Metal-organic supramolecular architectures derived from a new zwitterionic dicarboxylate ligand

A series of new coordination compounds with 1-carboxymethylpyridinium-4- benzoate (L) and transition metal ions have been synthesized. They are formulated as [M(L)₂(H₂O)₄] 4H₂O M=Mn (1) and Co (2), {[M(L)₂] xH₂O}_n M=Mn, x = 1 (3); M=Co, x = 2 (4), and M=Cu, x = 3 (5). In 1 and 2, the zwitterionic dicarboxylate ligand is monodentate through only one carboxylate to generate mononuclear molecules. The molecules are assembled through O-H O interactions to give 3-D pillared layer-like architectures, in which interesting 1-D tape-like hydrogen bonding motifs are connected into 2-D layers via carboxylate-mediated hydrogen bonds. In 3-5, the organic ligands serve as bridges with one carboxylate monodentate and the other chelating, and the metal ions are linked by double bridges to give 1-D polymeric chains, which are zigzag (3) or stair-like (4 and 5) due to the cis or trans coordination geometry around metal ions. The chains are further stabilized and associated into 3-D architectures through intra- and interchain hydrogen bonding and/or - stacking interactions.