Electrochemical and spectral probes of metal/ligand orbital mixing in Ru(NH3)4(bpy)2+ and Ru(NH3)4(phen)2+

Gary A. Mines, Jody A. Roberts, Joseph T Hupp

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Abstract

An electrochemical variational method (de la Rosa, et al. Inorg. Chem. 1985, 24, 4229) has been used to examine experimentally the extent of metal/ligand orbital mixing and electronic coupling in complexes of the type RuII(NH3)4L2+ (L = 2,2′-bipyridine or 1,10-phenanthroline). From the experiments, strong localization of dπ electrons at the ruthenium metal center is indicated. Nevertheless, some mixing of dπ(Ru) and π*(bpy; phen) is detected, implying a significant degree of delocalization (ca. 25%) These results differ substantially from those derived from metal-to-ligand charge-transfer (MLCT) oscillator strength measurements. The latter indicate less than 2% delocalization. The difference is particularly surprising in view of the fact that both approaches derive from Mulliken charge-transfer theory and the two are employed at similar (but not identical) levels of approximation. The origin of the discrepancies is unclear, but may be related to the choice of charge-transfer distance which must necessarily be made in the optical analysis. Independent estimates of electronic delocalization, based on partial oxidation-state markers in vibrational Raman spectra, corroborate the electrochemical findings.

Original languageEnglish
Pages (from-to)125-128
Number of pages4
JournalInorganic Chemistry
Volume31
Issue number1
Publication statusPublished - 1992

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Charge transfer
Metals
charge transfer
Ligands
orbitals
ligands
probes
metals
Ruthenium
electronics
oscillator strengths
markers
vibrational spectra
ruthenium
Raman scattering
Raman spectra
Oxidation
oxidation
Electrons
estimates

ASJC Scopus subject areas

  • Inorganic Chemistry

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Electrochemical and spectral probes of metal/ligand orbital mixing in Ru(NH3)4(bpy)2+ and Ru(NH3)4(phen)2+. / Mines, Gary A.; Roberts, Jody A.; Hupp, Joseph T.

In: Inorganic Chemistry, Vol. 31, No. 1, 1992, p. 125-128.

Research output: Contribution to journalArticle

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abstract = "An electrochemical variational method (de la Rosa, et al. Inorg. Chem. 1985, 24, 4229) has been used to examine experimentally the extent of metal/ligand orbital mixing and electronic coupling in complexes of the type RuII(NH3)4L2+ (L = 2,2′-bipyridine or 1,10-phenanthroline). From the experiments, strong localization of dπ electrons at the ruthenium metal center is indicated. Nevertheless, some mixing of dπ(Ru) and π*(bpy; phen) is detected, implying a significant degree of delocalization (ca. 25{\%}) These results differ substantially from those derived from metal-to-ligand charge-transfer (MLCT) oscillator strength measurements. The latter indicate less than 2{\%} delocalization. The difference is particularly surprising in view of the fact that both approaches derive from Mulliken charge-transfer theory and the two are employed at similar (but not identical) levels of approximation. The origin of the discrepancies is unclear, but may be related to the choice of charge-transfer distance which must necessarily be made in the optical analysis. Independent estimates of electronic delocalization, based on partial oxidation-state markers in vibrational Raman spectra, corroborate the electrochemical findings.",
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