In the present study, five nonphenolic (E)‐N′‐benzylidenebenzohydrazides including three new compounds were synthesized and evaluated for their free radical scavenging activities using 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH). X‐Ray analysis of a single crystal of (E)‐N′‐(4‐chlorobenzylidene)benzohydrazide (3c) revealed a triclinic, space group P‐1 structure with a trans configuration around the azomethine (C2N2) double bond. The three‐dimensional Hirshfeld surfaces and the related two‐dimensional fingerprint plots were also drawn to study the plausible intermolecular interactions. Density functional calculations of structures, electronic densities, frontier molecular orbitals modeling, and Mulliken charge analysis of all compounds were performed at the B3LYP/6‐311G level of theory. Theoretical vibrational frequencies were predicted and compared with experimental values, and results supported the validity of optimized geometry of noncrystalline compounds. All synthesized compounds showed significant DPPH radical scavenging activity, although compound 3d exhibited greatest antioxidant activity with an IC50
value of 11 μM. The results of DFT analysis were used to explain the proposed antioxidant mechanism of (E)‐N′‐benzylidenebenzohydrazide analogs. This analysis revealed that protons attached to N, O, and C atoms possessing high negative charge are involved in the production of free radicals that scavenge DPPH. Moreover, the antioxidant activities of (E)‐N′‐benzylidenebenzohydrazide analogs correlated well with HOMO–LUMO energy difference of molecules.
本研究合成了五种非酚类 (E)-N′-亚苄基苯并甲酰肼,其中包括三种新化合物,并使用 2,2-二苯基-1-苦基肼(DPPH)评估了它们清除自由基的活性。对 (E)-N′-(4-chlorobenzylidene)benzohydrazide (3c)单晶的 X 射线分析表明,该化合物呈三菱形,空间群为 P-1 结构,偶氮甲基 (C2N2) 双键周围呈反式构型。此外,还绘制了三维 Hirshfeld 表面和相关的二维指纹图谱,以研究分子间似有的相互作用。在 B3LYP/6-311G 理论水平上对所有化合物的结构、电子密度、前沿分子轨道建模和 Mulliken 电荷分析进行了密度泛函计算。对理论振动频率进行了预测,并与实验值进行了比较,结果证明了非晶化合物优化几何形状的有效性。所有合成的化合物都显示出显著的 DPPH 自由基清除活性,但化合物 3d 的抗氧化活性最强,其 IC50
值为 11 μM。DFT 分析结果被用来解释 (E)-N′-benzylidenebenzohydrazide 类似物的抗氧化机理。分析结果表明,N、O 和 C 原子上带有高负电荷的质子参与了清除 DPPH 的自由基的产生。此外,(E)-N′-亚苄基苯甲酰肼类似物的抗氧化活性与分子的 HOMO-LUMO 能量差密切相关。