Article

Ligand-Field Excited States of Metal Hexacarbonyls

California Institute of Technology, Mail Code 139-74, Pasadena, California 91125
Inorg. Chem., 2005, 44 (7), pp 2454–2458
DOI: 10.1021/ic048215n
Publication Date (Web): March 3, 2005
Copyright © 2005 American Chemical Society

Synopsis

This paper uses time-dependent density functional theory to obtain quantitative values for both ligand-field and charge-transfer transitions for V(CO)6-, Cr(CO)6, and Mn(CO)6+. Our work allows us to make complete assignments of the absorption spectra of these three metal hexacarbonyls, and we demonstrate that the commonly accepted assignment of the spectra is incorrect.

Abstract

Abstract Image

Over 35 years ago, the low-lying bands in the absorption spectra of metal hexacarbonyls were assigned to ligand-field (LF) excitations. Recent time-dependent density functional theory (TDDFT) calculations on M(CO)6 (M = Cr, Mo, W) are not in accord with this interpretation. Here we extend TDDFT calculations to the isoelectronic series V(CO)6-, Cr(CO)6, and Mn(CO)6+. By analyzing the trends in the energies of the various electronic excitations, we are able to fully assign the spectra of the complexes. In particular, we demonstrate that the LF excitation 1A1g1T1g is observed at 4.12 eV in the Mn(CO)6+ spectrum, but all LF features in the spectra of V(CO)6- and Cr(CO)6 are obscured by intense metal-to-ligand charge-transfer absorptions. Our results suggest that use of B3LYP as the exchange-correlation functional and inclusion of solvation effects through a continuum solvation model lead to the most accurate calculated transition energies.

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Metrics

Received 17 December 2004
Published online 3 March 2005
Published in print 1 April 2005
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