High-performance liquid chromatographic determination of (S)-(-)-ofloxacin and its metabolites in serum and urine using a solid-phase clean-up

A sensitive and selective method for the simultaneous determination of (S)-(-)-ofloxacin [(S)-(-)-OFLX] and its metabolites in serum and urine was developed using isocratic high-performance liquid chromatography with a specific solid-phase extraction procedure. (S)-(-)-OFLX and its metabolites, desmethyl-(S)-(-)-OFLX and (S)-(-)-OFLX N-oxide, were eluted from a C8 solid-phase column with recoveries of more than 98%. These compounds were separated and determined by means of a reversed-phase column with fluorimetric detection. Validation studies showed that the results were linear for (S)-(-)-OFLX in serum over the range 10-1200 ng/ml and in urine over the range 1-200 micrograms/ml. Analysis for (S)-(-)-OFLX and its metabolites showed good precision and accuracy with a relative standard deviation of less than 6%.     

Aerobic oxidation of 1,3,5-triisopropylbenzene using N-hydroxyphthalimide (NHPI) as key catalyst

The first systematic study on the aerobic oxidation of 1,3,5-triisopropylbenzene was examined by the use of N-hydroxyphthalimide (NHPI) as a key catalyst. It was found that 1,3,5-triisopropylbenzene was efficiently oxidized with O₂ in the presence of a catalytic amount of NHPI and azobisisobutyronitrile (AIBN) at 75 °C. Upon treatment of the resulting products with sulfuric acid followed by acetic anhydride led to 5-acetoxy-1,3-diisopropylbenzene and 3,5-diacetoxy-1-isopropylbenzene as major products and a small amount of 1,3,5-triacetoxybenzene. When t-butylperoxypivalate (BPP) was employed as a radical initiator, the oxidation could be achieved in good yield even at 50 °C. This oxidation provides a facile method for preparing phenol derivatives bearing an isopropyl moiety, which can be used as pharmaceutical starting materials.     

Molecular metamagnet [Ni(4ImNNH)(2)(NO(3))(2)] (4ImNNH = 4-imidazolyl nitronyl nitroxide) and the related compounds showing supramolecular H-bonding interactions

A new chelating radical ligand 4ImNNH (2-(4-imidazolyl)-4,4,5,5-tetramethylimidazolin-1-oxyl 3-oxide) was prepared, and complexation with divalent transition metal salts gave complexes, [M(4ImNNH)(2)X(2)], which showed intermolecular ferromagnetic interaction in high probability (7 out of 10 paramagnetic compounds investigated here). The nitrate complexes (X = NO(3); M = Mn (1), Co (2), Ni (3), Cu (4)) crystallize isomorphously in monoclinic space group P2(1)/a. The equatorial positions are occupied with two 4ImNNH chelates and the nitrate oxygen atoms are located at the axial positions. Magnetic measurements revealed that the intramolecular exchange couplings in 1, 2, and 4 were antiferromagnetic, while that in 3 was ferromagnetic with 2J/k(B) = +85 K, where the spin Hamiltonian is defined as H = -2J(S(1).S(2) + S(2).S(3)) based on the molecular structures determined as the linear radical-metal-radical triads. The intramolecular ferromagnetic interaction in 3 is interpreted in terms of orthogonality between the radical pi and metal dsigma orbitals. Compounds 1-3 exhibited intermolecular ferromagnetic interaction ascribable to a two-dimensional hydrogen bond network parallel to the crystallographic ab plane. Complex 3 became an antiferromagnet below 3.4 K and exhibited a metamagnetic transition on applying a magnetic field of 5.5 kOe at 1.8 K. The complexes prepared from metal halides, [M(4ImNNH)(2)X(2)] (X = Cl, Br; M = Mn, Co, Ni, Cu), showed intramolecular antiferromagnetic interactions, which are successfully analyzed based on the radical-metal-radical system. The crystal structures determined here on 1-4, [Mn(4ImNNH)(2)Cl(2)], and [Cu(4ImNNH)(2)Br(2)] always have intermolecular hydrogen bonds of H(imidazole).X(axial ligand)-M, where X = NO(3), Cl, Br. This interaction seems to play an important role in molecular packing and presumably also in magnetic coupling.     

