氮杂冠醚化单Schiff碱锰(III)配合物催化PNPP水解研究

将4种氮杂冠醚或吗啉取代的单Schiff碱锰(III)配合物作为仿水解酶模型催化α-吡啶甲酸对硝基苯酯(PNPP)水解。考察了单Schiff碱配体中取代基类型、氮杂冠醚取代的位置对其仿水解酶性能的影响;探讨了Schiff配合物催化PNPP水解的动力学和机理;提出了配合物催化PNPP水解的动力学模型。结果表明,在25℃条件下随着缓冲溶液pH值的增大,配合物催化PNPP水解速率提高,氮杂冠醚化单Schiff碱锰(III)配合物在催化PNPP水解反应中表现出良好的催化活性,Schiff碱配体结构显著影响配合物催化活性。     

氮杂冠醚或吗啉基取代的单Schiff碱配合物催化α-吡啶甲酸对硝基苯酯水解

两种含5-取代苯并-10-氮杂-15-冠-5的Schiff碱锰(III)、钴(II)配合物( , )及其吗啉基取代的类似物( , ) 用于催化α-吡啶甲酸对硝基苯酯(PNPP)水解。探讨了氮杂冠醚Schiff 碱配合物催化PNPP水解的动力学和机理;提出了配合物催化PNPP水解的动力学模型;考察了配合物结构、反应温度、缓冲溶液pH值等对PNPP水解反应的影响。结果表明,在25℃条件下随着缓冲溶液pH值的增大,催化PNPP水解速率提高;含取代苯并-10-氮杂-15-冠-5的Schiff碱配合物表现出更高的催化活性。根据阿累尼乌斯公式和不同温度下的表观一级常数求出水解反应的表观活化能。     

杂氮冠醚化Schiff碱钴(Ⅱ)配合物模拟磷酸二酯水解酶的研究

含杂氮冠醚的Schiff碱过渡金属配合物作为模拟水解酶被用于催化BNPP水解，讨论了两种杂氮冠醚化单Schiff碱钴(Ⅱ)配合物催化BNPP水解的动力学和机理，分析了反应体系的特征光谱变化。提出了配合物催化BNPP水解的动力学数学模型，结果表明，在反应过程中形成中间物种的假设是合理的；随着缓冲溶液pH的增大，两种配合物催化BNPP水解速率提高；两种配合物在催化BNPP水解中表现出好的催化活性。     

氮杂冠醚取代非对称双Schiff碱配合物催化氧化对二甲苯研究

将一系列苯并-10-氮杂-15-冠-5或吗啉基取代的不对称双Schiff碱配合物作为催化剂,在常压和120℃条件下用于催化氧化对二甲苯研究。探讨了Schiff配合物中心金属离子、Schiff碱配体中挂接的氮杂冠醚环、配体芳环上取代基等对催化氧化对二甲苯反应活性及其氧化产物选择性的影响。实验结果表明:配合物中氮杂冠醚的存在能显著缩短反应诱导期、提高催化活性和选择性;Schiff碱Mn(Ⅲ)配合物比Schiff碱Co(Ⅱ)和Schiff碱Cu(Ⅱ)具有更高的催化活性;氮杂冠醚Schiff碱Mn(Ⅲ)配合物催化氧化二甲苯的转化率和产物选择性分别达75%和90%。     

氮杂冠醚取代基对schiff碱锰(Ⅲ) 配合物催化苯乙烯环氧化反应的影响

合成并表征了苯并-10-氮杂-15-冠-5或吗啉基取代的单和双Schiff碱锰（Ⅲ）配合物MnL2^1Cl,MnL2^2Cl,Mnl^3Cl和MnL^4Cl．研究了它们作为仿P450模型化合物催化苯乙烯环氧化反应的性能,并考察了催化反应的动力学．结果表明,氮杂冠醚取代的Schifft碱锰（Ⅲ）配合物优于相应的吗啉基取代的Schiff碱锰（Ⅲ）配合物,且反应遵从Michaelis—Menten规律．这是由于具有特殊功能和空间构型的氮杂冠醚大环的引入。改善了催化中心周围的微环境,从而显著地提高了Schiff碱锰（Ⅲ）配合物的催化活性．     

不对称Salen-Mn(Ⅲ)配合物催化PNPP水解的动力学研究

用分光光度法研究了两种不对称Salen-Mn(Ⅲ)配合物催化α-吡啶甲酸对硝基苯酚酯(PNPP)的水解动力学.提出了相应的PNPP催化水解机理,讨论了底物浓度、体系的酸碱度、温度以及配合物结构对PNPP催化水解反应的影响.结果表明:此两种Schiff碱锰(Ⅲ)配合物在催化PNPP水解中均表现出较好的催化活性,PNPP水解速率随着底物浓度、体系pH值的增大而增大;在15～55℃温度范围内,未观察到催化剂失活现象;其中,带有苯并氮杂-15-冠-5侧基的不对称Salen-Mn(Ⅲ)配合物比带有吗啉基的另一配合物拥有更高的催化活性,这可能主要由这两种模拟水解酶之间较大的疏水微环境差异所引起.     

