Effective TiO2 supported Cu-Complex catalyst in NaBH4 hydrolysis reaction to hydrogen generation

This paper reports the experimental results on using TiO₂ based Cu(II)-Schiff Base complex catalyst for hydrolysis of NaBH₄. In the presence of Cu-Schiff Base complex which we reported in advance [1] and with titanium dioxide supports a novel catalyst named TiO₂ supported 4-4′-Methylenbis (2,6-diethyl)aniline-3,5-di-tert-buthylsalisylaldimine-Cu complex is prepared, successfully. The synthesized catalyst was characterized by means of X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Brunauer-Emmett-Teller Surface Area Analysis (BET) and Fourier Transform Infrared Spectroscopy (FT-IR). The as prepared catalyst was employed to generate hydrogen through hydrolysis reaction of NaBH₄. Effects of different parameters (e.g. amount of Cu-Schiff Base complex in all catalyst, percentage of NaBH₄, percentage of NaOH, amount of TiO₂ supported Cu-Schiff Base complex catalyst and different temperatures) are also investigated. A high apparent activation energy (Ea), 25,196 kJ.mol^-1 is calculated for hydrolysis of NaBH₄ at 20–50 °C. Hydrogen generation rate was 14,020 mL H₂/g_cat.min and 22,071 mL H₂/g_cat.min in order of 30 °C and 50 °C.     

Nutritional value and digestion rate of rhea meat proteins in association with storage and cooking processes

The nutritional value of proteins was investigated after the storage and cooking of rhea M. Gastrocnemius pars interna. Oxidation of basic and aromatic amino acids, surface hydrophobicity and aggregation state of proteins, were determined in raw and cooked meat. In addition, myofibrillar proteins were exposed in vitro to proteases of the digestive tract. Cooking markedly affected the protein surface hydrophobicity. The BBP bound content was three times greater in cooked than in fresh rhea meat. A small increment in tryptophan content after cooking was observed. Storage influenced Schiff bases formation indicating the presence of protein-aldehyde adducts after cooking. High content of Schiff bases was found after cooking of samples stored for 5 days, demonstrating a probable implication of free amino groups, most likely from lysine. Cooking decreased the myofibrillar protein susceptibility to pepsin activity. After cooking, the proteolysis rate by pancreatic enzymes increased. Our findings support the importance of protein aggregation in the nutritional value of meat proteins.     

Polymer‐bound schiff‐base complex catalyst for effective oxidation of olefins with molecular oxygen

Polymer‐bound Schiff‐base ligand (PS–SalPhe) was prepared from polystyrene‐bound salicylaldehyde and phenylalanine, and its complex (PS–SalPhe–M) (M = Co, Mn) was also synthesized. The polymer ligand and its complex were characterized by infrared spectra, small area X‐ray photoelectron spectroscopy, and ICP–AES. In the presence of the complex, cyclohexene can be effectively oxidized by molecular oxygen without a reductant. The major products of the reaction are 2‐cyclohexen‐1‐ol (—OH), 2‐cyclohexen‐1‐one (CO), and 2‐cyclohexen‐1‐hydroperoxide (—OOH ), which is different from the typical oxidation of cyclohexene. The mechanism of cyclohexene oxidation is also discussed. Long‐chain linear aliphatic olefins, such as 1‐octene, 1‐decene, 1‐dodecene, and 1‐tetradecene, can be directly oxidized by molecular oxygen catalyzed by PS–SalPhe–M (M = Mn, Co), which yields the 1,2‐epoxy alkane. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1138–1143, 2000     

Novel building blocks for oligonuclear copper complexes derived from β‐ketoenamines of histidine

Condensation products of L‐histidine with the 3‐oxoenolethers diethyl‐ethoxymethylene‐malonate ( 1 ) and ethyl‐ethoxymethylene‐cyanoacetate ( 2 ) react with copper(II) as di‐anionic ligands to give neutral 1:1 complexes Cu‐ His1 and Cu‐ His2 . Both complexes crystallize as oligonuclear units, even from strongly donating solvents like N‐methylimidazole (Meim) (Cu‐ His1 ) and pyridine (Cu‐ His2 ). X‐ray structure analyses show supramolecular structures, formed of two (Cu‐ His1 ) or four (Cu‐ His2 ) formula units of the complex, which arrange to macrocycles by means of intermolecular coordination of the imidazole‐N. Strong H‐bridges result in a face‐to‐face orientation of the hydrophilic sites of two great rings. ESI‐MS investigations in pyridine solution give evidence for the existence of dimeric, tetrameric and – in case of Cu‐ His2 – trimeric units, besides the monomeric adducts with one pyridine. In contrast to the dimeric or tetrameric (“cubane‐like”) copper(II) complexes of amino alcohols and their β‐ketoenamines, the complexes Cu‐ His1 and Cu‐ His2 show no significant spin coupling from room temperature down to 4 K. The complexes Cu‐ His1 and Cu‐ His2 give no electrochemically reversible Cu^II/I reduction in pyridine. However, the isolation of a stable diamagnetic copper(I) complex of the methylester derivative, Cu^I‐ HisMe1 , supports the assumption, that similar histidine‐derived copper complexes should display reversible redox behaviour and catalytic activity in reactions with O₂.     

