Mukherjee Debojyoti, Nag Probal, Shteinman Albert A, Vennapusa Sivaranjana Reddy, Mandal Ujjwal, Mitra Mainak
Department of Chemistry, University of Burdwan Golapbug Campus, Purba Bardhaman-713104 India
School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram (IISER TVM) Maruthamala P. O., Vithura Thiruvananthapuram-695551 Kerala India.
RSC Adv. 2021 Jun 29;11(37):22951-22959. doi: 10.1039/d1ra02787e. eCollection 2021 Jun 25.
A dinuclear copper(ii) complex [Cu(papy)(CHOH)] has been synthesized by reaction of one equiv. of Cu(OAc)·2HO with one equiv. of the tetradentate tripodal ligand Hpapy [-(2-hydroxybenzyl)--(2-picolyl)glycine] and has been characterized by various spectroscopic techniques and its solid state structure has been confirmed by X-ray crystal structure analysis. The single-crystal structure of the complex reveals that the two copper centers are hexa-coordinated and bridged by two O-atoms of the phenoxo moieties. The variable temperature magnetic susceptibility measurement of the complex reveals weak ferromagnetic interactions among the Cu(ii) ions with a value of 1.1 cm. The catecholase activity of the complex has been investigated spectrophotometrically using 3,5-di--butyl catechol as a model substrate in methanol solvent under aerobic conditions. The Michaelis-Menten kinetic treatment has been applied using different excess substrate concentrations. The parameters obtained from the catecholase activity by the complex are 2.97 × 10 M, 2 × 10 M s, and 7.2 × 10 h. A reaction mechanism has been proposed based on experimental findings and theoretical calculations. The catechol substrate binds to dicopper(ii) centers and subsequently two electrons are transferred to the metal centers from the substrate. The bridging phenoxo moieties participate as a Brønsted base by accepting protons from catechol during the catalytic cycle and thereby facilitating the catechol oxidation process.
通过使一当量的Cu(OAc)₂·2H₂O与一当量的四齿三脚架配体Hpapy [α-(2-羟基苄基)-α-(2-吡啶基)甘氨酸]反应，合成了一种双核铜(II)配合物[Cu(papy)(CH₂OH)]，并通过各种光谱技术对其进行了表征，其固态结构已通过X射线晶体结构分析得到证实。该配合物的单晶结构表明，两个铜中心均为六配位，且由苯氧基团的两个O原子桥连。该配合物的变温磁化率测量结果表明，Cu(II)离子之间存在弱铁磁相互作用，值为1.1 cm⁻¹。在有氧条件下，以3,5-二叔丁基邻苯二酚为模型底物，在甲醇溶剂中通过分光光度法研究了该配合物的邻苯二酚酶活性。使用不同的过量底物浓度进行了米氏动力学处理。该配合物通过邻苯二酚酶活性获得的参数为Km = 2.97 × 10⁻⁵ M，Vmax = 2 × 10⁻⁵ M s⁻¹，kcat = 7.2 × 10⁻³ h⁻¹。基于实验结果和理论计算提出了一种反应机理。邻苯二酚底物与双核铜(II)中心结合，随后两个电子从底物转移到金属中心。在催化循环中，桥连苯氧基团通过从邻苯二酚接受质子作为布朗斯特碱参与反应，从而促进邻苯二酚的氧化过程。
