Hydrogen bond properties of Se in [ROH–Se(CH3)2] complexes (R = H, CH3, C2H5): matrix-isolation infrared spectroscopy and theoretical calculations

Abstract

Se is now considered as a potential centre for hydrogen bond interactions. The hydrogen bond acceptor ability of Se has been investigated in [ROH–Se(CH₃)₂] complexes (R = H, CH₃, and C₂H₅) using matrix-isolation infrared spectroscopy and electronic structure calculations. The first impression of the IR spectra of the hydrogen bond complexes of [ROH–Se(CH₃)₂] in N₂ and Ar matrices is presented here. Moreover, no spectroscopic data are available for the [HOH–Se(CH₃)₂] complex. Vibrational spectra in the OH stretching region indicate the formation of the [ROH–Se(CH₃)₂] complex under the matrix-isolation conditions. Comparison of the experimental spectra with the simulated vibrational frequencies at different levels of theory confirms the formation of the 1 : 1 cluster of [ROH–Se(CH₃)₂] stabilised by O–H⋯Se hydrogen bond interactions. Multiple conformers of the [CH₃OH–Se(CH₃)₂] complex having marginally different stabilisation energies have been predicted from electronic structure calculations and signatures of the same have been observed under the cold conditions of matrix isolation. Conformer specific assignment of the 1 : 1 cluster of [C₂H₅OH–Se(CH₃)₂] (anti and gauche forms) has been carried out in both the matrices. Concentration dependent experiments indicate the formation of higher order clusters and/or mixed clusters along with the formation of a 1 : 1 cluster for CH₃OH and C₂H₅OH. The nature of the selenium centred hydrogen bond has been delineated using AIM, NBO and energy decomposition analysis. A comparison of similar complexes of H₂O, CH₃OH, and C₂H₅OH with O, S and Se indicates that Se is not far away in hydrogen bond acceptor ability compared to O and S.