A One-Dimensional Cadmium Coordination Polymer: Synthesis, Structure, and Application as Luminescent Sensor for Cu2+ and CrO42-/Cr2O72- Ions

A novel coordination polymer {[Cd-4(CPIP)(3)Cl-8]}(n) (CP1) was constructed from the reaction of CPIP (CPIP=1-chloro-3-(pyridine-2-yl)imidazo[1,5-a]pyridine) and CdCl2.2.5H(2)O under solvothermal conditions. The employment of CPIP as the ligand was based on the consideration that two types of Lewis basic sites (the fused nitrogen atom and the chlorine substituent) are present on the backbone of the ligand. These sites can be utilized for interacting with cations and anions, thus for the sensing functionality. Single-crystal X-ray diffraction studies revealed that CP1 exhibits interesting one-dimensional (1D) polymeric chain structure. The adjacent four Cd-II ions are connected by one mu(3)-Cl and five mu(2)-Cl atoms to form a Chinese-lantern-like topology. CP1 is an excellent luminescent sensor for detecting Cu2+, CrO42- and Cr2O72- ions with high selectivity, sensitivity, and recyclability. Moreover, CP1 is the first reported chloride-bridged coordination polymer that is capable of sensing Cu2+ ion. The mechanisms for sensing Cu2+, CrO42- and Cr2O72- ions were investigated and discussed.