Assemblies of meso-metallosupermolecules from tetrahedral metallohelicate units: Syntheses, structures, and fluorescence

摘要

Four new complexes, namely [Cd(H2L)I-2]center dot 2CH(3)OH (1), [Zn(HL)(2)] (2), [Zn(H2L)(TPA)](n)center dot 2nDMF center dot 2nH(2)O (3) and [Zn(H2L)(IPA)](n)center dot 1.5nH(2)O (4), were synthesized through the self-assembly reactions of transition metals Cd(II) and Zn(II) with a flexible bis(benzimidazole) ligand H2L (H2L = 1,2-bis((1H-benzo[d] imidazol-2-yl)methyl)benzene, TPA = terephthalate, IPA = isophthalate, and DMF = N, N-dimethylformamide). In all the complexes, ligands H2L or (HL) acting as helicands chelated metal ions to form uniquely tetrahedral helicate units which further assembled into meso-metallosupermolecules with various architectures, such as layer structures in 1 and 4, three-dimensional CdSO4-like framework in 2, and double-layered framework in 3. Those tetrahedral helicate units not only serve as intriguingly versatile supramolecular synthons, but also display interestingly chiral discrimination during the supramolecular assemblies. In a sense, the formation of those meso-metallosupermolecules based on mononuclear metallohelicates stands for a typical case, unlike commonly reported multi-metal-assisted helicates. Additionally, the solid-state photoluminescence of all the compounds has been investigated. (C) 2014 Elsevier B.V. All rights reserved.