Anti-hydrogen bond between chloroform and fluorobenzene

• Published in: Chemical physics letters Vol. 299; no. 2; pp. 180 - 186
• Main Authors: Hobza, Pavel, Špirko, Vladimı́r, Havlas, Zdeněk, Buchhold, Konstantin, Reimann, Bernd, Barth, Hans-Dieter, Brutschy, Bernhard
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 06.01.1999
• ISSN: 0009-2614; 1873-4448
• DOI: 10.1016/S0009-2614(98)01264-0

Accurate theoretical calculations (ab initio MP2/6-31G * counterpoise-corrected gradient optimization, harmonic and anharmonic vibrational analysis) on the fluorobenzene⋯chloroform complex predict a new type of bonding, termed the anti-hydrogen bond. This bond distinguishes itself by the contraction of the C–H bond of chloroform and a blue shift of the corresponding stretching frequency, i.e. features opposite to those characteristic for a hydrogen bond. The predicted blue shift was confirmed experimentally by double-resonance infrared ion-depletion spectroscopy. The calculated blue shift of the chloroform C–H stretching frequency (12 cm −1) agrees with the experimental value of 14 cm −1. The anti-hydrogen bond originates from the dispersive interaction between molecules (contrary to the hydrogen bond which is of electrostatic origin). It plays a significant role in benzene-containing molecular clusters and is expected to be of consequence for the structure of biomolecules.