The pH-controlled synthesis of three zinc-based complexes modeled by 5-carboxyl-1-carboxymethyl-2-oxidopyridinium with luminescence studies

Three new zinc compounds {[Zn2(ccop)2(4,4′-bpy)]·H2O}n (1), {[Zn(ccop)(bpp)]·H2O}n (2) and [Zn(ccop)(H2O)5]·H2O (3) (H2ccop = 5-carboxyl-1-carboxymethyl-2-oxidopyridinium, 4,4′-bpy = 4,4′-bipyridine, bpp = 1,3-bis(4-pyridyl) propane) have been prepared under hydrothermal conditions at different pH values, and characterized by elemental analysis, IR spectra, thermogravimetric analysis, powder X-ray diffraction, and single-crystal X-ray diffraction. Complex 1 features a 2D (4,4) net when the dinuclear [Zn2(COO)2N2O2] unit is regarded as a quadruply-connected node. Complex 2 also displays a 2D (4,4) net constructed by Zn-carboxylate chains and bpp struts. While 3 is a mononuclear complex which is further assembled into a 3D supramolecular structure through hydrogen boning interactions. All of 1–3 emit the intense indigotin photoluminescence at room temperature in solid state.