The IR spectrum of 7-azaindole monomer, 7-azaindole reactive and nonreactive dimers, and (7-azaindole)(H2O) n (n = 1−3) clusters in a supersonic jet from 2600 to 3800 cm-1 have been measured using IR dip spectroscopy. The vibrational transitions in the ground state were clearly observed and were assigned to the CH and NH stretching vibrations of 7-azaindole and the OH stretching vibrations of water molecules in the clusters. The observed IR spectra of 7-azaindole monomer and (7-azaindole)(H2O) n (n = 1−3) clusters were compared to theoretical ones obtained by ab initio MO calculations. From a comparison, it is concluded that (7-azaindole)(H2O) n (n = 1−3) clusters have a ring structure due to a cyclic hydrogen-bond network. This conclusion is consistent with an analysis based on high-resolution spectroscopy. Similarly, the IR dip spectrum suggests that the 7-azaindole reactive dimer has a cyclic hydrogen-bond network, forming a symmetric planar structure. It is strongly suggested from the IR spectrum and the ab initio calculations that the nonreactive dimer contains a water molecule between 7-azaindole molecules.

No abstract

The IR spectrum of cis-1-naphthol, trans-1-naphthol, and 1-naphthol‚(H 2 O) n (n ) 1-3) clusters has been measured by the IR dip spectroscopy in a supersonic jet. The spectra show clear vibrational structures of the monomers and the clusters in the energy region from 3000 to 3800 cm -1 . Observed vibrational transitions are assigned to the OH stretching vibrations of 1-naphthol and waters in the clusters. The size dependence of the IR bands and the cluster geometries are analyzed by using the ab initio MO method at the MP2/6-31G level. From the comparison between the observed and calculated IR spectra, we have concluded that the 1-naphthol acts as the proton donor and a cyclic hydrogen-bond network is formed in the n ) 2 and 3 clusters.