Modulating structural dimensionality of cadmium(II) coordination polymers by means of pyrazole, tetrazole and pyrimidine derivative ligands

• Synthesis of six new cadmium(II) coordination compounds with pyrazole, tetrazole, and pyrimidine derivatives.
• All complexes have been characterized by X-ray crystallography.
• Some compounds exhibit an open crystal structure with large voids.
• Topological analysis have been conducted and a new topology has been described.

Six new compounds with functionalized pyrazole, tetrazole, and pyrimidine ligands, namely [Cd(μ-4-Hampz)(μ-Cl)2]n(1), [Cd(μ3-pzdc)(μ-H2O)(H2O)]n(2), [Cd(μ-5-amtz)2(eda)]n(3), {[Cd9(μ4-5-amtz)8(μ-Cl)10(H2O)2]⋅xH2O}n(4), {[Cd2(μ-dm2-pmc)2Cl2(H2O)2]⋅H2O}n(5), and [Cd2(μ-Br2-pmc)(μ-Cl)3(H2O)2]n(6) (where 4-Hampz = 4-aminopyrazole, pzdc = 3,5-pyrazoledicarboxylate, 5-amtz = 5-aminotetrazolate, eda = ethylenediamine, dm2-pmc = 4,6-dimethoxy-2-pyrimidinecarboxylate, Br2-pmc = 5-bromopyrimidine-2-carboxylate) have been synthesized under hydrothermal conditions and structurally characterized by single crystal X-ray diffraction. Compounds 1 and 2 share the structural feature of being constructed from dinuclear building units that are further connected through the pyrazole based ligands, rendering a compact and a potentially open 3D frameworks, respectively. On the other hand, 5-amtz ligand exhibits two different coordination modes in compounds 3 and 4 as a result of the presence or absence of an additional blocking ligand. In this way, the μ-κ4N,N′,N″,  N‴N‴ mode in 4 affords robust clusters that are joined in a topologically novel 3D open architecture containing two types of channels, whereas a simple bidentate bridging mode is limited for 5-amtz in 3 due to the presence of the chelating eda ligand. 1D and 3D structures are obtained with pyrimidine ligands in compounds 5 and 6 according to the steric hindrance of the substituents.

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