An analysis of bifurcated H‐bonds: crystal and molecular structures of O,O‐diphenyl 1‐(3‐phenylthioureido)­pentanephosphonate and O,O‐diphenyl 1‐(3‐phenylthioureido)butanephosphonate

Abstract

AbstractIn the crystal structures of O,O‐diphenyl 1‐(3‐phenylthioureido)pentanephosphonate (1) and O,O‐diphenyl 1‐(3‐phenylthioureido)butanephosphonate (2) analysed here, bifurcated H‐bonds within R21(6) motifs are formed. It seems that such interactions play a crucial role in the crystal architecture. This is supported by ab initio MP2/6–311 ++ G** calculations on simple, modelled complexes of urea, thiourea and their derivatives with water, where the oxygen atom of water molecule is the bifurcated proton‐accepting centre. The calculations show that single H‐bonds within bifurcated systems are of medium strength (2.7–3.6 kcal mol−1). The topological parameters obtained from the Bader theory are applied for the analysis of these bifurcated H‐bonds. Copyright © 2003 John Wiley & Sons, Ltd.