Spectroscopic Observation of Ion-Induced Water Dimer Dissociation in the X^-·(H₂O)₂ (X = F, Cl, Br, I) Clusters

Abstract

We elucidate the interplay between the ion−water and water−water interactions in determining the structures of halide ion−water clusters using infrared spectroscopy, interpreted with ab initio theory. Vibrational predissociation spectra of the X-·(H2O)2·Ar m (X = F, Cl, Br, I) clusters in the OH stretching region (2300−3800 cm-1) reveal a strongly halide-dependent pattern of bands. These spectra encode the incremental weakening of the interaction between the water molecules with the lighter halides, finally leading to their complete dissociation in the fluoride complex. A consequence of this is that the F-·(H2O)2 cluster is likely to be a floppy system with high amplitude zero point motion, in contrast to the pseudo-rigid behavior of the other halide hydrates.

Ions at the Air/Water Interface

“…Also, one needs about six waters in order to distinguish between an interior and surface located ion. Therefore, we exclude from our discussion the large body of studies 4 concerning the structure of small water-halide clusters with less than six water molecules [10][11][12][13][14][15][16][17][18][19][20].…”

Hydrogen bonds and ionic interactions in Guanidine/Guanidinium complexes: a computational case study

“…His calculations support the idea that the quantum mechanically computed relative energies are mostly determined by Coulombic interactions. Xantheas and Johnson [21,22] have made the use of this concept to study cooperativity in water clusters. Additionally, attempts have been made to better describe the protein/nucleic acid interactions by developing an HB potential that accounts not only for the known Coulombic interactions (mostly by means of the phosphate groups), but also with the directionality inherent to the HBs [23].…”

Study of coulomb explosion and dissociation channels in dicationic argon clusters: a study based on stochastic optimization

“…Theoretical work on these systems has also been reported in which workers use either model empirical potentials or high-level quantum chemical calculations to arrive at the correct structures of these clusters, and once the structure is found out, do a normal mode calculation to get the IR spectrum. A close resemblance of the theoretically calculated spectrum indicates the essentially good quality of the empirical intermolecular potential energy function in the sense that it has been able to incorporate all major interactions in operation [15][16][17]. Another active area of research involving both atomic and molecular clusters is the phenomenon of coulomb explosion.…”