Photophysical effects of metal-carbon sigma bonds in ortho-metalated complexes of Ir(III) and Rh(III)
Dichloro-bridged dimers of the type (M(L)/sub 2/Cl)/sub 2/, where L is 2-phenylpyridine (ppy) or benzo(h)quinoline (bzq) and M is Rh(III) or Ir(III), have been characterized by /sup 13/C and /sup 1/H NMR spectroscopies and by absorption and emission spectroscopies. The NMR results confirm previous formulations of the complexes as dichloro-bridged ortho-metalated dimers in halocarbon solvents but indicate that they are cleaved to monomeric species of the type M(L)/sub 2/CIS in ligating solvents such as dimethylformamide (S = solvent). The absorption spectra of each of the complexes contain several low-energy bands which are assigned as metal-to-ligand charge-transfer (MLCT) transitions. All four of the dimers emit light following photoexcitation of their glassy solutions at 77 K. Their emission spectra and lifetimes lead to assignments of their emitting states as intraligand for the Rh(III) dimers and MLCT for the Ir(III) dimers. The Ir(III) dimers are also found to emit light following excitation at 295 K in deaerated dichloromethane. No emission is seen from the Rh(III) dimers under these conditions. Comparison of these results with previous results from studies of similar Rh(III) and Ir(III) complexes of 2,2'-bipyridine (bpy) and 1,10-phenanthroline (phen) indicates that the ortho-metalated ligands are considerably higher than bpy and phen in the spectrochemical series. In addition to raising the energy of ligand field excited states in their complexes, relative to similar bpy and phen species, they induce lower energy charge-transfer transitions. These effects are consistent with the synergistic function of the ortho-metalated ligands as both strong sigma donors and ..pi.. acceptors.
- Research Organization:
- Univ. of California, Santa Barbara
- DOE Contract Number:
- AT03-78ER70277
- OSTI ID:
- 6064259
- Journal Information:
- J. Am. Chem. Soc.; (United States), Vol. 106:22
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
BIPYRIDINES
PHOTOLYSIS
IRIDIUM CHLORIDES
ORGANOMETALLIC COMPOUNDS
QUINOLINES
RHODIUM CHLORIDES
CARBON 13
EXPERIMENTAL DATA
NMR SPECTRA
PROTONS
AROMATICS
AZAARENES
AZINES
BARYONS
CARBON ISOTOPES
CHEMICAL REACTIONS
CHLORIDES
CHLORINE COMPOUNDS
DATA
DECOMPOSITION
ELEMENTARY PARTICLES
EVEN-ODD NUCLEI
FERMIONS
HADRONS
HALIDES
HALOGEN COMPOUNDS
HETEROCYCLIC COMPOUNDS
INFORMATION
IRIDIUM COMPOUNDS
ISOTOPES
LIGHT NUCLEI
NUCLEI
NUCLEONS
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PYRIDINES
REFRACTORY METAL COMPOUNDS
RHODIUM COMPOUNDS
SPECTRA
STABLE ISOTOPES
TRANSITION ELEMENT COMPOUNDS
400500* - Photochemistry
400201 - Chemical & Physicochemical Properties
400301 - Organic Chemistry- Chemical & Physicochemical Properties- (-1987)