Photoexcited states of biruthenium(II) compounds bridged by 2,2 prime -bis(2-pyridyl)bibenzimidazole or 1,2-bis(2-(2-pyridyl)benzimidazolyl)ethane

Journal Article · Tue Feb 18 23:00:00 EST 1992 · Inorganic Chemistry; (United States)

DOI:https://doi.org/10.1021/ic00030a005· OSTI ID:6957439

Ohno, Takeshi; Nozaki, Koichi ^[1]; Haga, Masaaki ^[2]

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1. Osaka Univ. (Japan)
2. Mie Univ. (Japan)

Charge-transfer (CT) excited states of RuL{sub 2}(L{prime}-L{prime}){sup 2+} and RuL{sub 2}(L{prime}-L{prime}){sup 4+} have been studied by means of emission and transient absorption (TA) spectroscopy at 77-300 K. The bridging ligand (L{prime}-L{prime}) is either 2,2{prime}-bis(2-pyridyl)benzimidazole (bpbimH{sub 2}) or 1,2-bis(2-(2-pyridyl)benzimidazolyl)ethane (dpbime) and L is 2,2{prime}-bipyridine (bpy), 4,4{prime}-dimethyl-2,2{prime}-bipyridine (dmbpy), or 1,10-phenanthroline (phen). Transient absorption (TA) spectra of the ruthenium(II) compounds subjected to laser excitation, whose molar extinction coefficients were determined, are deconvoluted to {pi}-{pi}* bands of L and L{prime}-L{prime} coordinating to Ru(III), L (or L{prime}-L{prime})-to-Ru(III) CT bands, and a {pi}-{pi}* band of (L{prime}-L{prime}){sup {center dot}-} (or L{sup {center dot}-}) by comparison with the absorption spectra of the oxidized compounds (RuL{sub 2}(L{prime}-L{prime}){sup 3+}). The degree of electron population on the ligand decreases in the order bpbimH{sub 2} > bpy {approximately} phen > dpbime > dmbpy in the excited CT states, while there is no discernible difference in the reduction potential between bpbimH{sub 2} (or dpbime) and bpy coordinating to Ru(II). The excitation efficiency of the metal sites in (Ru(bpy){sub 2}){sub 2}(dpbime){sup 4+} is lower than 50% when the laser power was large enough to excite more than 80% of the mononuclear compounds. The low excitation efficiency of the former is ascribed to rapid intramolecular annihilation of the excited states.

• OSTI ID: 6957439
• Journal Information: Inorganic Chemistry; (United States), Journal Name: Inorganic Chemistry; (United States) Vol. 31:4; ISSN 0020-1669; ISSN INOCA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400500* -- Photochemistry
ABSORPTION SPECTRA
CHARGE TRANSPORT
CHEMICAL PREPARATION
CHEMICAL REACTIONS
CHEMISTRY
COMPLEXES
ELECTRIC POTENTIAL
ELECTROMAGNETIC RADIATION
EMISSION SPECTRA
ENERGY LEVELS
EXCITED STATES
LASER RADIATION
LIGANDS
LUMINESCENCE
MOLECULAR STRUCTURE
OXIDATION
PHOSPHORESCENCE
PHOTOCHEMISTRY
PHYSICAL PROPERTIES
RADIATIONS
RUTHENIUM COMPLEXES
SPECTRA
SYNTHESIS
TEMPERATURE RANGE
TEMPERATURE RANGE 0065-0273 K
TEMPERATURE RANGE 0273-0400 K
TRANSITION ELEMENT COMPLEXES
VOLTAMETRY