Six novel coordination polymers based on the 5-(1H-tetrazol-5-yl)isophthalic acid ligand: structures, luminescence, and magnetic properties

Abstract

Six new coordination polymers (CPs), namely, [Mn₂(OH)(TZI)(DMA)] (1), [Cu₂(OH)(TZI)(DMA)]·3.5H₂O (2), [Co₂(OH)(TZI)(H₂O)₂] (3), [Zn₂(OH)(TZI)(2,2′-bpy)]·H₂O (4), [Zn₂(OH)(TZI)(phen)]·2H₂O (5) and [Zn₂(OH)(TZI)(4,4′-bpy)_0.5] (6), (H₃TZI = 5-(4-(tetrazol-5-yl)phenyl)isophthalic acid, 2,2′-bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline, 4,4′-bpy = 4,4′-bipyridine, and DMA = N,N-dimethylacetamide), have been synthesized under solvo-/hydrothermal conditions. Both 1 and 2 exhibit 3D structures containing butterfly-shaped tetranuclear M₄(μ₃-OH)₂ clusters as secondary building units (SBUs). In 1, the SBUs are connected into 1D chains by the tetrazolate groups of the TZI ligands and the chains are further interlinked into a (4,8)-connected 3D net by the TZI spacers. In 2, the SBUs are directly connected by TZI to give a (3,6)-connected 3D framework. CP 3 features a double-layered structure based on corner-sharing Co₃(μ₃-OH) triangle Δ-chains in which Co(II) ions are bridged by mixed (μ₄-tetrazolate)(μ₃-OH)(μ₂-COO) bridges. CPs 4–6 were synthesized by the reactions of the H₃TZI ligands, Zn(NO₃)₂ and three different N-donor auxiliary ligands. The auxiliary ligands change from chelating ligands (2,2′-bpy, phen) to 4,4′-bpy, which leads to remarkable structural changes from 2D to 3D. CPs 4 and 5 display 2D structures with dinuclear motifs as SBUs. In 4, the dinuclear motifs with mixed double (μ₂-tetrazolate)(μ₂-OH) bridges are connected by the TZI spacers to produce a 2D framework. Differently, in 5, the dinuclear motifs with mixed double (μ₂-COO)(μ₂-OH) bridges are interlinked into a 2D framework with a (4,4)-connected net topology. In 6, the square Zn₄O₄ clusters are interlinked by the organic ligands into a 3D framework with a (4,10)-connected (4⁴·6²)(4¹²·5⁸·6¹⁶·7⁶·8³) topology. Magnetic studies indicate that CPs 1–3 exhibit antiferromagnetic coupling. Further magnetic measurement demonstrates that CPs 1 and 3 show no magnetic ordering above 2 K. CPs 4–6 exhibit strong luminescence with different energies in the solid state at room temperature.