Analytical control of organic additives in electrolytic baths by UV spectroscopy in combination with multivariate analysis

A method for the simultaneous determination of organic additives in Zn(II) and Ni(II) electrolytic baths is proposed. Absorbance and first-derivative spectra were subjected to direct and inverse multiple linear regression (CLS and ILS, respectively) in order to choose the optimum alternative. The use of a factor design to prepare the samples enables the identification of interactions between analytes and their correction by ILS. The results provided by first-derivative spectra were slightly better than those obtained with absorbance spectra (prediction errors were always less than 2% with the former). The ILS procedure was applied to three industrial baths used to a different extent, with highly satisfactory results. Received: 15 June 1998 / Revised: 7 September 1998 / Accepted: 15 September 1998     

Experimental and theoretical analysis of electropolymerized PMeT thin films

It is reported that the physical analysis of poly(3‐methylthophene) (PMeT) thin films were doped with BF anions, which were deposited on tin oxide‐coated glass and stainless steel substrates using electropolymerization technique. The atomistic and electronic structures were evaluated to understand the main principles for the pure and doped PMeT polymers that give the photonic and conductivity properties for this kind of materials. It is found that galvanostatic method is more suitable for the electropolymerization of PMeT on conducting glass or flexible metal surfaces. The films were characterized using SEM, AFM, XRD, FTIR, Raman, and UV–vis absorption techniques. Raman and FTIR spectra of the samples revealed no signal related to the Li or the anion BF dopant, indicating that the optimum dopant concentration was well below the threshold value. Apart from the dopant influence, which is a well understood phenomenon, an attempt has been made to explain the influence of the lithium in the polymer matrix. The Li⁺ ions incorporated into the PMeT films form highly confined conjugational defects, neither dynamically nor electronically coupled with the host lattice. Using density function theory calculations, we could determine the optimum geometrical configurations of the cis and trans polymers and their corresponding electronic structure modification because of the presence of Li⁺ atoms controlling the electronic band gaps. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3058–3068, 2005     

Synthesis and characterization of reactive liquid crystalline Schiff bases,Rh(I) complexes,and their derived polymers

Two series of salicylaldimines have been synthesized that consist of model compounds with terminal methylenic chains and reactive compounds in which the terminal chains have been modified with acrylate groups. The dicarbonylrhodium(I) complexes of these systems were prepared by reacting the ligands with the dimer [RhCl(cod)]₂ and CO. Characterization of the metal‐containing acrylates by ¹H NMR spectroscopy revealed that the Rh(I) can coordinate to the terminal double bond to produce pentacoordinated complexes. Furthermore, investigation of the mesogenic properties of the complexes revealed that the bulkiness of the metallic center requires the presence of at least a three‐ring aromatic core to avoid the suppression of liquid crystallinity. The study was extended to include the side‐chain polymers obtained from the acrylate‐functionalized Schiff bases. Chelation of the preformed polyacrylate with low percentages of Rh(I) emerged as the best strategy to prepare Rh(I)‐containing polyacrylates. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4466–4477, 2000     

Gibbs energy based procedure for the correlation of type 3 ternary systems including a three-liquid phase region

Equilibrium data for type 3 ternary systems comprising a liquid–liquid–liquid equilibrium region (LLLE tie-triangle) are not frequently correlated, as is evidenced by a lack of studies in the literature. In the present paper, a robust algorithm to calculate or correlate equilibrium data for this type of system is proposed. This algorithm is based on geometric aspects related to the Gibbs energy of mixing (g^M) and possesses some interesting advantages that are discussed in the text. The methodology put forward is applied to correlate the equilibrium data of three type 3 ternary systems. The NRTL model is used to define g^M, and the common tangent plane criterion to define the equilibrium condition for the calculations. The lack in flexibility of the NRTL equation to model these systems is discussed.     

Hierarchical control of porous silica by pH adjustment: Alkyl polyamines as surfactants for bimodal silica synthesis and its carbon replica

Bimodal macro-mesoporous silica networks have been prepared in a simple one-pot synthesis using an inexpensive tetramine surfactant and tetraethoxysilane as a silica precursor. These novel materials show high pore volumes and templated mesopores (average pore size 3.0 nm) embedded in 20 nm thick walls forming interparticle large meso/macropores. The judicious control of the pH during the silica formation allows for the precise control of the interparticle condensation, likely due to the change in the interaction between the tetramine surfactant and the silica precursors. Finally, a highly porous carbon replica with bimodal porosity was prepared by using the bimodal silica as a hard sacrificial template. The microstructure of the silica template was accurately transferred to the carbon material obtaining high surface areas (up to 1300 m² g⁻¹) and total pore volumes ≥2 cm³ g⁻¹.     

