A novel hydrolytically stable fluorescent Cd(II) coordination polymer showing solvent-dependent multi-responsive fluorescence sensing to pH and some metal ions

Herein, the assembly between the multi-functional 2-amino-4-sulfonyl-benzoic acid (H 2 asba) and Cd(II) in the presence of the hydrophobic ligand 4-bis[(2-methyl-1H-imidazole-1-yl)methyl]benzene (2-mmzm) results in a novel hydrolytically sTable 1D Cd(II)-FCP, {[Cd(asba)(2-mmzm)(H 2 O) 2 ] center dot 3H 2 O} n ( 1 ). The water tetramer-based hydrogen-bonded ring R 2 2 (8) bridges the chains into a 2D supramolecular layer. The novel discrete water decamer further links the layers into a 3D supramolecular network . 1 shows extremely acidic and basic resistance in a wide pH range of 1.0-12.0. More importantly, 1 exhibits accurate sensing of pH of the artificial gastric juices. Interestingly, 1 demonstrates solvent-dependent multi-responsive fluorescence sensing behavior to metal ions. 1 can sense Fe 3 + /Cu 2 + /Tb 3+ in water, Fe 3 + /Cu 2 + /Tb 3 + /Co 2 + in MeOH and Fe 3 + /Cu 2 + /Tb 3 + /Co 2 + /Ba 2 + in ethanol, respectively. The fluorescence sensing of 1 toward Fe 3 + /Tb 3 + /Ba 2 + is resulted from the structural collapse in the corresponding solvents. However, 1 keeps integrity and shows higher chemical resistance to Cu 2+ and Co 2 + in the corresponding solvents. The fluorescence sensing of Cu 2 + can be ascribed to the photo-induced electron transfer (PET) and fluorescence resonance energy transfer (FRET) mechanism. The sensing of Co 2 + can be attributed to the PET mechanism. The solvents have great influence on the sensing sensitivities to Cu 2 + and Co 2 + . 1 shows the highest sensing sensitivity to Cu 2 + and Co 2 + in ethanol. (c) 2022 Elsevier B.V. All rights reserved.

Automated summary

In this study, a novel hydrolytically stable Cd(II)-FCP was synthesized through the assembly of multi-functional 2-amino-4-sulfonyl-benzoic acid and Cd(II) in the presence of the hydrophobic ligand 4-bis[(2-methyl-1H-imidazole-1-yl)methyl]benzene. The resulting compound exhibited acid and base resistance in a wide pH range and accurate sensing of pH in artificial gastric juices. Additionally, it demonstrated solvent-dependent multi-responsive fluorescence sensing behavior towards different metal ions.