Hou Ya-Jun, Wu Kai, Wei Zhang-Wen, Li Kang, Lu Yu-Lin, Zhu Cheng-Yi, Wang Jing-Si, Pan Mei, Jiang Ji-Jun, Li Guang-Qin, Su Cheng-Yong
MOE Laboratory of Bioinorganic and Synthetic Chemistry, Lehn Institute of Functional Materials, School of Chemistry , Sun Yat-Sen University , Guangzhou 510275 , China.
State Key Laboratory of Applied Organic Chemistry , Lanzhou University , Lanzhou 730000 , China.
J Am Chem Soc. 2018 Dec 26;140(51):18183-18191. doi: 10.1021/jacs.8b11152. Epub 2018 Dec 14.
The stereochemistry of chiral-at-metal complexes is much more abundant, albeit complicated, than chiral-at-carbon compounds, but how to make use of stereolabile metal-centers remains a formidable challenge due to the highly versatile coordination geometry of metal ions and racemization/epimerization problem. We demonstrate herein a stepwise assembly of configurationally stable [Pd(FeL)] (Δ/Λ-MOCs-42) homochiral octahedral cages from unstable D-symmetry tris-chelate-Fe type metalloligands via strong face-directed stereochemical coupling and facile chiral-induced resolution processes based on stereodifferentiating host-guest dynamics. Kinetic studies reveal that the dissociation rate of MOC-42 cages is 100-fold slower than that of Fe-metalloligands and the racemization is effectively inhibited, making the cages retain their chirality over extended periods of time (>5 months) at room temperature. Recyclable enantioseparation of atropisomeric compounds has been successfully achieved, giving up to 88% ee.
金属手性配合物的立体化学比碳手性化合物丰富得多，尽管很复杂，但由于金属离子高度多样的配位几何结构以及外消旋化/差向异构化问题，如何利用立体不稳定的金属中心仍然是一个巨大的挑战。我们在此展示了通过基于立体区分主客体动力学的强面定向立体化学偶联和简便的手性诱导拆分过程，从不稳定的D对称三螯合铁型金属配体逐步组装构型稳定的[Pd(FeL)]（Δ/Λ-MOCs-42）同手性八面体笼。动力学研究表明，MOC-42笼的解离速率比铁金属配体慢100倍，并且有效地抑制了外消旋化，使得笼子在室温下长时间（>5个月）保持其手性。已经成功实现了阻转异构化合物的可回收对映体拆分，对映体过量值高达88%。
