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．     

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。     

氮杂冠醚化双Schiff碱配合物催化羧酸酯水解的研究

将4种氮杂冠醚取代的双Schiff碱钴(H)、锰(m)配合物作为仿水解酶模型催化羧酸酯(PNPP)水解.考察了Schiff碱配合物中氮杂冠醚取代的位置、氮杂冠醚的数目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;四种氮杂冠醚取代的双Schiff碱配合物在催化PNPP水解反应中表现出良好的催化活性;氮杂冠醚3-取代的Schiff碱配合物CoL2的催化活性高于5-取代的Schiff碱配合物CoL1,含有2个氮杂冠醚的配合物CoL3的催化活性高于含有1个氮杂冠醚的配合物CoL2.     

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。     

四氮金属配合物仿生催化不对称氧化研究进展

非血红素四氮锰、铁配合物催化的不对称氧化反应是有机合成化学中的重要转化.这类催化剂通过模拟自然界中金属酶的结构与功能特点实现了高效的催化不对称氧化,成功地在产物分子中引入手性中心,从而构建出一类有潜在应用价值的化合物.在这些四氮配体的设计中, N,N’-二甲基-1,2-环己二胺、联吡咯和脯氨酸的衍生物是主要的二胺骨架,与吡啶、苯并咪唑侧基的不同组合可以制备出各种催化活性的仿生配合物.同时配体取代基的调整也会对不对称氧化反应产生巨大的影响.给电子基和大位阻羧酸效应显著提高了仿生催化不对称氧化反应的效率和对映选择性.我们综述了近年来非血红素锰、铁配合物催化不对称氧化反应的研究进展,主要包含N,N’-二甲基-1,2-环己二胺、联吡咯和脯氨酸的衍生物作为二胺骨架,吡啶和苯并咪唑作为侧基的四氮配合物的结构设计以及配体结构对不对称环氧化和C-H键氧化反应活性的影响,并对该领域的发展前景做出了展望.     

手性过渡金属(Mn,Co,Ni)-Salen配合物催化NaOCl不对称环氧化苯乙烯的反应研究

本文论述了由手性1,2-二苯基乙二胺与适当取代的邻羟基苯甲醛生成的希佛碱作为过渡金属Co(Ⅱ)、Ni(Ⅲ)、Mn(Ⅲ)的配体合成的6种过渡金属-Salen配合物在NaOCl下均相催化苯乙烯不对称环氧化反应的效果。对环氧化反应进行控制性研究,我们发现环氧化反应与中心金属离子的相关性可能主要源于配体结构、金属离子的选择及二者结合而形成的配合物的空间构型。好的不对称环氧化反应催化剂要求中心金属离子具有适当的氧化还原电位,对底物烯烃因其取代基的大小,催化剂结构的空间构型应有好坏之分,我们得到的循环伏安数据及实验结果部分说明这一点。同时对手性镍(Ⅱ)-Salen及手性锰(Ⅲ)-Salen配合物的催化反应机理配合实验现象分别作出假设,都经过自由基历程,但却是截然不同的活性氧化物种,同时,由于起主要作用的不对称诱导因素不同,不对称诱导方向有异。对同一催化剂在不同pH值下起作用的活性氧化物种类别也可能不同。     

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     

含吡啶环系西佛碱大环配合物和氮杂大环自由配体的合成

2,6-二羟甲基吡啶(1)经活性MnO_2氧化得到2,6-二甲酰基吡啶(2)。邻硝基苯酚与N-取代的二(氯乙基)胺在DMF溶液中反应,得到N-取代的1,5-二(邻硝基苯氧基)-3-氮杂戊烷(3a～3c),再经水合肼/Raney Ni还原,获得N-取代的1,5-二(邻氨基苯氧基)-3-氮杂戊烷(4a～4c)。利用Ba~(2 )作为模板离子,(2)分别与(4a～4c)反应,合成了一类新的含吡啶环系西佛碱大环配合物Ⅰ～Ⅲ,配合物Ⅰ、Ⅲ经与NaBH_4的乙醇溶液还原解络,得到氮杂大环自由配体Ⅳ和Ⅴ。所有西佛碱大环配合物和氮杂大环自由配体均经元素分析、IR、~1H NMR、MS等证实了它们的结构和组成。     

Synthesis and Study of Unsymmetrical Schiff Base Mn(III) Complexes with Pendant Aza-crown or Morpholino Groups as Catalyst in Aerobic Oxidation for p-Xylene to p-Toluic Acid

A series of novel unsymmetrical Schiff base Mn(III) complexes with pendant aza-crown or morpholino groups have been synthesized and studied as catalysts in aerobic oxidation of `p-xylene to p-toluic acid (PTA). The oxidation of p-xylene to p-toluic acid with air at 120°C under normal atmospheric pressure occurred efficiently in the presence of aza-crown ether substituted unsymmetrical Schiff base Mn(III) complexes. Significant selectivity (up to ～90%) and conversion levels (up to ～40%) were obtained. The effect of the aza-crown ring appended in Mn(III) Schiff base complexes on the oxidation of p-xylene were also investigated by comparison with the morpholino group pendant analogues. The addition of alkali metal ions accelerates the rate of conversion of p-xylene to p-toluic acid.     

Synthesis,O_2-binding ability and catalytic oxidation performance of cobalt(Ⅱ) complexes with dihydroxamic acid functionalized N-pivot lariat ethers

Novel Co(Ⅱ) complexes with dihydroxamic acids functionalized N-pivot lariat ether CoL~1-CoL~4 were synthesized and characterized.Their oxygenation constants(ln K_(O2)) and thermodynamic parameters(△H°,△S°) were measured.And their catalytic performance in oxidation of p-xylene to p-toluic acid(PTA) was investigated.The enhancement of O_2-binding and catalytic oxidation activity by the oxa aza crown ether ring of the cobalt complexes were discussed.     

