Swati Bugalia

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.

A new series of Cd(II) macrocyclic complexes has been synthesized via template condensation of 1,13-diamino-4,7,10-trioxatridecane with tribulin and its derivatives in the presence of CdCl₂·H₂O (1:1:1 molar ratios). Structural characterization by FTIR, UV–Vis, ¹H & ¹³C NMR, XRD, mass spectrometry, and elemental analyses supports an octahedral geometry. The stability of the complexes in solution phase was validated through time-resolved UV–Visible spectroscopic analysis over 24 h, revealing no detectable signs of dissociation. Photoluminescence properties were examined in the solid state, revealing a common excitation maximum at 230 nm and distinct emission maxima at 467 nm, 395 nm, and 398 nm, respectively. These results demonstrate the significant optical response of Cd(II) macrocycles and highlights their potential for applications in luminescent devices and optical sensors. The antioxidant capacity was assessed using a DPPH-free radical scavenging experiment, which exhibited significant results. The newly synthesized complexes have also been screened for antibacterial and antifungal activities. In vitro antimicrobial screening of the complexes was evaluated against Gram-negative E. coli and Gram-positive S. aureus bacterial strains and A. niger and P. chrysogenum fungal strains. Antimicrobial evaluation demonstrates that these complexes exhibit superior antifungal efficacy compared to the standard drug ketoconazole, highlighting their promise as potent antifungal agents. Graphical Abstract

Novel luminescent N₃O₃-donor Sm(III) macrocyclic complex i.e., [Sm(C₁₇H₂₅N₃O₅)].3NO₃; [(2Z,17Z)-7,10,13-trioxa-3,17-diaza-1(2,6)-pyridinacycloocta-decaphane-2,17-diene-2,18-diol] has been synthesized through the template synthetic route by using 1,13-diamino-4,7,10-trioxatridacane and pyridine-2,6-dicarboxylic acid ligand precursors in the presence of Sm(NO₃)₃.6H₂O in (1:1:1) molar ratios. Elemental analysis, ¹H NMR, ¹³C NMR, UV-Vis, FTIR, XRD, and mass spectrometry techniques have been utilized for the characterization of the synthesized complex. The crystalline nature of the complex is confirmed by the existence of sharp narrow peaks in the X-ray diffractogram. Optical property (Photoluminescence) is analyzed by PL-spectroscopy and results manifested that under 272 nm excitation wavelength, the complex exhibited three characteristic emission peaks at 563 nm, 602 nm, and 644 nm corresponded to the ⁴G_5/2→⁶H_5/2, ⁴G_5/2→⁶H_7/2, and ⁴G_5/2→⁶H_9/2 transitions respectively. This property leads the use of this reported complex as an optical active material which could be used as sensor for analysis and detection purpose such as cell or tissue imaging, solar cell, luminescent probe etc. Antimicrobial screening of the complex against E. coli, & S. aureus bacterial strains and Alternaria alternate & Fusarium solani fungal strains has also been performed to investigate their antimicrobial potential and revealed satisfactory results. Antioxidant potential of the complex has been checked by applying a DPPH free radical scavenging assay and the complex appeared with notable result. Cyclic voltammetry results indicated the electrochemical nature of the complex as prominent redox material for redox reactions.

Role of synthetic coordination chemistry in pharmaceutical science is expeditiously increased due to its sundry relevances in this field. The present review endows the synthesized macrocyclic complexes of transition metal ions containing isatin and its derivatives as ligand precursors, their characterization and their copious pharmaceutical applications. Isatin (1H-Indole-2,3-dione) is a protean compound (presence of lactam and keto moiety permits to change its molecular framework) that can be obtained from marine animals, plants, and is also found in mammalian tissues and in human fluids as a metabolite of amino acids. It can be used for the synthesis of miscellaneous organic and inorganic complexes and for designing of drugs since it has remarkable utility in pharmaceutical industry due to its wide range of biological and pharmacological activities, for instance anti-microbial, anti-HIV, anti-tubercular, anti-cancer, anti-viral, anti-oxidant, anti-inflammatory, anti-angiogenic, analgesic activity, anti-Parkinson’s disease, anti-convulsant etc. This review provides extensive information about the latest methods for the synthesis of isatin or its substituted derivatives based macrocyclic complexes of transition metals and their plentiful applications in medicinal chemistry. Graphical Abstract