A highly efficient and reusable mesoporous supported Co(II) catalyst for chemoselective deprotection of aryl acetates

Chemoselective deprotection of aryl acetates is successfully carried out in excellent yield using a mesoporous silica-supported (Salen) Co(II) catalyst. The catalyst shows high thermal stability and also can be recovered and reused at least 10 times without any significant loss of its catalytic activity. The present process is environmentally benign and economical.     

Copper(II) tetrafluoroborate as a novel and highly efficient catalyst for acetal formation

Commercially available copper(II) tetrafluoroborate hydrate has been found to be a highly efficient catalyst for dimethyl/diethyl acetal formation in high yields from aldehydes and ketones by reaction with trimethyl/triethyl orthoformate at room temperature and in short period. Acetalisation was carried out under solvent-free conditions with electrophilic aldehydes/ketones. For weakly electrophilic aldehydes/ketones (e.g., benzaldehyde, cinnamaldehyde and acetophenone) and for aldehydes having a substituent that can coordinate with the catalyst, the corresponding alcohol was used as solvent.     

A heterogeneous cobalt(II) Salen complex as an efficient and reusable catalyst for acetylation of alcohols and phenols

Acetylation of various alcohols and phenols was performed successfully using an immobilized cobalt(II) catalyst in high yield. The catalyst shows high thermal stability and was also recovered and reused at least 10 times without any considerable loss of activity.     

A novel method for Co(Ⅱ) and Cu(Ⅱ) analysis by capillary electrophoresis with chemiluminescence detection

Based on the fact that some metal ions can catalyze the chemiluminescence(CL)reaction of luminol with K_3Fe(CN)_6,a novel capillary electrophoresis CL method was developed for the determination of Co(Ⅱ)and Cu(Ⅱ).The separation was carried out with a 10 mmol/L sodium acetate solution containing 0.8 mmol/L luminol and 2.0 mmol/Lα-HIBA(adjusted to pH 4.8 by HAc solution).The post-capillary reagent was 2.0 mmol/L K_3Fe(CN)_6 which was adjusted to pH 13.0 by NaOH solution.Under the optimum conditions,the detection limits(S/N=3)for Co(Ⅱ)and Cu(Ⅱ)were 7.5×10~(-11)mol/L and 7.5×10~(-9)mol/L,with the linear range of 7.5×10~(-9)mol/L to 1.0×10~(-6)mol/L and 7.5×10~(-8)mol/L to 5.0×10~(-5)mol/L, respectively.     

Dual molecular light switches for pH and DNA based on a novel Ru(II) complex. A non-intercalating Ru(II) complex for DNA molecular light switch

A new Ru(II) complex of [Ru(phen)(2)(Hcdpq)](ClO(4))(2) {phen = 1,10-phenanthroline, Hcdpq = 2-carboxyldipyrido[3,2-f:2',3'-h]quinoxaline} was synthesized and characterized. The spectrophotometric pH and calf thymus DNA (ct-DNA) titrations showed that the complex acted as a dual molecular light switch for pH and ct-DNA with emission enhancement factors of 17 and 26, respectively. It was shown to be capable of distinguishing ct-DNA from yeast RNA with this binding selectivity being superior to two well-known DNA molecular light switches of [Ru(bpy)(2)(dppz)](2+) {bpy =2,2'-bipyridine, and dppz = dipyrido-[3,2-a:2',3'-c]phenazine}and ethidium bromide. The complex bond to ct-DNA probably in groove mode with a binding constant of (4.67 ± 0.06) × 10(3) M(-1) in 5 mM Tris-HCl, 50 mM NaCl (pH = 7.10) buffer solution, as evidenced by UV-visible absorption and luminescence titrations, the dependence of DNA binding constants on NaCl concentrations, DNA competitive binding with ethidium bromide, and emission lifetime and viscosity measurements. To get insight into the light-switch mechanism, theoretical calculations were also performed by applying density functional theory (DFT) and time-dependent DFT.     

Copper(II) trans-bis-(glycinato): an efficient heterogeneous catalyst for cross coupling of phenols with aryl halides

Copper(II) trans-bis-(glycinato) complex, easily prepared by the solid state reaction of copper(II) acetate and glycine (trans-[Cu(glyo)₂·H₂O]) was found to be an efficient, recyclable, and high yielding catalyst for the Ullmann type synthesis of diaryl ethers via the cross coupling of phenols with aryl halides without using any additives at relatively low reaction temperature. The catalyst could easily be recovered by simple filtration and was reused for several runs with consistent catalytic activity.     

