STRUCTURALLY SYMMETRICAL N+H-CENTER-DOT-CENTER-DOT-CENTER-DOT-N-REVERSIBLE-ARROW-N-CENTER-DOT-CENTER-DOT-CENTER-DOT-H+N BONDS - THE PROTON POTENTIAL AS A FUNCTION OF THE PK(A), OF THE N-BASE, FTIR RESULTS AND QUANTUM-CHEMICAL CALCULATIONS

Ten substituted pyridinium-pyridine systems were studied in the middle and far infrared region as binary systems and as acetonitrile solutions. Furthermore, quantum chemical calculations of these systems were performed. All systems show an intense infrared continuum. The continuum does not change with the pK(a) of the protonated N-base in the pK(a) range 2.5-6.5. The hydrogen bond vibration nu(sigma) in the far infrared region was found in all systems, and its wavenumber changes are caused by the change of the mass of the N-base. Almost no change in the harmonic force constant of the hydrogen bond vibration is found. Quantum chemical calculations yield a double minimum proton potential with no change of the barrier height of the well. Therefore, all systems show almost the same proton polarizability, resulting in continua with the same intensity distribution. For the systems, effective hydrogen bond vibration masses are calculated with various methods, and the obtained results are compared.