Hydrogen bonded pyridine N-oxide/trichloroacetic acid complex in polar media: 2D potential energy surface and O–H⋯O vibration analysis using exact vibrational Hamiltonian

The analysis of O–H⋯O stretching vibrations of the pyridine N-oxide/trichloroacetic acid (PyO/TCA) H-bond complex in acetonitrile solution was carried out. 1D and 2D potential energy surfaces associated with the variation of valence coordinates of hydroxyl and hydrogen bonds were calculated for this purpose in the B3LYP/cc-pVTZ approximation. The exact form of kinetic energy operator was obtained using these coordinates and Wilson’s vectors. The numerical solution of 2D Schrödinger equation using Fourier series was realized and the wave numbers of O–H and O⋯H vibrations were calculated and compared with the results obtained using different sets of vibrational coordinates. The values of the O–H⋯O stretching frequencies obtained as a result of the matrix diagonalization were discussed and compared with the experimental data, the results of harmonic- and anharmonic computations as well as with the results of 3D computations of potential energy surfaces of the PyO/TCA complex using simplified form of kinetic energy operator.