Catalytic, Antifungal, and Antiproliferative Activity Studies of a New Family of Mononuclear [V^IVO]/[V^VO₂] Complexes

Ligands derived from 2-(1-phenylhydrazinyl)pyridine and salicylaldehyde (HL¹), 3-methoxysalicylaldehyde (HL²), 5-bromosalicylaldehyde (HL³), and 3,5-di-tert-butylsalicylaldehyde (HL⁴) react with [V^IVO(acac)₂] in MeOH followed by aerial oxidation to give [V^VO₂(L¹)] (1), [V^VO₂(L²)] (2), [V^VO₂(L³)] (3), and [V^VO₂(L⁴)] (4). Complex [V^IVO(acac)(L¹)] (5) is also isolable from [V^IVO(acac)₂] and HL¹ in dry MeOH. Structures of all complexes were confirmed by single-crystal X-ray and spectroscopic studies. They efficiently catalyze benzyl alcohol and its derivatives’ oxidation in the presence of H₂O₂ to their corresponding aldehydes. Under optimized reaction conditions using 1 as a catalyst precursor, conversion of benzyl alcohol follows the order: 4 (93%) > 2 (90%) > 1 (86%) > 3 (84%) ≈ 5 (84%). These complexes were also evaluated for antifungal and antiproliferative activities. Complex 3 with MIC₅₀ = 16 μg/mL, 4 with MIC₅₀ = 12 μg/mL, and 5 with MIC₅₀ = 16 μg/mL are efficient toward planktonic cells of Candida albicans and Candida tropicalis. On Michigan cancer foundation-7 (MCF-7) cells, they show comparable cytotoxic effects and exhibit IC₅₀ in the 27.3–33.5 μg/mL range, and among these, 4 exhibits the highest cytotoxicity. A similar study on human embryonic kidney cells (HEK293) confirms their less toxicity at lower concentrations (4 to 16 μg/mL) compared to MCF-7.