The fluoroform⋯ethylene oxide complex exhibits a C–H⋯O anti-hydrogen bond

A new, recently discovered type of intermolecular bond, called an anti-hydrogen bond, is found in the fluoroform⋯ethylene oxide complex. The complex structure and properties were predicted on the basis of counterpoise-corrected gradient optimization performed at a correlated ab initio level. Formation of the C–H⋯O anti-hydrogen bond is manifested by an 0.1 pm contraction of the C–H bond and a significant (∼30 cm−1) blue-shift of the C–H stretching frequency, accompanied by a lowering of intensity of the respective vibration. In contrast to previous cases, the studied C–H⋯O anti-hydrogen bond originates from dipole–dipole electrostatic interaction. The fluoroform molecule a has properly oriented dipole moment vector, the size of which is further enhanced by the C–H bond contraction.