Ligand-ligand charge-transfer excited states of Os(II) complexes

Journal Article · Thu Jun 01 00:00:00 EDT 1989 · Journal of Physical Chemistry; (USA)

DOI:https://doi.org/10.1021/j100348a025· OSTI ID:7022279

Perkins, T A; Schanze, K S ^[1]; Pourreau, D B; Netzel, T L ^[2]

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1. Univ. of Florida, Gainesville (USA)
2. Amoco Research Corp., Naperville, IL (USA)

This paper examines the photophysics of metal-to-ligand charge-transfer (MLCT) and ligand-to-ligand charge-transfer (LLCT) excited states in a series of ((bpy){sub 2}Os{sup II}(CO)L){sup 2+} (Os-L) complexes. For each of the complexes studied, the d{pi}(Os) {yields} {pi}*(bpy) absorption band is the lowest energy transition that is apparent. For L = pyridine and benzonitrile, only long-lived, highly luminescent MLCT states are observed. However, when L = an electron-donor aminobenzonitrile (ABN) species (DMABN, TMABN, or CMI; see text), MLCT emission is quenched and in < 30 ps LLCT excited states are formed, *((bpy{sup {sm bullet}{minus}})-(bpy)OS{sup II}(CO)ABN{sup {sm bullet}+}){sup 2+}. The observed, weight-average radiationless decays of the LLCT excited states in acetonitrile and dichloromethane follow the squence Os-DMABN < Os-TMABN < Os-CMI in each solvent, and the calculated energies of the LLCT states for these complexes are in inverse order to the decay rates as expected if an energy gap law is followed. Finally, multiexponential relaxations of the LLCT states are pronounced in the nonpolar solvent dichloromethane. The dependence of these relaxations on the concentration of added electrolyte suggests that they may be due to ion-pair structure and dynamics.

• OSTI ID: 7022279
• Journal Information: Journal of Physical Chemistry; (USA), Journal Name: Journal of Physical Chemistry; (USA) Vol. 93:11; ISSN 0022-3654; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical &amp; Physicochemical Properties
CHARGE-EXCHANGE REACTIONS
COMPLEXES
DATA
DATA ANALYSIS
ENERGY LEVELS
EXCITED STATES
EXPERIMENTAL DATA
INFORMATION
MEASURING INSTRUMENTS
MEASURING METHODS
NUCLEAR REACTIONS
NUMERICAL DATA
OSMIUM COMPLEXES
TRANSITION ELEMENT COMPLEXES