H. Tachikawa et al., Vibrational frequency-shifts of H2O caused by complex formation with a molecular cation: a density functional study, PHYS CHEM P, 3(15), 2001, pp. 3052-3056
Structure and vibrational frequencies of the benzene-water complex cation [
BzH(2)O](+) have been calculated by means of density functional theory (B3L
YP calculation). A planar structure with a C-s symmetry, in which all heavy
atoms are located on a molecular plane, was obtained as the most stable fo
rm of the [BzH(2)O](+) cation. Hydrogen atoms of the water molecule are loc
ated above and below the molecular plane. From the present calculations, it
was predicted that vibrational frequencies of symmetric and asymmetric O-H
stretching modes of H2O (nu (1) and nu (3) modes, respectively) are red-sh
ifted from those of a free H2O by the formation of a complex, whereas the H
-O-H bending mode (nu (2) mode) is blue-shifted. Infrared intensities of th
e three modes of H2O were significantly increased by the complex formation.
Similar features were obtained for the ethylene-H2O complex cation [C2H4-H
2O](+). The origin of the frequency-shifts is discussed on the basis of the
oretical results. The hydrogen-hyperfine coupling constants of the complex
cations were also predicted theoretically.