Picosecond spectroscopic studies of (d/sup 8/-d/sup 8/) binuclear rhodium and iridium complexes: a comparison of /sup 1/B/sub 2/ and /sup 3/B/sub 2/ reactivity in bis(1,5-cyclooctadiene)bis(. mu. -pyrazolyl)diiridium(I)

Journal Article · Wed Apr 30 00:00:00 EDT 1986 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00269a023· OSTI ID:5532301

Winkler, J R; Marshall, J L; Netzel, T L; Gray, H B

Picosecond transient kinetics and difference spectra have been recorded for the singlet and triplet (dsigma*psigma) excited states in the d/sup 8/-d/sup 8/ dimers Rh/sub 2/(TMB)/sub 4//sup 2 +/ (TMB = 2,5-dimethyl-2,5-diisocyanohexane) and (Ir(..mu..-pz)(COD))/sub 2/ (pz = pyrazolyl, COD = 1,5-cyclooctadiene). The singlet excited state in the rhodium dimer (tau=- 820 ps) displays a strong transient absorption feature maximizing at 440 nm that is not present in the spectrum of the triplet excited state. This intense absorption feature, characteristic of a /sup 1/(dsigma-psigma) electronic configuration, is assigned to a /sup 1/(dsigma*psigma) ..-->.. /sup 1/(psigma/sup 2/) excitation. This singlet excited state lifetime of the iridium dimer in cyclohexane is less than 20 ps. Though the solvent 1,2-dichloroethane (DCE) quenches luminescence from both singlet and triplet excited states in (Ir(..mu..-pz)(COD))/sub 2/ and oxidatively adds to the dimer upon steady-state illumination, picosecond spectroscopy finds no evidence for any chemical reactivity of the very short-lived singlet excited state. The quenching of (Ir(..mu..-pz)(COD))/sub 2/ singlet luminescence in DCE appears to result from enhanced singlet ..-->.. triplet intersystem crossing in DCE relative to that in cyclohexane. Also, the invariance of triplet yield in these two solvents indicates that the efficiency of intersystem crossing is near unity.

• Research Organization: Brookhaven National Lab., Upton, NY
• DOE Contract Number: AC02-76CH00016
• OSTI ID: 5532301
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 108:9; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400500* -- Photochemistry
ABSORPTION SPECTRA
ABSORPTION SPECTROSCOPY
AZOLES
CHEMICAL REACTION KINETICS
COMPLEXES
DATA
DE-EXCITATION
DIENES
DIMERS
ENERGY LEVELS
ENERGY TRANSFER
ENERGY-LEVEL TRANSITIONS
EXCITED STATES
EXPERIMENTAL DATA
HETEROCYCLIC COMPOUNDS
HYDROCARBONS
INFORMATION
IRIDIUM COMPLEXES
KINETICS
LIFETIME
LUMINESCENCE
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
POLYENES
PYRAZOLES
RADIATIONLESS DECAY
REACTION KINETICS
RHODIUM COMPLEXES
SPECTRA
SPECTROSCOPY
TRANSITION ELEMENT COMPLEXES