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Density functional theory (DFT) was used to investigate the acidity of the various silica alkyl sulfonic acids. In this regard, cluster models with various alkyl spacer lengths were selected to mimic the surface of silica gel. The effects of distance from the surface and the role of hydrogen bond (H–bond) on the ΔHacidityvalues of these catalysts were investigated. DFT calculations revealed that a notable gap of ΔHacidityvalues exists between the structures considering lateral hydrogen bonding with the surface of the silicaHB structureand the structures with omitted surface interactions (non-HB structures). Natural bonding orbital (NBO) and quantum theory of atoms in molecules (QTAIM) analyses were carried out to obtain detailed information about the nature of the H–bonds. [ABSTRACT FROM AUTHOR]

Silica gelâ€confined ionic liquid (IL) is a class of heterogeneous catalysts with broad catalytic applications. Leaching of the IL from the surface of the support is the major drawback of these catalysts, which reduce the catalyst efficiency during the chemical reactions. To investigate the effect of the hydrogen bonding on the leaching phenomena, the interaction between the 1â€ethylâ€3â€methylimidazoliumâ€based IL with various anions (Clâˆ', Brâˆ', HSO4âˆ', NO3âˆ', BF4âˆ', and PF6âˆ') and the surface of the silica gel were studied using density functional theory. Hence, a hydroxylated cageâ€like cluster of silica gel, Si4O6(OH), was selected to mimic the surface. The values of Î'Einteraction show that ILs with halogen counter ions have stronger interactions than that of the IL with BF4âˆ' and PF6âˆ' counter ions. We also carried out stirringâ€'filtration method for some prepared samples of IL@silica to experimentally explore the leaching phenomena. The results show good agreement with computational achievements. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) method and B3LYP/6-311++G(d,p) basis set were used to determine coordination geometries, binding strength, and metal ion affinity (MIA) for interaction of 2′-deoxythymidine (dT) with alkali metal cations including , and . Calculations demonstrated that the interaction of dT with these cations is tri-coordinated η (O2, O4′, O5′). Among these cations, cation exhibited the most tendency for interaction with dT. Cations via their interaction with dT can affect the N-glycosidic bond length, the values of pseudorotation of the sugar ring, the orientation of base unit with respect to sugar ring and the acidity of O5′H, O3′H, and N3H groups in 2′-dT nucleoside. Natural bond orbital (NBO) analysis was performed to calculate the charge transfer and natural population analysis of the complexes. Quantum theory of atoms in molecules (QTAIM) was also applied to determine the nature of interactions. It was shown that in these complexes, (dT-, dT-, and dT-), the bonds are an electrostatic (closed-shell) interaction in the nature. [ABSTRACT FROM AUTHOR]