Four metal–organic frameworks based on the 5-(1H-tetrazol-5-yl)isophthalic acid ligand: luminescence and magnetic properties

Abstract

Four transition metal coordination polymers with 5-(1H-tetrazol-5-yl)isophthalic acid ligand (H₃TZI) were synthesized and structurally characterized. They are formulated as [Zn(TZI)]·(CH₃)₂NH₂⁺·H₂O (1), [Cd₂(OH)(TZI)(H₂O)₂]·DMF·0.5H₂O (2), [MnNa(TZI)]·2H₂O (3), and [Mn₃(TZI)₂(12H₂O)]·4H₂O (4). Compound 1 displays a 3D (4,4)-connected framework with a Schläfli symbol of 4²6²8². 2 exhibits 3D frameworks in which strip-shaped chains with Cd₃(μ₃-OH) triangles are linked by TZI ligands, presenting a rare (3,4,5,6)-connected 4-nodal net topology with the point symbol (4³)(4⁴6²)(4⁶6⁴)(4⁷6⁸). 3 features 2D 2p–3d heterometallic layers in which 1D chains with mixed bridges linking alternating Mn(II) ions and Na(I) ions are interlinked by TZI spacers. The layers are further stabilized and associated into 3D architectures through intra- and interchain hydrogen bonds and/or π–π stacking. 4 consists of 1D double chains, and the 1D chains are assembled through hydrogen bonds to give a 3D supramolecular architecture. Intriguingly, Mn(II) ions from different double chains are linked through hydrogen bonding bridges to give unprecedented hydrogen bonded chains with alternating single O–H⋯O bridges and double (O–H⋯O)₂ bridges. Compounds 1 and 2 display intense photoluminescence properties in the solid state at room temperature, while 4 exhibits an antiferromagnetic interaction between Mn(II) ions.