Electron density topological analysis of the C-H ••• O anti-hydrogen bond in the fluoroform-oxirane complex

The C-H . . . O interaction in the fluoroform-oxirane complex has recently been shown to exhibit features of anti-hydrogen bonding, which is characterized by a shortening of the C-H bond and a blue-shift of the C-H stretching frequency. We present here the results of a topological analysis of the electron density following the theory of atoms in molecules in order to gain insight into the nature of the anti-hydrogen bond. The study is focused on the two energetically most stable complexes, which correspond to a planar complex with a colinear C-H . . . O bond, and a non-planar structure with a bent C-H . . . O bond. The origin of the anti-H bond is discussed in terms of the electron density changes induced upon complexation. (C) 1999 Elsevier Science B.V. All rights reserved.