Yan-Feng Yue

Unprecedented 3D entanglement of 1D zigzag coordination polymers leading to a robust microporous framework

One-dimensional zigzag coordination chains in four different directions are hierarchically entangled to generate an unprecedented 3D interwoven framework, which exhibits permanent porosity and guest selectivity.

High-dimensional azido-bridged cadmium(II) polymeric complexes with bis(bidentate) diazine ligands

Five new Cd(II)-azido polymeric complexes with bis(bidentate) diazine Schiff bases as auxiliary bridging ligands have been synthesized and crystallographically characterized. The differences in side constituents of the coligands lead to different diazine-bridged binuclear units and hence to three different types of polymeric networks, all being 3-connected nets. In complex 1, [Cd2(L1)2(N3)4]n (L1 = 1,4-bis(2-pyridyl)-2,3-diaza-1,3-butadiene), a single diazine ligand links two metal ions into a centrosymmetric binuclear unit, and each unit is connected with four neighbors via double azido bridges in the end-on (EO) mode, yielding 2-D layers with the (6,3) net topology. Complex 2, [Cd2(L2)2(N3)2]n(ClO4)n·nH2O (L2 = 1,4-bis(2-pyridyl)-1-amino-4-methyl-2,3-diaza-1,3-butadiene), shows a layer structure with the (6,3) net topology, but the binuclear unit contains two diazine bridges and the neighboring units are interlinked via single azido bridges in the end-to-end (EE) mode. The remaining three complexes, [Cd2(L)2(N3)4]n (L = 1,4-bis(2-pyridyl)-1-amino-2,3-diaza-1,3-butadiene for 3, 1-(2-pyridyl)-4-(2-pyrazinyl)-4-amino-1-methyl-2,3-diaza-1,3-butadiene for 4, and 2,5-bis(2-pyridyl)-3,4-diaza-2,4-hexadiene for 5), are isostructural and form the 3-D (10,3)-b net with three different connectors around each node (the cadmium ion): adjacent cadmium ions are alternately bridged by double EO azido bridges and mixed EO azido-diazine double bridges to produce a chain, and each chain is connected to four neighboring chains by single EE azido bridges to generate the 3D framework.

An enhanced fluorescence in a tunable face-to-face π⋯π stacking assembly directed by the H-bonding

A simple anthryl derivative 1-((anthracen-10-yl)methylene)-4-ethylthiosemicarbazide (ANS) shows a methanol-tunable solid state fluorescence enhancement based on different molecular packing structure; the emission is stronger in crystal 2 than that in crystal 1 under the same condition. This is mainly due to the formation of face-to-face π⋯π stacking assembly in crystal 2 which is directed and enhanced by intermolecular H-bonding interactions. The observation of fluorescence decay corroborates the formation of an emissive excimer in the π⋯π stacking assembly.

The crystal structures of four azido-bridged Zn(II) complexes based on open-chain diazine Schiff-base ligands

Four new Zn(II)-azido polymeric complexes with open-chain diazine Schiff-bases as auxiliary bridging ligands have been synthesized and crystallographically characterized. The differences in the constituents of the auxiliary ligands lead to three different types of polymeric structures. Complex 1, [Zn2(L1–H)(N3)3]n (L1 = 1,4-bis(2-pyridyl)-1-amino-4-methyl-2,3-diaza-1,3-butadiene), and complex 2, [Zn2(L2–H)(N3)3·H2O]n (L2 = 1,4-bis(2- pyridyl)-1,4-diamino-2,3-diaza-1,3-butadiene), show a similar one-dimensional (1D) coordination polymeric structure in which the building blocks of tetranuclear rings are interlinked by double end-on (EO) azido bridges, resulting in a “chain of rings” topology. Complex 3, {[Zn17(N3)24(L3–H)2(L3–2H)4(CH3OH)2]·(CH3OH)6·(H2O)3}n (L3 = butanedione monoxime picolinamide hydrazone) has a two-dimensional (2D) structure in which the Zn13 clusters are interlinked by Zn2 binuclear linkers to result in a (4,4) topology. The remaining complex 4, [Zn2(L4–H)(N3)3]n (L4 = 1-(2-pyridyl)-1-amino-4-methyl-4-thiazolyl-2,3-diaza-1,3-butadiene), has a three-dimensional (3D) network with a counterfeit CdSO4 topology, in which the 1D chains similar to those in complexes 1 and 2 are further interlinked by double EO azido bridges.