Size-selected infrared predissociation spectroscopy of neutral and cationic formamide-water clusters: Stepwise growth of hydrated structures and intracluster hydrogen transfer induced by vacuum-ultraviolet photoionization

作者：Sakai Daichi; Matsuda Yoshiyuki^*; Hachiya Masaki; Mori Mayumi; Fujii Asuka; Mikami Naohiko

来源：Journal of Physical Chemistry A, 2008, 112(30): 6840-6849.

DOI：10.1021/jp800743b

Vibrational spectroscopy of size-selected formamide-water clusters, FA-(H2O)(n), n = 1-4, prepared in a supersonic jet is performed with vacuum-ultraviolet-ionization detected-infrared predissociation spectroscopy (VUV-ID-IRPDS). The cluster structures are determined through comparisons of the observed IR spectra with theoretical calculations at the MP2/6-31++G** level. The FA-(H2O)(n), n = 1-3, clusters have ring-type structures, where water molecules act as both single donor and single acceptor in the hydrogen-bond network between the amino and carbonyl groups of FA. For FA-(H2O)(4), on the other hand, the absence of the free NH stretching vibration indicates formation of a double ring type structure, where two NH bonds of the amino group and the carbonyl oxygen of FA form hydrogen bonds with water molecules. An infrared spectrum of the formamide-water cluster cation, [FA-H2O](+), is also observed with infrared predissociation spectroscopy of vacuum-ultraviolet-pumped ion (IRPDS-VUV-PI). No band is observed for the free OH stretches of neutral water. This shows [FA-(HO)-O-2](+) has such a structure that one of the hydrogen atoms of the water moiety is transferred to the carbonyl oxygen of FA(+).

• 出版日期2008-7-31