Features of three-centered hydrogen bonding in di(vinylpyrrolyl)pyridine and di(vinylpyridyl)-pyrrole from the
ab initio calculation data and QTAIM analysis
A. V. Vashchenko, A. V. Afonin
A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Division, Russian Academy of Sciences, Irkutsk
Keywords: three-centered hydrogen bond, rocking vibrations, ab initio calculations, QTAIM, 2,6-bis-[2-(1Н-pyrrole-2-yl)-vinyl]-pyridine, 2,5-bis-[2-(pyridine-2-yl)-vinyl]-1Н-pyrrole
Abstract
Within the calculation at MR2/6-311++G (d,p) and the analysis was conducted QTAIM structural investigation of 2,6-bis [2-(1H-pyrrol-2-yl) vinyl]-pyridine and 2,5-bis [2-(pyridin-2-yl) vinyl]-1H-pyrrole. Found that the molecule is formed in a first symmetrical three-center hydrogen bond, the components of which are substantially weakened in comparison with two-centered H-bond in the Z-isomer of 2-[2-(1H-pyrrol-2-yl) vinyl]-pyridine. This weakening is due to the steric interaction of the two hydrogen bond donors. At the same time, more stringent steric conditions for forming the three-center interaction 2,5-bis [2-(pyridin-2-yl) vinyl]-1H-pyrrole lead to an actual breaking of one of the three-center hydrogen bond component involving increased preserved components. This makes the possibility of pendulum oscillation of the hydrogen bond in the latter case by alternately entering the hydrogen bond acceptors in the coordination sphere of the hydrogen atom.
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