A Multifunctional Rhodamine‐Triazine Platform for Selective Aqueous Cu ²⁺ Sensing and Anticancer and Bio‐imaging Activities: Experimental, Structural, and Computational Perspectives

ABSTRACT

A rhodamine‐triazine‐based chemosensor ligand (HL) was designed, synthesized, and characterized for the selective Cu ^{2 +} detection. Upon interaction with Cu ^{2 +} , HL displays a distinct and reversible colour change from baby pink to deep purple, confirming the formation of a stable [Cu(HL)Cl ₂ ] complex. Spectroscopic analyses reveal that Cu ^{2 +} coordinates with the spirolactam ring through triazenyl–benzohydrazonate nitrogen and oxygen donor atoms. The chemosensor demonstrates high selectivity for Cu ^{2 +} at physiological pH (5 to 8) with a low detection limit of 2.6 µM and a relative quantum yield of HL with respect to commonly used rhodamine B is 0.36 (36%). The life‐time of the ligand (HL) was found to be 6.05 ns. The NMR titration, DFT, and TD‐DFT studies provide insights into the electronic and structural changes upon complexation. Additionally, HL exhibits promising anticancer activity against HepG2 cells, with an IC ₅₀ value of 17.73 ± 0.48 µM. Cell imaging studies further show that the HL localizes primarily within the living breast cancer cell (MDA‐MB‐231) under physiological pH conditions. Molecular docking and dynamics simulations indicate stable binding of HL within the Topoisomerase II active site (ΔG = –6.36 kcal mol ^{− 1} ), underscoring its potential applications in biological monitoring and environmental sensing.