Schiff碱钴(Ⅱ)配合物催化PNPP水解研究

摘要：两种分别带吗啉侧基和氮杂冠醚侧基的Schiff碱钴(Ⅱ)配合物CoL¹ 和CoL²，作为模拟水解金属酶，用于羧酸酯（PNPP）的催化水解。通过对水解反应体系的特性吸收光谱的分析，表明在PNPP催化水解的反应过程中形成了由PNPP和Co(Ⅱ)配合物组成的关键中间体。在分析特性吸收光谱的基础上提出了PNPP的催化水解的机理，由此机理上建立了PNPP催化水解的动力学数学模型。在本文中讨论缓冲溶液酸度、配合物结构以及反应温度对配合物催化PNPP水解速率的影响。     

氮杂冠醚取代单Schiff碱过渡金属配合物催化氧化对二甲苯研究

本文将苯并-10-氮杂-15-冠-5或吗啉基取代的单Schiff碱过渡配合物作为催化剂,在常压和120℃条件下,以空气为氧源,研究了对二甲苯催化氧化反应。实验探讨了Schiff碱配合物中心金属离子、Schiff碱配体中挂接的氮杂冠醚环、配体芳环上取代基和反应时间等对对二甲苯催化氧化反应的影响。实验结果表明:Schiff碱配合物中氮杂冠醚的存在能显著缩短反应诱导期,提高催化反应活性和产物选择性;Schiff碱Mn(III)配合物比Schiff碱Co(II)具有更高的催化反应活性;氮杂冠醚Schiff碱Mn(III)配合物对于二甲苯的催化氧化反应转化率大于60%,对甲苯甲酸产物的选择性均高于70%。     

氮杂冠醚取代的单Schiff碱的合成及其钴(Ⅱ)配合物的氧加合性能

由苯并 10 氮杂 15 冠 5出发 ,经 2～ 4步反应合成了氮杂冠醚取代的单Schiff碱HL1,HL2及其异构体HL3 ,HL4.并以元素分析 ,IR ,1 HNMR和MS进行了表征 .在不同温度下 ,测定了它们的钴 (Ⅱ )配合物的氧合反应平衡常数及热力学参数ΔH°和ΔS° ,并与合成的非冠醚类似物CoL2 5 ,CoL2 6和CoL2 7比较 ,考察了配体芳环上取代的氮杂冠醚环及其取代位置对氧加合性能的影响     

苯并氮杂冠醚-15-冠-5 Schiff碱钴(Ⅱ)配合物在胶束中催化BNPP水解研究

在催化磷酸二酯水解的模拟酶模型中,配合物配体结构扮演了非常重要的角色[1-2]。由于冠醚环具有主客体识别功能,在酶学理论中把它作为模拟酶的第一代生物有机体。镶嵌有过渡金属离子的冠醚配合物对催化磷酸二酯水解具有很好的活性[3];Schiff碱过渡金属离子配合物对催化磷酸二酯水解也具有很好的活性[4]。因此,冠醚Schiff碱过渡金属离子配合物对催化磷酸二酯水解也应具有很好的活性,这已有所报道[5]。但冠醚结构和过渡金属离子相同而取代基不同的配合物作为模拟酶催化磷酸二酯水解还未见报道。本文按文献设计合成了三种冠醚结构相同而取代基…     

Synthesis and studies of Schiff base complexes with aza-crown ether or morpholino pendants as synthetic hydrolases for <Emphasis Type="Italic">p</Emphasis>-nitrophenyl picolinate

Three symmetrical bis-Schiff bases with either benzo-10-aza-crown ether or morpholino pendants and their Mn(III) and Co(II) complexes have been synthesized and employed as models for hydrolase enzymes by studying the kinetics of their hydrolysis reactions with p-nitrophenyl picolinate (PNPP). A kinetic model of PNPP cleavage catalyzed by these complexes is proposed. The effects of complex structures and reaction temperature on the rate of PNPP hydrolysis have been examined. All four complexes exhibit high catalytic activity and the rate increases with pH. The complexes of ligands containing a crown ether group exhibit higher catalytic activities than the non-crown analogs, and the catalytic activity of the phenyl-bridged Schiff base complex is larger than that of ethyl-bridged analogue for the same substituents and metal.     

