Four 2D Ln–Cd heterometal–organic coordination polymers based on tetranuclear Ln–Cd oxo-cluster with highly selective luminescent sensing of organic molecules and metal cations†
Abstract
Two series of novel lanthanide–cadmium (Ln–Cd) heterometal–organic coordination polymers, i.e., [Ln2Cd2(DTPA)2(H2O)4] (H2O)4 (I: Ln = Eu 1a; Gd 1b) and [Ln2Cd3(DTPA)2Cl2(H2O)6] (II: Ln = Eu 2a; Sm 2b) (H5DTPA = diethylenetriamine pentaacetic acid), have been synthesized using a hydrothermal method. Compounds I and II both possess 2D grid-layer structure based on distinct tetranuclear Ln–Cd oxo-cluster units as secondary building units (SBUs). Two enantiomeric forms, i.e., α and β, exist in [Cd(DTPA)]3− in compounds I. Interestingly, compound 1a displays not only a highly sensitive sensing of small molecular organic solvents, especially methanol, triethylamine and ethanol amine, but also the sensing of cations, especially Cr3+ and Fe3+ ions. Moreover, Cr3+, Fe3+, Co2+, Ni3+, Cu2+, Nd3+ cations quenched the emissions of the Eu3+ ions of compound 2a, which indicates the potential of 1a and 2a for sensing of metal cations.