Guanidinium cation-water clusters

The gas-phase structure, stabilities, and vibrational stretching frequencies of hydrated guanidinium cation (Gdm(+)W(n), n = 1-6) have been calculated using ab initio and density functional theory methods. It is found from the optimized geometries of various clusters that water molecules interact with the Gdm(+) through double H-bond (N-H...O) acceptor model. Evidences reveal that the sequential binding energies of Gdm(+)W(n) clusters are similar to that of hydration of monovalent alkali metal ions and isoelectronic protonated carbonic acid. The calculated binding energy of the clusters increases with the increase in the number of water molecule. Results elicit that the stability of completely and symmetrically hydrated clusters is the highest when compared to that of partially and asymmetrically hydrated ones. It is interesting to note from the findings that the symmetrically hydrated Gdm(+)W(6) cluster forms a tripod structure. The