Biological and Catalytic Potential of Vanadium Complexes of <i>N</i> -Methyl- <i>N</i> -phenylhydrazinecarbothioamide Based ONS Donor Ligands

Designing vanadium complexes that can simultaneously address environmental and biomedical challenges is an emerging research direction. The ONS donor ligands derived from <i>N</i>-methyl-<i>N</i>-phenylhydrazinecarbothioamide and salicylaldehyde (H₂<b>L</b>¹) or 5-bromosalicylaldehyde (H₂<b>L</b>²) have been used to synthesize four different types of new vanadium complexes, [V^IVO(<b>L</b>¹/<b>L</b>²)(H₂O)] (<b>1</b> and <b>2</b>), [V^VO(OMe) (<b>L</b>¹/<b>L</b>²)] (<b>3</b> and <b>4</b>), Cs/K(H₂O)₂[V^VO₂(<b>L</b>¹/<b>L</b>²)] (<b>5</b>-<b>8</b>), and [(μ-O){V^VO(<b>L</b>¹/<b>L</b>²)}₂] (<b>9</b> and <b>10</b>), to address these issues. Different instrumental methods have been used to characterize these complexes. The anticancer activities of <b>1</b>-<b>8</b> toward different cancer cell lines were evaluated through the MTT assay, and among these, <b>8</b> exhibited pronounced cytotoxicity against A549 lung cancer cells (IC₅₀ = 4.02 μM), nearly 4-fold more potent than cisplatin (IC₅₀ = 17.07 μM), while remaining nontoxic to normal HEK293 cells. Its anticancer activity operates via chemodynamic therapy (CDT) through a Fenton-like reaction that generates intracellular hydroxyl radicals, as confirmed by EPR spectroscopy. Apoptosis induction was evidenced by DNA damage and chromatin condensation (DAPI assay), with live/dead staining that further validated its potential as an efficient CDT agent. Catalytically, they demonstrated excellent activity for the cycloaddition of CO₂ with epoxide under mild conditions (45 °C, ∼1 atm (<i>p</i>CO₂ using a balloon)), affording cyclic carbonates with efficient conversion (99%) and selectivity (>99%).