Three ONNO donor tetradentate diamino bis(phenolato) “salan” ligands, N, N′-dimethyl-N, N′-bis-(5-chloro-2-hydroxy-3-methyl-benzyl)-1,2-diaminoethane (H₂L¹), N, N′-dimethyl-N, N′-bis-(5-chloro-2-hydroxy-3-isopropyl-6-methyl-benzyl)-1,2-diamino-ethane (H₂L²) and N, N′-bis-(5-chloro-2-hydroxy-3-isopropyl-6-methyl-benzyl)-1,2-diaminocyclohexane (H₂L³) have been synthesized by following Mannich condensation reaction. Reaction of these ligands with their corresponding vanadium metal precursors gave one oxidomethoxidovanadium(V) [V^VOL¹(OCH₃)] (1) and two monooxido-bridged divanadium (V, V) complexes [V^VOL^2–3]₂(μ-O) (2–3). The complexes were characterized by IR, UV–vis, NMR and ESI mass spectrometry. Also, the structure of all the complexes (1–3) was confirmed by the Single-Crystal X-ray diffraction analysis, which revealed a distorted octahedral geometry around the metal centres. The solution behavior of the [V^VOL¹(OCH₃)] (1) reveals the formation of two different types of V(V) species in solution, the structurally characterized compound 1 and its corresponding monooxido-bridged divanadium (V, V) complex [V^VOL¹]₂(μ-O), which was further studied by IR, and NMR spectroscopy. The electrochemical behavior of all the complexes was evaluated through cyclic voltammetry. Interaction of the salan-V(V) complexes with human serum albumin (HSA) and bovine serum albumin (BSA) were analysed through fluorescence quenching, UV–vis absorption titration, synchronous fluorescence, circular dichroism studies, and förster resonance energy transfer (FRET). Finally, the in vitro cytotoxicity of the complexes was investigated against MCF-7 and HT-29 and NIH-3T3 cell lines. Cytotoxicity value of complexes in both MCF-7 and HT-29 follows the same trend that is 3 > 1 > 2 which is in line with protein binding affinity of the complexes.

三个 ONNO 供体四齿二氨基双（苯酚）“salan”配体，N，N'-二甲基-N，N'-双-（5-氯-2-羟基-3-甲基-苄基）-1,2-二氨基乙烷（ H ₂ L ¹ ), N , N'-二甲基-N , N'-双-(5-氯-2-羟基-3-异丙基-6-甲基-苄基)-1,2-二氨基-乙烷(H ₂ L ² ) 和N , N'-双-(5-氯-2-羟基-3-异丙基-6-甲基-苄基)-1,2-二氨基环己烷(H ₂ L ³) 已通过以下曼尼希缩合反应合成。这些配体与其相应的钒金属前体反应生成一种氧化甲氧化钒 (V) [V ^V OL ¹ (OCH ₃ )] ( 1 ) 和两种单氧化桥联二钒 (V, V) 配合物 [V ^V OL ^2-3 ] ₂ ( μ -O) ( 2-3 )。配合物通过 IR、UV-vis、NMR 和 ESI 质谱进行表征。此外，所有配合物 ( 1-3 ) 的结构都通过单晶 X 射线衍射分析得到证实，该分析揭示了金属中心周围的八面体几何形状扭曲。^{[V V}的解行为OL ¹ (OCH ₃ )] ( 1 ) 揭示了溶液中两种不同类型的 V(V) 物质的形成，即结构特征化合物1及其相应的单氧化桥联二钒 (V, V) 络合物 [V ^V OL ¹ ] ₂ ( μ-O)，通过 IR 和 NMR 光谱进一步研究。通过循环伏安法评估了所有配合物的电化学行为。通过荧光猝灭、紫外-可见吸收滴定、同步荧光、圆二色性研究和 förster 共振能量转移 (FRET) 分析了 salan-V(V) 复合物与人血清白蛋白 (HSA) 和牛血清白蛋白 (BSA) 的相互作用）。最后，研究了复合物对 MCF-7 和 HT-29 和 NIH-3T3 细胞系的体外细胞毒性。MCF-7 和 HT-29 中复合物的细胞毒性值遵循相同的趋势，即3 > 1 > 2，这与复合物的蛋白质结合亲和力一致。