Studies on the Kinetics and Mechanism of Hydrolysis of p-nitrophenyl Picolinate (PNPP) by Unsymmetrical bis-Schiff Base Complexes with Aza-crown Ether or Morpholino Pendants

Two novel unsymmetrical bis-Schiff base manganese(III) and cobalt(II) complexes with benzo-10-aza-crown ether pendants (MnL¹Cl, CoL¹), and their analogoues with morpholino pendants (MnL²Cl, CoL²), have been synthesized and employed as models to mimic hydrolase in p-nitrophenyl picolinate (PNPP). The kinetics and the mechanism of PNPP hydrolysis catalyzed by these complexes were investigated. A kinetic mathematical model of PNPP cleavage catalyzed by these complexes was proposed. The effects of the complexes structure and reactive temperature on the rate of catalytic PNPP hydrolysis have been also examined. The results showed that the rate for the catalytic PNPP hydrolysis increased following the increase in pH of the buffer solution; four complexes exhibited high activity in the catalytic PNPP hydrolysis. Compared with the crown-free analogoues MnL²Cl and CoL², the crowned Schiff base complexes (MnL¹Cl, CoL¹) exhibit a higher catalytic activity; the pseudo-first-order-rate (k_obs) for the PNPP hydrolysis catalyzed by the complex MnL¹Cl containing benzo-10-aza-crown ether is 1.04 × 10³ that of spontaneous hydrolysis of PNPP at pH = 7.00, [S] = 2.0×10⁻⁴ mol dm⁻³.     

Studies on Schiff Base Complexes with Aza-Crown Ether Pendants as Synthetic Hydrolases for p-Nitrophenyl Picolinate in Brij35 Surfactant Micellar Solution

Schiff base complexes with aza-crown ether pendants have been synthesized and employed as models for hydrolase enzymes by studying the kinetics of their hydrolysis reactions with p-nitrophenyl picolinate (PNPP) in Brij35 surfactant micellar solution. A kinetic model of PNPP cleavage catalyzed by these complexes is proposed. The effects of complex structures and reaction temperature on the rate of catalytic PNPP hydrolysis have also been examined. The rate increases with pH of the buffered Brij35 micellar solution under 25°C; all four complexes exhibited high activity in the catalytic PNPP hydrolysis. The catalytic activity of the phenyl-bridged Schiff base complex is larger than that of ethyl-bridged Schiff base complex for the same substituent and metal. The catalytic activity of manganese(III) complex is superior over cobalt(II) complex in catalyzing hydrolysis of PNPP under the same ligand. The pseudo-first-order rate for PNPP hydrolysis catalyzed by CoL¹ containing aza-crown ether is 2.96 × 10⁴ times that of spontaneous hydrolysis of PNPP in Brij35 surfactant micellar solution at pH = 7.60, [S] = 2.0 × 10^?4 mol dm^?3.     

Studies on <Emphasis Type="Italic">p</Emphasis>-nitrophenyl picolinate cleavage by mono-Schiff base complexes with aza-crown ether or morpholino pendants

