Formation of Semi - Covalent Bond in [ (

IR photodissociation (IRPD) spectra of [(N2O)nH2O] with n = 2–7 are measured in the 1100–3800 cm region. In parallel, the geometry optimization and the vibrational analysis are carried out at the B3LYP/6-311++G(d,p) level of theory. In the OH stretching (2400–3800 cm) region, the IRPD spectrum of the [(N2O)2H2O] ion shows a sharp band at 3452 cm and a broad one at around 2700 cm, which are assignable to the stretching vibrations of the free and hydrogen-bonded OH groups, respectively. The IRPD spectra of the [(N2O)nH2O] (n = 3–7) ions show no band of the free OH stretching vibration, indicating that both of the OH groups are hydrogen-bonded to solvent N2O molecules. The IRPD spectra of the n = 2–7 ions also show the ν1 and ν3 vibrations of the N2O components at around 1250 and 2200 cm, respectively. Comparison of the IRPD spectra with the calculated IR spectra suggests that the [(N2O)nH2O] cluster ions have an (N2O・H2O) ion core, in which the positive charge is delocalized over the H2O and N2O components, and that an intermolecular semi-covalent bond is formed between the oxygen atoms of H2O and N2O through the charge resonance interaction. Author to whom correspondence should be addressed ([email protected]).