Stockman T G, Klevickis C A, Grisham C M, Richardson F S
Department of Chemistry, University of Virginia, Charlottesville 22901, USA.
J Mol Recognit. 1996 Sep-Dec;9(5-6):595-606. doi: 10.1002/(sici)1099-1352(199634/12)9:5/6<595::aid-jmr307>3.0.co;2-v.
Time-resolved chiroptical luminescence (TR-CL) measurements are used to study the kinetics of chirality-dependent excited-state quenching processes in aqueous solution. Experiments are carried out on samples that contain a racemic mixture of chiral luminophore molecules (L) in solution with a small, optically active concentration of chiral quencher molecules (Q). The luminophores are excited with a pulse of unpolarized light to create an initially racemic excited-state population of lambda L* and delta L* enantiomers, and TR-CL measurements are then used to monitor the differential decay kinetics of the lambda L* and delta L* subpopulations. Observed differences between the lambda L* and delta L* decay kinetics reflect differential rate processes and efficiencies for lambda L*-Q versus delta L*-Q quenching actions, and they are diagnostic of chiral discriminatory interactions between the luminophore and quencher molecules. In this study, the luminophores are either Eu(dpa)3(3-) or Tb(dpa)3(3-) coordination complexes (where dpa denotes a dipicolinate dianion ligand), and the quenchers are diastereomeric structures of Cr(H2O)4(ATP), Rh(H2O)4(ATP) and Rh(H2O)3(ATP) (where ATP identical to adenosine triphosphate). The Ln(dpa)3(3-) (Ln identical to En3+ or Tb3+) complexes have three-bladed propeller-like structures of D3 symmetry, and in aqueous solution they exist as a racemic mixture of left-handed (lambda) and right-handed (delta) configurational isomers (enantiomers). The results show that the chiral quencher molecules can distinguish between the lambda and delta enantiomeric structures of the luminophores in their excited-state quenching actions. The degree and sense of enantiomeric preference in these quenching actions are governed by the electronic and stereochemical properties of the quencher molecules. Twenty-one different luminophore-quencher systems are examined in this study, and they exhibit interestingly diverse enantiodifferential quenching kinetics. The results reflect the extraordinary sensitivity of chiral recognition and discrimination processes to relatively small, and sometimes subtle, changes in molecular electronic and stereochemical structure.
时间分辨圆二色发光（TR-CL）测量用于研究水溶液中手性相关激发态猝灭过程的动力学。实验针对含有手性发光体分子（L）的外消旋混合物溶液进行，其中加入少量具有旋光性的手性猝灭剂分子（Q）。用非偏振光脉冲激发发光体，以产生初始外消旋的λL和δL对映体激发态群体，然后使用TR-CL测量来监测λL和δL亚群体的差异衰减动力学。观察到的λL和δL衰减动力学之间的差异反映了λL*-Q与δL*-Q猝灭作用的差异速率过程和效率，它们可诊断发光体与猝灭剂分子之间的手性识别相互作用。在本研究中，发光体为Eu(dpa)3(3-)或Tb(dpa)3(3-)配位络合物（其中dpa表示吡啶二甲酸二价阴离子配体），猝灭剂为Cr(H2O)4(ATP)、Rh(H2O)4(ATP)和Rh(H2O)3(ATP)的非对映异构体结构（其中ATP等同于三磷酸腺苷）。Ln(dpa)3(3-)（Ln等同于Eu3+或Tb3+）络合物具有D3对称的三叶螺旋桨状结构，在水溶液中它们以左旋（λ）和右旋（δ）构型异构体（对映体）的外消旋混合物形式存在。结果表明，手性猝灭剂分子在其激发态猝灭作用中能够区分发光体的λ和δ对映体结构。这些猝灭作用中对映体偏好的程度和方向由猝灭剂分子的电子和立体化学性质决定。本研究中考察了21种不同的发光体-猝灭剂体系，它们表现出有趣的多样对映体差异猝灭动力学。结果反映了手性识别和区分过程对分子电子和立体化学结构中相对较小且有时细微的变化具有非凡的敏感性。
