New palladium(II)–N‐heterocyclic carbene complexes containing benzimidazole‐2‐ylidene ligand derived from menthol: synthesis,characterization and catalytic activities

A new series of sterically hindered ligands containing (1R,2S,4R)‐(+)‐menthoxymethyl group attached to benzimidazole‐based N‐heterocyclic carbene (NHC), palladium–bis‐NHC complexes and (κ²‐C,N)‐palladacyclic NHC complexes have been synthesized and characterized using appropriate spectroscopic techniques. Catalytic performance of the palladium complexes has been investigated for allylic alkylation, Suzuki and Heck carbon–carbon coupling reactions. These complexes smoothly catalyse the carbon–carbon bond formation reactions. Copyright © 2016 John Wiley & Sons, Ltd.     

New Amperometric Cholesterol Biosensors Using Poly(ethyleneoxide) Conducting Polymers

Accumulation of cholesterol in human blood can cause several health problems such as heart disease, coronary artery disease, arteriosclerosis, hypertension, cerebral thrombosis, etc. Therefore, simple and fast cholesterol determination in blood is clinically important. In this study, two types of amperometric cholesterol biosensors were designed by physically entrapping cholesterol oxidase in conducting polymers; thiophene capped poly(ethyleneoxide)/polypyrrole (PEO-co-PPy) and 3-methylthienyl methacrylate-co-p-vinyl benzyloxy poly(ethyleneoxide)/polypyrrole (CP-co-PPy). PEO-co-PPy and CP-co-PPy were synthesized electrochemically and cholesterol oxidase was immobilized by entrapment during electropolymerization. The amperometric responses of the enzyme electrodes were measured by monitoring oxidation current of H₂O₂ at +0.7 V in the absence of a mediator. Kinetic parameters, such as Km and Imax, operational and storage stabilities, effects of pH and temperature were determined for both entrapment supports. Km values were found as 1.47 and 5.16 mM for PEO-co-PPy and CP-co-PPy enzyme electrodes, respectively. By using these Km values, it can be observed that ChOx immobilized in PEO-co-PPy shows higher affinity towards the substrate.     

Enantioselective sorption of some chiral carboxylic acids by various cyclodextrin-grafted iron oxide magnetic nanoparticles

A new enantioselective sorption approach to chiral carboxylic acid molecules such as (R)-(?)-N-(3,5-dinitrobenzoyl)phenylglycine (R)-(?)DNBPG, (S)-(+)-N-(3,5-dinitrobenzoyl)phenylglycine (S)-(+)DNBPG, (R)-(+)-N-(1-phenylethyl)phthalamic acid (R)-(+)PEPA and (S)-(?)-N-(1-phenylethyl)phthalamic acid (S)-(?)PEPA regarding their complexation with three diversely functionalized β-cyclodextrin grafted iron oxide nanoparticles in the aqueous phase, was developed. The sorption efficiencies of these carboxylic acids were carried out by high-performance liquid chromatography (HPLC) with an Ace 5 C18 column. The effects of temperatures on the sorption were also investigated. The results showed that the ether functionalized derivative of β-cyclodextrin Al-CD-MNPs has a specific affinity for (R)-(?)DNBPG at 30 °C and pH 7.0. The amine functionalized derivative of β-cyclodextrin Am-CD-MNPs has a greater affinity towards not only (S)-(?)DNBPG, but also (R)-(+)PEPA compared with their other isomers, which are the (R)-isomer of DNBPG and the (S)-isomer of PEPA at 30 °C and pH 7.0. In addition, although amide functionalized derivatives of β-cyclodextrin (Amd-CD-MNPs) have an affinity towards both isomers of some chiral carboxylic acids; no selective affinity was observed at 30 °C and pH 7.0.     

