PIO and IBO analysis to unravel the hidden details of the CO2 sequestration mechanism of aromatically tempered N/B-based IFLPs

Orbital and free energy landscape expedition towards the unexplored catalytic realm of aromatically modified FLPs for CO2 sequestration

The emergence of frustrated Lewis pairs (FLPs) has created a whole new dimension in the development of metal free catalysts for CO2 sequestration. Efforts have been made to enhance the catalytic activity of the FLPs. The aromatic modulation of the catalytic sites has been successfully demonstrated to enhance the activity towards CO2. Although various aromatically modified geminal FLPs have been investigated for CO2 capture, the catalytic space of these FLPs has not been fully resolved yet. Thus, to fulfil the knowledge gap in the understanding of the catalytic behaviour and to extend the concept of aromatically enhanced FLPs, in the present study all the possible combinations of aromatic and antiaromatic modulations of the acidic and basic sites have been proposed and examined using density functional theory based orbital analysis. Further to verify the results obtained from the orbital analysis and to fully explore the catalytic space of the proposed systems, free energy landscapes have been examined using metadynamics simulations. The detailed intrinsic bond orbital (IBO) and principal interacting orbital (PIO) analyses capture crucial details of the reactions. Furthermore, evolution of anisotropy of induced current density (AICD) along the reaction justifies the effect of aromatic/antiaromatic modulation on the catalytic sites. The results show that highly asynchronous mechanisms have been found due to the aromatic/antiaromatic modulations. The simultaneous favourable aromatic/antiaromatic modification on the acidic and basic sites may greatly reduce the CO2 activation barrier. The enhancement of the acidic character of the B atom in the intramolecular FLPs (IFLPs) leads to a thermodynamically more feasible reaction with stable CO2 adducts. The acidic site has been found to play a major role in controlling the kinetics and thermodynamics of the reaction. This study provides valuable insights into the catalytic realm of the aromatically modified FLPs, which can be utilized to design more efficient and specific next-generation FLPs.

(Pyridin-2-ylmethyl)triel Derivatives as Masked Frustrated Lewis Pairs. Interactions and CO2 -Sequestration

The isolated (pyridin-2-ylmethyl)triel derivatives (triel=B, Al and Ga) show an intramolecular N⋅⋅⋅Tr triel bond as shown by compounds found in the Cambridge Structural Database and DFT calculations. The possibility to use them as masked frustrated Lewis pairs (mFLP) has been explored theoretically concerning their reaction with CO2 . The adduct formation proceeds in two steps. In the first one, the (pyridin-2-ylmethyl)triel derivatives break the intramolecular N⋅⋅⋅Tr bond assisted by CO2 and in the second step the adduct is formed with Tr-O and N-C covalent bonds. The corresponding energy minima and transition states (TS) of the reaction have been characterized and analyzed. The distortion/interaction model analysis of the stationary points indicates that the whole process can be divided in two parts: reorganization of the mFLP in the first steps of the reaction while the reaction with CO2 (associated to the distortion of this molecule) is more important in the formation of the final adduct. In all cases studied, the final products are more stable than the starting molecules that combine with reasonable TS energies indicating that these reactions can occur.