One Luminescent Cadmium Iodide with Free Bifunctional Azole Sites as a Triple Sensor for Cu2+, Fe3+, and Cr2O72– Ions

The exploration of an excellent triple sensor for monitoring Cu2+, Fe3+, and Cr2O72– ions is of exceeding significance because of their serious effects on the human body. Herein, optically active 1H-3,5-bis(pyrazinyl)-1,2,4-triazole (Hbpt) with triazolyl and pyrazinyl groups was applied for the construction of a new type of organic hybrid cadmium iodide [Cd6I8(bpt)4(H2O)4]·2H2O (1) incorporating a hitherto-unknown [Cd3I4(H2O)2]2+ trimeric-cationic unit, which shows an orange light emission at 589 nm with a large Stokes shift of 246 nm. In virtue of the existence of free bifunctional azole sites as the receptors, 1 exhibits a highly selective and sensitive sensing property toward Cu2+, Fe3+, and Cr2O72– ions in aqueous solution with lower detection limits of 0.70∼4.46 ppm, which offers the sole example of cadmium iodide as an excellent triple sensor for detecting Cu2+, Fe3+, and Cr2O72– ions. Moreover, temperature-dependent luminescent determinations also reveal that 1 can be used as the potential luminescent molecular thermometer.