Two azido-bridged copper(II) coordination polymers with isonicotinate-N-oxide and picolinate-N-oxide acting as co-ligands
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abstract
Two one-dimensional coordination polymers [Cu1.5(L 1)(N3)2(H2O)]n (1) and [Cu1.5(L2)(N3)2]n (2) were synthesized by hydrothermal reactions of Cu(ii) salt with NaN3 in the presence of two secondary ligands, isonicotinate-N-oxide (L1) and its isomer, picolinate-N-oxide (L2). Single-crystal X-ray diffraction studies reveal that azide anions adopt a -1,1 bridging coordination mode linking the metal ions by both double and single azide bridges in 1, but they adopt both -1,1 and -1,1,1 bridging modes in 2. The magnetic measurements showed strong ferromagnetic coupling and the onset of magnetic ordering in 1 (a metamagnet with a small glass behaviour), but antiferromagnetic interactions between the ferromagnetic trimers in 2. This result indicates that the judicious selection of co-ligands can effectively tune the formation of metal-azide coordination polymers and thereby, their magnetic properties. The Royal Society of Chemistry 2011.