Fluorescence-Detected Exciton-Coupled Circular Dichroism: Scope and Limitation in Structural Studies of Organic Molecules

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• 作者：Tatsuo Nehira ; Craig A. Parish ; Steffen Jockusch ; Nicholas J. Turro ; Koji Nakanishi ; and Nina Berova
• 刊名：Journal of the American Chemical Society
• 出版年：1999
• 出版时间：September 29, 1999
• 年：1999
• 卷：121
• 期：38
• 页码：8681 - 8691
• 全文大小：813K
• 年卷期：v.121,no.38(September 29, 1999)
• ISSN：1520-5126

文摘

The potential of fluorescence-detected circular dichroism (FDCD) to extend the scope of the excitonchirality method is rooted in the increased sensitivity and selectivity of fluorescence as compared with absorbancemeasurements. In this paper, several practical aspects of FDCD are addressed with model compounds possessinga (1R,2R)-trans-1,2-cyclohexanediol skeleton and two chromophores attached to the diol through ester linkages.We have probed the utility of fluorescent chromophores that have previously been shown to be excellentchromophores for the conventional absorbance-based circular dichroism (CD) exciton chirality method. Certainfluorophores, such as 2-naphthoate or 6-methoxy-2-naphthoate, provide FDCD spectra that are in good agreementwith the conventional CD. In other cases, a bischromophoric derivative results in an FDCD spectrum thatsignificantly deviates from the absorbance based data. Here it is shown that the extent of fluorescencepolarization, an estimate of sample anisotropy, is directly correlated with the ability to extract a meaningfulexciton-coupled FDCD spectrum. If fluorescence polarization is negligible, the solution is isotropic, and theFDCD and conventional CD are in good agreement. Fluorescence lifetime measurements are used to addressthe origin of solution anisotropy.