UV-vis, IR and 1H NMR spectroscopic studies of some mono- and bis-azo-compounds based on 2,7-dihydroxynaphthalene and aniline derivatives

The absorption spectra of mono- and bis-azo-derivatives obtained by coupling the diazonium salts of aromatic amines and 2,7-dihydroxynaphthalene have been studied in six organic solvents. The different absorption bands have been assigned and the effect of solvents on the charge transfer band is also discussed. The diagnostic IR spectral bands and 1H NMR signals are assigned and discussed in relation to molecular structure. Also, semi-empirical molecular orbital calculations using the atom superposition and electron delocalization molecular orbital (ASED-MO) theory have been performed to investigate the molecular and electronic structures of these compounds. According to these calculations, an intramolecular hydrogen bonding is essential for stabilization of such molecules.     

SiCl4-Zn induced reductive coupling of carbonyl compounds: novel and efficient routes for one-pot syntheses of 1,2,3-triaryl-2-propen-1-ones and pinacolones at room temperature

An unprecedented one-pot reductive trimerization of aromatic aldehydes to 1,2,3-triaryl-2-propen-1-ones as well as tandem reductive coupling-rearrangements of aryl ketones to pinacolone analogues was efficiently achieved using tetrachlorosilane-zinc at room temperature.     

A search-and-track algorithm for controlling the number of guided modes of planar optical waveguides with arbitrary refractive index profiles

A search-and-track algorithm is proposed for controlling the number of guided modes of planar optical waveguides with arbitrary refractive index profiles. The algorithm starts with an initial guess point in the parameter space that supports a specific number of guided modes. Then, it searches for, and tracks, the boundaries of this space or another space supporting different number of modes. It does so by monitoring the sign of a unified cutoff dispersion function. The algorithm is applied to both symmetric and asymmetric silicon-based parabolic-index waveguides. It shows that unlike asymmetric waveguides, the single-mode condition of symmetric waveguides is controlled by TM-, as opposed to TE-, polarization. This abnormal polarization control is strongest for high index contrast waveguides of sub-micrometer core sizes. The results are verified by full-vectorial beam propagation method.     

A matrix formulation for the dynamic analysis of planar mechanisms using point coordinates and velocity transformation

This paper presents a matrix formulation for the dynamic analysis of planar mechanisms consisting of interconnected rigid bodies. The formulation initially uses the rectangular Cartesian coordinates of an equivalent constrained system of particles to define the configuration of the mechanical system. This results in a simple and straightforward procedure for generating the equations of motion. The equations of motion are then derived in terms of relative joint coordinates through the use of a velocity transformation matrix. The velocity transformation matrix relates the relative joint velocities to the Cartesian velocities. For the open-loop case, this process automatically eliminates all of the non-working constraint forces and leads to an efficient integration of the equations of motion. For the closed-loop case, suitable joints should be cut and few cut-joints constraint equations should be included for each closed loop. Two examples are used to demonstrate the generality and efficiency of the proposed method.     

Nano-sized Co(II)-8-hydroxyquinolate complex thin film via surface layer-by-layer chemical deposition method: Optimized factors and optical properties

An extensive study was performed and reported for evaluation and optimization of the factors affecting thin film formation of nano-sized Co(II)-8-hydroxyquinolate complex by surface layer-by-layer chemical deposition method. The formation of uniform thin films of nano-crystalline metal complex is heavily dependent on several important factors. Variation in metal and ligand concentrations (1:1–1:3) was found to show insignificant contribution to the molar stoichiometric ratio of the synthesized thin film of nano-sized Co(II)-8-hydroxyquinolate. The number of dipping cycles (2–50) was characterized by strong influence on the thin film thickness. The dependence of the immersion time (2–50 s) was proved to influence the crystal growth and homogeneity of the thin film. The role of pH of metal and ligand solutions was identified by strong contribution in development and formation of deposited Co(II)-8-hydroxyquinolate complex thin film. Finally, the role of solvent on the thin film formation was also studied and evaluated. Metal analysis, SEM, EI-MS, FT-IR and TGA were applied as monitoring techniques of these factors. The optical properties of Co(II)-8-hydroxyquinolate complex were also studied and the complex thin films were characterized by the highest optical transition from π–π* or n, π* states with energy gap in the UV-range at 3.13 eV. The lowest optical transition resulted from d–d transition or metal centered transition with energy 1.5 eV while, the optical transition at 2.35 eV is the contribution of metal ligand or ligand metal transition. In the light of the optical measurement, Co(II)-8-hydroxyquinolate complex can be considered as an organic semiconductor with the potential applications in the design of organic light-emitting diodes (OLEMs).     

