Kaustubh A. Joshi

Theoretical studies on the electronic structure, charge distribution and vibrational spectra of diglyme–M+-AsF6− (M = Li, Na, K)

Electronic structure and the vibrational spectra of CH(3)(OCH(2)CH(2))(2)OCH(3)-M(+)-AsF(6)(-) (M=Li, Na, K) have been obtained using the density functional theory. Lithium ion exhibits a pentavalent coordination via 3 oxygens from diglyme and two fluorines of AsF(6)(-) whereas Na(+) and K(+) exhibit coordinate number 6 with 3 fluorines of the anion binding to alkali metal in these complexes. Analysis of calculated spectra reveal that the CH(2) wag (840-1120 cm(-1)) vibrations in the complex are sensitive to metal ion coordination. A frequency downshift relative to the free anion has been predicted for the vibrations of AsF(6)(-) anion when the fluorines are directly bonded (denoted by F) to metal ion. Consequent reorganization of electron density in the complex engenders a frequency shift in the opposite direction for As-F vibrations wherein the fluorine atoms are not coordinating to the alkali metal ion. An approach based on the molecular electron density topography coupled with the difference electron density map explains the direction of the frequency shifts of C-O-C and the As-F stretchings compared to those of free diglyme or AsF(6) anion. A new method, which includes the color-mapping function for the difference molecular electron density (MED), superimposed on the bond critical points in MED topography has been suggested to explain the direction of the frequency shifts in a single attempt.

Molecular electrostatic potentials in aromatic substituted 4-hydroxyquino-2-lones: Glycine/NMDA receptor antagonists

AbstractHydroxyquinolone derivatives have proven to be useful for inhibition at the glycine binding site of N-methyl-D-aspartate (NMDA) receptor. In this work the electronic structure, molecular electrostatic potential (MESP) and vibrational characteristics of a set of C3 substituted 4-hydroxyquino-2-lone (HQ) derivatives, which act as Glycine/NMDA receptor antagonists, have been investigated using the density functional calculations. In the optimized structures a substituent at the C3 site of HQ tends to adopt a helical structure. MESP investigations reveal that the ligands showing better inhibition activity should possess electron-rich regions extending over the substituent and carbonyl group of HQ. A correlation of inhibitory activity to the molecular electrostatic potential topography at the carbonyl oxygen as well as to the molecular electron density topography turns out to be a significant output of the investigation. FigureQuantam chemical approach has been employed to understand the reactivity of a set of hydroxyquinolone derivatives known for their inhibition activity towards Glycine/NMDA receptor. Molecular electrostatic potential topography has been used as a tool to understand the reactivity pattern