Spectroscopic and conformational comparative study of trimethyl chalcogenphosphates

Geometrical. conformational and spectroscopical properties of three chalcog enphosphates were studied comparatively. Rotational isomerism and conformat ional flexibility were evaluated for trimethyl phosphate, O,O,O-trimethyl t hiophosphate and O,O,O-trimethyl selenophosphate by studying the vibrationa l and NMR spectroscopy. Semi empirical and ab initio calculations have been carried out. Experimental and theoretical results show similar conformatio nal behavior, founding equivalent symmetries for conformations of minimal e nergies, but a decrease in the conformational flexibility is observed when going from O, to S and to Se species. This result would represent a new fac tor to explain the higher ability of interaction of O-organophosphorus comp ounds in some biological active sites, in esterases for example, with respe ct To the analogous S-organophosphorus compounds and Se-organophosphorus co mpounds, (C) 2001 Elsevier Science B,V. All rights reserved.