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The influence of treatment of electron correlation, size of basis set and choice of solvation model on the predicted stabilization of zwitterionic phosphonic acid gamma-aminobutyric acid (GABA) analogues is investigated. Phosphinic and phoshonic acid GABA analogues constrained in a cis-configuration are found to possess only folded, intramolecularly hydrogen bonded stable conformers.

The solution-phase structures of a number of conformationally restricted gamma-aminobutyric acid (GABA) analogues are investigated. The results give a high-quality starting point for subsequent quantitative structure-activity relationship analysis that is expected to provide insight into which conformers of GABA and its conformationally restricted analogues are biologically active.

A study of the vibrational effects on the F-F spin-spin coupling constant ((super 2h)J(sub F-F)) in FHF(super -) and FDF(super -) are evaluated. The results show that in the ground vibrational state, the expectation value of the F-F distance increases and the expectation value of (super 2h)J(sub F-F) decreases to 212.7 Hz. significantly less than the equilibrium value of 254.4 Hz.

An ab initio study of the hydrogen-bonded complexes of the deuterated analogues carried out is reported. The computed results provide insight into the nature of the hydrogen bonds that stabilize these complexes in low-temperature matrixes.

The stabilization of Gamma-aminobutyric acid (GABA) zwitterions in aqueous solution is investigated at various levels of theory by considering both short- and long-range solvent interactions. Zwitterionic forms of GABA are expected to exist in various conformations in aqueous solution at 310 K.

IR proton-stretching frequencies and NMR properties of hydrogen-bonded complexes, ClH:pyridine are investigated. Results reveal that the zero-field, gas-phase structure of this complex is stabilized by a traditional Cl-H...N hydrogen bond and as the field strength increases, the equilibrium structure exhibit quasi-symmetric structure at a field of 0.0040 au, and then ion pair complex at higher fields.