Fabrication of polymer Langmuir-Blodgett films containing regioregular poly(3-hexylthiophene) for application to field-effect transistor

Semiconducting thin films consisting of regioregular poly(3-hexylthiophene) (RR-PHT) and poly(N-dodecylacrylamide) (pDDA) were constructed by the Langmuir-Blodgett (LB) technique. A mixture of RR-PHT and pDDA spread from a chloroform solution on a water surface forms a stable monolayer, which can be transferred onto solid substrates by the LB method, yielding a well-defined polymer LB film. Surface morphology studies of the LB film indicate that the RR-PHT is dispersed uniformly throughout the surface. The polymer thin film was chemically doped by contacting with FeCl3 acetonitrile solution, and a conductivity of 5.6 S/cm was achieved. Further, the LB film was utilized as the semiconducting film in the field-effect transistor (FET), and mobilities of 2.2 x 10(-4) and 4.4 x 10(-4) cm2 V(-1) s(-1) were obtained by analyzing the saturated and linear regions of the current-voltage characteristic, respectively.     

Convenient synthesis of 7-aryl-3,4,5,6-tetrahydro-2H-pyrido[4,5-b]- and [2,3-b]-1,5-oxazocine-6-ones

A convenient and diversity-oriented method for synthesis of the novel 7-aryl-3,4,5,6-tetrahydro-2H-pyrido[4,5-b]-1,5-oxazocine-6-one skeleton 1 and the very rarely described 7-aryl-3,4,5,6-tetrahydro-2H-pyrido[2,3-b]-1,5-oxazocine-6-one skeleton 2, featuring cyclization using nucleophilic aromatic substitution (S_NAr) and Suzuki coupling, is described.     

Ozonolysis of five-membered heterocycles

The relative reaction rate of five-membered heterocycles with ozone was evaluated. These relative rates were correlated to the highest bond order value in the corresponding ring, calculated by the convenient HMO method. From this correlation, the reactivity of heterocycles with ozone was able to be predicted. Also it was concluded that the predominant product in the ozonolysis of five-membered heterocycles containing an oxygen atom was the corresponding carboxylic acid, while nitrogen heterocycles gave the corresponding amide.     

High-molecular-weight poly(p-phenyleneterephthalamide) by the direct polycondensation reaction with triphenyl phosphite

Poly(p-phenyleneterephthalamide) of high molecular weight was obtained when the polycondensation of terephthalic acid and p-phenylenediamine was carried out in N-methylpyrrolidone (NMP) that contained dissolved CaCl₂ and LiCl in the presence of pyridine. The molecular weight of the polymer obtained varied with the amount of pyridine relative to the metal salts and with the molar ratios of CaCl₂ to LiCl, the maximum η_inh value of 4.5 being obtained under the conditions Py/(CaCl₂ + LiCl) ≈ 2.5 (mol/mol), CaCl₂/LiCl ≈ 1.2 (mol/mol), and LiCl + CaCl₂ ≈ 4 g. Among the solvents tested, NMP was significantly effective for the reaction. Polycondensations of several combinations of other dicarboxylic acids and diamines were carried out with limited success.     

Effect of intramolecular pi-pi and CH-pi interactions between ligands on structure, electrochemical and spectroscopic properties of fac-[Re(bpy)(CO)3(PR3)]+(bpy = 2,2'-bipyridine; PR3= trialkyl or triarylphosphines)

