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1.
Pavan Mathur 《Journal of Chemical Sciences》2006,118(6):553-568
New tetradentatebis-benzimidazole ligands have been synthesized and utilized to prepare copper (II) complexes. Some of these copper (II) complexes
have been characterized structurally. The copper (II) in these complexes is found to possess varying geometries. A distorted
octahedral geometry is found with a highly unsymmetrical bidentate nitrate group. An unusual polymeric one-dimensional structure
is observed where copper (II) is in a distorted square pyramidal geometry with a monodentate nitrate ion, having long Cu-O
bond, while a distorted triagonal bipyramidal geometry is found with two carbonyl O atoms and a Cl atom in the equatorial
plane, and two benzimidazole imine N atoms occupy the axial position. These compounds are found to activate the cumylperoxyl
group, and this has been utilized in the facile oxidation of aromatic alcohols to aldehydes, where they act as catalysts with
large turnovers. The yields of the respective products vary from 32 to 65%. The role of molecular oxygen has been studied
and an attempt has been made to identify the “active copper species”. Activation of molecular oxygen has also been observed
and has been used for oxidative dealkylation of a hindered phenol, producing di-butyl quinones with yields of 20–25% and 10–12
fold catalytic turnover. Dihydroxybenzenes and substituted catechols are also readily oxidized to the corresponding quinones,
in oxygen-saturated solvents. Yields of 84% have been observed with 34-fold catalyst turnover, with di-t-butylcatechol. The activity of these copper (II) —bis-benzmidazolediamide compounds is reminiscent of the functioning of copper centres in galactose oxidase, tyrosinase and catechol
oxidase. 相似文献
2.
Huseyin Bekir Yildiz Jaime Castillo Dmitrii A. Guschin Levent Toppare Wolfgang Schuhmann 《Mikrochimica acta》2007,159(1-2):27-34
An amperometric biosensor for the detection of phenolic compounds was developed based on the immobilization of tyrosinase
within an Os-complex functionalized electrodeposition polymer. Integration of tyrosinase within the redox polymer assures
efficient catechol recycling between the enzyme and the polymer bound redox sites. The non-manual immobilization procedure
improves the reproducibility of fabrication process, greatly reduces the desorption of the enzyme from the immobilization
layer, and, most importantly prevents fast inactivation of the enzyme by its substrate due to fast redox cycling.
A two-layer sensor architecture was developed involving ascorbic acid oxidase entrapped within an electrodeposition polymer
in a second layer on top of the redox polymer/tyrosinase layer. Using this sensor architecture it was possible to eliminate
the current interference arising from direct ascorbate oxidation up to a concentration of 630 μM ascorbic acid. The effects
of the polymer thickness, the enzyme/polymer ratio, and the applied potential were evaluated with respect to optimal sensor
properties. The sensitivity of the optimized sensors for catechol was 6.1 nA μM−1 with a detection limit of 10 nM, and for phenol 0.15 nA μM−1 with a detection limit of 100 nM. 相似文献
3.
Stability constants of the ternary complexes [CuAL] whereA = 5-Nitro-1,10-phenanthroline, bis(2-pyridyl) ketone (DPK) orbis(2-pyridyl)amine (DPA) andL is the dianion of catechol, tiron, protocatechic acid, pyrogallol, 1,8-dihydroxynaphthalene, catecholaldehyde, 2,3-dihydroxynaphthalene,
dopamine or adrenaline have been determined by potentiometric titration in dioxane water (1:1 v/v) medium using a SCOGS computer
programme. The observed trend of stability is explained on the basis of the nature of substitution over the ligands, chelate
ring size and also the composition of mixed solvent in case of DPK. Structural changes in DPK have also been discussed as
a function of pH, composition of medium and coordinating mode of the secondary ligand in the ternary complexes. 相似文献
4.
Halina Y. Neujahr 《Applied biochemistry and biotechnology》1982,7(1-2):107-111
The enzyme phenol 2-hydroxylase was immobilized on Sepharose and used in conjunction with an O2 electrode for quantitating phenol. Similarly, catechol 1,2-oxygenase was used for quantitating catechol. A third probe was
prepared by immobilization ofTrichosporon cutaneum cells rather than purified phenol 2-hydroxylase for phenol quantitation. The whole cell system gave results comparable to
the immobilized enzyme system. 相似文献
5.
