Synthesis, Structures, and Properties of Complexes Based on 3,5-bis(triazol-1-yl) Benzoic Acid as the Main Ligand

In this paper, 3,5-bis(triazol-1-yl)-benzoic acid (L) is selected as the main ligand to combine with Cd(NO3)2·4H2O to synthesize two complexes of Cd(L)2 (1) and [Cd(L)(PCA)(H2O)]·H2O (2) (PCA = 2-pyrazinecarboxylic acid) under solvothermal conditions. Single-crystal X-ray diffraction analysis shows that complexes 1 and 2 exhibit different three-dimensional framework structures of the network and waveform, respectively. Solid-state fluorescence experiments show that 1 and 2 have excellent fluorescence properties. Ion sensing experiments illustrate that complex 1 can detect Fe3+ with a detection limit (LOD) of 0.132 μM, and complex 2 can selectively sense Cr2O72– (LOD: 0.066 μM). In addition, amino acid and antibiotic sensing experiments reveal that complex 1 has the ability to selectively sense tryptophan (LOD: 0.120 μM) by the fluorescence enhancement effect and tetracycline hydrochloride (LOD: 0.023 μM) by fluorescence quenching. Complex 2 can test sulfadiazine antibiotics (LOD: 4.780 μM) by fluorescence enhancement.