Domingos Sérgio R, Pérez Cristóbal, Schnell Melanie
Deutsches Elektronen-Synchrotron, 22607 Hamburg, Germany.
Christian-Albrechts-Universität zu Kiel, Institut für Physikalische Chemie, 24118 Kiel, Germany.
Annu Rev Phys Chem. 2018 Apr 20;69:499-519. doi: 10.1146/annurev-physchem-052516-050629. Epub 2018 Feb 28.
Chiroptical spectroscopy techniques for the differentiation of enantiomers in the condensed phase are based on an established paradigm that relies on symmetry breaking using circularly polarized light. We review a novel approach for the study of chiral molecules in the gas phase using broadband rotational spectroscopy, namely microwave three-wave mixing, which is a coherent, nonlinear, and resonant process. This technique can be used to generate a coherent molecular rotational signal that can be detected in a manner similar to that in conventional Fourier transform microwave spectroscopy. The structure (and thermal distribution of conformations), handedness, and enantiomeric excess of gas-phase samples can be determined unambiguously by employing tailored microwave fields. We discuss the theoretical and experimental aspects of the method, the significance of the first demonstrations of the technique for enantiomer differentiation, and the method's rapid advance into a robust choice to study molecular chirality in the gas phase. Very recently, the microwave three-wave mixing approach was extended to enantiomer-selective population transfer, an important step toward spatial enantiomer separation on the fly.
用于区分凝聚相中对映体的手性光谱技术基于一种既定的范式，该范式依赖于使用圆偏振光打破对称性。我们综述了一种利用宽带旋转光谱研究气相中手性分子的新方法，即微波三波混频，这是一个相干、非线性且共振的过程。该技术可用于产生一个相干的分子旋转信号，其检测方式类似于传统傅里叶变换微波光谱中的检测方式。通过应用定制的微波场，可以明确确定气相样品的结构（以及构象的热分布）、手性和对映体过量。我们讨论了该方法的理论和实验方面、该技术首次用于对映体区分的意义，以及该方法迅速发展成为研究气相中分子手性的可靠选择。最近，微波三波混频方法已扩展到对映体选择性布居转移，这是朝着即时空间对映体分离迈出的重要一步。
