Template‐Derived Synthesis and Functional Evaluation of Dysprosium(III) Macrocyclic Complexes: Structural, Electrochemical, Fluorescence and Biological Insights

ABSTRACT Dysprosium(III) complexes are of significant interest on account of their high magnetic anisotropy, strong luminescence and ability to form stable coordination geometries with diverse donor atoms. In this work, we report the synthesis of macrocyclic Dy(III) complexes via a Schiff base condensation reaction between isatin and its chloro‐ and bromo‐substituted derivatives with 1,13‐diamino‐4,7,10‐trioxatridecane, carried out in the presence of the metal salt Dy(NO 3 ) 3 ·5H 2 O. The resulting ligands formed stable macrocyclic scaffolds that effectively coordinated to Dy 3+ , affording the corresponding Dy(III) complexes. Structural elucidation and confirmation of complex formation were accomplished using comprehensive spectroscopic techniques. Fluorescence (FL) emission studies of the complexes displayed characteristic and well‐resolved bands at approximately 480, 575 and 660 nm, corresponding to the 4 F 9/2 → 6 H 15/2 , 4 F 9/2 → 6 H 13/2 and 4 F 9/2 → 6 H 11/2 transitions, respectively. The preliminary in vitro biological efficacy of the complexes was evaluated through antimicrobial assays, in which they exhibited promising activity against selected bacterial and fungal strains. Antioxidant activity assessed by the DPPH radical scavenging assay revealed improved free‐radical neutralization. Electrochemical analysis by cyclic voltammetry showed quasi‐reversible redox behaviour characteristic of Dy(III) macrocyclic systems. Notably, one complex, [ C 18 H 25 N 3 O 3 Dy ( NO 3 )]( NO 3 ) 2 ( 24 K ), demonstrated significant DNA‐cleavage activity, inducing oxidative strand scission and disruption of the Escherichia coli genome through reactive oxygen species (ROS)‐mediated pathways. Based on these preliminary evaluations, the synthesized complexes appear to be of considerable interest and may serve as promising candidates for further investigation in diverse applications such as medicinal chemistry, sensing and single‐molecule magnets (SMMs) in future studies.