Common Emissive Intermediates in the Thermal and Photochemical Reactions of Nonemissive Cyclopentadienylruthenium(II) Complexes of Coumarin Laser Dyes

Robert S. Koefod, Kent R. Mann

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Abstract

Fluorescent intermediates are observed in the reaction of [CpRu(CH3CN)3]+ (Cp = η5-C5H5) with five highly emissive 7-aminocoumarin laser dyes (laser dye = coumarin-334 (10-acetyl-2,3,6,7-tetrahydro-1H,5H,11H-[1]benzopyrano[6,7,8-ij]-quinolizin-11-one), coumarin-338 (2,3,6,7-tetrahydro-11-oxo-1H,5H,11H-[1]benzopyrano[6,7,8-(7]quinolizine-10-carboxylic acid 1,1 -dimethylethyl ester), coumarin-314 (2,3,6,7-tetrahydro-11 -oxo-1 H,5H, 11H-[1]benzopyrano[6,7,8-ij]quinolizine-10-carboxylic acid ethyl ester), coumarin-337 (2,3,6,7-tetrahydro-11-oxo-\H,5H,l lH-[1]benzopyrano[6,7,8-ij]quinolizine-10-nitrile), and coumarin-6 (3-(2-benzothiazolyl)-7-(diethylamino)coumarin). The intermediates exhibit intense, dye-centered absorption and emission bands that are red-shifted 27-79 nm with respect to the free laser dye bands. Similar intermediates are observed when the corresponding nonemissive [CpRu(η6-laser dye)]+ complexes of coumarin-314, coumarin-338, and coumarin-334 are photolyzed in dichloromethane. IR spectral studies suggest that the intermediates contain the laser dye bound to the ruthenium through ligating substituent groups present in the dyes. Both the thermally and photochemically generated intermediates are metastable. The photochemically generated intermediate decays to give free laser dye, while the thermally generated intermediate decays to the (CpRu(ηδ-dye)]+ complex. This behavior is proposed to result from the relative ability of the differing ancillary ligands present in the thermal and photochemical reactions to stabilize energetic CpRu+ reaction intermediates.

Original languageEnglish (US)
Pages (from-to)2221-2228
Number of pages8
JournalInorganic Chemistry
Volume30
Issue number9
DOIs
StatePublished - May 1 1991

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