TY - JOUR

T1 - A cryosolution FTIR and ab initio study of the blue shifting C-H···F hydrogen bonded complexes F2ClCH · FCD3 and Cl2FCH · FCD3

AU - Rutkowski, Konstantin S.

AU - Herrebout, Wouter A.

AU - Melikova, Sonia M.

AU - van der Veken, Benjamin J.

AU - Koll, Aleksander

PY - 2008/12/10

Y1 - 2008/12/10

N2 - The mid (4000-500 cm-1) and near (10,000-4000 cm-1) infrared spectra of solutions in liquid krypton containing mixtures of F2ClCH and FCD3 or of Cl2FCH and FCD3 show the formation of 1:1 complexes. MP2/6-311++G(2d, 2p) ab initio calculations suggest that the main interaction responsible for the formation of the complexes is the hydrogen bond between the haloform C-H bond and the fluorine atom of the base molecule. The observation of blue shifts upon complexation of 24.8, 51.5 and 87 cm-1 for the fundamental, the first and the second overtone of the haloform ν1 in F2ClCH, and of 25.0, 50.2 and 87 cm-1 in Cl2FCH show that in either case the hydrogen bond is of the blue-shifting type. Upon complexation the intensity of the fundamental ν1 in F2ClCH decreases by a factor of approximately 5, while that in Cl2FCH increases, by a factor of approximately 4. At the same time, the intensities of the first and second overtones reveal only modest decreases. The MP2/6-311++G(2d, 2p) calculations predict the existence of more than one conformer for either complex. No spectral evidence for conformational equilibria in the complexes has been detected. One-dimensional anharmonic model calculations have been made to simulate the blue shift and intensity behaviour of the haloform ν1 vibrations. For both complexes these calculations reproduce the experimental data with reasonable success.

AB - The mid (4000-500 cm-1) and near (10,000-4000 cm-1) infrared spectra of solutions in liquid krypton containing mixtures of F2ClCH and FCD3 or of Cl2FCH and FCD3 show the formation of 1:1 complexes. MP2/6-311++G(2d, 2p) ab initio calculations suggest that the main interaction responsible for the formation of the complexes is the hydrogen bond between the haloform C-H bond and the fluorine atom of the base molecule. The observation of blue shifts upon complexation of 24.8, 51.5 and 87 cm-1 for the fundamental, the first and the second overtone of the haloform ν1 in F2ClCH, and of 25.0, 50.2 and 87 cm-1 in Cl2FCH show that in either case the hydrogen bond is of the blue-shifting type. Upon complexation the intensity of the fundamental ν1 in F2ClCH decreases by a factor of approximately 5, while that in Cl2FCH increases, by a factor of approximately 4. At the same time, the intensities of the first and second overtones reveal only modest decreases. The MP2/6-311++G(2d, 2p) calculations predict the existence of more than one conformer for either complex. No spectral evidence for conformational equilibria in the complexes has been detected. One-dimensional anharmonic model calculations have been made to simulate the blue shift and intensity behaviour of the haloform ν1 vibrations. For both complexes these calculations reproduce the experimental data with reasonable success.

KW - Anharmonicity

KW - Blue shifting hydrogen bond

KW - C-H···B interactions

KW - ClFCH

KW - FClCH

KW - FCD

KW - Liquid krypton

UR - http://www.scopus.com/inward/record.url?scp=56949101448&partnerID=8YFLogxK

U2 - 10.1016/j.chemphys.2008.09.009

DO - 10.1016/j.chemphys.2008.09.009

M3 - Article

AN - SCOPUS:56949101448

VL - 354

SP - 71

EP - 79

JO - Chemical Physics

JF - Chemical Physics

SN - 0301-0104

IS - 1-3

ER -