The ligand, N′-(furan-2-ylmethylene)-2-hydroxybenzohydrazide (H2L), was synthesized characterized through various spectral studies which cleared out that the free ligand existed in keto form. The ligand upon reaction with Cu(II), Co(II), Ni(II) and Zn(II) acetates yielded complexes with stoichiometric ratio 1:2 (M:L) which has been validated through the elemental and mass spectral measurements. The IR and NMR spectral studies of the isolated complexes disclosed that the ligand chelated to metal ion in mononegative bidentate fashion via the azomethine nitrogen and deprotonated enolized carbonyl oxygen. Moreover, the DFT quantum chemical calculations designated that the ligand and Ni(II) complex exhibited the highest and lowest values of HOMO, LUMO energies and HOMO-LUMO energy gap, respectively. Furthermore, the in vitro cytotoxic activity towards HePG-2 and HCT-116 cell lines of the isolated compounds was investigated and the data cleared out that the ligand was more potent than the metal complexes.

中文翻译：

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N′-(呋喃-2-基亚甲基)-2-羟基苯甲酰肼及其金属配合物：合成、光谱研究、DFT 计算和细胞毒性分析

通过各种光谱研究合成了配体 N'-(呋喃-2-基亚甲基)-2-羟基苯甲酰肼 (H2L)，表明游离配体以酮形式存在。该配体与 Cu(II)、Co(II)、Ni(II) 和 Zn(II) 乙酸盐反应生成化学计量比为 1:2 (M:L) 的配合物，该配合物已通过元素和质谱测量得到验证。分离的配合物的红外和核磁共振谱研究表明，配体通过偶氮甲碱氮和去质子化的烯醇化羰基氧以单负二齿形式螯合到金属离子。此外，DFT量子化学计算表明配体和Ni(II)配合物分别表现出最高和最低的HOMO、LUMO能量和HOMO-LUMO能隙。此外，研究了分离化合物对 HePG-2 和 HCT-116 细胞系的体外细胞毒活性，数据表明配体比金属配合物更有效。