Department of Chemistry, Diamond Harbour Women's University, Diamond Harbour Road, Sarisha, South 24 Pgs, 743368, India.
Indian Association for the Cultivation of Science, 2A & 2B, Raja S. C. Mullick Road, Jadavpur, Kolkata-700032, India.
Dalton Trans. 2024 Jan 30;53(5):2373-2385. doi: 10.1039/d3dt03775d.
The inhibitory action of Schiff base complexes of 3d metals against the urease enzyme is well explored in the scientific community. However, the ability of such complexes in mimicking active metallobiosites of urease enzymes, possessing ureolytic behavior, still remains unexplored. With this aim firstly, two Zn(II)-complexes (PPR-HMB-Zn and PZ-HMB-Zn) have been developed from two different Schiff base ligands (HL1 = 2-(()-(2-(piperidin-1-yl)ethylimino)methyl)-5-methylphenol and HL2 = 2-(()-(2-(piperizin-1-yl)ethylimino)methyl)-5-methylphenol) and structurally characterized using single crystal XRD. The hydrolytic enzymatic activity of both complexes was demonstrated by the gradual increase in the absorption maxima at 425 nm for the formation of the -nitrophenolate ion from catalytic hydrolysis mediated by the Zn(II) complexes with a disodium salt of -nitrophenyl phosphate as a model substrate. Associated kinetic parameters, pH dependency and a relevant hydrolysis mechanism have also been explored. After confirming the hydrolytic ability, the complexes were exploited to mimic the hydrolytic activity of Jack bean urease that catalytically hydrolyses urea into ammonia and CO. The change in the pH of the solution owing to the formation of ammonia under the complex catalysed hydrolytic action of urea has been monitored spectrophotometrically using the pH dependent structural change of phenol red. The amount of ammonia has been quantified using the Nessler's reagent spectrophotometric method. The ureolytic reaction mechanism has been investigated using density functional theory (DFT) calculations using the B3LYP and TPSSH methods for the systematic calculation of the interaction energy. In contrast to PZ-HMB-Zn, PPR-HMB-Zn functions more effectively as a catalyst due to the existence of a lattice-occluded water molecule in its crystal structure and the protonation of the non-terminal N to attract urea by H-bonding, which was further confirmed by AIM analysis.
3d 金属的席夫碱配合物对脲酶的抑制作用在科学界得到了很好的研究。然而，这些配合物在模拟具有脲酶酶活性的金属生物位点方面的能力仍然未知。为此，首先从两个不同的席夫碱配体（HL1=2-（（（2-（哌啶-1-基）亚乙基亚氨基）甲基）-5-甲基苯酚和 HL2=2-（（（2-（哌嗪-1-基）亚乙基亚氨基）甲基）-5-甲基苯酚）合成了两个 Zn(II)-配合物（PPR-HMB-Zn 和 PZ-HMB-Zn），并通过单晶 XRD 进行了结构表征。通过 Zn(II)配合物催化水解介导的 -硝基苯酚盐的形成，在 425nm 处吸收最大值逐渐增加，证明了两种配合物的水解酶活性，以 -硝基苯酚磷酸盐的二钠盐作为模型底物。还探索了相关的动力学参数、pH 依赖性和水解机制。在确认水解能力后，将配合物用于模拟 Jack 豆脲酶的水解活性，Jack 豆脲酶催化尿素水解为氨和 CO。在尿素在配合物催化水解作用下形成氨的过程中，溶液的 pH 值发生变化，通过酚红的 pH 依赖性结构变化，用分光光度法进行监测。氨的量通过 Nessler 试剂分光光度法进行定量。使用密度泛函理论（DFT）计算，使用 B3LYP 和 TPSSH 方法对脲酶的水解反应机制进行了研究，以系统计算相互作用能。与 PZ-HMB-Zn 相比，PPR-HMB-Zn 作为催化剂的效果更好，因为其晶体结构中存在晶格封闭水分子，并且非末端 N 的质子化通过氢键吸引尿素，这通过 AIM 分析得到了进一步证实。
