The Hydration Structure of Carbon Monoxide by Ab Initio Methods

摘要

The solvation of carbon monoxide (CO) in liquid water is important forunderstanding its toxicological effects and biochemical roles. In this paper,we use ab initio molecular dynamics (AIMD) and CCSD(T)-F12 calculations toassess the accuracy of the Straub and Karplus molecular mechanical (MM) modelfor CO(aq). The CCSD(T)-F12 CO--H2O potential energy surfaces show that themost stable structure corresponds to water donating a hydrogen bond to the Ccenter. The MM-calculated surface it incorrectly predicts that the O atom is astronger hydrogen bond acceptor than the C atom. The AIMD simulations indicatethat CO is solvated like a hydrophobic solute, with very limited hydrogenbonding with water. The MM model tends to overestimate the degree of hydrogenbonding and overestimates the atomic radius of the C atom. The calculated Gibbsenergy of hydration is in good agreement with experiment (9.3 kJ/mol calc. vs10.7 kJ/mol exptl.). The calculated diffusivity of CO(aq) in TIP3P-model waterwas 5.19 x 10-5 cm2/s calc., more than double the experimental value of 2.32 x10-5 cm2/s