Homo- and Heterochiral Aggregations of Samarium(III) Complexes with Acetate and Tripod Ligand Containing Three Imidazole Groups

Abstract

Abstract Three SmIII complexes with tripod heptadentate N7 ligands containing three imidazole groups, [Sm(H3L2-Me)(ac)](ClO4)2·2MeOH·H2O (1), [Sm(H3L2-Me)(ac)](ClO4)2·2EtOH (2), and [Sm(H3L4-Me)(ac)](ClO4)2·MeOH (3), were synthesized and the crystal structures were determined, where H3L2-Me and H3L4-Me are the 1:3 condensation products of tris(2-aminoethyl)amine and either 2-methyl-4-formylimidazole and 4-methyl-5-formylimidazole, respectively, and ac denotes acetate ion. Each SmIII ion is coordinated by a tripod heptadentate N7 ligand and two oxygen atoms of the acetate ion. Due to the screw coordination arrangement of the achiral tripod ligand to the SmIII ion, the complex-cation [SmIII(H3L2- or 4-Me)(ac)]2+ gives Δ- and Λ-enantiomorphs. In compounds 1 and 2, two adjacent [Sm(H3L2-Me)(ac)]2+ species with the same chirality are linked by an intermolecular imidazole···acetate hydrogen bond to form a homochiral 1D chain structure. Adjacent chains with the same chirality are stacked to give a conglomerate crystal in 1, while adjacent chains with opposite chiralities are stacked to give a racemic crystal in 2. In compound 3, two adjacent [Sm(H3L4-Me)(ac)]2+ species with the opposite chiralities are doubly bridged by two intermolecular imidazole···acetate hydrogen bonds to form a heterochiral dimer and the adjacent dimers are connected by ClO4− ion through the hydrogen bonds to form a racemic crystal.