Green synthesis of a new Schiff base linker and its use to prepare coordination polymers

Solid-state synthesis is an approach to organic synthesis that is desirable because it can offer minimal or no solvent waste, high yields, and relatively low energy footprints. Herein, we report the solid-state synthesis of a novel Schiff base, 4-{(E)-[(4-methylpyridin-3- yl)imino]methyl}benzoic acid (4-PIBZ), synthesized through the reaction of an amine and an aldehyde. 4-PIBZ was prepared via solvent-drop (water) grinding (SDG) on a multigram scale with 97% yield and was characterized using FTIR, 1 H NMR, and SCXRD. The pyridyl and carboxylate moiety present in 4-PIBZ make it suitable for use as a linker ligand and indeed 4-PIBZ was found to coordinate with Cu(II), Zn(II), and Cd(II) cations, enabling it to serve as a linker ligand for the assembly of coordination polymers. 4-PIBZ thereby formed 1D (spiro chain) and 2D (square lattice, sql, topology) coordination polymers via solvent-induced (layering or slurry) methods. The resulting coordination polymers were characterized though X-ray diffraction (SCXRD, PXRD) and TGA, further demonstrating the utility of green synthesis methods for the preparation of some classes of new linker ligands that can in turn be used for the preparation of coordination polymers.