Abstract

This paper describes the synthesis and properties of a new nitro-substituted bidentate Schiff base ligand (HL) and its nickel complex (Ni(II)-2L). Its ligand was derived from the condensation of 2′-methoxyphenyl-2-ethylamine with 5-nitro-2-hydroxybenzaldehyde. This ligand and its nickel complex were characterized through elemental analysis, UV–Vis, IR, ¹H NMR and ¹³C NMR. The molecular structure of the nickel complex was confirmed using single-crystal X-ray diffraction. This complex crystallizes in dichloromethane in triclinic system, space group of P-1 with a = 6.6803 (2), b = 9.6702 (2), c = 12.1836 (3) and 1 formula unit in the cell. The obtained data revealed that the Ni(II) center is tetra-coordinated by two oxygen and two nitrogen atoms involving two ligands. Cyclic voltammograms of the nickel complex, recorded in DMF solutions, showed one quasi-reversible redox couple related to the Ni(II)/Ni(I) couple, demonstrating its electro-activity. This indicates a slow redox transition and/or electron exchange process, which implies that this electrochemical process is mainly diffusion-controlled. The antioxidant activity of the synthesized compounds was evaluated from the reactivity with the free radical DPPH, showing IC₅₀ values between 0.4 and 4.5 mg/mL.

Graphic abstract

中文翻译：

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新型非对称双齿席夫碱配体及其Ni（II）配合物的合成与表征：电化学和抗氧化剂研究

摘要

本文介绍了一种新型的硝基取代的双齿席夫碱配体（HL）及其镍配合物（Ni（II）-2L）的合成和性能。其配体源自2'-甲氧基苯基-2-乙胺与5-硝基-2-羟基苯甲醛的缩合。通过元素分析，UV-Vis，IR，¹ H NMR和¹³ C NMR表征了该配体及其镍配合物。使用单晶X射线衍射确认了镍配合物的分子结构。该配合物在三斜晶系系统的二氯甲烷中结晶，P- 1的空间群为a  = 6.6803（2），b  = 9.6702（2），c = 12.1836（3）和单元格中的1个公式单位。获得的数据表明，Ni（II）中心是由两个氧和两个氮原子（涉及两个配体）四配位的。在DMF溶液中记录的镍络合物的循环伏安图显示了一个与Ni（II）/ Ni（I）对相关的准可逆氧化还原对，表明了其电活性。这表明氧化还原过渡和/或电子交换过程缓慢，这意味着该电化学过程主要受扩散控制。从与自由基DPPH的反应性评估了合成化合物的抗氧化活性，显示出IC ₅₀值在0.4至4.5 mg / mL之间。

图形摘要