Composites of poly[4-((p-tolylimino)methyl)phenyl acrylate] and the Ni-complex with aminated MWCNT: Thermal,electrical and magnetic investigation

Abstract

Its nickel complex and a polyacrylate with side chain the Schiff base obtained from the condensation reaction of 4-hydroxybenzaldehide and p-toluidine, have been synthesized. The three-component composites were prepared using the polyacrylate, poly[4-((p-tolylimino) methyl) phenyl acrylate], its Ni-complex, and aminated MWCNT at three different percent (2%, 8% and 15% by wt). For characterization, FT-IR, 1H-NMR, SEM-EDX, SEM images and VSM (vibrating sample magnetometer) were used. The specific magnetic susceptibility for the Ni-complex is calculated as 3.0?×?10^?8 m³/kg from the slope of VSM straight line and the Ni-complex shows paramagnetic property. Thermal stabilities of the composites decreased compared with the polymer and Ni-complex. The AC conductivities of the samples increased with increasing frequency and increasing temperature. Frequency exponent of the equation connecting the AC conductivity to angular frequency was calculated as between 1.06 and 0.86 at 298?K and between 0.97 and 0.71 at 320?K, for all samples. Log σ_ac vs 1000/T straight lines were generated above and below the T_g temperature and the activation energies were calculated from the slopes as the values between 0.097 and 0.331?eV below Tg and the values between 1.134 and 0.768?eV above T_g.     

Synthesis of new iron–NHC complexes as catalysts for hydrosilylation reactions

A series of new piano‐stool iron(II) complexes comprising N‐heterocyclic carbene ligands [Fe(Cp)(CO)₂(NHC)]I (NHC = 1,3‐disubstituted imidazolidin‐2‐ylidene) have been synthesized and analyzed by ¹H NMR, ¹³C NMR, IR, elemental analysis and mass spectrometric techniques. These compounds were easily prepared from the reaction of disubstituted imidazolidin‐2‐ylidene with [FeI(Cp)(CO)₂] in toluene at room temperature. These complexes were tested in the catalytic hydrosilylation reaction of aldehydes and ketones with phenylsilane in solvent‐free conditions. After a basic hydrolysis step, the corresponding alcohols were obtained in good yields. Copyright © 2013 John Wiley & Sons, Ltd.     

Reversible cation/anion extraction from K2La2Ti3O10: formation of new layered titanates, KLa2Ti3O9.5 and La2Ti3O9

A new soft-chemical transformation of layered perovskite oxides is described wherein K2O is sequentially extracted from the Ruddlesden-Popper (R-P) phase, K2La2Ti3O10 (I), yielding novel anion-deficient KLa2Ti3O(9.5) (II) and La2Ti3O9 (III). The transformation occurs in topochemical reactions of the R-P phase I with PPh4Br and PBu4Br (Ph = phenyl; Bu = n-butyl). The mechanism involves the elimination of KBr accompanied by decomposition of PR4+ (R = phenyl or n-butyl) that extracts oxygen from the titanate. Analysis of the organic products of decomposition reveals formation of Ph3PO, Ph3P, and Ph-Ph for R = phenyl, and Bu3PO, Bu3P along with butane, butene, and octane for R = butyl. The inorganic oxides II and III crystallize in tetragonal structures (II: P4/mmm, a = 3.8335(1) A, c = 14.334(1) A; III: I4/mmm, a = 3.8565(2) A, c = 24.645(2) A) that are related to the parent R-P phase. II is isotypic with the Dion-Jacobson phase, RbSr2Nb3O10, while III is a unique layered oxide consisting of charge-neutral La2Ti3O9 anion-deficient perovskite sheets stacked one over the other without interlayer cations. Interestingly, both II and III convert back to the parent R-P phase in a reaction with KNO3. While transformations of the R-P phases to other related layered/three-dimensional perovskite oxides in ion-exchange/metathesis/dehydration/reduction reactions are known, the simultaneous and reversible extraction of both cations and anions in the conversions K2La2Ti3O10 right harpoon over left harpoon KLa2Ti3O9.5 right harpoon over left harpoon La2Ti3O9 is reported here for the first time.