Polymer immobilized Fe(III) complex of 2-phenylbenzimidazole: An efficient catalyst for photodegradation of dyes under UV/Visible light irradiation

Fe(III) complex of 2-phenylbenzimidazole has been covalently anchored on polymer and characterized by elemental analysis, FT-IR, far-IR, BET surface area measurements, UV–Vis/DRS spectroscopy, thermo-gravimetric analysis and magnetic moment measurements by VSM which confirmed an octahedral environment around Fe(III) in the bound complex. The photocatalytic performance of this complex was evaluated in the photodegradation of dyes in presence of H₂O₂ as an oxidizing agent. Suitable reaction conditions have been optimized by considering the effects of various reaction parameters such as pH, oxidants, concentration of dye, H₂O₂ and catalyst for the maximum degradation of dye. The photodegradation was found to be 100% with complete mineralization in 150?min. The comparison of photocatalytic efficiency of the catalyst under visible light, sunlight and dark conditions are accomplished. Comparison between catalytic activity of the polymer-supported complex and unbound complex demonstrated that the polymer-supported complex was more active. Photocatalytic performance of PS-Fe(III)PBMZL was also compared with commercial TiO₂ (P25). This heterogeneous complex retained its activity up to 8 runs. A tentative mechanism has been proposed.     

Tethering of nickel(II) Schiff-base complex onto mesoporous silica: An efficient heterogeneous catalyst for epoxidation of olefins

A new hybrid catalyst has been prepared by tethering a nickel(II) Schiff-base complex via post-synthesis modification of mesoporous silica, MCM-41. The Schiff-base has been derived from salicylaldehyde and 3-aminopropyltriethoxysilane (3-APTES) which is chemically anchored on MCM-41 via silicon alkoxide route. The anchored Schiff-bases imposed a stable planar coordination geometry around the central nickel ions. The catalyst has been characterized by elemental analysis, FT-IR, UV-Vis, small angle X-ray diffraction (SAX) and transmission electron microscopy (TEM) studies. The SAX and TEM measurement showed the mesoporosity of the catalyst. The activity of the catalyst has been assessed in the epoxidation of olefins using tert-butyl-hydroperoxide (tert-BuOOH) as oxidant in heterogeneous condition. Immobilized nickel catalyst was found to be catalytically more active and selective compared to the similar type of nickel(II) complex as well as Ni(NO₃)₂·6H₂O in homogeneous media. The catalyst can be recycled and reused several times without significant loss of activity.     

NiO nanoparticles prepared via thermal decomposition of the bis(dimethylglyoximato)nickel(II) complex: A novel reusable heterogeneous catalyst for fast and efficient microwave-assisted reduction of nitroarenes with ethanol

NiO nanoparticles with an average size of 12 nm and a high specific surface area of 88.5 m²/g were easily prepared via the thermal decomposition of the complex Ni(dmgH)₂ and were characterized by TGA, XRD, FT-IR, TEM and BET surface area measurement. This nanosized transition metal oxide was used as a new heterogeneous catalyst for the reduction of nitroarenes under microwave irradiation. The efficient and selective reduction of aromatic nitro compounds into their corresponding amines was observed by using ethanol as a hydrogen donor (reducing agent) and KOH as a promoter under microwave irradiation. This highly regio- and chemoselective method is fast, simple, inexpensive, high yielding, clean and compatible with several sensitive functionalities, such as halogens, -OH, -OCH₃, -CHO, -COCH₃, -COOH, -COOEt, -CONH₂, -CN, -CHCH₂ and -NHCOCH₃. This method is suitable for the large scale preparation of different substituted anilines as well as other arylamines. In addition, the catalytic activity of nanosized NiO is higher than that of the bulk sample.     

