Novel Insight into the Molecular Frustration of IFLPs Based on Boron-Functionalized Pyrimidines for CO₂ Sequestration

The emergence of frustrated Lewis pairs (FLPs) as organocatalysts for CO2 sequestration has opened a new dimension in this area. To date, various inter- and intramolecular frustrated Lewis pairs have been experimentally and theoretically explored for CO2 activation, still there is plenty of room for new insights into FLPs. Thus, in the present study intramolecular frustrated Lewis pairs (IFLPs) based on boron-functionalized pyrimidines have been proposed for CO2 activation and computationally investigated to gain new insights into the molecular frustration. The extensive natural bond orbital (NBO) analysis unveils an interesting relationship between the orbital charge transfer and the activity. The result shows that the greater the charge transfer between the acidic and basic sites, the higher will be the frustration in the molecule. Also, the presence of atoms bearing a lone pair attached to the acidic site relieves the frustration by charge transfer. Based on the orbital charge transfer, the predicted activity order for the proposed IFLPs is supported by the energetics for the reaction of CO2 with the IFLPs. Further, the activation strain analysis (ASA) provides a different viewpoint about the reactivities of the IFLPs and highlights the importance of the geometrical structure of the catalyst. Furthermore, the ab initio molecular dynamics (AIMD) uplights the reversibility of the formed products.