Adsorption of small molecules with the hydroxyl group on sodium halide cluster ions.

We have investigated adsorption of molecules with hydroxyl group, ROH, on sodium halide cluster ions, Na(n)X(n-1)(+) (X = F and I, n = 10-17) by mass spectrometry and by theoretical calculations. From analysis of the cluster ion intensities, the adsorption of one water molecule (R = H) is most efficient for Na(13)X(12)(+), whose structure has a NaX defect from a 3 x 3 x 3 cubic structure of n = 14. This result suggests that the defect has an important role in the adsorption reaction. However, it is also found that the reactivity diminishes with increasing bulk size of the R group from H to CH(3), (CH(3))(2)CH, and (CH(3))(3)C. These results imply that the adsorption reactivity is dominated by steric hindrance; the smaller molecules are adsorbed inside the basket structures of Na(13)X(12)(+). Reactivity dependence on the basket size is also discussed by comparing the results of Na(n)F(n-1)(+) and Na(n)I(n-1)(+).

Infrared photodissociation spectroscopy of Al(+)(CH(3)OH)(n) (n = 1-4).

Infrared photodissociation spectra of Al(+)(CH(3)OH)(n) (n = 1-4) and Al(+)(CH(3)OH)(n)-Ar (n = 1-3) were measured in the OH stretching region, 3000-3800 cm(-1). For n = 1 and 2, sharp absorption bands were observed in the free OH stretching region, all of which were well reproduced by the spectra calculated for the solvated-type geometry with no hydrogen bond. For n = 3 and 4, there were broad vibrational bands in the energy region of hydrogen-bonded OH stretching vibrations, 3000-3500 cm(-1). Energies of possible isomers for the Al(+)(CH(3)OH)(3),4 ions with hydrogen bonds were calculated in order to assign these bands. It was found that the third and fourth methanol molecules form hydrogen bonds with methanol molecules in the first solvation shell, rather than a direct bonding with the Al(+) ion. For the Al(+)(CH(3)OH)(n) clusters with n = 1-4, we obtained no evidence of the insertion reaction, which occurs in Al(+)(H(2)O)(n). One possible explanation of the difference between these two systems is that the potential energy barriers between the solvated and inserted isomers in the Al(+)(CH(3)OH)(n) system is too high to form the inserted-type isomers.

Size-dependent structures of NanI+n-1 cluster ions with a methanol adsorbate: a combined study by photodissociation spectroscopy and density-functional theory calculation.

Methanol adsorption sites on NanI+n-1 ions were investigated. Photoexcitation to charge-transfer states of NanI+n-1 (methanol) predominantly produces two fragment ions: Nan-1I+n-2 (methanol) (neutral NaI loss) and Nan-1I+n-2(neutral NaI and methanol loss), without forming NanI+n-1 (methanol loss). The relative intensities of these fragments are correlated with the geometries and binding energies.