Cd^II-based compound as a multi-responsive fluorescent probe for sensing Fe^III cations and Cr^VI oxyanions

A new luminescent CdII compound, poly[[μ2-1,4-bis(1H-imidazol-1-yl)benzene]{μ2-5-[(3-carboxylphenoxy)methyl]isophthalato}cadmium(II)], [Cd(C16H10O7)(C12H10N4)]n or [Cd(HL)(1,4-bib)]n {H3L is 5-[(3-carboxyphenoxy)methyl]isophthalic acid and 1,4-bib is 1,4-bis(1H-imidazol-1-yl)benzene}, I, has been synthesized successfully from CdII and a semirigid tricarboxylic ligand under hydrothermal conditions. Structure analysis shows that I is a two-dimensional structure with the point symbol {44.62}. The three-dimensional framework is constructed by O-H...O hydrogen bonds and π-π stacking interactions. Furthermore, the obtained CdII compound displays high solvent stability and excellent thermal stability, as shown by powder X-ray diffraction and thermogravimetry measurements. Studies of the luminescence properties reveal that compound I can act as a promising luminescent sensor for detecting FeIII cations and CrVI oxyanions with high selectivity and low detection limits (0.19 µM for Fe3+ and 1.13 µM for Cr2O72-), and is additionally free from the interference of other ions. The mechanism of selective quenching was studied by measuring the UV-Vis absorption of the host compound and the target analytes.