Ab initio Study on Structures, Energies and Vibrations of Methylammonium-(water)n (n=1-3) Complexes

Bulletin of the Korean chemical society

Doo Wan Boo¹  Kwang-Yon Kim¹  Ung-In Cho¹ 

关键词: Ab initio;    Solvation;    Hydrogen bond cooperativity;    Many-body interaction.;   

DOI  :  

学科分类：化学（综合）

来源: Korean Chemical Society

【 摘 要 】

The B3LYP/6-31+G(d) calculations on the structures, the hydration energies, the thermodynamic functions, and the vibrations of various isomers of CH3NH3+ (H2O)n (n=1, 2, 3) have been performed. Results indicate that not only the direct charge-dipole two-body interactions, but also the three-body interactions involving water-water hydrogen bonding and indirect charge-dipole interactions play significant roles in determining the overall structures and relative stabilities of isomers. Particularly, the hydrogen bond cooperativity plays a critical role in stabilizing the cyclic isomer vs. tripod isomer for n=3. The calculated thermodynamic functions match well the recent experimental thermodynamic functions by Meot-Ner within 1 kcal/mol. The trends of calculated hydration energies and vibrational frequencies correlate excellently with the local many-body hydrogen bond interactions in each isomer. Finally, it is proposed that the distinct spectral patterns of bonded-NH, bonded-OH, and free OH stretches can be used as fingerprints in identifying the structural isomers that contribute to the vibrational predissociation spectra.

【 授权许可】

Unknown