Ag/AgCl/铁-海泡石异相可见光Fenton催化降解双酚A

光-Fenton技术是高级氧化技术中的一种,常用于难降解废水处理,由于其反应速度快、毒性低、反应条件温和而受到广泛关注.然而,传统的光-Fenton体系具有可见光利用率低、回收困难等缺点.为了解决这些问题,本文采用廉价易得、无污染、吸附能力强的天然矿物海泡石作为催化剂载体,并利用Ag/AgCl能够吸收可见光的表面等离子响应这一光学性质,合成了一种有潜力的非均相等离子体光催化剂Ag/AgCl/铁-海泡石催化剂(Ag/AgCl/Fe-S),并对该催化剂的形貌结构、性能和机理等进行了系统研究.通过XRD,SEM,XPS,BET,UV-vis等表征手段对催化剂形貌、结构和可见光性能进行了分析.其中,XRD和SEM结果显示,Ag/AgCl粒子已经成功负载在Fe-海泡石上;XPS结果显示,铁氧化物的组成主要为FeOOH和Fe2O3;UV-vis结果显示,催化剂有较好的可见光吸收性能.以双酚A为目标污染物,分别考察了Ag/AgCl/Fe-S,Ag/AgCl和Fe-海泡石的光-Fenton催化性能.结果显示,Ag/AgCl/Fe-S降解双酚A的效果明显优于另外两种催化剂,在H2O2浓度为6mmol/L,pH为4,光照强度500W,Ag/AgCl/Fe-S催化剂量为1.0 g/L,双酚A初始浓度为10 mg/L的条件下,1 h时,双酚A基本被完全降解,且3 h时,其矿化率达到61.2%;而Ag/AgCl和Fe-海泡石催化剂在同样的条件下完全降解双酚A至少要3 h,且其矿化率分别只有46.61%和28.85%.另外,还分别探讨了H2O2浓度、pH值、光照强度和催化剂剂量对双酚A降解的影响.最后,通过活性物种捕获、ESR、电化学和PL实验对该体系的反应机理进行了探讨.活性物种捕获实验和ESR实验结果表明,羟基自由基(?OH)和空穴(h+)是该体系中的主要活性物种,且Ag/AgCl/Fe-S+H2O2+vis体系产生的?OH明显多于Fe-S+H2O2+vis体系.为了探讨?OH增多的原因,我们进行了电化学实验和PL实验.电化学实验结果显示,Ag/AgCl/Fe-S催化剂具有更低的阻抗,因此有利于电子-空穴分离.PL结果显示,Ag/AgCl/Fe-S催化剂的电子-空穴复合率更低.结合以上实验,我们提出了Ag/AgCl/Fe-S+H2O2+vis体系对双酚A的降解机理,即一方面催化剂能够发生Fenton反应而产生?OH,另一方面,催化剂中的Ag/AgCl在可见光下由于表面等离子响应而产生电子-空穴,空穴本身可作为活性物种降解双酚A.同时,产生的电子被体系中的Fe3+捕获生成Fe2+,从而促进了铁循环,有利于体系中产生更多的?OH.最后,空穴和羟基自由基发生协同作用共同促进污染物降解.     

New hybrid inorganic-organic polymers as supports for heterogeneous catalysis: a novel Pd(0) metalated cyclophosphazene-containing polymer as an efficient heterogeneous catalyst for the Heck reaction

[reaction: see text] A new Pd(0) complex of a pendant cyclophosphazene-containing cross-linked polymer is found to be an effective heterogeneous catalyst for the Heck arylation reaction. The catalyst is robust and can be recycled without significant loss of activity.     

A new copper(II) complex as an efficient catalyst of luminol chemiluminescence

A new copper complex (2) has exhibited highly efficient catalytic activity of luminol chemiluminescence in water in the presence of ascorbic acid and dissolved O2 under conditions that conventional catalysts such as Cu(OAc)2, hemin or cyclen-Cu(II) did not show significant activity.     

Co3O4 nanoparticles prepared by oxidative precipitation method: an efficient and reusable heterogeneous catalyst for N-formylation of amines

Research on Chemical Intermediates - N-formylation of different amines was carried out with formic acid in the presence of the Co3O4 nanoparticles as an efficient, stable heterogeneous catalyst to...     

A novel montmorillonite-enwrapped scandium as a heterogeneous catalyst for Michael reaction

Treatment of a Na+-exchanged montmorillonite with an aqueous Sc(OTf)3 solution afforded a robust Sc3+ aqua complex enwrapped by the silicate layers of the montmorillonites (Sc3+-mont). The resulting Sc3+-mont showed outstanding catalytic activities for the Michael reaction of 1,3-dicarbonyls under aqueous and solvent-free conditions. Moreover, this heterogeneous catalyst had an advantage of a strikingly simple workup procedure over the Lewis acids reported to date and was reusable without any appreciable losses in its activity and selectivity.     

A polyoxometalate-based Pd(II)-coordinated ionic solid catalyst for heterogeneous aerobic oxidation of benzene to biphenyl

An ionic solid catalyst by pairing Keggin polyoxometalate-anions with Pd(II)-coordinated nitrile-tethered ionic liquid cations was synthesized, characterized, and tested for aerobic oxidation of benzene to biphenyl. A unique heterogeneous intramolecular electron transfer mechanism is proposed to understand its high activity.     

Copper(II) bromide as efficient catalyst for silyl- to bisarylmethyl ethers interconversion (transprotection)

Primary and secondary silylated alcohols are easily converted to bis(methoxyphenyl)methyl (BMPM) ethers in good yields using CuBr₂ as catalyst in acetonitrile at room temperature. Various other protecting groups are compatible with this mild and convenient process.     

A cellulose-supported Mn(salen)Cl complex as an efficient heterogeneous catalyst for the selective oxidation of benzylic alcohols

[Mn(salen)Cl-cellulose] was synthesized by immobilization of homogeneous Mn(salen)Cl complex on cellulose and characterized by FT-IR, TGA and atomic absorption spectroscopy. The resulted catalyst exhibited moderate to high reactivity in the oxidation of benzylic alcohols into carbonyl compounds using oxone as oxidant in ambient conditions. The catalytic activity of Mn(salen)Cl and [Mn(salen)Cl-cellulose] in this reaction was investigated. The heterogeneous catalyst showed higher catalytic activity with respect to neat Mn(salen)Cl complex.