Electronic structure, charge distribution and vibrational characteristics of glycine/NMDA receptor antagonists

Electronic structure, charge distribution and vibrational characteristics in a series of 4-hydroxyquino-2-lone (HQ) derivatives have been derived employing the ab initio Hartree-Fock calculations. Hydrogen bonded interactions in these molecules are analyzed. The strength of intra-molecular O-H ⋯ O interactions is predicted to be: amide > keto > thioamide > ester > acid; which can be explained using the molecular electrostatic potential and electron density topography. Electrostatic potential investigations have shown that the electron-rich regions localized near quinolinic oxygen (O12) exhibit (3, +3) minima and thus show affinity towards binding of ligand to N-methyl-d-aspartate receptors. Further, the bond critical points for the CO bond in the electron density topography yields a measure of the corresponding bond strength. Both the minimum near O12 in the electrostatic potentials and the bond critical point in the electron density topography are correlated to the frequency of CO stretching in these derivatives.