyl)porphine) and L = piperidine, methanol, 1-methyhmidazole, has been prepared [216] in moderate yields by the reductive nitrosylation of the (por)MnCl complex with NO in piperidine. The crystal structures of these compounds give indication of a linear Mn-NO bond [215]. 

NO adds reversibly to reduced cobalamin, Cbl(II).156 It does not react directly with aquacobalamin(III), (0blni(H2O)), but it does add to Cbl,n(N02 ) and Cblm(NO).175 Acid hydrolysis of the dinitroso species releases nitrite, and binding of nitrite to Cblln(H20) generates Cbln,(. 02 ). This sequence thus affords a nitrite-catalyzed mechanism for NO substitution at Cblln(H20). The reaction of NO with Com porphyrins is quite complex.176 In the first step, NO displaces an axial water ligand to form a weakly bound mono NO complex this mono NO complex reacts with a second molecule of NO to form nitrite and a reduced Co-NO complex. This latter process is called reductive nitrosylation. Manganese(II) porphyrins bind NO very rapidly.177 Stability constants have been measured for the formation of mono and bis NO complexes of Cun(dithiocarbamate)2.157... 

Keywords HNO NO Nitroxyl Azanone Nitroxyl anion Nitrosyl Porphyrin Heme Iron Manganese Ruthenium Cobalt Reductive nitrosylation Kinetics Oxidation Protein Myoglobin NOS. 

Manganese porphyrins with a nitrosyl axial ligand have also been examined for their electrochemical properties. The oxidation of (TPP)Mn(NO) to its Mn(III) form is accompanied by a loss of the NO ligand (Fig. 7). However, the two reductions of the compound are reversible and stepwise generate a Mn(II) nitrosyl porphyrin 7T-anion radical and a nitrosyl porphyrin dianion at more negative potentials [100]. High valent manganese porphyrins have... 

Nitrosyl-aryl porphyrin complexes, with iron, 6, 107 Nitrosyl complexes with chromium, 5, 301 with manganese, 5, 773... 

In contrast to its behaviour towards 02, manganese-substituted haemoglobin binds NO reversibly at room temperature. Moreover, the Mn" + NO system is isoelectronic with Fe11 + CO and has been argued to be a close model for the binding of CO to haemoglobin.503 Examples of nitrosyl adduct formation by simple Mn porphyrins have also been reported.504... 

Manganese porphyrins also form nitrosyl complexes. Fast (ca. 10°M s ) reaction of Mn(II) with NO yields stable MnNO complexes (73) that show a linear Mn—N—0 geometry (74). Interestingly, no reductive nitrosylation is observed for the reaction of Mn(III) with NO (73). Cobalt porphyrins also form stable nitrosyl complexes. The CoNO species obtained, for example, by reaction of NO with Co(Il) porphyrins have been explored as isoelectronic... 

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