Studies of energy-transfer and electron-transfer processes involving the /sup 3/Au/sub 2u/ excited states of binuclear rhodium isocyanide complexes

Journal Article · Wed Oct 22 04:00:00 EDT 1980 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00542a015· OSTI ID:6904000

Milder, S J ^[1]; Goldbeck, R A; Kliger, D S; Gray, H B

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1. California Inst. of Tech., Pasadena

The lowest electronic excited states of Rh/sub 2/(br)/sub 4//sup 2 +/ (br = 1,3-diisocyanopropane) and Rh/sub 2/(TMB)/sub 4//sup 2 +/ (TMB = 2,5-dimethyl-2,5-diisocyanohexane) are relatively long-lived emissive triplets (/sup 3/A/sub 2u/). The /sup 3/A/sub 2u/ lifetimes in acetonitrile are 8.5 +- 0.5 ..mu..s for Rh/sub 2/(br)/sub 4//sup 2 +/ and 25 +- 5 ns for Rh/sub 2/(TMB)/sub 4//sup 2 +/ (21/sup 0/C). The triplet energy of Rh/sub 2/(br)/sub 4//sup 2 +/ has been estimated to be about 39 kcal/mol (approximately 1.7 eV, approximately 730 nm) from energy-transfer quenching experiments. The /sup 3/A/sub 2u/ excited states of Rh/sub 2/(br)/sub 4//sup 2 +/ and Rh/sub 2/(TMB)/sub 4//sup 2 +/ undergo electron-transfer reactions with oxidative and reductive quenchers. Reductive quenching by N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD), and oxidative quenching by paraquat (PQ/sup 2 +/) have been studied in detail. In methanol solution, Rh/sub 2/(br)/sub 4//sup 2 +/*(/sup 3/A/sub 2u/) reacts with TMPD to give Rh/sub 2/(br)/sub 4//sup 2 +/ and TMPD/sup +/ (k/sub b/, the back-reaction rate constant, is 1 x 10/sup 9/ M/sup -1/s/sup -1/); similarly, Rh/sub 2/(TMB)/sub 4//sup 2 +/*(/sup 3/A/sub 2u/) reacts with TMPD to give Rh/sub 2/(TMB)/sub 4//sup +/ and TMPD/sup +/ (k/sub b/ = 1.4 x 10/sup 9/ M/sup -1/s/sup -1/). Oxidation of Rh/sub 2/(TMB)/sub 4//sup 2 +/*(/sup 3/A/sub 2u/) by PQ/sup 2 +/ in methanol gives Rh/sub 2/(TMB)/sub 4//sup 3 +/ and PQ/sup +/ (k/sub b/ = 2.2 x 10/sup 8/ M/sup -1/s/sup -1/; ..mu.. = 1.95 x 10/sup -2/ M). One-electron oxidation of Rh/sub 2/(br)/sub 4//sup 2 +/*(/sup 3/A/sub 2u/) by PQ/sup 2 +/ is observed, but the kinetics of the back-reaction are complex, owing to competing oligomerization processes.

• OSTI ID: 6904000
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 102:22; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

08 HYDROGEN
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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400500* -- Photochemistry
ALCOHOLS
AMINES
AROMATICS
CHEMICAL REACTIONS
COMPLEXES
DECOMPOSITION
DYE LASERS
ELECTRON TRANSFER
ENERGY LEVELS
ENERGY TRANSFER
EXCITED STATES
HYDROXY COMPOUNDS
LASERS
METHANOL
NITRILES
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
RHODIUM COMPLEXES
TRANSITION ELEMENT COMPLEXES