Coordination and topology versatility of metal-organic frameworks based on cadmium iodide and 5-azaarylpyrazole-3-carboxylic acids

This paper studied the coordination behavior of azaarylpyrazole carboxylic acids for the first time. Hydrothermal reaction of 5-(pyridine-3-yl)pyrazole-3-carboxylic acid (H2L1) or 5-(pyrazine-2-yl)pyrazole-3-carboxylic acid (H2L2) with CdI2 afforded crystalline {[CdI(HL1)]}n (1) or {[CdI(HL2)(H2O)]·H2O}n (2), respectively. The X-ray diffraction analyses reveal that the different properties of the pyrazolecarboxylate, the iodide, and the cadmium atoms give rise to different crystal structures. The two complexes show covalently bonded two-dimensional metal-organic frameworks with different topology. The two-dimensional layers are further linked to form three-dimensional supramolecular networks through I⋯π halogen bonds or hydrogen bonds. Both complexes show luminescence enhancement compared to the corresponding ligands.