Synthesis and Characterization of Macrocyclic Ferrocenyl Chalcone and Their Co(II) and Cu(II) Complexes: Photonuclease and Photocytotoxicity

Ferrocenyl chalcone complex (Fc₂L) has been synthesized from the condensation of 3,4:10,11-dibenzo-1,13[N,N′-bis{(3-formyl-2-hydroxy-5-methyl)benzyl}]-5,9-dioxocyclohexa decane (the precursor compound) with acetyl ferrocene. The Co(II) and Cu(II) Complexes (CoFc₂L [1] and CuFc₂L [2]) were synthesized from the ferrocenyl chalcone (Fc₂L) with metal chloride salts and characterized by various physicochemical techniques (UV–Vis, FT-IR, ¹H NMR,¹³C NMR, ESI-MS, and TGA). The electrochemical studies exhibit a quasireversible reduction wave with E_pc near −1.02 V for Complex 1 and −0.95 V for Complex 2. TGA analysis proposed that Complexes 1 and 2 showed thermal stability. The calf thymus DNA (CT-DNA) binding studies of the complexes were examined by spectral studies and electrochemical measurements. The absorption spectrum analyses demonstrated that Complexes 1 and 2 have intrinsic binding strengths of 7.5 × 10⁵ M⁻¹ and 9.18 × 10⁵ M⁻¹, respectively, and bind to CT-DNA via an intercalative binding mechanism. The pUC19 DNA cleavage studies of the complexes using gel electrophoresis assay were performed in the presence of MPA for Complex 1 and in the presence of Asc for Complex 2. After radiation exposure, the plasmid SC DNA in both complexes was completely cleaved into NC DNA and photo nick DNA via a singlet oxygen pathway. The antimicrobial activity of Complexes 1 and 2 exhibits better bacterial and fungal growth inhibition at the higher study concentration. The complexes' cytotoxicity was evaluated on MDA-MB-231 breast cancer cells, exhibiting IC₅₀ values of 10, 50, and 5, 25 μg/mL under dark and light irradiation, respectively. The fluorescence microscopy analysis of cell morphology studies using AO/EB dual labeling, propidium iodide (PI) staining, and the Hoechst staining on MDA-MB-231 cancer cells revealed a significant increase in cell mortality during irradiation due to the photodynamic effect. The present study demonstrates that Complexes 1 and 2 without radiation in breast cancer cells stimulate intrinsically mediated apoptosis. In the meantime, radiation triggers Complexes 1 and 2 intrinsic- and extrinsic-mediated apoptosis pathways. The biotoxicity assay using Artemia nauplii was evaluated for Complexes 1 and 2 to identify its biocompatibility.