HüCKEL MOLECULAR ORBITAL CALCULATIONS OF BIS-(SUBSTITUTED-2-HYDROXYPHENYL)-SULPHIDES

A series of bis-(substituted-2-hydroxyphenyl)-sulphides was synthesized previously, and many of such compounds were found to be active against Schistosoma japonica. We have now carried out Hückel molecular orbital(HMO)calculations on these compounds, and correlated with their anthelmintic activities. It has been found that active compounds possess higher electronic densities at oxygen atoms. Moreover, those compounds with bond order between C₁ and oxygen greater than 0.27, with nucleo-superdelocalizability lying between 0.83 and 1.0, and with electronic density at C₂ lying between 1.5 and 1.9 are pharmacologically active. Besides, conversion of the sulphides to sulphoxides enhances the bond order of C-S linkage. These compounds are less toxic, possibly because the C-S bond is more difficult to break to produce toxic substituted phenols.