THE MICROWAVE SPECTRUM AND STRUCTURE OF A HYDROGEN BONDED PYRROLE-WATER COMPLEX

Abstract

Twelve a-type rotational transitions of a pyrrole-water van der Waals complex were observed using a Fourier-transform microwave spectrometer; these transitions were split into doublets by an internal motion of the complex. Microwave spectra were recorded for the $^{15}N$ isotopomer and the triply deuterated complex as well as the normal isotopic species. The spectra of these isotopomers were found to be consistent with a structure in which the pyrrole acts as a hydrogen bond donor. Quadrupole hyperfine structure of the normal isotopic species was assigned and discussed in terms of the electronic environment of the $^{14}N$ nucleus. Stark effect splittings of the $^{15}N$ substituted complex were measured and fit to obtain $\mu_{a} =4.35 (6)$ Debye. Likely pathways for the internal motion are discussed in terms of spin statistical weights and model potentials calculated using the STO-3G and 6-31G basis sets.