A two-dimensional Cd(II) coordination polymer as a fluorescence-enhancement probe with high selectivity and sensitivity toward tyrosine and lysine

In this paper, we synthesized a new Cd(II) coordination polymer {[Cd(IPA)(L)]·H 2 O} n under hydrothermal conditions using isophthalic acid (H 2 IPA) and the typical pyridamide polynitrogen ligand N, N′-bis(4-pyridylcarbamido)-4, 4′-diphenyl ether (L). The X-ray single-crystal structure analysis showed that the complex had a two-dimensional layered structure. Surprisingly, the complex can act as a dual-responsive probe to detect tyrosine (Tyr), lysine (Lys), Fe 3+ and Cr 2 O 7 2- , exhibiting fluorescence enhancement for Lys and Tyr, a significant blue shift for Tyr, and fluorescence quenching for Fe 3+ and Cr 2 O 7 2- . It also possesses excellent anti-interference and cycling performance, making it a promising candidate for multifunctional optical sensors. The detection limits are Tyr: 3.1×10 -8 M, Lys: 9.4×10 -7 M, Fe 3+ : 1.461× 10 -6 M, Cr 2 O 7 2- : 1.31× 10 -6 M. Finally, combining experimental research and theoretical simulation, the fluorescence enhancement mechanism of the complex on two amino acids and the quenching mechanism on two ions were discussed in detail. The fluorescence enhancement and blue shift caused by Tyr may be due to strong hydrogen bonding and π-π conjugation effects, while Lys causes fluorescence enhancement through weak hydrogen bonding. The quenching effect on Fe 3+ and Cr 2 O 7 2- is a result of competitive absorption and interatomic interactions.