Four Metal Complexes Based on Bulky Imidazole Ligands: Solvothermal Syntheses, Crystal Structures, and Fluorescence Properties

In order to explore the influences of (de-)protonation of the imidazole ring on the structural diversity of the resulting complexes, the imidazole-based ligands 4,5-diphenylimidazole (Hdpi) and 1H-phenanthro[9,10-d]imidazole (Hpi) were utilized as bulky building blocks to construct four complexes by solvothermal reactions, i.e. [Ag(Hdpi)(2)](NO3)center dot(H2O) (1), [Cu(dpi)](infinity) (2), [Cu(Hpi)(NO3)](infinity) (3), and [(H(2)pi)(NO3)]center dot H2O (4). In complex 1, two Hdpi ligands adopt a monodentate pattern and coordinate with one Ag-I ion to form a mononuclear unit, which is further connected by hydrogen bonds into a 1D supramolecular helix. The deprotonated dpi ligand of 2 acts in bidentate mode, and bridges Cu-I ions to afford a 1D chain. In 3, the NO3- ion, acts as a monodentate bridging ligand and joins CuI ions to generate a 1D chain. The Hpi ligand employs a monodentate mode to bond with CuI ions of the 1D chain. 4 is protonated and two H(2)pi nitrogen atoms are free of coordination. Interestingly, hydrogen bonds among the NO3- ion, the H(2)pi ligand, and the water molecule yield a macro ring R-4(4)(14). The resulting structural diversity reveals that the (de-)protonation of imidazole ring directly steers the coordination number of ligand, and thus causes a significant effect on the structure, especially the dimensionality. Furthermore, the solid-state fluorescence properties of the free ligands and compounds 1-4 were studied at room temperature.