Structural and biological studies of organotin(IV) derivatives with 2-mercapto-benzoic acid and 2-mercapto-4-methyl-pyrimidine

Four organotin(IV) complexes with the heterocyclic thioamides 2-mercapto-4-methyl-pyrimidine hydrochloride (H2MPMT+Cl−, C5H7N2SCl) and 2-mercapto-benzoic acid (H2MBA, C7H6O2S), of the formulae [Ph3Sn(MPMT)] (1), [Me2Sn(MPMT)2] (2), {[(n-Bu)2Sn(MBA)]2}n (3), already reported in the literature, and {[Me2Sn(MBA)]2}n (4), with a different structure to the one already reported, have been used to study their influence upon the catalytic peroxidation of linoleic acid by the enzyme lipoxygenase (LOX). The IC50 values found lie in the range 20–30 μΜ. The crystal structure of 4 was determined by X-ray diffraction at room temperature (293(2) K). The structure of 4 is polymeric and it consists of {[Me2Sn(MBA)]2} dimeric building blocks in contrast to the complex of the same formula reported earlier which has a hexameric cyclic structure. Intermolecular Sn–O bonding interactions between these units in 4 lead to the formation of infinite chains with helical conformations. In addition the crystal structure of 3, previously reported with R = 9.9%, was now reduced to R = 6.1%. Comparison with the already reported hexanuclear macrocycle complexes {[(n-Bu)2Sn(MBA)]6} (5) and {[Me2Sn(MBA)]6 H2O} (6) to the helical polymeric 3 and 4 was made. DFT calculations performed for the hexameric complex 6 and helical polymeric complex 4 have shown that the energy (ΔΕ) difference between the two polymeric and hexanuclear conformers is only 1.65 Kcal/mol. Finally, the crystal structure of complex 2, previously solved in the orthorhombic Cmc21 space group, was now solved in the monoclinic P21/n space group.

Di-organotin(IV) complexes of the formulae [Ph3Sn(MPMT)] (1), [Me2Sn(MPMT)2] (2), {[(n-Bu)2Sn(MBA)]2}n (3), already reported in the literature, and {[Me2Sn(MBA)]2}n (4) (H2MPMT+Cl− = 2-mercapto-4-methyl-pyrimidine hydrochloride and H2MBA = 2-mercapto-benzoic acid), with a different structure to the one already reported, have been synthesized and used to study their influence upon the catalytic peroxidation of linoleic acid by the enzyme lipoxygenase (LOX). The IC50 values were found to lie in the range 20–30 μΜ. A comparison of the structures of the helical polymeric complexes 3 and 4 with the already reported hexanuclear macrocycles complexes {[Me2Sn(MBA)]6 H2O} (5) and {[(n-Bu)2Sn(MBA)]6} (6) has been made. The results show that the self-assembly process of these type of complexes might be fortuity dependent and not based on intermolecular C_H···S weak hydrogen bonds and π–π interactions.Figure optionsDownload as PowerPoint slide