Effect of pH on the construction of CdII coordination polymers involving the 1,1′‐[1,4‐phenylenebis(methylene)]bis(3,5‐dicarboxylatopyridinium) ligand

Changing the pH value of a reaction system can result in polymers with very different compositions and architectures. Two new coordination polymers based on 1,1′‐1,4‐phenylenebis(methylene)]bis(3,5‐dicarboxylatopyridinium) (L^2?), namely catena‐polytetraaquacadmium(II)]‐μ₂‐1,1′‐1,4‐phenylenebis(methylene)]bis(3,5‐dicarboxylatopyridinium)] 1.66‐hydrate], {Cd(C₂₂H₁₄N₂O₈)(H₂O)₄]·1.66H₂O}_n, (I), and poly{μ₆‐1,1′‐1,4‐phenylenebis(methylene)]bis(3,5‐dicarboxylatopyridinium)}cadmium(II)], Cd(C₂₂H₁₄N₂O₈)]_n, (II), have been prepared in the presence of NaOH or HNO₃ and structurally characterized by single‐crystal X‐ray diffraction. In polymer (I), each Cd^II ion is coordinated by two halves of independent L^2? ligands, forming a one‐dimensional chain structure. In the crystal, these chains are further connected through O—H…O hydrogen bonds, leading to a three‐dimensional hydrogen‐bonded network. In polymer (II), each hexadentate L^2? ligand coordinates to six Cd^II ions, resulting in a three‐dimensional network structure, in which all of the Cd^II ions and L^2? ligands are equivalent, respectively. The IR spectra, thermogravimetric analyses and fluorescence properties of both reported compounds were investigated.