Binding sites, rotational conformers, and electronic states of Sc–C6H5X (X=F, CH3, OH, and CN) probed by pulsed-field-ionization electron spectroscopy

Abstract

Scandium (Sc) complexes of fluorobenzene (C(6)H(5)F), toluene (C(6)H(5)CH(3)), phenol (C(6)H(5)OH), and benzonitrile (C(6)H(5)CN) are produced in a laser-vaporization molecular beam source. These complexes are studied with pulsed-field-ionization zero-electron-kinetic-energy (ZEKE) spectroscopy and density functional theory calculations. Adiabatic ionization energies and low-frequency metal-ligand and ligand-based vibrational modes are measured from the ZEKE spectra. Metal binding sites and strengths and electronic states are obtained by comparing the ZEKE spectra with the theoretical calculations. The ionization energies of Sc-C(6)H(5)X (X = F, CH(3), OH, and CN) follow the trend of CN > F > OH > CH(3), whereas the bond energies are in the order of CN > CH(3) approximately OH > F. The metal-ligand stretching frequency of Sc(+)-C(6)H(5)CN is nearly twice as those of the other three complexes. All neutral complexes are in low-spin doublet ground states and singly-charged cations are in singlet states. The preferred Sc binding site in these complexes are the phenyl ring with X = F, CH(3), and OH and the nitrile group with CN. For the phenol complex, two rotational conformers are identified in different OH orientations.