15min:

BRADFORD R. SOHNLEIN, YUXIU LEI AND DONG-SHENG YANG, Department of Chemistry, University of Kentucky, Lexington, KY 40506-0055.

In the gas phase, the two phenyl rings of biphenyl (C₁₂H₁₀) are twisted with respect to each other by about 45⁰. This rotation of the phenyl rings about the bridging C-C bond is driven by -conjugation of the phenyl rings and steric repulsions between the ortho hydrogen atoms. We have discovered that metal coordination induces phenyl ring rotation and bending to form a clam structure, where a metal atom is clamped by the two phenyl rings. In this talk, we will present examples of how this clam-type structure was identified using pulsed field ionization zero electron kinetic energy photoelectron spectroscopy and density functional theory calculations. The examples include the biphenyl complexes of scandium (Sc), lanthanum (La), and titanium (Ti), which are synthesized by laser vaporization molecular beam techniques. All these complexes are determined to have C_2v symmetry. The ground electronic states are ²B₁ for the neutral Sc- and La-C₁₂H₁₀ complexes and ¹A₁ for the corresponding ions. The ground electronic states of Ti- and Ti⁺-C₁₂H₁₀ are ¹A₁ and ²B₁, respectively. In addition, we will discuss the binding effects of metal atomic size and electron configuration in these molecular systems.