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Mid-Infrared Spectrum of [Ru(phen)(3)](2+)
Kristin M. Omberg1, Jon R. Schoonover, Stefan Bernhard
1Bioscience and Biotechnology Group (CST-4), Chemical Science and Technology Division, Mail Stop J586, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, and Department of Chemistry, CB#3290, University of North Carolina, Chapel Hill, North Carolina 27599-3290.
Inorganic Chemistry
|October 24, 2001
Summary
Time-resolved infrared spectroscopy reveals the excited state of ruthenium and osmium complexes. Evidence supports a localized electronic description for [Ru(III)(phen(*)(-)())(phen)(2)](2+) on the 100 ns timescale.
Area of Science:
- Inorganic Chemistry
- Photochemistry
- Spectroscopy
Background:
- Metal-to-ligand charge-transfer (MLCT) excited states are crucial in photochemistry.
- Understanding the electronic structure of these excited states is key to their applications.
- Ruthenium and osmium polypyridyl complexes are widely studied for their photophysical properties.
Purpose of the Study:
- To investigate the electronic structure of MLCT excited states in [Ru(phen)(3)](2+) and [Os(phen)(DAS)(2)](2+).
- To assign time-resolved infrared spectra by comparison with electrochemically generated species.
- To provide insights into the electronic distribution and excited-state dynamics.
Main Methods:
- Time-resolved infrared spectroscopy in the fingerprint region (1300-1700 cm(-1)).
- Electrochemical generation of reference species: [Ru(III)(phen)(3)](3+) and [Ru(II)(phen(*)(-)())(phen)(2)](+).
- Spectroscopic analysis in acetonitrile-d(3) at 298 K.
Main Results:
- Assignment of time-resolved infrared spectra for the MLCT excited states.
- Clear evidence for a localized electronic description, [Ru(III)(phen(*)(-)())(phen)(2)](2+), on the ~100 ns timescale.
- Insights into electronic distribution within the excited states.
Conclusions:
- The study confirms a localized electronic description for the excited state of [Ru(phen)(3)](2+).
- The findings aid in interpreting complex spectroscopic data, including resonance Raman spectra.
- Difficulties in measuring ground- and excited-state resonance Raman spectra of phenanthroline complexes are suggested.