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Facile access to extremely efficient energy-transfer pairs via an unexpected reaction of squaraines with ketones.

Journal of the American Chemical Society (2012-07-04)
Shuaijun Yang, Jingsong You, Jingbo Lan, Ge Gao
ABSTRACT

We have discovered that squaraine NCSQ easily react with ketones in the presence of ammonium acetate to form a novel type of squaraine CCSQ. It is interesting to find that NCSQs exhibit unusual solid-state fluorescence, whereas CCSQs only exhibit fluorescence in solution. The quantum yield of solid NCSQ-g is measured to be 0.36, which is the highest among solid squaraines found so far. The large spectral overlap between the emission of NCSQs and the absorption of CCSQs, and the structural similarity of these molecules make them excellent energy-transfer (ET) pairs, as exemplified by the ET pair of CCSQ-1/NCSQ-g. When a very small amount (0.05 mol%) of CCSQ-g is doped into NCSQ-g, the ET efficiency reaches up to 96%. The Stern-Volmer quenching constant K(SV) is calculated to be 65 800, indicating that CCSQ-1/NCSQ-g forms an extremely efficient ET pair. This study provides a novel skeleton and a facile route to efficient ET pairs.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Ammonium acetate solution, for molecular biology, 7.5 M
Sigma-Aldrich
Ammonium acetate, reagent grade, ≥98%
Sigma-Aldrich
Ammonium acetate, BioUltra, for molecular biology, ≥99.0%
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Ammonium acetate solution, BioUltra, for molecular biology, ~5 M in H2O
Supelco
Ammonium acetate, LiChropur, eluent additive for LC-MS
Sigma-Aldrich
Ammonium acetate, 99.999% trace metals basis
Sigma-Aldrich
Ammonium acetate, BioXtra, ≥98%
Sigma-Aldrich
Ammonium acetate, for molecular biology, ≥98%
Sigma-Aldrich
Ammonium acetate, ACS reagent, ≥97%
Sigma-Aldrich
Ammonium acetate, ≥99.99% trace metals basis