Widely different luminescence lifetimes of the [Delta]RRR, [Lambda]SSS and the [Delta]RRS, [Lambda]SSR diastereomers of fac-tris[(8-quinolyl)phenylmethylsily] iridium(III): Exciplex formation with solvents by distinct [sigma]-donor and [pi]-acceptor binding mechanisms

Journal Article · Thu Jan 13 00:00:00 EST 1994 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100053a008· OSTI ID:5154308

Djurovich, P I; Cook, W; Joshi, R; Watts, R J ^[1]

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1. Univ. of California, Santa Barbara, CA (United States)

Luminescence lifetimes ([tau][sub m]) of the [sigma]-bond-to-ligand charge-transfer (SBLCT) excited states of two diastereomers of fac-tris[(8-quinolyl)phenylmethylsilyl]iridium(III) differ by about a factor of 2 and are strongly solvent dependent. The [tau][sub m] values of the more symmetric [Delta]RRR, [Lambda]SSS diastereomer (A) are generally longer than those of the less symmetric [Delta]RRS, [Lambda]SSR diastereomer (B); [tau][sub m]'s of both diastereomers are substantially shortened relative to their values in aliphatic hydrocarbons by exciplex formation with a variety of weakly coordinating solvents including aromatic hydrocarbons, olefins, ethers, ketones, alcohols, and nitriles. Quenching constants (k[sub q]) due to exciplex formation are found to be much larger for B than they are for A in the [sigma]-donor solvents (cyclic ethers, ketones, alcohols, and nitriles); however, k[sub q] values of B are slightly smaller than those of A in [pi]-acceptor solvents (aromatic hydrocarbons, olefins). The results suggest that [sigma]-donor solvents form exciplexes by binding at the metal center, whereas [pi]-acceptor solvents bind at a quinolyl radical anion ligand site. A and B may prove useful as luminescent environmental probes which can distinguish between [sigma]-donor and [pi]-acceptor binding sites. 19 refs., 1 fig., 1 tab.

• DOE Contract Number: FG03-88ER13842
• OSTI ID: 5154308
• Journal Information: Journal of Physical Chemistry; (United States), Vol. 98:2; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
IRIDIUM COMPLEXES
LUMINESCENCE
LIFETIME
SILICON COMPLEXES
CHEMICAL BONDS
COMPILED DATA
EXCITED STATES
GROUND STATES
SOLVATION
SOLVENTS
STEREOCHEMISTRY
COMPLEXES
DATA
ENERGY LEVELS
INFORMATION
NUMERICAL DATA
TRANSITION ELEMENT COMPLEXES
400201* - Chemical & Physicochemical Properties
400500 - Photochemistry