Constructing a Series of Azide-Bridged CuII Magnetic Low-Dimensional Coordination Polymers by using Pybox Ligands.

Four azide-copper coordination polymers, [Cu₂L¹(N₃)₄] _n, [Cu₂L²(N₃)₄] _n, [Cu₂L^{3 R}(N₃)₄] _n, and [Cu₂L^{3 S}(N₃)₄] _n, were synthesized by using pybox [pyridine-2,6-bis(oxazolines)] as coligands {L ¹: 2,6-bis(4,5-dihydrooxazol-2-yl)pyridine; L ²: 2,6-bis(5,6-dihydro-4 H-1,3-oxazin-2-yl)pyridine; L ^{3 R or 3 S}: 2,6-bis[( R or S)-4-benzyl-4,5-dihydrooxazol-2-yl]pyridine}. Compounds 1 and 2 possess similar 1D infinite azide-copper hexagonal tapes with three types of N₃ bridges (two single end-on N₃ bridges and one double end-on N₃ bridge). Compounds 3 R and 3 S possess an azide-copper 2D honeycomb layer with two types of N₃ bridges (a single end-to-end N₃ bridge and a double end-on N₃ bridge). The chirality of these enantiopure layered structures is controlled by the addition of the chiral pybox ligand in the synthesis, which is very rare for the reported azide-copper coordination polymers. The double end-on N₃ bridge transfers mainly ferromagnetic exchange coupling interactions in these four compounds. Owing to the steric hindrance of the pybox ligands, the interchain and interlayer separations are broadened, which weakens the magnetic interactions between them. Thus, no long-range ferromagnetic ordering was observed above 1.8 K. A magnetostructural correlation was also discussed in detail. [ABSTRACT FROM AUTHOR]