Laser studies of radiationless decay mechanisms in Os/sup 2 +///sup 3 +/ polypyridine complexes
The lowest energy excited states in Os(II) polypyridine complexes are of a metal-to-ligand charge transfer (MLCT) type and live for 10 to 40 ..mu..s at 4.2/sup 0/K. The long wavelength absorptions in the visible region of the spectrum in Os(III) polypyridine complexes arise from ligand-to-metal charge transfer (LMCT) transitions and do not produce detectable luminescence. This suggests that these LMCT states are very short lived. Results of picosecond absorption studies on the lifetimes the LMCT states in OsL/sub 3//sup 3 +/ complexes (L = 2,2'-bipyridine(bpy) or 1,10-phenanthroline(phen)) as functions of temperature and isotopic substitution are reported. The LMCT lifetimes at low temperature are contrasted with the low temperature lifetimes of the MLCT states of OsL/sub 3//sup 2 +/ complexes and both are examined from the perspective of a coarse-grained radiationless decay theory developed by Englman, R. and Jortner, J. (Molec. Phys. 1970, 18, 145). The agreement between experiment and theory suggests the following: (1) Englman and Jortner's theory of radiationless decay is useful for inorganic as well as organic systems; (2) mid-frequency (1300 to 1600 cm/sup -1/) vibrations are the important energy accepting modes for radiationless decay of the charge transfer excited states of OsL/sub 3//sup 2 +///sup 3 +/ complexes and; (3) the 10/sup 5/-10/sup 6/ difference in lifetimes between the MLCT states of OsL/sub 3//sup 2 +/ complexes and the LMCT states of OsL/sub 3//sup 3 +/ complexes is largely due to the difference in their energy gaps.
- Research Organization:
- Brookhaven National Lab., Upton, NY (USA)
- DOE Contract Number:
- AC02-76CH00016
- OSTI ID:
- 5146536
- Report Number(s):
- BNL-31632; CONF-8205114-1; ON: DE82019530; TRN: 82-019115
- Resource Relation:
- Conference: American Chemical Society symposium on inorganic chemistry, Bloomington, IN, USA, 16 May 1982
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
BIPYRIDINES
ABSORPTION SPECTRA
RADIATIONLESS DECAY
OSMIUM COMPLEXES
PHENANTHROLINES
CHARGE TRANSPORT
EXCITED STATES
LASER RADIATION
LIGANDS
LOW TEMPERATURE
MEDIUM TEMPERATURE
REACTION KINETICS
TEMPERATURE DEPENDENCE
AZINES
COMPLEXES
DE-EXCITATION
ELECTROMAGNETIC RADIATION
ENERGY LEVELS
ENERGY TRANSFER
ENERGY-LEVEL TRANSITIONS
HETEROCYCLIC COMPOUNDS
KINETICS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PYRIDINES
RADIATIONS
SPECTRA
TRANSITION ELEMENT COMPLEXES
400201* - Chemical & Physicochemical Properties
400301 - Organic Chemistry- Chemical & Physicochemical Properties- (-1987)
400500 - Photochemistry