The tunable coordination architectures of a flexible multicarboxylate N-(4-carboxyphenyl)iminodiacetic acid via different metal ions, pH values and auxiliary ligand

Abstract

{[Pb 3(CPIDA) 2(H 2O) 3]·H 2O} n 1, {[Cd 3(CPIDA) 2(H 2O) 4]·5H 2O} n 2, [Cd(HCPIDA)(bpy)(H 2O)] n 3 (bpy=4,4′-bipyridine) and {[Co 3(CPIDA) 2(bpy) 3(H 2O) 4]·2H 2O} n 4 were synthesized with N-(4-carboxyphenyl) iminodiacetic acid (H 3CPIDA). In 1, the CPIDA 3− ligands adopt chelating and bridging modes with Pb(II) to possess a 3D porous framework. In 2D-layer 2, the CPIDA 3− ligands display a simple bridging mode with Cd(II). The 2D layers have parallelogram-shaped channels along a axis. With bpy ligands, the HCPIDA 2− ligands in 3 show more abundant modes, but 3 still displays a 2D sheet on bc plane for the unidentate bpy molecules. However, in 3D-framework 4, the bpy ligands adopt bridging bidentate at a higher pH value and the CPIDA 3− ligands show bis-bidentate modes with Co(II). Additionally, 2D correlation analysis of FTIR was introduced to ascertain the characteristic adsorptions location of the carboxylate groups with different coordination modes in 4 with thermal and magnetic perturbation. Compounds 1, 2 and 4 exhibit the fluorescent emissions at room temperature.