Circularly polarized luminescence induced

Similarities between CD and absorbance extend to CD and fluorescence (FDCD) and circularly polarized luminescence (CDL) detection as well [13,14]. Chiral fluorophores can be both natural and induced. The former are considerably fewer in number because of the fact that three prerequisites are necessary to create CD fluorescence activity. Because CD signals are inherently small, and even smaller for induced forms, the higher emission signals normally associated with fluorescence are attractive to use for the... 

Photoderacemization is the simplest case of direct asymmetric photoreactions induced by cpl. The enantiomers are interconverted, and the mixture becomes optically active. Reaction scheme 2 is a modification of Scheme 1 ground state racemization is excluded. The enantiomerization step R S was observed directly by Metcalf et al. [9] by means of the time-resolved circularly polarized luminescence of europium-tris(bipicolinate). By means of a cpl laser pulse, a difference in the excited state population is created, and the decay of circular... 

Similarities between CD and absorbance methods are also found between CD and fluorescence and CD and circularly polarized luminescence (CPL). Three prerequisites are needed to produce FDCD and CPL activities. Intense emission signals normally associated with fluorescence are attractive because limits of detection are lowered considerably. FDCD finds more uses as a chromatographic detection device. A CD signal is usually induced by some kind of molecular complexation reaction. Association can be with a simple molecule or with an aggregate of molecules, such as chiral micelles, which are known to be fluorescence enhancers. In cases of color induction combined with fluorescence induction, FDCD can lead to even higher levels of selectivity among analytes that have been derivatized by the same color reagent. 

The interaction of an external magnetic field with an ensemble of excited molecules provides a novel method for determining excited state parameters by inducing circularly polarized luminescence. The signal obtained from a sample of tris(2,2 -bipyridine) ruthenium (II) chloride... 

The other key point is that the recognition event should then produce differences in the fluorescence properties of the sensor molecule in the presence of the two enantiomers of the analyte. Several mechanisms can be used to generate the fluorescence response (Figs. 2 and 11) by changing the electronic properties and the conformation of the sensor. Aggregation induced emission enhancement (AIEE) [49] was recently shown to be able to generate an enantioselective fluorescence response. Special optical techniques such as circularly polarized luminescence (CPL) are now available to detect enantioselective interactions occurring in the excited state or in the second coordination-sphere interactions [49]. 

See also Biochemical Applications of Raman Spectroscopy Biomacromolecular Applications of Circular Dichroism and ORD Carbohydrates Studied by NMR Circularly Polarized Luminescence and Fluorescence Detected Circular Dichroism Induced Circular Dichroism Magnetic Circular Dichroism, Theory Nucleic Acids and Nucleotides Studied Using Mass Spectrometry Organometallics Studied Using Mass Spectrometry Polymer Applications of IR and Raman Spectroscopy Proteins Studied Using NMR Spectroscopy Vibrational CD Spectrometers Vibrational CD, Theory. 

Muller G, Riehl JP. Use of Induced Circularly Polarized Luminescence (CPL) fiom Racemic D3 Lanthanide Complexes to Determine the Absolute Configuration of Amino Adds. J Eluores-cence 2005 15 553-558. 

Direct asymmetric cpl-induced photoreactions are only observed if there are two enantiomeric ground state reactants presgntthat absorb different amounts of light. Thus the asymmetry of the cpl source is transformed into a different concentration of excited-state enantiomeric species, which becomes obvious in emitting systems in the circular polarization of luminescence [7]. These in turn react in a nonchiral environment with the same rate constants for the different deactivation channels. Thus asymmetric photoreactions are dependent or independent parallel reactions of the enantiomers with different net rates. 

The interaction of aspartic acid and other ligands with complexes of Tb " with edta and related ligands has also been studied and association constants determined. The complex formation between Tb " or Eu " and (r)-( — )-l,2-propanediaminetetraacetic add or (r,r)-trons-1,2-cyclohexanediaminetetraacetic acid has been similarly investigated. The pH dependence of the circularly polarized and total luminescence shows a drastic configurational change of the chelate system at pH 10.5-11, corresponding, it is believed, to formation of hydroxide complexes. Tlie technique of magnetic-field-induced circularly polarized emission has been introduced for lanthanide ions the mechanisms of lanthanide transition intensities are also discussed in the paper. 

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