Geometry of the common dynamics of Pisot substitutions with the same incidence matrix

Any Pisot substitution can be associated with a bounded set with interesting properties, called the Rauzy fractal. This set is obtained by projection of the broken line associated with an infinite fixed point. Two substitutions having the same incidence matrix can have different Rauzy fractals. We show that under weak conditions, the intersection of these two fractals has strictly positive measure, and can also be generated by a substitution.     

Multi-analyte HPLC–DAD Method for Concurrent Analysis of Six Antimicrobials and Three Proton Pump Inhibitors Frequently used in Management of Helicobacter pylori Infection: Application to Simulated Intestinal Fluid Samples

Chromatographia - The present work deals with the optimization, validation and application of a versatile HPLC–DAD method for concurrent estimation of nine antimicrobials and proton pump...     

Synthesis and photophysical properties of poly-(phenylenevinylene) dendrimers with a ruthenium tris-bipyridine core

The photophysical processes have been investigated in first, second and third generation dendrimers with poly-(phenylenevinylene) branches and a ruthenium tris-bipyridine core, RuDn (n = 1–3). These dendrimers show very efficient forward singlet–singlet energy transfer from the branches to the ruthenium core upon UV irradiation, with efficiencies of 0.99 for RuD1 and 0.88 for RuD2 and RuD3 in CH₂Cl₂. The RuDn dendrimers show a bi-exponential emission decay in CH₂Cl₂, when excited with a 460 nm light with short lifetimes, however, the emission decay lifetimes become mono-exponential in 10% Triton X-100 aqueous solution (τ = 840 ns for RuD1, 890 ns for RuD2 and 1120 ns for RuD3).     

Oxidative degradation of nitrogen-containing organic compounds: vaccum-ultraviolet (VUV) photolysis of aqueous solutions of 3-amino 5-methylisoxazole

The oxidative degradation of 3-amino 5-methyl isoxazole initiated by the VUV photolysis of water at 172 nm has been studied. Mineralization of CO₂, H₂O, NO ₃ ^– and NH ₄ ⁺ is more efficient when reductive conditions (argon saturated solutions) are favoured. Formation of compounds which cannot be completely oxidised to CO₂ is observed. Experiments performed under strictly oxidative conditions show higher yields of these inert compounds and, hence, incomplete mineralization. Cyanide was formed in concentrations lower than 5×10^–5 mol/l. In alkaline aqueous solutions, cyanide is completely transformed into CO ₃ ^2– , NH ₄ ⁺ and NO ₃ ^– during the irradiation time needed to mineralize the isoxazole. Therefore, cyanide does not present a potential risk for the use of the VUV photolysis for isoxazole degradation. Similarly, organic nitrogen is converted into both, NO ₃ ^– and NH ₄ ⁺ . The relative concentrations of the two ions depend on total irradiation time, oxygen saturation and reactor geometry. A sequence of reactions is proposed and discussed.Dedicated to Professor Dr. Dieter Klockow on the occasion of his 60th birthday     

Chelates and corrosion inhibition of newly synthesized Schiff bases derived from <Emphasis Type="Italic">o</Emphasis>-tolidine

New copper(II), nickel(II), iron(III) and palladium(II) Schiff base complexes derived from o-tolidine and selected aldehydes, namely salicyaldehyde and 2-hydroxynaphthaldehyde have been synthesized and characterized by a combination of elemental analyses, magnetic moments, spectral (u.v.–vis., i.r.) and thermal (tg, dtg) mesurements. The corrosion inhibition of aluminium and copper in 1 M HCl and chromium–nickel steel in crude oil using N,N′bis(salicyledene)-o-tolidine have been studied by weight loss method.