Molecular electrostatic potential and field as descriptors of hydrogen bonding and molecular activity. Effects of hybridization displacement charge

Molecular electrostatic potential (MEP) and field (MEF) maps have been studied for certain epoxides, ethers and nitriles. The MNDO method was used to optimize geometries of the molecules fully. Hybridization displacement charges (HDC) recently defined by us, which preserve atomic contributions to molecular hybridization dipole moment, were combined with the Mulliken and Lowdin charges to compute the MEP and MEF maps. Linear correlation coefficients between our MEP and MEF values and the observed hydrogen bond accepting parameters (beta) for ethers and nitriles, and the corresponding ab initio MEP values for epoxides were found to be quite high (>0.9). Thus it has been shown that combination of HDC with the Mulliken and Lowdin charges usually improves the quality of MEP and MEF maps appreciably in comparison with those computed using the Mulliken and Lowdin charge distributions alone. Furthermore, the study demonstrates great utility of MEP and MEF - describing hydrogen bonding and molecular activity.