Energy Redistribution and Localization in the Excited States of Ruthenium(II) Polypyridyl Complexes

Challa V. Kumar, Jacqueline K. Barton, Ian R. Gould, Nicholas J. Turro, J. Van Houten

Research output: Contribution to journalArticle

52 Scopus citations

Abstract

Excited-state absorption and resonance Raman spectra of the mixed-ligand complexes Ru(bpy)2phen2+ (1) and Ru(bpy)2DIP2+ (2) (DIP = 4,7-diphenylphenanthroline) are reported. The excited-state spectra of these mixed-ligand complexes show that the excited-state electron is localized on individual ligands but show nonstatistical contributions from states corresponding to each of the ligands present in the coordination sphere. On the basis of the excited-state absorption spectra, the bpy contribution to 1 is twice as much as that of phen, whereas in case of 2 the contribution of DIP is much more than that of bpy. Excitation of the mixed-ligand complexes at different wavelengths gave identical spectra, showing that the initial excited-state population relaxed quickly to an equilibrium mixture, which depends very much on the type of ligand. Intramolecular energy transfer is rapid. Excited-state absorption spectra of mixtures of parent tris chelates, in contrast, which depend upon the wavelength of excitation, show that intermolecular energy transfer is very slow. Excited-state localization and rapid relaxation to an equilibrium distribution is further supported by excited-state resonance Raman spectra of these mixed-ligand complexes. Vibrational transitions corresponding to bpy dominate the spectrum of 1 whereas the vibrational bands of DIP dominate in case of 2. Consistent with these results are the resonance Raman spectra of the excited states of the mixed-ligand complexes Ru(bpy)2(4,4′-Ph2-bpy)2+ (3) and Ru(bpy)(4,4′-Ph2-bpy)2 2+ (4). These spectra clearly indicate preferential localization of excited-state energy on the 4,4′-Ph2-bpy ligand. Thus, it may be possible to design systematically mixed-ligand complexes that would absorb light at a wavelength of choice but would funnel the energy onto a desired ligand.

Original languageEnglish (US)
Pages (from-to)648-651
Number of pages4
JournalInorganic chemistry
Volume27
Issue number4
DOIs
StatePublished - Feb 1 1988
Externally publishedYes

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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