Synthesis and Study of Mono-Schiff Base MnIII Complexes with Aza-crown or Morpholino Pendant as Catalyst in Aerobic Oxidation of p-xylene to p-toluic Acid

Novel mono-Schiff base Mn^III complexes with pendant aza-crown or morpholino groups have been synthesized and studied as catalysts in aerobic oxidation of p-xylene to p-toluic acid. The oxidation of p-xylene to p-toluic acid with air at 120 °C under normal atmospheric pressure occured efficiently in the presence of aza-crown ether substituted mono-Schiff base Mn^III complexes. Significant selectivity (up to ~90%) and conversion levels (up to ~38%) were obtained. The effect of the aza-crown ether pendant in Mn^III Schiff base complexes on the oxidation of p-xylene was also investigated by comparison with the morpholino pendant analogues. The addition of alkali metal ions accelerated the rate of conversion of p-xylene to p-toluic acid.     

Synthesis and catalytic performance of mono-Schiff base manganese(III) complexes with aza-crown or morpholino pendants

Abstract  

Mono-Schiff base Mn(III) complexes of general formula MnL₂Cl, with pendant aza-crown or morpholino substituents, have been synthesized and investigated as catalysts for the epoxidation of styrene at ambient temperature and pressure. The highest conversion yield of styrene and selectivity for epoxide were 40 and 96%, respectively. These complexes have been also studied as catalysts for the aerobic oxidation of p-xylene to p-toluic acid. The effects of the crown ether group on the catalytic properties of the complexes are discussed. The oxidation of p-xylene to p-toluic acid with air at 120 °C under normal pressure proceeded efficiently in the presence of the aza-crown ether substituted complexes. Significant selectivity for p-toluic acid (up to ~87%) and conversion of p-xylene (up to ~30%) were obtained.     

Dioxygen Affinities and Catalytic Oxidation Performance of Co (II) Complexes with Phenol Ether Bridged Dihydroxamic Acids

Synthetic oxygen carriers are of great interest as models to mimic oxygen-carrying metalloenzymes for oxygen storage and transport1,2. Moreover, they possess great significance to realize high efficiency and selectivity catalytic oxidation of organic subs…     

Catalytic epoxidation performance and dioxygen affinities of unsymmetrical Schiff base transition–metal complexes with pendant aza-crown or morpholino groups

Abstract  Unsymmetrical Schiff base Co^II complexes (CoL¹–CoL⁶) and Schiff base Mn^III complexes (MnL¹Cl–MnL⁶Cl) with pendant aza-crown or morpholino groups were synthesized according to the literature. The oxygen uptake of Schiff base Co^II complexes in MeOCH₂CH₂OMe solution was determined at different temperatures, and the equilibrium constants (KO₂) and thermodynamic parameters (∆H ⁰, ∆S ⁰) for oxygenation were calculated. The corresponding Mn^III complexes, MnL¹Cl–MnL⁶Cl, were employed to catalyze epoxidation of styrene at ambient temperature and pressures. The effects of crown ether on the modulation of O₂-binding capability and the catalytic oxidation of styrene are discussed. The results indicate that the dioxygen affinities of the Co^II complexes are much more enhanced by aza-crown pendant group than that by morpholino pendant group, and the O₂-binding capabilities of CoL¹–CoL³ with aza-crown pendant group can also be enhanced by adding alkali metal cations (Li⁺, Na⁺, and K⁺); similarly, the catalytic activities of the Mn^III complexes with aza-crown pendant group, MnL¹Cl–MnL³Cl, are higher than those of the Mn^III complexes with morpholino pendant group, MnL⁴Cl–MnL⁶Cl. Graphical abstracts   Catalytic epoxidation performance and dioxygen affinities of unsymmetrical Schiff base transition–metal complexes with pendant aza-crown or morpholino groups. Jian-zhang Li*, Bin Xu, Wei-dong Jiang Key Laboratory of Green and Technology, Department of Chemistry, Sichuan University of Science & Engineering, Zigong, Sichuan 643000, People’s Republic of China Bo Zhou, Wei Zeng, Sheng-ying Qin Department of Chemistry, Sichuan University, Chengdu, Sichuan 610064, People’s Republic of China The oxygen uptake of Schiff base Co^II complexes in MeOCH₂CH₂OMe solution was determined at different temperatures, and the equilibrium constants (KO₂) and thermodynamic parameters (∆H ⁰, ∆S ⁰) for oxygenation were calculated. The corresponding MnIII complexes, MnL¹Cl-MnL⁶Cl, were employed to catalyze epoxidation of styrene at ambient temperature and pressures. The effects of crown ether on the modulation of O₂-binding capability and the catalytic oxidation of styrene are discussed.     

Dioxygen Affinities and Catalytic Oxidation Performance of Cobalt (II)Complexes with N-Aryl Hydroxamic Acid

It is well known that the study on biomimetic oxygen carriers not only has important theoretic significance to discover the mechanism of reversible bonding, activating oxygen as well as the oxidation reaction in organism, but also has potential application in separating oxygen from air and realizing the high efficiency and selectivity of catalytic oxidation reaction under a mild condition1. Metal- porphyrin and metal- phthalol- gaunine have been extensively used as biomimetic oxygen carriers u…     

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.