Spontaneous Resolution of Racemic Salen-Type Ligand in the Construction of 3D Homochiral Lanthanide Frameworks

A series
of three 3D homochiral lanthanide–organic frameworks
{[Ln­(H2LSS)­(NO3)2Cl]·2CH2Cl2}n [Ln = La (1), Ce (2), and Nd (3)] with the
unique diamond (dia) topology have been obtained
by utilizing racemic salen-type ligand and mixed lanthanide salts.
Complexes 1–3 are isostructural,
crystallizing in the chiral tetragonal space group P43212 and adopting an individual dia network formed by lanthanide ions and bridging ligand trans-N,N′-bis­(salicylidene)-(1S,2S)-cyclohexanediamine (H2LSS). This “from racemate to homochiral”
approach may point to a new avenue for the preparation of homochiral
materials.

本研究通过外消旋salen型配体（salen-type ligand）与混合镧系金属盐，成功合成三例具有独特金刚石（dia）拓扑结构的三维同手性镧系有机框架，其通式为{[Ln­(H2LSS)­(NO3)2Cl]·2CH2Cl2}n，其中Ln分别为镧(La，化合物1)、铈(Ce，化合物2)及钕(Nd，化合物3)。化合物1~3均为同构体，结晶于手性四方晶系空间群P43212，其骨架为由镧系离子与桥联配体反式-N,N'-双(水杨醛亚胺)-(1S,2S)-环己二胺（H2LSS）构筑的独立dia拓扑网络。这种“从外消旋体到同手性”的合成策略，可为同手性材料的制备提供全新的研究思路。