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

A new luminescent Cd compound, poly[[μ-1,4-bis(1H-imidazol-1-yl)benzene]{μ-5-[(3-carboxylphenoxy)methyl]isophthalato}cadmium(II)], [Cd(CHO)(CHN)] or [Cd(HL)(1,4-bib)] {HL 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 Cd and a semirigid tricarboxylic ligand under hydrothermal conditions. Structure analysis shows that I is a two-dimensional structure with the point symbol {4.6}. The three-dimensional framework is constructed by O-H...O hydrogen bonds and π-π stacking interactions. Furthermore, the obtained Cd 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 Fe cations and Cr oxyanions with high selectivity and low detection limits (0.19 µM for Fe and 1.13 µM for CrO), 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.