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We have reported for the first time designed silylene superbases involving intramolecular H(+)···π interaction using density functional theory (DFT) calculations. The non-covalent interactions augment the proton affinity values by 13 kcal mol−1 in the designed superbase (1) compared to the acyclic silylene, [:Si(NMe2)2]. These divalent Si(II) compounds can act as powerful neutral organic superbases in gas and solvent phases. The DFT calculations performed at the B3LYP/6-311+G**//B3LYP/6-31+G* level of theory showed that the gas phase proton affinity of the paracyclophane based silylene superbase (8) reaches up to ~271.0 kcal mol(−1), which is the highest in paracyclophane Si(II) compounds. In tetrahydrofuran solvent medium, the calculated proton affinity of 8 was found to be 301.4 kcal mol(−1). The paracyclophane-based silylene systems are used for binding with small alkali metal ions. The calculated results showed that these systems selectively bind to lithium ions over sodium ions due to the small size of lithium ions which is well fitted in the space between the silicon atom and the phenyl ring. Furthermore, we have used the lithiated silylene 1 and 9 (which exhibits bis-protonation) for gas storage (CO and CO2). The calculated results showed both the lithiated silylene 1 and 9 bind preferentially to CO2 than CO. The calculated gravimetric density of CO2 is found to be 26.97 wt% for 9-Li2–(CO2)4. The energy decomposition analysis (EDA) has been performed to investigate the role of various contributing factors to the total binding strength of the CO2 or CO molecules with lithiated silylene superbases. EDA reveals that the electrostatic energy and polarization energy are the major driving force for higher total interaction energy of the lithiated-silylene–CO2 complex than the lithiated-silylene–CO complex. The lithiated silylene systems showed a higher binding energy with CO2 than the previously reported imidazopyridamine at the same level of theory. These results suggest that the lithiated silylene systems can be used as a more efficient CO2 storage material than the aforementioned system. The calculated desorption energies per CO2 and CO (ΔEDE) also indicate the recyclable property of the materials.

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The efficacy of S-omeprazole as a proton pump inhibitor compared with that of its enantiomer R-omeprazole is studied using density functional theoretical calculations. The pharmacokinetic studies suggest that the efficacy of S-omeprazole presumably depends on metabolic pathway and excretion from the human body. The density functional theory calculations at SMD-B3LYP-D3/6-311+G(d,p)/LANL2DZ//B3LYP/6-31G(d)/LANL2DZ with triradicaloid model active species, [PorFe(SH)O], of CYP2C19 enzyme with high-spin quartet and low-spin doublet states demonstrate C-H bond activation mechanism through a two-state rebound process for the hydroxylation of R-omeprazole and S-omeprazole. The calculated activation free energy barriers for the hydrogen abstraction are 15.7 and 17.5 kcal/mol for R-omeprazole and S-omeprazole, respectively. The hydroxylation of R-omeprazole and S-omeprazole is thermodynamically favored; however, the hydroxylated intermediate of S-omeprazole further disintegrates to metabolite 5- O-desmethylomeprazole with a higher kinetic barrier. We have examined the sulfoxidation of S-omeprazole to omeprazole sulfone metabolite by CYP3A4, and the observed activation free energy barrier is 9.9 kcal/mol. The computational results reveal that CYP2C19 exclusively metabolizes R-omeprazole to hydroxyomeprazole, which is hydrophilic and can easily excrete, whereas CYP3A4 metabolizes S-omeprazole to lipophilic sulfone; hence, the excretion of this metabolite would be relatively slower from the body. The spin density analysis and molecular orbital analysis performed using biorthogonalization calculations indicate that R-omeprazole favors high-spin pathway for metabolism process whereas S-omeprazole prefers the low-spin pathway.