Effect of cluster of protic pyrazolium ionic liquids or epoxides on the cycloaddition of CO2

The reaction mechanism for the coupling reaction of carbon dioxide with epoxides catalyzed by single-component protic pyrazolium ionic liquids has been extensively elucidated. However, the calculated barrier heights are not accurate enough to predict the catalytic results for a series of ionic liquids with similar structures. The cluster of protic pyrazolium ionic liquids is regarded as catalyst to consider the effect of interactions among ionic liquids on the barrier heights. Moreover, the ionic liquids or epoxides would also affect the barrier heights as the environmental factors, which is also considered by ONIOM method. When the environmental influence is involved, the accuracy is greatly improved. The analysis of interactions between ionic liquid and reactant indicates that the electrophilic attacking plays the more critical role than nucleophilic attacking. (C) 2019 Elsevier B.V. All rights reserved.