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(H₂L_SS)­(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 (H₂L_SS). This “from racemate to homochiral” approach may point to a new avenue for the preparation of homochiral materials.