Enantioselective detection of chiral phosphorescent analytes in cyclodextrin complexes |
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Authors: | García-Ruiz Carmen Scholtes Maarten J Ariese Freek Gooijer Cees |
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Affiliation: | Department of Analytical Chemistry and Applied Spectroscopy, Laser Centre, Vrije Universiteit, De Boelelaan 1083, NL-1081 HV Amsterdam, The Netherlands |
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Abstract: | Inclusion complexes between camphorquinone (CQ) and cyclodextrins (CDs) in deoxygenated aqueous solutions are shown to exhibit relatively strong room temperature phosphorescence (RTP). Among the various CDs tested, α-CD showed the strongest RTP signals. Interestingly, these signals differed significantly for the two enantiomers of CQ; the phosphorescence lifetime of (+)-CQ was about four times longer than that of (−)-CQ, being 352 ± 16 and 89 ± 6 μs, respectively. This enantiomeric selectivity is attributed to a difference in dissociation rates (competing with the radiative emission process) for the diastereoisomeric inclusion complexes dealt with, which have a 2:1 stoichiometry (α-CD:CQ:α-CD). Time-resolved RTP detection using different delay times enables the determination of the two enantiomers in a mixture without involving a separation technique. The minimum detectable fraction of (+)-CQ in a 2 mM sample was 13%. |
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Keywords: | Camphorquinone Inclusion complex Room temperature phosphorescence Phosphorescence lifetime |
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