A spectroelectrochemical study on single-oscillator model and optical constants of sulfonated polyaniline film

The optical properties of sulfonated polyaniline (SPAN) thin film prepared by electrochemical method have been investigated. Polychromic behavior of SPAN thin film (transparent yellow-green-dark blue) was observed when the cyclic voltammograms were taken between -0.25 V and +1.90 V (vs. Ag/AgCl, sat.) during the growth of polyaniline film. In situ UV-vis spectra of the polymers-indium tin oxide (ITO) glass electrode were taken during the oxidation of the polymers at different applied potentials. The direct band gap values of SPAN thin film changed from 3.771 eV to 3.874 eV with the applied potentials. From in situ UV-vis spectra, the optical constants such as refractive index and dielectric constant of the SPAN thin film were determined. The important changes in absorption edge, refractive index and the dielectric constant were observed due to the applied potentials. The refractive index dispersion curves of the film obey the single-oscillator model and oscillator parameters changed with the applied potentials. The most significant result of the present work is in situ spectroelectrochemical method, which can be used to modify the optical band gaps and constants.     

Linearly connected sequences and spectrally optimal dual frames for erasures

In the case that a frame is prescribed for applications and erasures occur in the process of data transmissions, we examine optimal dual frames for the recovery from single erasures. In contrast to earlier papers, we consider the spectral radius of the error operator instead of its operator norm as a measure of optimality. This notion of optimality is natural when the Neumann series is used to recover the original data in an iterative manner. We obtain a complete characterization of spectrally one-erasure optimal dual frames in terms of the redundancy distribution of the prescribed frame. Our characterization relies on the connection between erasure optimal frames and the linear connectivity property of the frame. We prove that the linear connectivity property is equivalent to the intersection dependent property, and is also closely related to the well-known concept of a k-independent set. Additionally, we also establish several necessary and sufficient conditions for the existence of an alternate dual frame to make the iterative reconstruction work.     

Various Shapes of 3 D Resonators Pass-Band Filters

The integral equations technique based on a three dimensional finite element method is applied as a quick and accurate analysis tool for the design of microwave passband filters. A three resonator H-plane bandpass filters with the various shapes of cavities and the irises are analyzed with this method in a single step and for only one mode, take into account all the electromagnetic effects. Consequently, it consumes less memory and CPU time. We propose also to study the same filters filled by homogeneous high dielectric material (ε_τ = 9.6) for Both resonator and coupling section. All these numerical results have been validated through a comparison with the results available in the scientific literature.     

N‐[Bis(2,4,6‐tri­methyl­phenoxy)­phos­phinoyl]‐P,P,P‐tris(2,4,6‐tri­methyl­phenoxy)phosphazene

The title compound, C₄₅H₅₅NO₆P₂, consists of an acyclic P=N—P(O) monophosphazene chain and five bulky 2,4,6‐tri­methyl­phenoxy side groups which predominantly determine the molecular shape. Although the P—N single [1.586 (3) Å] and P=N double [1.517 (3) Å] bonds are significantly different from each other, both are substantially shorter than the ideal P—N single bond. The P—N—P angle [146.0 (2)°] corresponds to the upper limit reported for acyclic phosphazene derivatives in the literature.     

Synthesis and characterization of oxime‐bearing hexakis(2‐formylphenoxy)‐phosphazene and its derivatives

Hexakis(2‐formylphenoxy)cyclotri‐phosphazene ( 2 ) was obtained from the reaction of hexachlorocylotriphosphazene ( 1 ) with 2‐hydroxy‐benzaldehyde. Hexakis(2‐[(hydroxyimino)methyl]‐phenoxy)cyclotriphosphazene (3) was synthesized from the reaction of 2 with hydroxlaminehydrochloride in pyridine. Hexasubstituted compounds 4, 5, 6, 8, 9 , and 10 were obtained from the reactions of 3 with methyl iodide, ethyl bromide, allyl bromide, propanoyl chloride, benzoyl chloride, and 4‐methoxybenzoyl chloride, respectively. Disubstituted product 7 was obtained from the reaction of 3 with chloroacetyl chloride. Pure and defined products could not be obtained from the reaction of 3 with acetyl chloride, benzyl chloride, and 2‐chlorobenzoyl chloride. The compounds were characterized by elemental analysis and IR, ¹H, ¹³C, and ³¹P NMR spectroscopy. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:791–797, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20350     

Tetra(diethyl)amide-p-tert-butyl-thiacalix[4]arene in Cone Conformation: Synthesis and Binding Properties with Alkali,Alkaline Earth,Heavy and Transition Metal Ions

Tetra(diethyl)amide-p-tert-butylthiacalix[4]arene 1a in the cone conformation was synthesized and its binding properties towards a large variety of metal ions were established on the basis of liquid–liquid and solid–liquid extraction as well as complexation experiments. This compound is a less efficient and selective compound than the “classical” tetra(diethyl)amide-p-tert-butylcalix[4]arene 3 in the cone conformation for alkali and alkaline earth metal ions. However, Pb²⁺ is selectively extracted and complexed within heavy and transition metal ions.