Conformational Changes of trans-1,2-Dichlorocyclohexane Adsorbed in Zeolites Studied by FT-Raman Spectroscopy and Molecular QM/MM Simulations

The conformational behavior of trans-1,2-dichlorocyclohexane (T12D) adsorbed inside zeolites with Faujasite structure (FAU) including sodium Y (Na–Y) and siliceous Y (Si–Y) was investigated by FT-Raman spectroscopy and molecular simulations. The results have clearly shown that the conformational and dynamic properties of T12D strongly depend on the presence of charge-balancing cations as well as Si/Al ratio. Upon loading into Na–Y, the population of the diequatorial (ee) conformer increases compared with pure T12D liquid due to the strong interaction with the extra-framework Na+ ions. Molecular simulations of T12D in Na–Y and Si–Y have also been carried out. The T12D molecule was modeled by quantum and semiempirical quantum chemistry methods and embedded in a zeolite framework that was described by empirical force field. Conformational changes were sampled using quantum mechanics/molecular mechanics molecular dynamics and replica exchange molecular dynamics. Molecular simulations revealed that the ee conf...