Computational study of glycine-(water)3 complex by density functional method

Glycine-(water)3 complexes have been studied by means of B3LYP density functional method using 6-311++G* basis set. In the complex considered here, the three water molecule are either attached to the carboxylic group or bridge between the amino group and carboxylic group of glycine. Four such complexes are studied. Relaxation energies, two-, three- and four-body interaction energies are obtained by applying many-body analysis to know their role in binding energy of the complex. The results are compared with recent work on glycine-(water)3 complex with (-NH3+) group as proton donor [A. Chaudhari, P.K. Sahu, S.L. Lee, J. Chem. Phys. 120 (2004) 170]. In the most stable structure of glycine-(water)3 complex, the three water molecules are attached to the carboxylic group of glycine and it is 5.3 kcal/mol lower in energy than that of the most stable structure reported earlier. The three-body term from water-water-water interaction in the most stable in this work and that reported earlier is unique since the distances between the water molecules are almost same. The two-body term from water-water interaction has significant contribution to the total two-body term when the distance between water molecules is less than 3 Å.