15min:
STRUCTURAL STUDIES OF PYRROLE-BENZENE COMPLEXES BY CHIRPED-PULSE ROTATIONAL SPECTROSCOPY.

SIMON LOBSIGER, CRISTOBAL PEREZ, DANIEL P. ZALESKI, NATHAN A. SEIFERT, BROOKS H. PATE, Department of Chemistry, University of Virginia, McCormick Rd., Charlottesville, VA 22904; CHANTAL PFAFFEN, MARIA A. TRACHSEL, SAMUEL LEUTWYLER, Departement für Chemie und Biochemie, Universität Bern, Freiestrasse 3, 3012 Bern, Switzerland.

Non-covalent intermolecular interactions are important in structural biology. The N-H cdots pi hydrogen bond between amino acid side chains is an important structural determinant and highly affects the secondary structure of proteins. The pyrrole-benzene complex can be viewed as a model system for studying these fundamental interactions. Previous IR and UV spectroscopic studies of the pyrrole-benzene complex by Dauster et al. and Pfaffen et al. support a T-shaped structure with an N-H cdots pi hydrogen bond to the benzene ring.

In order to obtain accurate structural information we have investigated the broadband rotational spectrum of the supersonic-jet cooled complexes of pyrrole with benzene and benzene- d 1 in the 2-18 GHz frequency range. In addition to the hetero dimer we have also observed the two cyclic mixed trimers (pyrrole)2-benzene and pyrrole-(benzene)2.