Facile Synthesis of Bis(crown ether)benzils: Prospective Building Blocks for Metal Ion Sensors

A new facile synthetic route to benzils containing fragments of 12-crown-4, 15-crown-5, and 18-crown-6 by oxidation of corresponding stilbenes was developed. The first representative of a new family of fluorescent sensors was obtained by reaction of bis(15-crown-5)benzil with o-phenylenediamine. The latter exhibits great fluorescence enhancement upon association with K⁺ and Rb⁺ compared to Na⁺ and Cs⁺.     

Characterization of H3PO4/HNO3–NANO2 oxidized bacterial cellulose and its usage as a carrier for the controlled release of cephalexin

Biocompatibility, biodegradation, good sorption characteristics, and unique structure of highly oxidized bacterial cellulose (OBC) are of great interest for the development of new drug delivery systems. In this study, OBC with 9.6, 13.0 and 19.5% carboxyl groups for 5, 20, and 48 h of synthesis, respectively, was successfully obtained using the HNO₃/H₃PO₄–NaNO₂. The results of morphological analysis showed that with an increase in the number of carboxyl groups, OBC fibers become thicker and rougher. Fourier-transform infrared spectroscopy showed the formation of carboxyl groups in the OBC after the oxidation reaction. The crystallinity of the samples according to X-Ray diffraction analysis decreased with increasing reaction time. The immobilization of cephalexin in the polymer matrix was studied in detail, it took 120 min to achieve balance in the solution with a concentration of 1 mg/ml, and the maximum amount of a sorbed antibiotic reached 43 mg/g. The drug release in vitro at 37 °C in PBS with pH 7.4 and 2.0 was prolonged. Various models were used to describe the release mechanism, the best of which was Ritger-Peppas with a diffusion exponent value ranging from 0.743 to 0.830, which explains the drug release mainly through non-Fickian diffusional release. The cephalexin-loaded OBC showed high antimicrobial activity against Gram-negative bacteria Escherichia coli and Gram-positive bacteria Staphylococcus aureus. The structure and properties of the resulting highly oxidized cellulose make it an excellent candidate as a drug delivery carrier with prolonged antimicrobial drug release characteristics.

     

A new synthesis of pentafluorosulfanylbenzene

[reaction: see text] A new and convenient three-step synthesis of pentafluorosulfanylbenzene from 1,4-cyclohexadiene with an overall yield of >70% is reported along with a number of derivatization reactions.     

$\Phi $-functions for complex 2D-objects

Within two-dimensional cutting and packing problems with irregular shaped objects, the concept of -functions has been proven to be very helpful for several solution approaches. In order to construct such -functions a previous work, in which so-called primary objects are considered, is continued. Now -functions are constructed for pairs of objects which can be represented as a finite combination (union, intersection, complement) of primary objects which allows the handling of arbitrary shaped objects by appropriate approximations of sufficient accuracy.Received: October 2002, Revised: October 2003, AMS classification: 65K05, 90C26, 90B06All correspondence to: Guntram Scheithauer     

Low-temperature IR and NMR studies of the interaction of group 8 metal dihydrides with alcohols

The reactions of the octahedral dihydrido complexes [MH(2)(PP(3))] [M=Fe, Ru, Os; PP(3)=P(CH(2)CH(2)PPh(2))(3)] with a variety of weak ROH acids have been studied by IR and NMR methods in either CH(2)Cl(2) or THF in the temperature range from 190 to 290 K. This study has allowed the determination of the spectral and thermodynamic properties associated with the formation of dihydrogen bonds (DHB) between the terminal hydrides and the OH group. Both the DHB enthalpy values and the hydride basicity factors (E(j)) have been found to increase in the order Fe < Ru < Os. The proton transfer process, leading to the DHB complexes, and eventually to eta(2)-H(2) products, has been found to depend on the acidic strength of the alcohol as well as the nature of the solvent. Low temperature IR and NMR techniques have been used to trace the complete energy profile of the proton transfer process involving the osmium complex [OsH(2)(PP(3))] with trifluoroethanol.     

Ultrasonic Broadband Spectrometry of Liquids A Research Tool in Pure and Applied Chemistry and Chemical Physics

This review is a survey of the many scientific applications of ultrasonic broadbandspectrometry (absorption and velocity measurements with coherent sound waves)in liquids and liquid systems, covering, at present, a frequency range from nearly10 kHz to 10 GHz. Ultrasonic spectrometry has proved to be an almost universalresearch tool in many laboratories, one that is useful for investigation of variouschemical, biochemical, and physicochemical systems. Sound waves traversingliquids induce periodic perturbations in pressure and temperature, which can shiftequilibria, resulting in characteristic sound absorption and velocity dispersionspectra. An analysis of such spectra yields valuable information about thermodynamic and kinetic parameters of the particular system that is often difficult toobtain by other methods. Since such periodic perturbations imposed on the systemare incremental in nearly all cases, the system can be studied under equilibriumconditions. All nonlinear effects (heating, nonconstant fluid compressibility, andothers) are negligible, permitting, for instance, the application of linearized rateequations. In this review, various examples of measured broadband spectra arepresented. Related elementary processes are discussed. Among these are ionicand molecular reactions, including mechanisms of association and complexation,proton transfer, solvation, isomerization, interconversion, side-group rotation,hydrogen-bonding, as well as stacking processes and micelle formation. Specialattention will be given to the extensive research on chemical relaxation.Fundamental early and recent publications are cited and discussed. Many referencesare included with particular emphasis on less well known research and publicationsfrom countries of the former USSR. This review aims at a demonstration of thewidespread applications of modern ultrasonic techniques in many fields ofliquid-state research.     

New type of biosensor based on magnetic nanoparticle detection

A new type of biosensor has been developed based on detection of nanosized superparamagnetic particles that serve as labels in bioreactions. The method is based on non-linear magnetic material detection by a magnetic field having components at two frequencies f₁ and f₂. The response is measured at the combinatorial frequencies f_i=mf₁+nf₂, where m and n are integers, e.g., f_i=f₁±2f₂. Several highly sensitive readers of superparamagnetic particles have been designed and used for development of various formats of immunoassays, including those compatible with immunoconcentration and magnetic enrichment of antigens.