Photocontrol of supramolecular architecture in azopolymers: Achiral and chiral aggregation

The absorption spectra and circular dichroism responses upon irradiation with 488 nm circularly polarized light (CPL) have been studied on polymeric films processed from two nematic copolymers containing azobenzene chromophores. Influence of the aggregation and orientation of azobenzenes on the photoinduced chiroptical properties has been analyzed. Moreover, polymeric films and 4 μm planar cells filled with the copolymers were studied by polarized optical microscopy (POM) with the aim of investigating the change of macroscopic optical properties and textures of azopolymers upon irradiation with CPL.     

Molecular dynamics of an epoxy resin modified with an epoxidized poly(styrene-butadiene) linear block copolymer during cure and microphase separation processes

Molecular dynamics of diglycidyl ether of bisphenol A (DGEBA) epoxy resin modified with an epoxidized poly(styrene-b-butadiene) (SepB) linear block copolymer has been monitored during cure and microphase separation process by dielectric relaxation spectroscopy (DRS) for wide frequency and temperature ranges. Different primary and secondary relaxation processes have been analyzed for neat components and ternary mixture. Relaxational behaviour has been modelled with Havriliak-Negami, Vogel-Fulcher-Tammann and Arrhenius equations and fitting parameters and their evolution have been obtained. The retention of the epoxidized poly(butadiene) (PepB) block in the epoxy-rich phase during all the polymerization process, previously detected by our group with atomic force and transmission electron microscopies, has been confirmed by dielectric relaxation spectroscopy. The evolution of molecular dynamics during the polymerization process of the epoxy resin in the ternary system indicates a change in the trend of the main relaxation at times that agree with phase separation detected by rheology.     

Stereocontrolled conjugate additions to dihydroindolizinone systems. Synthesis of enantiopure polysubstituted tetrahydropyrrolo[2,1-a]isoquinolones

Conjugate addition reactions of various types of nucleophiles to the γ-lactam unit of dihydroindolizinone systems have been studied. The addition of cuprates, amines or stabilized carbanions requires the activation of the unsaturated bicyclic lactam with a EWG at C-2, while sulfur-stabilized carbanions are reactive enough to add to the unsubstituted lactam. The stereochemical outcome of the conjugate addition reaction depends on the nature of the substituent at the angular position, and the incoming nucleophile. Thus 1,10b-cis or 1,10b-trans diastereomers could be obtained selectively with dr>95:5. The tandem conjugate addition–alkylation also takes place in good yields. These reactions have been applied to the synthesis of enantiopure tetrahydropyrrolo[2,1-a]isoquinolines.     

Review on immunoanalytical determination of tetracycline and sulfonamide residues in edible products

The state of the art of immunoanalysis for the determination of tetracycline and sulfonamide residues in food products is reviewed. Special attention is paid to the design and synthesis of haptens, providing an overview of the efforts spent on developing antibiotic screening methods to determine residue levels in agreement with the legislation. The results and observations published, focused on tetracycline and sulfonamide enzyme-linked immunosorbent assays, are discussed.     

Non-Covalent Interactions in a Nickel(II) Complex with Benzilate and 1,10-Phenanthroline

Abstract  

A new mixed-ligand nickel(II) coordination compound [Ni(bz)₂(phen)₂] (1) (bz = benzilate and phen = 1,10-phenanthroline) has been synthesized by refluxing nickel(II) acetate with benzilic acid and 1,10-phenantholine. Compound 1 has been characterized by elemental analysis, IR and electronic absorption spectroscopy, magnetic measurements, thermogravimetric analysis and single-crystal X-ray diffraction The crystal of 1 belongs to monoclinic crystal system, space group C2/c and its unit cell parameters are a = 25.881(3), b = 11.1728(15), c = 17.609(2) ? and β = 124.104(3)°. The effect of non-covalent interactions, such as π···π and C–H···π, on the 3D supramolecular organization of this molecular complex is analyzed.