Excited-state absorption spectroscopy and spectroelectrochemistry of tetrakis(2,2 prime -bipyridine)(. mu. 2,3-bis(2-pyridyl)pyrazine)diruthenium(II) and its mononuclear counterpart: A comparative study

Journal Article · Wed May 16 04:00:00 EDT 1990 · Inorganic Chemistry; (USA)

DOI:https://doi.org/10.1021/ic00335a031· OSTI ID:6664287

Berger, R M ^[1]

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1. Univ. of Notre Dame, IN (USA)

Excited-state absorption spectra of the complexes ((bpy){sub 2}Ru(dpp)Ru(bpy){sub 2}){sup 4+} and (Ru(bpy){sub 2}(dpp)){sup 2+} (bpy = 2,2{prime}-bipyridine, dpp = 2,3-bis(2-pyridyl)pyrazine) in ethanol have been obtained. The excited-state spectra of both complexes exhibit bands in the near-uv region (350 nm for the binuclear complex and 370 nm for the mononuclear complex). In the visible region, a residual metal-to-ligand charge-transfer transition from the remaining Ru(II) center of the binuclear complex to the second lowest {pi}* orbital of the dpp ligand occurs. No comparable band appears in the spectrum of the mononuclear complex. Weak bands also occur in the 610-630-nm region in both complexes. The excited states of the binuclear and mononuclear complex decay with lifetimes of 80 {plus minus} 10 and 210 {plus minus} 20 ns, respectively, and both complexes emit in room-temperature ethanol solution ({phi} = 0.0012 {plus minus}0.0003 and 0.011 {plus minus} 0.001). Spectroelectrochemistry has been used to characterize the reduced forms of the complexes. The first reduction of each complex occurs at the dpp ligand, and the spectra of these singly reduced complexes resemble the excited-state spectra. There is, however, significantly more absorption in the 450-500-nm region for the reduced complexes, consistent with the presence of one or two Ru(II) centers capable of engaging in MLCT transitions. The second reduction of the binuclear complex occurs at the dpp ligand, while the second reduction of the mononuclear complex occurs at one of the bpy ligands. 55 refs., 4 figs.

• OSTI ID: 6664287
• Journal Information: Inorganic Chemistry; (USA), Journal Name: Inorganic Chemistry; (USA) Vol. 29:10; ISSN 0020-1669; ISSN INOCA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ABSORPTION SPECTROSCOPY
AZINES
BIPYRIDINES
COMPLEXES
DATA
ENERGY LEVELS
EXCITED STATES
EXPERIMENTAL DATA
HETEROCYCLIC COMPOUNDS
INFORMATION
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PYRAZINES
PYRIDINES
RUTHENIUM COMPLEXES
SPECTROSCOPY
TRANSITION ELEMENT COMPLEXES