Novel thiophene symmetrical Schiff base compounds as corrosion inhibitor for mild steel in acidic media

The inhibiting effect of two Schiff bases on the corrosion of the mild steel (MS) in 1 M HCl has been studied by electrochemical impedance spectroscopy (EIS) and Tafel polarisation measurements. The Schiff bases, 4,4′-bis(3-carboxaldehyde thiophene) diphenyl diimino ether (L₁) and 4,4′-bis(3-carboxaldehyde thiophene) diphenyl diimino ethane (L₂), were synthesized using 3-carboxaldehydethiophene and its corresponding amine. Polarisation curves reveal that both compounds are mixed type (cathodic/anodic) inhibitors and inhibition efficiency (% IE) increases with increasing concentration of compounds. It is suggested that their effects depend on their concentrations and the molecular structures. Adsorption of compounds on mild steel surface is spontaneous and obeys Langmuir’s isotherm.     

席夫碱结构对Cu缓蚀作用的影响

用自组装技术使席夫碱在Cu表面自组装成膜,用扫描电子显微镜(SEM)、交流阻抗方法及量子化学法研究了席夫碱结构对Cu缓蚀作用的影响.结果表明:席夫碱类化合物在发挥其活性时应以接受电子为主,此类化合物的亚胺或甲亚胺特性基团(-RC=N-)和苯环上的-OH是该类化合物的主要活性区,席夫碱苯环的-H被给电子基团取代会提高对Cu的缓蚀效率,且取代基团越靠进-C=N-,形成的螯合物越稳定,缓蚀效率越高.     

席夫碱与硝酸铈复配物对1060纯铝的缓蚀作用

采用极化曲线、电化学阻抗谱、扫描电镜和能谱分析,研究合成的3-吡啶-4-氨基-1,2,4-三唑-5-硫酮席夫碱及其复配物硝酸铈在质量分数为3.5%NaCl溶液中对1060纯铝的缓蚀作用。结果表明：在293 K时席夫碱可有效抑制纯铝在3.5%NaCl溶液中的腐蚀,当席夫碱浓度为0.4 g.L_-1时缓蚀率最高,可达76.0%。席夫碱为混合型缓蚀剂,其在1060纯铝表面的吸附符合Langmuir吸附模型,且同时存在物理吸附和化学吸附。0.2 g.L_-1席夫碱与0.03 g.L_-1硝酸铈复配缓蚀率可达88.2%,二者具有协同缓蚀作用。     

席夫碱缓蚀剂的研究进展

席夫碱主要指含有亚胺或甲亚胺特征基团 (—RC=N—) 的一类有机化合物。目前席夫碱缓蚀剂具有良好的应用前景,被广泛地应用于工业生产中。本文介绍了近年来国内外席夫碱缓蚀剂的发展概况,阐述了席夫碱缓蚀剂的制备方法及作用机理,并对席夫碱缓蚀剂的发展趋势进行了展望。     

Corrosion inhibition of mild steel using Novel Bis Schiff’s Bases as corrosion inhibitors: Electrochemical and Surface measurement

Purpose: The aim of the present investigation is to evaluate the corrosion inhibiting properties of four novel synthesize compounds namely N¹,N^1′-(1,4-phenylene)bis(N⁴-(4-nitrobenzylidene)benzene-1,4-diamine) SB-I, N¹,N^1′-(1,4-phenylene)bis(N⁴-benzylidenebenzene-1,4-diamine) SB-II, N¹,N^1′-(1,4-phenylene)bis(N⁴-(4-methylbenzylidene)benzene-1,4-diamine) SB-III, N¹,N^1′-(1,4-phenylene)bis(N⁴-(4-methoxybenzylidene)benzene-1,4-diamine) SB-IV for mild steel in 1 M HCl. Corrosion inhibitors find wide application in industries during pickling of steel, descaling and oil well acidization. Inhibitors have attracted great attention due to cost effectiveness and simplicity of the methods. Method: Different experimental techniques such as weight loss, open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization were used to evaluate the corrosion inhibition performance of SBs for mild steel in acid solution. After the corrosion experiments, the surface morphology of metal surface in the absence and presence of SBs were studied by scanning electron microscopy (SEM) and Atomic force microscopy (AFM). Findings: The corrosion inhibition efficiency of SBs for mild steel are 71.42% (SB-I), 89.52 (SB-II), 92.85 (SB-III), 96.19 (SB-IV). Tafel polarization revealed that all the SBs behaved as mixed-type inhibitor but predominantly of cathodic type. The inhibition actions of these Schiff base molecules blocked the electrode surface by means of adsorption of the inhibitor molecule on metal surface, obeying the Langmuir adsorption isotherm. SEM/AFM studies of the metal surfaces confirm the protection of metal surface in presence of inhibitor as compared to the damaged surface in blank acid solution.     

A ratiometric fluorescent sensor for zinc(II) with high selectivity

Spectroscopic studies revealed that the compound [N,N′-di(quinoline-2-methylene) -1,2-phenylenediimine] (1) exhibited a rather high selectivity toward Zn²⁺ over other metal ions, even Cd²⁺. In acetonitrile, the red shift of fluorescent emission from 396 nm to 426 nm upon zinc binding is due to the formation of a 1:1 metal/ligand complex.