Synthesis and Characterization of Cobalt(III), Nickel(II) and Copper(II) Mononuclear Complexes with the Ligand 1,3-bis[(2-aminoethyl)amino]-2-propanol and Their Catalase-Like Activity

In this work, we present the synthesis and characterization of two new mononuclear complexes with the ligand 1,3-bis[(2-aminoethyl)amino]-2-propanol (HL), [Co(L)(H2O)](ClO4)2 (1), [Ni(HL)](ClO4)2 (2), as well as the known complex [Cu(HL)](ClO4)2 (3) for comparison. Their abilities to catalyze the dismutation of H2O2 and the oxidation of cyclohexane were investigated. The complexes were characterized by X-ray diffraction, elemental analysis, electronic and infrared spectroscopy, cyclic voltammetry, electrospray ionization mass spectrometry (ESI-MS) and conductivity measurements. The X-ray structures showed that the nickel (2) and copper (3) complexes are tetracoordinated, with the metal ion bound to the nitrogen atoms of the ligand. On the other hand, the cobalt complex (1) is hexacoordinated, possessing additional bonds to the alkoxo group of the ligand and to a water molecule. Neither of the complexes was able to catalyze the oxidation of cyclohexane, but all of them exhibited catalase-like activity, following Michaelis-Menten kinetics, which suggest resemblance with the catalase natural enzymes. The catalytic activity followed the order: [Ni(HL)](ClO4)2 (2) > [Cu(HL)](ClO4)2 (3) > [Co(L)(H2O)](ClO4)2 (1). As far as we know, this is the first description of a nickel complex presenting a significant catalase-like activity.本工作报道了以配体1,3-双[(2-氨乙基)氨基]-2-丙醇(HL)合成并表征的两种新型单核配合物：[Co(L)(H₂O)](ClO₄)₂ (1)、[Ni(HL)](ClO₄)₂ (2)，以及用于对照的已知配合物[Cu(HL)](ClO₄)₂ (3)。本研究考察了上述配合物催化过氧化氢(H₂O₂)歧化反应与环己烷氧化反应的能力。采用X射线衍射、元素分析、电子光谱、红外光谱、循环伏安法、电喷雾电离质谱(ESI-MS)及电导率测定对所合成的配合物进行了表征。X射线晶体结构分析表明，镍配合物(2)与铜配合物(3)均为四配位结构，金属离子与配体的氮原子配位结合；而钴配合物(1)为六配位结构，除与配体的烷氧基配位外，还结合了一个水分子。所有配合物均无法催化环己烷的氧化反应，但三者均表现出类过氧化氢酶活性，且催化动力学符合米氏(Michaelis-Menten)动力学模型，提示其与天然过氧化氢酶具有相似的催化特性。催化活性顺序为：[Ni(HL)](ClO₄)₂ (2) > [Cu(HL)](ClO₄)₂ (3) > [Co(L)(H₂O)](ClO₄)₂ (1)。据我们所知，本研究首次报道了具有显著类过氧化氢酶活性的镍配合物。