Extremely high polarizability of hydrogen bonds

Abstract

SCF-MO-LCGO calculations are performed for H502+ as a model illustrating the properties of a symmetrical hydrogen bond with a double-minimum potential well. The potential curves for the proton in the hydrogen bond with and without electrical fields for various 0-0 distances are calculated, along with the dipole moments, polarizabilities, hyperpolarizabilities, and transition moments of the OH stretching vibrations in the hydrogen bond. The total dipole moment is almost twice as large as the contribution of the proton alone for displacements which are not too large. The relation between the dipole moment and the displacement cannot be approximated linearly. Thus hyperpolarizabilities are of importance. The most important result obtained is that the polarizability is about two orders of magnitude larger than usual polarizabilities. The polarizability of unsymmetric hydrogen bonds may also be considerably larger. The large polarizability causes three interaction effects: an interaction between symmetrical hydrogen bonds via proton dispersion forces, an induced-dipole interaction of the hydrogen bonds with the anions and the dipole fields of the solvation molecules, and an interaction between the transitions in the hydrogen bond and other, especially the intermolecular, vibrations. These interactions cause the strong continuous absorption which is observed in the ir spectra with liquid systems containing such hydrogen bonds. The smaller polarizability of unsymmetrical hydrogen bonds causes band broadening.A continuous absorption was observed in the infrared spectrum on investigating acid and base solutions in the range of the fundamental vibrations1 2 and in the range of the overtones,3•4 567as well as with acidic and basic polyelectrolytes.5-8 This is caused in the acid solutions by H502+ groupings and with bases by H302_ groupings.8 The continuum is not only observed in the presence of these bonds between water molecules

Low-temperature (120 K) structure and vibrational spectrum of protonated proton sponge: the adduct of 1,8-bis(dimethylamino)naphthalene (DMAN) with 4,5- dicyanoimidazole (DCI)

“…Scheiner 29 showed that [NHN] bridges behave similarly to [OHO] , which are about 0.1 Å shorter. Janoschek et al 31 showed that of two possible transitions, 0 →0 À , and 0 →1 À , the latter is characterized by a probability that is the lower the higher is the barrier. If the distance between the 0 and 0 À levels is considerable, then we do not observe transitions from the 0 À levels.…”

“…A reduction in temperature causes an intensification of that band, particularly in the low-frequency wing. As follows from calculation, 31 the transition moment for the 0 →0 À transition is the larger the higher is the barrier. Thus the increase in population of low-lying local levels should lead to an enhancement of the integrated intensity, especially in the low-frequency wing.…”

The influence of neutral salts on the easily polarizable hydrogen bond of H5O2+ groupings in acid solutions

“…11, 12, 15a). The polarizability of a hydrogen bond decreases with increasing polarization of the hydrogen bond (13,14 to the local electrical fields in the solution. the external field can no longer polarize the hydrogen bond and induce a preferred direction of the H 5 0 1 structure diffusion.…”

Controlling low-temperature tunneling dynamics with external fields

“…The origin of the b(t) term is the coupling of an external electric field to the transition dipole moment of the tunneling object. In the delocalized basis it has the form [50][51][52] 2b͑t͒ϭm•E͑t͒.…”