Two new luminescent Cd(II)-based coordination polymers by regulating the asymmetrical tetracarboxylate and auxiliary ligands displaying high sensitivity for Fe3+ and CrO42-

Two new coordination polymers (CPs), namely [Cd2(L)(2,2′-bipy)] (1) and [Cd2(L)(H2O)4] (2) (H4L = [1,1′-biphenyl]-2,3,3′,5′-tetracarboxylic acid and 2,2′-bipy = 2,2′-bipyridine), have been successfully synthesized under solvothermal conditions. 1 exhibits a 2D layer that was further extended into a 3D supramolecular framework through the packing interaction. 2 has a 3D 3,3,4-c network with a point symbol of (62·82)(63)2. The sensing results illustrated that both of them could be prospective candidates for developing luminescent sensors for the probing of Fe3+ and CrO42−. The probe effects remained highly selective to the Fe3+ and CrO42− ions even if there are other interfering ions. The limits of detection (LODs) for Fe3+/CrO42− were calculated to be ca. 2.47 × 10−8 M−1/1.12 × 10−8 M−1 and 1.35 × 10−9 M−1/2.23 × 10−8 M−1 for 1 and 2, respectively. The fluorescence resonance energy transfer process may be the major pathway behind the quenching mechanism for Fe3+ and CrO42- ions. The recycling operation indicated that compounds 1 and 2 are promising reusable probes for their effective capability of detecting Fe3+ and CrO42− ions.