Novel Fluorescent Tetrahedral Zinc (II) Complexes Derived from 4-Phenyl-1-octyl-1H-imidazole Fused with Aryl-9H-Carbazole and Triarylamine Donor Units: Synthesis, Crystal Structures, and Photophysical Properties.

We present here the design, synthesis, and photophysical properties of two novel fluorescent zinc (II) complexes, ZnCl2(ImL1)2 and ZnCl2(ImL2)2, containing 4-(1-octyl-1H-imidazol-4-yl)-N,N-diphenyl-[1,1-biphenyl]-4-yl)-4-amine ImL1 and 9-(4-(1-octyl-1H-imidazol-4-yl)-[1,1-biphenyl]-4-yl)-9H-carbazole ImL2 ligands. The newly synthesized free ligands and their zinc (II) complexes were characterized using several spectroscopic techniques; their structures were identified by single-crystal X-ray diffraction; and their photophysical properties have been studied in the context of their chemical structure. The ZnCl2(ImL1)2 and ZnCl2(ImL2)2 complexes showed good thermal stability at 341 °C and 365 °C, respectively. Photophysical properties, including UV-Vis absorption spectra in ethanol solution and photoluminescence (PL) in both solid state and ethanol solution, were determined. UV-Vis adsorption data indicated that both free ligands had similar UV-Vis absorption properties, while their Zn (II) complexes had distinctive absorption characteristics. The fluorescence spectra show that both ligands and their corresponding Zn (II) complexes emit violet to cyan luminescence in the solid state at room temperature, while in ethanol solution at the same temperature, they exhibit efficient photoluminescence properties in the UV-A emission spectral region. Because of these photophysical properties, the synthesized ligands and their cognate Zn (II) complexes can be used as scaffolds for the potential development of optoelectronic materials.