交替三线性分解算法与反相高效液相-二极管阵列检测方法相结合同时测定苯二酚的位置异构体 总被引:3,自引:0,他引:3
利用交替三线性分解算法与反相高效液相 二极管阵列检测 (RP HPLC DAD)相结合 ,在洗脱时间为1 0 86min~ 1 399min(间隔 1 / 1 50min)、紫外吸收波长为 2 68nm~ 2 98nm(间隔 1nm)时对苯二酚位置异构体的重叠及光谱体系进行了分辨研究。分辨结果与实际结果一致。同时测定了水溶液中共存的邻苯二酚、间苯二酚和对苯二酚的含量 ,回收率分别为 (1 0 0 1± 1 0 ) % ,(99 4± 1 4) % ,(1 0 0 5± 1 7) %。研究结果表明 :该方法定量快速准确 ,实验操作步骤简单 ,解决了在干扰物存在条件下三者很难同时分辨的问题。 相似文献
6.
Hidetake Sakuraba Hiroshi Maekawa 《Journal of inclusion phenomena and macrocyclic chemistry》2006,54(1-2):41-45
The two modified β-cyclodextrin (β-CD) derivatives having catechol-type ligand (2,3- and 3,4-dihydroxy groups on the benzoate
ring) were synthesized. The chiral catalytic activity of their MoV and CuII complexes was examined in the asymmetric oxidation of aromatic sulfides using hydrogen peroxide in water (pH 6.0). The oxidation
with the MoV complexes of two β-CD derivatives were more accelerated than that with the CuII complexes. The sign of the optical rotation of the sulfoxides obtained in the above two cases showed the opposite configuration
in the oxidation of the same sulfide. The difference of the enantioselectivity appeared also between the two complexes of
the 2,3- and 3,4-dihydroxybenzoate derivatives with the same metal ion. While the use of the MoV complexes with the catechol derivatives yielded the sulfoxides with 35–65% ee, the use of the CuII complexes gave the products with the␣opposite configuration at 26–52% ee. The chiral induction in the oxidation, observed
conversely between the␣catalysts, was reflected on the chiral conformation of the respective metal catalysts, showed in Induced
Circular Dichroism (ICD) spectra. The highest optical yield, 65%, was observed in the oxidation of butyl phenyl sulfide using
the catalytic amount (0.1 equiv) of the MoV complex with mono-6-O-(3,4-dihydroxybenzoyl)-β-CD. The reaction gave predominantly the (S)-sulfoxide in 95% chemical yield. 相似文献
7.
邻对苯二酚的合成方法 总被引:4,自引:1,他引:4
用自制的钛硅沸石TS-1为催化剂,对H2O2存在下苯酚直接羟基化合成邻、对苯二酚的反应条件,主要影响因素及机理进行了探讨,发现该民传统的合成方法相比,反应的选择性及转化率较高,工艺简单,成本低和污染少。 相似文献
8.
在有无5 mmol·L-1 CuSO4存在的两种情况下,运用荧光光谱研究了烟草多酚氧化酶在盐酸胍诱导下的变性和复性平衡。烟草多酚氧化酶在6.0 mol·L-1盐酸胍变性30 min(25 ℃)即完全失活。荧光光谱结果表明:铜离子能够提高烟草多酚氧化酶的结构稳定性和抗盐酸胍变性的能力,进而影响烟草多酚氧化酶在盐酸胍诱导下的变性和复性过程。没有外源铜存在的情况下,盐酸胍诱导的烟草多酚氧化酶变性和复性是一个可逆的二态过程;在5 mmol·L-1 CuSO4存在的条件下,由于结合了Cu2+的酶的中间态稳定性增加,显示特征荧光,结果显示,外源铜存在时,盐酸胍诱导的烟草多酚氧化酶变性和复性是一个可逆的三态过程。根据相应模型,进行了热力学计算。上述实验结果得到酶活性测定的进一步证实,在6 mol·L-1盐酸胍中放置5,10,15,20,25,30 min,烟草多酚氧化酶的剩余活性分别为18.7%,11.7%,8.9%,6.6%,3.6%,0.06%,但在5 mmol·L-1 CuSO4存在的条件下,剩余活性则分别为60.3%,44.6%,42.5%,40.2%,25.6%,25.3%。 相似文献
9.
用电子自旋共振技术研究了水溶液中邻苯二酚、DOPA和槲皮素等化合物与O2-反应中产生的活性自由基中间体,根据所观察别的ESR谱的超精细结构常数可以推断它们都是邻半醌负离子基,在自旋捕获实验中发现无水乙腈中碱性条件下这些化合物与O2反应时会产生O2-,这表明在某些重要的生物抗氧化剂的抗氧化过程中,可能产生新的活性氧. 相似文献
10.
AbstractAnilines are rapidly, often within 60?minutes, converted into the corresponding phenols in up to 87% isolated yield. The presented experimentally simple protocol display broad compatibility with a variety of functional groups, and in particular, well suited for the preparation of methyl-substituted phenols. Such phenols are not easily available by other synthetic approaches. The formation of phenolic radical coupling products was not observed even for activated anilines using this open flask method. 相似文献