CNRS, ICMCB, UMR 5026, 33600, Pessac, France.
Université de Bordeaux, ICMCB, UMR 5026, 33600, Pessac, France.
Chemistry. 2020 Oct 21;26(59):13363-13366. doi: 10.1002/chem.202001783. Epub 2020 Sep 21.
An original method for determining the handedness of individual non-centrosymmetric crystals in a mixture using a tightly-focused, circularly polarized X-ray beam is presented. The X-ray natural circular dichroism (XNCD) spectra recorded at the metal K-edge on selected crystals of Δ-M(en) and Λ-M(en) (M=Co , Ni ) show extrema at the metal pre-edge (7712 eV for Co, 8335 eV for Ni). A mapping of a collection of some 220 crystals was performed at the respective energies by using left and right circular polarizations. The difference in absorption for the two polarizations, being either negative or positive, directly yielded the handedness of the crystal volume probed by the beam. By using this technique, it was found that the addition of l-ascorbic acid during the synthesis of Co(en) resulted in an enantiomeric enrichment of the Λ-isomer of 67±13 %, whereas the Ni analogue was similarly, but conversely, enriched in the Δ-isomer (65±22 %).
提出了一种使用聚焦紧密、圆偏振 X 射线束确定混合物中单个非中心对称晶体手性的原始方法。在 [Δ-M(en)] (NO )和 [Λ-M(en)] (NO )（M=Co, Ni ）的选定晶体上在金属 K 边缘记录的 X 射线自然圆二色性（XNCD）光谱在金属预边缘处显示出极值（Co 为 7712 eV，Ni 为 8335 eV）。通过使用左和右圆偏振光，在各自的能量下对大约 220 个晶体的集合进行了映射。两种偏振光的吸收差异（为负或正）直接给出了光束探测的晶体体积的手性。通过使用该技术，发现在 [Co(en)] (NO )的合成过程中添加 l-抗坏血酸导致 Λ-异构体的对映体富集了 67±13％，而 Ni 类似物则相反，在 Δ-异构体中富集了 65±22％。
