Homochiral Frameworks Formed by Reactions of Lanthanide Ions with a Chiral Antimony Tartrate Secondary Building Unit

A chiral cluster compound, dipotassium bis(μ-tartrato)diantimony(III), K2Sb2L2 (H4L = l-tartaric acid), was used as a secondary building unit to react with lanthanide ions. Three series of homochiral coordination compounds were obtained: 0D [La(H2L)(H2O)4]2[Sb2L2]·7H2O (0D-La), 1D Ln(Sb2L2)(H2O)5(NO3)·H2O (1D-Ln) (Ln = La–Lu or Y, expect Pm), 2D(I) [(Ln(H2O)5)2(Sb2L2)3]·5H2O (2D(I)-Ln) (Ln = La, Ce, Pr), and 2D(II) [(La(H2O)5)2(Sb2L2)3]·6H2O (2D(II)-La). Single-crystal X-ray diffraction studies indicated that 0D-La crystallizes in space group P1, and the structure contains isolated Sb2L22– units located between chains of composition La(H2L)(H2O)4. The series of 1D-Ln compounds is isostructural and crystallizes in space group P212121. In the structure, Sb2L22– units are coordinated to two Ln ions by two out of the four free tartrate oxygen atoms to form a linear chain. To the best of our knowledge, this is the first example of a homochiral structure that can be formed for the whole lanthanide series. In the 2D(I)-Ln structure series, which crystallizes in space group P21, the Sb2L22– units have two distinct coordination modes: one is the same as that found in the 1D structure, while in the other all four free tartrate oxygen atoms are coordinated to four Ln ions in a very distorted tetrahedral arrangement. The connectivity between Sb2L22– secondary units and LnO9 polyhedra gives rise to infinite layers. 2D(II) [(La(H2O)5)2(Sb2L2)3]·6H2O, which crystallizes in space group C2, has a similar network to the 2D(I)-Ln compounds. The trends in lattice parameters, bond lengths, and ionic radii in the 1D-Ln series were analyzed to show the effect of the lanthanide contraction.