Induced circular dichroism (ICD) is the CD observed in the absorption of an achiral molecule bound to a transparent chiral molecule through noncovalent interactions. ICD spectroscopy has been used to probe the binding between molecules, such as protein–ligand interactions. However, most ICD spectra have been measured in solution, which only exhibit the averaged CD values of all conformational isomers in solution. Here, we obtained the first isomer-selective ICD spectra by applying resonant two-photon ionization CD spectroscopy to jet-cooled phenol complexes with (−)-methyl l-lactate (PhOH-(−)ML). The well-resolved CD bands in the spectra were assigned to two conformers, which contained different types of hydrogen-bonding interactions between PhOH and (−)ML. The ICD values of the two conformers have different signs and magnitudes, which were explained by differences both in the geometrical asymmetries of PhOH bound to (−)ML and in the electronic coupling strengths between PhOH and (−)ML.

中文翻译：

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（-）-L-乳酸甲酯的射流冷却的苯酚配合物的异构体诱导圆二色性光谱

诱导圆二色性（ICD）是在通过非共价相互作用与透明手性分子结合的非手性分子的吸收中观察到的CD。ICD光谱已用于探测分子之间的结合，例如蛋白质-配体相互作用。但是，大多数ICD光谱是在溶液中测量的，仅显示溶液中所有构象异构体的平均CD值。在这里，我们通过将共振双光子电离CD光谱应用于具有（-）-甲基l的射流冷却的苯酚配合物，获得了第一个异构体选择性ICD光谱-乳酸盐（PhOH-（-）ML）。光谱中良好分辨的CD带分配给两个构象异构体，其中包含PhOH和（-）ML之间不同类型的氢键相互作用。两个构象异构体的ICD值具有不同的符号和大小，这可以通过与（-）ML结合的PhOH的几何不对称性以及PhOH与（-）ML之间的电子耦合强度的差异来解释。