Clamshell structure of Sc(biphenyl) from high resolution photoelectron spectroscopy

Sc(biphenyl) is produced in a laser vaporization molecular beam source and characterized by pulsed field ionization-zero electron kinetic energy (ZEKE) photoelectron spectroscopy and density functional theory. The theory predicts two low-energy isomers: a clamshell structure with Sc binding to both phenyl rings and a half-sandwich structure with Sc binding to single ring. The joint experimental and theoretical study shows that the Sc(biphenyl) complex prefers the clamshell structure with a twelve-fold binding mode. From the free ligand to the clamshell structure of the complex, phenyl rings first rotate to become coplanar, then bend toward the Sc atom, and finally are clamped in place by Sc binding.