Structures and magnetism of metal(II) compounds with mixed azide and carboxylate bridges derived from zwitterionic dicarboxylate ligands

Three coordination polymers of different transition metal ions with azide and flexible zwitterionic dicarboxylate ligand 1-carboxymethylpyridinium-4-benzoate (L) were synthesized and structurally and magnetically characterized. They are formulated as [M(L)(N3)]·H2O (M = Co, 1 and Ni, 2) and [Cu3(L)2(N3)4]·7H2O (3). In the isomorphous compounds 1 and 2, neighboring metal ions are linked by mixed triple (μ-EO-N3)(μ-COO)2 bridges to give an anionic chain of [M(N3)(COO)2]n, and each chain is cross-linked by the cationic 1-methylpyridinium-4-phenyl spacers to give a two-dimensional coordination layer. Magnetic studies demonstrated that the triple bridge transmits intrachain ferromagnetic interactions but show different bulk properties: compound 1 diplays a new SCM-based material exhibiting antiferromagnetic ordering, metamagnetic transition, and field-modulated slow dynamics, while compound 2 shows the usual one-dimensional ferromagnetism. Compound 3 consists of three-dimensional coordination framework in which Cu(II) chains with alternating double (μ-EO-N3)2 bridges and triple (μ-EO-N3)(μ-COO)(μ-Ocarboxylate) bridges are interlinked by the organic spacer. Magnetic studies suggested that ferromagnetic interactions between the neighboring Cu(II) ions through the alternating bridges.

The triple (COO)2(N3) bridge has been demonstrated to mediate ferromagnetic coupling in the isomorphous Co(II) and Ni(II) compounds. The copper Compound contains alternating double (μ-EO-N3)2 bridges and (μ-EO-N3)(μ-COO)(μ-Ocarboxylate) triple bridges that induce ferromagnetic interactions between the neighboring Cu(II) ions.Figure optionsDownload as PowerPoint slideHighlights
► Three coordination polymers with azide and zwitterionic dicarboxylate ligand were synthesized.
► Structural analysis reveals 2D and 3D polymeric networks.
► The isomorphous Co(II) and Ni(II) compounds mediate intrachain ferromagnetic coupling.
► The Cu(II) compound contains alternating bridges that induce ferromagnetic interactions.