Photophysical properties of covalently attached Ru(bpy)[sub 3][sup 2+] and Mcyclam[sup 2+] (M = Ni, H[sub 2]) complexes

Journal Article · Wed May 27 00:00:00 EDT 1992 · Inorganic Chemistry; (United States)

DOI:https://doi.org/10.1021/ic00037a019· OSTI ID:6915486

Fujita, Etsuko; Milder, S J; Brunschwig, B S ^[1]

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1. Brookhaven National Lab., Upton, NY (United States)

Absorption and emission spectra, emission quantum yields, and excited-state lifetimes of the metal-to-ligand charge-transfer (MLCT) excited state(s) of Ru(bpy)[sub 2](6-Mebpy)[sup 2+], Ru(bpy)[sub 2](bpy-cyclamH[sub 2])[sup 4+], and Ru(bpy)[sub 2](bpy-cyclamNi)[sup 4+] are reported. The absorption and emission spectra of these complexes are similar to those of Ru(bpy)[sub 3][sup 2+] in H[sub 2]O at room temperature except for small shifts in the maxima. The emission lifetime decreases by a factor of about 80 for 6-Mebpy, and the emission quantum yield decreases by a factor of about 300 for the bpy-cyclam pendant complexes as compared to the parent Ru(bpy)[sub 3][sup 2+] complex at 25C. Decay of the [sup 3]MLCT excited state takes place by two independent channels: a temperature-independent pathway to the ground state and a thermal-activated pathway via a ligand-field excited state. Activation free energies, E[sub a], for the latter pathway were obtained from fits of the temperature-dependent emission lifetime measurements. Smaller E[sub a] were observed for the 6-substituted complexes (1,500-2,300 cm[sup [minus]1]) relative to Ru(bpy)[sub 3][sup 2+] (3,000-3,910 cm[sup [minus]1]) in EtOH and CH[sub 3]CN, indicating that either the energy difference decreases and/or the reorganization parameter changes between the emissive [sup 3]MLCT and the ligand-field state to which it is strongly coupled. The smaller E[sub a] can be attributed to the increased Ru-N bond distance in the 6-substituted complexes caused by steric hindrance that decreases the ligand-field strength and lowers the energy and/or reorganization parameter of the ligand-field excited state. For the bpy-cyclamNi[sup 2+] pendant complex, an energy-transfer pathway may also provide a deactivation channel.

• DOE Contract Number: AC02-76CH00016
• OSTI ID: 6915486
• Journal Information: Inorganic Chemistry; (United States), Journal Name: Inorganic Chemistry; (United States) Vol. 31:11; ISSN 0020-1669; ISSN INOCAJ
• Country of Publication: United States
• Language: English

Related Subjects

25 ENERGY STORAGE
250800 -- Energy Storage-- Chemical
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400500* -- Photochemistry
ABSORPTION SPECTRA
ACTIVATION ENERGY
AMBIENT TEMPERATURE
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CHALCOGENIDES
CHARGE TRANSPORT
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMISTRY
COMPLEXES
EMISSION SPECTRA
ENERGY
ENERGY LEVELS
ENERGY TRANSFER
EXCITED STATES
INFRARED SPECTRA
ISOMERS
KINETICS
LIGANDS
NICKEL COMPLEXES
NMR SPECTRA
OXIDES
OXYGEN COMPOUNDS
PHOTOCHEMISTRY
PHYSICAL PROPERTIES
REACTION KINETICS
REAGENTS
REDUCTION
RUTHENIUM COMPLEXES
SENSITIZERS
SPECTRA
TEMPERATURE DEPENDENCE
TRANSITION ELEMENT COMPLEXES
VOLTAMETRY