15min:

XU WANG, JASON F. FULLER AND DONG-SHENG YANG, Department of Chemistry, University of Kentucky, Lexington, KY, 40605-0055.

Single-photon pulsed field ionization-zero electron kinetic energy (PFI-ZEKE) photoelectron spectroscopy has been used to study the complexes of copper with pyridine (C₅H₅N), 2,2'-bipyridine (C₁₀H₈N₂) and 1,10-phenanthroline (C₁₂H₈N₂). In all cases, adiabatic ionization potentials and Cu-ring vibrational frequencies were measured from the ZEKE spectra. Additional ring-based vibrations were observed for Cu-bipyridine and -phenanthroline. All three Cu complexes were determined to be in C_2v symmetry with the metal atom bonding to the nitrogen of pyridine or two nitrognes of the polypyridines. Since the most stable conformation of the free 2,2'-bipyridine ligand is coplanar with trans -standing nitrogens, Cu coordination has induced a ring rotation of 180^o to bring the two nitrogens in a cis configuration.