Sensitized photoreduction of bis(acetylacetonato)nickel(III) by triplet state aromatic ketones
Journal Article
·
· J. Am. Chem. Soc.; (United States)
Bis(acetylacetonato)nickel(II), Ni(acac)/sub 2/, quenched triplet state aromatic ketones with high efficiency but only certain aromatic ketones with high triplet energy levels successfully sensitized the photoreduction of Ni(acac)/sub 2/ to give the acetylacetone radical and Ni(I) complexes. A short-lived Ni(I) species was detected by ESR and UV spectroscopy, and the acetylacetonyl radical was trapped by 2-nitroso-2-methylpropane or phenyl-tert-butylnitrone as a stable nitroxide and by H atom donors as acetylacetone. The transient Ni(I) complexes decayed by either first-order or second-order kinetics, depending on the concentrations, to give Ni(0) complexes or ferromagnetic colloidal nickel. The photoreduction of Ni(acac)/sub 2/ occurs only if the acetylacetonyl radical was trapped. Various evidence suggested that the quenching mechanism was not likely to occur by energy transfer and was best interpreted to involve a partial charge transfer within an excited-state complex. The acetylacetonyl radical in the complex undergoes hydrogen abstraction from solvent in competition with reverse electron transfer. The quantum efficiency of the photoreduction is attributed to the extent of charge-transfer contribution and the hydrogen atom donating ability of solvents. It is also confirmed that the ketyl radical derived from triplet state ketones is not responsible for the reduction of Ni(acac)/sub 2/.
- Research Organization:
- Simon Fraser Univ., Burnaby, British Columbia
- OSTI ID:
- 7202304
- Journal Information:
- J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 108:24; ISSN JACSA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201 -- Chemical & Physicochemical Properties
400500* -- Photochemistry
AROMATICS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMISTRY
DATA
DE-EXCITATION
EFFICIENCY
ENERGY LEVELS
ENERGY TRANSFER
ENERGY-LEVEL TRANSITIONS
EXCITED STATES
EXPERIMENTAL DATA
HYDROGEN TRANSFER
INFORMATION
KETONES
KINETICS
MULTIPLETS
NICKEL COMPOUNDS
NUMERICAL DATA
ORGANIC COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOCHEMISTRY
QUANTUM EFFICIENCY
RADIATIONLESS DECAY
RADICALS
REACTION KINETICS
REDUCTION
TRANSITION ELEMENT COMPOUNDS
TRIPLETS
400201 -- Chemical & Physicochemical Properties
400500* -- Photochemistry
AROMATICS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMISTRY
DATA
DE-EXCITATION
EFFICIENCY
ENERGY LEVELS
ENERGY TRANSFER
ENERGY-LEVEL TRANSITIONS
EXCITED STATES
EXPERIMENTAL DATA
HYDROGEN TRANSFER
INFORMATION
KETONES
KINETICS
MULTIPLETS
NICKEL COMPOUNDS
NUMERICAL DATA
ORGANIC COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOCHEMISTRY
QUANTUM EFFICIENCY
RADIATIONLESS DECAY
RADICALS
REACTION KINETICS
REDUCTION
TRANSITION ELEMENT COMPOUNDS
TRIPLETS