Abstract  Mono-Schiff base manganese(III) and cobalt(II) complexes with either benzo-10-aza-crown ether pendants (MnL¹ ₂ Cl, CoL¹ ₂) or morpholino pendants (MnL² ₂Cl, CoL² ₂) have been employed as models for hydrolase enzymes by studying the kinetics of their hydrolysis reactions with p-nitrophenyl picolinate (PNPP). A kinetic model of PNPP cleavage catalyzed by these complexes is proposed. The effects of complex structures and reaction temperature on the rate of catalytic PNPP hydrolysis have been also examined. The rate increases with pH of the buffer solution; all four complexes exhibited high activity in the catalytic PNPP hydrolysis. Compared with the crown-free analogues MnL² ₂Cl and CoL² ₂, the crowned Schiff base complexes (MnL¹ ₂Cl, CoL¹ ₂) exhibit higher catalytic activity. The pseudo-first-order-rate ( k _obs ) for the PNPP hydrolysis catalyzed by the complex MnL¹ ₂Cl containing benzo-10-aza-crown ether is 1.06 × 10³ times that of spontaneous hydrolysis of PNPP at pH = 7.00, 25 °C, [S] = 2.0 × 10⁻⁴ mol dm⁻³. Graphical Abstract   Studies on p-nitrophenyl picolinate cleavage by mono-Schiff base complexes with aza-crown ether or morpholino pendants Jian-zhang Li*, Fa-mei Feng, Bin Xu,Wei-dong Jiang Key Laboratory of Green and Technology, Department of Chemistry, Sichuan University of Science & Engineering, Zigong, Sichuan, 643000, P.R. China Sheng-ying Qin Department of Chemistry, Sichuan University, Chengdu, Sichuan, 610064, P.R. China Mono-Schiff base manganese(III) and cobalt(II) complexes with either benzo-10-aza-crown ether pendants (MnL¹ ₂Cl, CoL¹ ₂) or morpholino pendants (MnL² ₂Cl, CoL² ₂) have been employed as models for hydrolase enzymes by studying the kinetics of their hydrolysis reactions with PNPP. A kinetic model of PNPP cleavage catalyzed by these complexes is proposed. Compared with the crown-free analogy MnL² ₂Cl and CoL² ₂, the crowned Schiff base complexes (MnL¹ ₂Cl, CoL¹ ₂) exhibit higher catalytic activity.      

Studies on p-Nitrophenyl Picolinate Cleavage by Unsymmetrical Bis-Schiff Base Manganese(III) and Cobalt(II) Complexes in CTAB Surfactant Micellar Solution

The unsymmetrical bis-Schiff base manganese(III) and cobalt(II) complexes with either benzo-10-aza-crown ether pendants (MnL¹Cl, MnL²Cl) or morpholino pendant (MnL³Cl, CoL³) have been employed as models for hydrolase by studying the kinetics of their hydrolysis reactions with p-nitrophenyl picolinate (PNPP) in the buffered CTAB micellar solution. A kinetic model of PNPP cleavage catalyzed by these complexes is proposed. The effects of complex structures and reaction temperature on the rate of PNPP hydrolysis have been examined. All four complexes exhibit higher catalytic activity in the buffered CTAB micellar solution and the rate increases with pH of the buffered CTAB micellar solution under 25°C. The complexes containing a crown ether group exhibit higher catalytic activities than the free-crown analogues. The catalytic activity of manganese(III) complex is superiority over cobalt(II) complex in catalyzing hydrolysis of PNPP under the same ligand.     

Studies on PNPP Hydrolysis Catalyzed by Schiff Base Cobalt（Ⅱ） Complexes

Two cobalt（Ⅱ） complexes of the Schiff base with morpholino or aza-crown ether pendants, CoL^1 and CoL^2, as mimic hydrolytic metalloenzyme, were used in catalytic hydrolysis of carboxylic ester （PNPP）. The analysis of specific absorption spectra of the hydrolytic reaction systems indicates that key intermediates, made up of PNPP and Co（Ⅱ） complexes, have been formed in reaction processes of the PNPP catalytic hydrolysis. The mechanism of PNPP catalytic hydrolysis has been proposed based on the analytic result of specific absorption spectrum. A kinetic mathematical model, applied to the calculation of the kinetic parameter of PNPP catalytic hydrolysis, has been established based on the mechanism proposed. The acid effect of buffer solution, structural effect of the complexes, and effect of temperature on the rate of PNPP hydrolysis catalyzed by the complexes have been also discussed.     

p‐Nitrophenyl Picolinate Cleavage by Unsymmetrical Bis‐Schiff Base Manganese(III) and Cobalt(II) Complexes with Aza‐Crown Ether or Morpholino Pendants

The unsymmetrical bis‐Schiff base manganese(III) and cobalt(II) complexes with either benzo‐10‐aza‐crown ether pendants (MnL¹Cl, MnL²Cl) or morpholino pendant (MnL³Cl, CoL³) have been employed as models for hydrolase by studying the kinetics of their hydrolysis reactions with p‐nitrophenyl picolinate (PNPP). A kinetic model of PNPP cleavage catalyzed by these complexes is proposed. The effects of complex structures and reaction temperature on the rate of PNPP hydrolysis have been examined. All four complexes exhibit high catalytic activity and the rate increases with pH under 25°C. The complexes of ligands containing a crown ether group exhibit higher catalytic activities than the non‐crown analogues. The catalytic activity of the complexes follows the order Mn(III)>Co(II) under the same ligands.