ZEKE SPECTROSCOPY OF $Al(C_{5}H_{5}N$): A STUDY OF METAL-$\sigma$ INTERACTION WITH A HETEROCYCLIC AROMATIC LIGAND
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Date
2003
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Publisher
Ohio State University
Abstract
A few years ago, a computational study was reported on cation-$\pi$ interactions in $Al^{+}$ complexes with a series of aromatic $compounds^{a}$. However, for $Al^{+}(C_{5}H_{5}N)$, the calculations indicated that $Al^{+}$ was $\pi$-bound to the nitrogen in the ground electronic state. If $Al^{+}$ was $\sigma$-bound to the ring, the potential energy surface was very flat and no minimum was located. Our photoelectron measurements on $Al/Al^{+}$-pyridine vibrations agree with the theoretical predictions. The ground electronic states of $Al^{+}(C_{5}H_{5}N)$ and its neutral species were determined to be $^{1}A_{1}$ and $^{2}B_{1}$ in $C_{2\nu}$ symmetry. The aluminum-pyridine stretching frequencies were measured to be $278 cm^{-1}$ in the ionic $^{1}A_{1}$ state and $366 cm^{-1}$ in the neutral $^{2}B_{1}$ state. It is unusual that the metal-ligand stretching frequency of a cation complex is much smaller than that of the corresponding neutral species. This anomaly will be discussed in terms of orbital and electrostatic interactions.
Description
$^{a}$D. St\""{o}ckigt, J. Phys. Chem. A 101, 3800 (1997)
Author Institution: Department of Chemistry, University of Kentucky
Author Institution: Department of Chemistry, University of Kentucky