2‑Propyl-4,5-dicarboxylate-imidazole (H3PIDC) Based Cadmium(II) Coordination Compounds Stabilized by Supramolecular Interactions: From Mononuclear and Tetranuclear Oligomers to One-Dimensional (1D) Chain and Two-Dimensional (2D) Layer Polymers

Six cadmium­(II) coordination compounds with 2-propyl-imidazole-4,5-dicarboxylate (H3PIDC), including two mononuclear complexes, [Cd­(H2PIDC)2(H2O)2]·4H2O (1) and [Cd2(H2PIDC)4(H2O)4]·7H2O (2), two square tetranuclear complexes, [Cd4(HPIDC)4(H2O)8]·2H2O (3) and [Cd4(HPIDC)4(py)8]·10H2O (py = pyridine, 4), one one-dimensional chain polymer, [Cd2(H2PIDC)4(H2O)2]n·2nH2O (5), as well as one two-dimensional layer polymer, [Cd­(H2PIDC)2]n (6), have been prepared using solvent evaporation method and hydrothermal method. The results of single-crystal X-ray diffraction analyses indicate that, besides the common supramolecular interactions such as hydrogen bond and π···π stacking, the hydrophobic interaction among the propyl groups in the H3PIDC ligands also contributes to the stabilities of 1–6. The study of substance transformation for 3 reveals that the coordinated H2O molecules in 3 can be well replaced by pyridine molecules, indirectly leading to the formation of 4. The results of photoluminescent measurements illustrate upon photoexcitation that 3–6 can emit fluorescence in the wavelength range of 451–473 nm in the solid state.