Photochemical, photophysical, and thermal behavior of the tris(1,10-phenanthroline)chromium(III) ion in aqueous solution

Journal Article · Wed Aug 31 04:00:00 EDT 1983 · Inorg. Chem.; (United States)

DOI:https://doi.org/10.1021/ic00160a008· OSTI ID:5596419

Bolletta, F ^[1]; Maestri, M; Moggi, L; Jamieson, M A; Serpone, N; Henry, M S; Hoffman, M Z

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1. Univ. Bologna, Italy

The rate constant of the thermal aquation of chromium complex (Cr(phen)/sub 3//sup 3 +/(phen = 1,10-phenanthroline)) has been determined as a function of pH and temperature; the quantum yield of the photoaquation has been evaluated as a function of excitation wavelength, as a function of pH in the presence of excited-state quenchers iodide, oxygen (I/sup -/, O/sub 2/), and as a function of substrate concentration. The luminescence lifetime and intensity from the /sup 2/T/sub 1///sup 2/E excited states have been measured as a function of pH, (O/sub 2/), (I/sup -/), and (Cr(phen)/sub 3//sup 3 +/). The absorption spectrum of the /sup 2/T/sub 1///sup 2/E excited states has been obtained; the decay of the absorption has been monitored as a function of temperature and solution medium. The thermal, photochemical, and photophysical behavior of Cr(phen)/sub 3//sup 3 +/ in aqueous solution is very similar to that exhibited by Cr(bpy)/sub 3//sup 3 +/ (bpy = 2,2'-bipyridine) and is interpreted in terms of analogous mechanistic steps. It is believed that excitation into spin-allowed states yields /sup 4/T/sub 2/, which undergoes very efficient intersystem crossing to /sup 2/T/sub 1///sup 2/E: these latter states can depopulate via nonradiative decay (including ground-state quenching) or interact with H/sub 2/O and hydroxyl radicals (OH/sup -/) to yield a Cr(phen)/sub 3/(H/sub 2/O)/sup 3 +/ intermediate, which is the direct precursor of the aquation products. Back intersystem crossing is not regarded as an important process. The thermal aquation of the ground state is visualized as occurring via the same intermediate. The relationship of the results reported here to photoracemization and thermal racemization observatons in the literature is made. 11 figures.

• OSTI ID: 5596419
• Journal Information: Inorg. Chem.; (United States), Journal Name: Inorg. Chem.; (United States) Vol. 22:18; ISSN INOCA
• Country of Publication: United States
• Language: English

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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
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ABSORPTION SPECTRA
ACTIVATION ENERGY
ADDITIVES
ALKALI METAL COMPOUNDS
AQUEOUS SOLUTIONS
AROMATICS
AZAARENES
BUFFERS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHLORIDES
CHLORINE COMPOUNDS
CHROMIUM COMPLEXES
COMPARATIVE EVALUATIONS
COMPLEXES
DATA
DE-EXCITATION
DECOMPOSITION
DISPERSIONS
ELEMENTS
ENERGY
ENERGY LEVELS
ENERGY-LEVEL TRANSITIONS
EQUILIBRIUM
EXCITED STATES
EXPERIMENTAL DATA
HALIDES
HALOGEN COMPOUNDS
HETEROCYCLIC COMPOUNDS
INFORMATION
IODIDES
IODINE COMPOUNDS
KINETICS
MIXTURES
MONITORING
NONMETALS
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXYGEN
OXYGEN COMPOUNDS
PERCHLORATES
PH VALUE
PHENANTHROLINES
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
QUANTITY RATIO
RACEMIZATION
RADICALS
REACTION KINETICS
SODIUM CHLORIDES
SODIUM COMPOUNDS
SOLUTIONS
SPECTRA
STOICHIOMETRY
TIME DEPENDENCE
TRANSITION ELEMENT COMPLEXES
WAVELENGTHS