7-Azaindole and Its Clusters with Ar, CH4, H2O, NH3, and Alcohols: Molecular Geometry and Nature of the First Excited Singlet Electronic State.

摘要

Mass resolved excitation vibronic spectra of jet-cooled 7-azaindole and its clusters with Argon, Methane, Ammonia, H2O, D2O, and Methyl Alcohol, Ethyl Alcohol are reported and analyzed with regard to molecular and cluster geometry and the nature of the first excited sinlet state. Large changes in the various spectra are observed upon clustering and upon deuteration of 7-azaindole. The observed vibronic spectra of both 7-azaindole and its clusters can be rationalized with two general assumptions: 1. the hydrogen attached to the pyrrole nitrogen of 7-azaindole is out of the molecular plane in the first excited singlet state; and 2. the observed spectra are characterized by strong n(Pi) *-Pi(Pi)* mixing not completely removed by the clustering. MOPAC 5 calculations of molecular geometry suggest that the S(1) state is nonplanar. Additional cluster potential energy calculations suggest that the formation of cyclic hydrogen bonded clusters is not likely for these gas phase 1:1 or 1:2 7-azaindole/solvent clusters: the major gas phase solvent clustering probably takes place at the Pi-system of the 7-azaindole molecule. Keywords: Molecular orbital package, MNDO(Modified Neglect of Differential Overlap). (aw)