Theoretical evidences for resonance-assisted hydrogen bonding

In this research, high level of theoretical calculations have been used to obtain insights into the nature of resonance-assisted hydrogen bonding (RAHB). The geometry variations caused by intramolecular hydrogen bond formation on the molecular fragment HY-(CdropC)(n)-CdropX have been studied at the B3LYP/6-311++G** level of theory. The electronic charge distribution and some other related properties obtained by using the atom in molecule theory (AIM) are found as a powerful source of information for characterizing such RAHB. The calculations are carried out in four different cases and in each case the formation of RAHB are confirmed by the results of AIM analysis, geometry variation and stabilization energies. (C) 2004 Elsevier B.V. All rights reserved.