Bis(渭-alkoxo) bridged dinuclear Cu^II₂ and Zn^II₂ complexes of an isoindol functionality based new ligand: Synthesis, structure, spectral characterization, magnetic properties and catechol oxidase activity

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• 作者：Ayan Patra ; Gopal C. Giri ; Tamal K. Sen ; Luca Carrella ; Swadhin K. M ; al ; Manindranath Bera
• 关键词：Dinucleating ligand ; Isoindol functionality ; Copper(II)/zinc(II) ; Magnetism ; Catecholase activity ; DFT calculations
• 刊名：Polyhedron
• 出版年：8 January, 2014
• 年：2014
• 卷：67
• 期：Complete
• 页码：495-504
• 全文大小：1011 K

文摘

Two new dinuclear copper(II) and zinc(II) complexes of an isoindol functionality based new dinucleating ligand, H₃hdpa (H₃hdpa = 2-({[2-hydoxyethyl]-[2-hydroxy-3-(1-oxo-1,3-dihydro-isoindol-2-yl)-propyl]-amino}-methyl)-benzoic acid) have been synthesized and characterized. In methanol, the reaction of stoichiometric amounts of Cu(OAc)₂路H₂O and the ligand H₃hdpa in the presence of NaOH at ambient temperature afforded a new dinuclear copper(II) complex, [Cu₂(Hhdpa)₂]路2CH₃OH路6H₂O (1). Similarly, in methanol, the reaction of stoichiometric amounts of Zn(OAc)₂路2H₂O and H₃hdpa in the presence of NaOH yielded a new dinuclear zinc(II) complex, Na₄[Zn₂(hdpa)₂](OAc)₂ (2). Characterization of the complexes has been performed using various analytical techniques, including single crystal X-ray structure determination. The X-ray crystal structure of complex 1 reveals that two copper(II) centers adopt a five-coordinate square pyramidal geometry with a Cu-Cu separation of 2.910 脜. The DFT optimized structure of complex 2 shows that two zinc(II) centers are in a distorted trigonal bipyramidal geometry with a Zn-Zn separation of 3.124 脜. ¹H and ¹³C NMR spectroscopic investigations authenticate the integrity of complex 2 in solution. Further, the mass spectroscopic analyses of complexes 1 and 2 reconfirm their dimeric nature, even in solution. Variable-temperature (2-300 K) magnetic susceptibility measurements show the presence of antiferromagnetic interactions (J = 鈭?2.20 cm^鈭?) between the two copper(II) centers in complex 1. The catechol oxidase activity of complexes 1 and 2 has been investigated in methanol medium by the UV-Vis spectrophotometric technique using 3,5-di-tert-butylcatechol as a model substrate. Both complexes are active in catalyzing the aerobic oxidation of 3,5-di-tert-butylcatechol (3,5-DTBC) to 3,5-di-tert-butyl-1,2-benzoquinone (3,5-DTBQ). A DFT calculation has been performed to find the Fukui functions at the metal centers in complexes 1 and 2 to predict the possible metal centers involved in the binding process with 3,5-DTBC during the catalytic oxidation reactions.