The $\tilde{A} \leftrightarrow \tilde{X}$ Transitions of $MgC_{5}H_{5}$ and $ZnC_{5}H_{5}$, Are They Charge Transfer or ns $\leftrightarrow$ np Excitations?

Abstract

1. E. J. Robles, A.M. Ellis, and T.A. Miller, J. Chem. Phys., (accepted). 2. E. J. Robles, A.M. Ellis, and T.A. Miller, J. Chem. Phys., (accepted).Author Institution: Department of Chemistry and The Laser Spectroscopy Facility, The Ohio State UniversityThe ground and first excited states of the recently $observed ^{1,2}$ $MgC_{5}H_{5}$ and $ZnC_{5}H_{5}$ were studied at the MCSCF level of theory utilizing the dzp basis set obtained from the study of $MgCH_{3}$ and $ZnCH_{3}$. The $\bar{A} \leftrightarrow \tilde{X}$ transition was found to involve a charge transfer excitation from a cyclopentadiencyl anion ligand to a non-bonding M sp hybrid orbital, (M = Mg, Zn). The fact that the ZnCp $\bar{A} \leftrightarrow \tilde{X}$ transition is within $522 cm^{-1}$ of the ZnH A $(^{2}\Pi) \leftrightarrow X (^{2}\Sigma^{+})$ transition and within $1,211 cm^{-1}$ of the $ZnCH_{3}$ $\tilde{A}(^{2}E) \leftrightarrow \tilde{X}(^{2}A_{1}$) metal centered Zn(4s) $\leftrightarrow$ Zn(4p) transitions is coincidental. The ground states of these complexes are primarily ionic and of $^{2}A_{1}$ symmetry. The first excited states are primarily covalent and of $^{2}E_{1}$ symmetry