In order to obtain a better molecular understanding of inhibitory role of
tin metal in the
verdoheme ring opening process, hydrolysis of three possibly six, five, and four coordinate
verdoheme complexes of
tin(IV) and (II) have been studied using DFT method. The results of calculations indicate that, in excellent accord with experimental reports, hydrolysis of different possibly coordinated
tin(IV) and (II) verdohemes does not lead to the opening of the macrocycle. Contrary to
iron and
zinc verdohemes, in five and four coordinate
verdoheme complexes of
tin(IV) and (II), formation of open ring helical complexes of
tin are unfavorable both thermodynamically and kinetically. In these pathways, coordination of
hydroxide nucleophile to
tin metal due to the highly charged, exclusive oxophilicity nature of the Sn center, and high affinity of Sn to increase coordination state are proposed responsible as inhibiting roles of
tin via the ring opening. While, in saturated six coordinate
tin(IV) and (II)
verdoheme complexes the ring opening of
tin verdohemes is possible thermodynamically, but it is not predicted to occur from a kinetics point of view. In the six coordinate pathway,
tin plays no coordination role and direct addition of
hydroxide nucleophile to the positive oxo-
carbon centers and formation of closed ring hydroxy compounds is proposed for preventing the
verdoheme ring opening. These key points and findings have been corroborated by the results obtained from atomic charge analysis, geometrical parameters, and molecular orbital calculations. In addition, the results of inhibiting ring opening reaction of
tin verdoheme complexes could support the great interest of
tin porphyrin analogues as pharmacologic means of
chemoprevention of
neonatal jaundice by the competitive inhibitory action of
tin porphyrins on
heme oxygenase.