Intramolecular pi-pi and CH-pi interactions between the bpy and PR3 ligands of fac-[Re(bpy)(CO)3(PR3)]+ affect their structure, and electrochemical and spectroscopic properties. Intramolecular CH-pi interaction was observed between the alkyl groups on the phosphine ligand (R =nBu, Et) and the bpy ligand, and intramolecular pi-pi and CH-pi interactions were both observed between the aryl group(s) on the phosphorus ligand (R =p-MeOPh, p-MePh, Ph, p-FPh, OPh) and the bpy ligand, while no such interactions were found in the trialkylphosphite complexes (R = OiPr, OEt, OMe). The intramolecular interactions distort the pyridine rings of the bpy ligand as long as 3.7 x 10(-2)A in crystals. Molecular orbital calculations of the bpy ligand suggest that this distortion decreases the energy gap between its pi and pi* orbitals. An absorption band attributed to the pi-pi*(bpy) transition of the distorted rhenium complexes, measured in a KBr pellet, was red-shifted by 1-5 nm compared to the complexes without the distorted bpy ligand. Even in solution, similar red shifts of the pi-pi*(bpy) absorption were observed. The redox potential E1/2(bpy/bpy*-) of the complexes with the trialkylphosphine and triarylphosphine ligand are shifted positively by 110-120 mV and 60-80 mV respectively, compared with those derived from the electron-attracting property of the phosphorus ligand. In contrast with these properties, three nu(CO) IR bands, which are sensitive to the electron density on the central rhenium because of pi-back bonding, were shifted to higher energy, and a Re(I/II)-based oxidation wave was observed at a more positive potential according to the electron-attracting property of the phosphorus ligand.     

Molecular numbers in core and shell: structural dependence of reactivity of alkylcarboxylate-stabilized silver nanoparticles

Spectroscopic, chemical, thermal, and voltammetric analyses on six kinds of alkylcarboxylate-stabilized silver nanoparticles 4.7 nm in diameter were carried out with an aim to reveal the effect of alkylcarboxylates on the optical, thermal, geometric, and electrochemical properties of the nanoparticles. These nanoparticles are composed of silver atoms and silver alkylcarboxylates having even numbers, m, of carbon atoms from 8 to 18. As a measure of the structure of the nanoparticles, the ratio of the number of silver atoms (nAg) to that of alkylcarboxylates (ns) per nanoparticle was evaluated by means of titration through chemical oxidation, voltammetric currents, and thermal gravimetric analysis. It increased with an increase in m and ranged from 1.3 to 9.8. Properties of the nanoparticle have been exhibited in absorbance of the UV-vis spectra at the point of the proportionality to n(Ag), voltammetric currents of which values were close to the theoretical values at the diffusion of particle itself, and the m-independent kinetic energy of the thermal decomposition and the overpotential of the reduction. They are not observed for the composed species, that is, silver atoms and silver alkylcarboxylate molecules.     

A redox-active ionic liquid manifesting charge-transfer interaction between a viologen and carbazole and its effect on the viscosity,ionic conductivity,and redox process of the viologen

Redox-active ionic liquids (RAILs) are gaining attention as a material that can create a wide range of functions. We herein propose a charge-transfer (CT) RAIL by mixing two RAILs, specifically a carbazole-based ionic liquid ([CzC₄ImC₁][TFSI]) as a donor and a viologen-based ionic liquid ([C₄VC₇][TFSI]₂) as an acceptor. We investigated the effect of CT interaction on the physicochemical properties of the CT ionic liquid (CT-IL) using the results of temperature-dependent measurements of UV-vis absorption, viscosity, and ionic conductivity as well as cyclic voltammograms. We employed the Walden analysis and the Grunberg–Nissan model to elucidate the effect of the CT interaction on the viscosity and ionic conductivity. The CT interaction reduces the viscosity by reducing the electrostatic attraction between the dicationic viologen and TFSI anion. It also reduces the ionic conductivity by the CT association of the dicationic viologen and carbazole. The electrochemically reversible responses of the viologens in [C₄VC₇][TFSI]₂ and CT-IL are consistent with the Nernstian and the interacting two-redox site models. Notably, the transport and electrochemical properties are modulated by CT interaction, leading to unique features that are not present in individual component ILs. The inclusion of CT interaction in RAILs thus provides a powerful means to expand the scope of functionalized ionic liquids.

A redox-active ionic liquid (RAIL) consisting of a carbazole and viologen shows charge transfer (CT) interaction. The physicochemical properties are modulated by the CT interaction by comparison with the individual RAILs.