Guest-triggered assembly of zinc(II) supramolecular isomers with accompanying dimensional change and reversible single-crystal-to-single-crystal transformation

摘要

Solvent-directed assembly of two-dimensional (2D) and 3D supramolecular isomers as well as guest-exchange induced transformation of the 2D isomer accompanied by photoluminescence switching are reported. Solvothermal reaction of Zn(NO3)(2)center dot 4H2O, 1,4-bis(4-pyridyl)piperazine (bpp), and benzene-1,3-dicarboxylic acid (H(2)bdc) in dimethylformamide (DMF) afforded a self-penetrated 3D coordination polymer, {[Zn-2(bpp)(2)(bdc)(2)]center dot 4DMF center dot 4H(2)O}(n) (1), adopting a firewood-like stacking structure. When the above synthetic procedure was repeated employing dimethylacetamide (DMA) as a solvent, a 2D coordination polymer, {[Zn-2(bpp)(2)(bdc)(2)]center dot 4DMA center dot 6H(2)O}(n) (2), was obtained, whose structure shows a crinkled square (4,4) grid type, as a supramolecular isomer of 1. The dimensional difference between isomers 1 and 2 stems mainly from the directional arrangement and the conformation of the bpp ligand. In the guest-exchange experiment, isomer 2 with the crinkled square grid structure not only represents a reversible spreading-folding conversion due to the conformational change of the bpp ligand but also displays a photoluminescence switching behaviour.