Tabrizi Leila, Dao Duy Quang, Vu Thuy An
School of Chemistry, National University of Ireland, Galway University Road Galway H91 TK33 Ireland
Institute of Research and Development, Duy Tan University 03 Quang Trung Da Nang 550000 Viet Nam
RSC Adv. 2019 Jan 25;9(6):3320-3335. doi: 10.1039/c8ra09763a. eCollection 2019 Jan 22.
A new copper(ii) complex, Cu(LC)(Ibu-phen)(HO) (LC: lidocaine, Ibu-phen: ibuprofen amide-phenanthroline), was synthesized and characterized. The antioxidant activities of the free ligands and the copper(ii) complex were evaluated by experiments and theoretical calculations using density functional theory (DFT). Structures of the ligand Ibu-phen and the complex were identified by H and C NMR, FT-IR spectroscopies, mass spectrometry, thermogravimetric analysis and elemental analysis. The antioxidant potentials of LC and Ibu-phen ligands as well as copper(ii) complex were also evaluated by DPPH˙, ABTS˙, HO˙ essays and EPR spectroscopy. The experimental results show that the radical scavenging activity (RSA) at various concentrations is decreased in the following order: copper(ii) complex > ascorbic acid > LC > Ibu-phen. Structural and electronic properties of the studied compounds were also analyzed by DFT approach at the M05-2X/6-311++g(2df,2p)//M05-2X/LanL2DZ level of theory. ESP maps and NPA charge distributions show that the highly negative charge regions found on the N and O heteroatoms make these sites more favorable to bind with the central copper ion. Frontier orbital distributions of copper(ii) complex indicate that HOMOs are mainly localized at Ibu-phen, while its LUMOs are distributed at LC. Based on natural bond orbitals (NBO) analyses, Cu(ii) ion plays as electron acceptor in binding with the two ligands and two water molecules. Thermochemical properties including bond dissociation enthalpy (BDE), ionization energy (IE), electron affinity (EA), proton affinity (PA) characterizing three common antioxidant mechanisms hydrogen transfer (HT), single electron transfer (SET) and proton loss (PL) were finally calculated in the gas phase and water solvent for two ligands and the copper(ii) complex at the same level of theory. As a result, the higher EA and lower BDE and PA values obtained for copper(ii) complex show that the complex shows higher antioxidant potential than the free ligands.
合成并表征了一种新型铜（II）配合物Cu(LC)(Ibu-phen)(HO)（LC：利多卡因，Ibu-phen：布洛芬酰胺-菲咯啉）。通过实验和使用密度泛函理论（DFT）的理论计算评估了游离配体和铜（II）配合物的抗氧化活性。通过氢谱和碳谱、傅里叶变换红外光谱、质谱、热重分析和元素分析确定了配体Ibu-phen和配合物的结构。还通过DPPH˙、ABTS˙、HO˙实验和电子顺磁共振光谱评估了LC和Ibu-phen配体以及铜（II）配合物的抗氧化潜力。实验结果表明，不同浓度下的自由基清除活性（RSA）按以下顺序降低：铜（II）配合物＞抗坏血酸＞LC＞Ibu-phen。还在M05-2X/6-311++g(2df,2p)//M05-2X/LanL2DZ理论水平上通过DFT方法分析了所研究化合物的结构和电子性质。静电势图和自然原子电荷分布表明，在氮和氧杂原子上发现的高负电荷区域使这些位点更有利于与中心铜离子结合。铜（II）配合物的前线轨道分布表明，最高占据分子轨道（HOMO）主要定域在Ibu-phen上，而其最低未占据分子轨道（LUMO）分布在LC上。基于自然键轨道（NBO）分析，铜（II）离子在与两个配体和两个水分子结合时充当电子受体。最后在相同理论水平上，在气相和水溶剂中计算了表征三种常见抗氧化机制——氢转移（HT）、单电子转移（SET）和质子损失（PL）的热化学性质，包括键解离焓（BDE）、电离能（IE）、电子亲和能（EA）、质子亲和能（PA）。结果表明，铜（II）配合物获得的较高EA值以及较低的BDE和PA值表明该配合物比游离配体具有更高的抗氧化潜力。
