Synthesis and characterization of some rhodium(III) cyclometallated complexes of 2-substituted benzylideneamino thiazoles

Summary Schiffs bases derived from 2-aminothiazole and substituted benzaldehydes were reacted with [RhCl(PPh₃)₃] or [Rh(-Cl)(COD)]₂ (COD = 1,5-cyclooctadiene) in the presence of four equivalents of PPh₃ to give Rh^III cyclometallated complexes of the type [RhHCl{(X-benzylidene) thiazole}(PPh₃)₂], in which the imine C-H added oxidatively to the metal. The complexes were characterized using i.r., u.v. and n.m.r. spectroscopy. The disposition of the hydride ligand was inferred as trans to a N-donor ligand.     

Spin and parity of isomeric and ground states of the doubly-odd nucleus184Au

Low-spin states in doubly-odd¹⁸⁴Au have been populated in the ⁺/EC decay of¹⁸⁴Hg produced by bombarding¹⁸⁴Sm targets with an 185 MeV⁴⁰Ar beam. Radioactive Hg nuclei were transported by a He jet system. A new level scheme has been established from --t and X--t coincidence measurements. Spin and parity values I=5⁺, I =2⁺ and I=3^– were assigned to the ground state and the two isomeric states of¹⁸⁴Au, respectively. The structure of these states is discussed using B(E1) values.     

Complexes of hydroxamates X. Interaction of methioninehydroxamic acid with Ni(II) and Pd(II). Kinetics and reaction mechanism

The kinetic stopped flow method has been used to study the reaction rates of Ni(II) and Pd(II) with methioninehydroxamate (MX). Two reaction rates were observed in the MX? Ni(II) system whereas three rates were observed in the MX? Pd(II) system. Most of the rate steps were dependent on pH as well as on T_MX (total concentration of methioninehydroxamate). The observed pseudo-first-order rate constants at constant pH are expressed empirically as k = m_i + m′_i T_MX. The parameters m_i and m′_i are pH-dependent. It has been concluded that hydroxy metal species contributed to the explanation of the rate of the metal complexation with MX. Similar systems have been correlated with the systems of current work. © 1995 John Wiley & Sons, Inc.     

Chemical behaviours of 3-[1′-chloro-3′-(2″-phenyl-1″,3″-oxazol-5″-one=4″-ylidene)propen-1′-yl]coumarin towards some nucleophilic reagents

The chemical behaviours of 3-[1′-chloro-3′-(2″-phenyl-1″,3″-oxasol-5″-one-4″-ylidene)-propen-1′-yl]coumarin towards nucleophilic reagents (such as hydrolysis, aminolysis, hydroxyl-aminolysis, methanolysis and hydrazinolysis) were described.     

Amino Acid Derivatives,IV [1]: Synthesis and Antiviral Evaluation of New α-Amino Acid Esters Bearing Methyl β-<Emphasis Type="SmallCaps">d</Emphasis>-Ribofuranoside Side Chain

Summary. Methyl 2,3-O-isopropylidene-β-d-ribofuranoside was synthesized and oxidized with HIO₄ to afford the corresponding carboxylic acid. The latter was coupled with the appropriate acylated amino acids in the presence of HOBt and DDC as coupling reagents to give the corresponding amides. The methyl acetate derivative was hydrolyzed with 2 N KOH/MeOH to the corresponding carboxylic acid, which was coupled with l-glycine methyl ester to furnish the amide. Deprotection was carried out with 70% AcOH at reflux temperature. The prepared glycopeptides were tested for antiviral activity against Herpes Simplex virus type-1 (HSV-1) and hepatitis-A virus (HAV). The plaque reduction infectivity assay was used to determine virus count reduction as a result of treatment with tested compounds.     

Rapid Characterization of Wood Pulp Lignin by Fourier Transform Raman Spectroscopy

FT-Raman spectroscopy is used for the rapid measurement of wood pulp lignin. A total of 23 western softwood pulp samples with known kappa numbers (10–38) are used. Each sample is divided into three portions and scanned separately. The integrated area of the lignin band at approximately 1600 cm⁻¹is ratioed against the integrated area of the cellulose bands in the 1200–1010 cm⁻¹region and correlated to known kappa numbers. The measured ratios behave linearly with the kappa number (r= 0.99) and can be reproducibly determined with an error of approximately 2% or less. The data are presented and discussed in view of the potential for at-line analysis of lignin associated with chemical delignification of wood pulp.     

Kinetic Spectrophotometric Determination of Ranitidine

Two spectrophotometric methods were developed for the determination of ranitidine. The first method was a kinetic spectrophotometric method based on the catalytic effect of ranitidine on the reaction between sodium azide and iodine in an aqueous solution. The calibration graph was linear from 4–24 μg/mL. The drug was determined by measuring the decrease in the absorbance of iodine at 348 nm using a fixed time method. The decrease in the absorbance after 1 minute from the initiation of the reaction was related to the concentration of drug. The detection limit of the procedure was 0.76 μg/mL. The proposed procedure was successfully utilized in the determination of the drug in pharmaceutical preparations with mean recovery in the range of 99.83 ? 101.16%. The second method is a colorimetric method, which depends on the measurement of absorbances of tris (o‐phenanthroline) iron(II) [method 2A] and tris (bipyridyl) iron(II) [method 2B] complexes at 512 nm. The complexes obeyed Beer's law over the concentration range of 2–16 μg/mL and 4–40 μg/mL for methods 2A and 2B, respectively. The developed method has been successfully applied for the determination of ranitidine in bulk drugs and pharmaceutical formulations. The common excipients and additives did not interfere in its determination.     

The morphology and thermal properties of liquid natural rubber (LNR)-compatibilized 60/40 NR/LLDPE blends

The effects of LNR as a compatibilizer in binary blends of 60/40 NR/LLDPE have been investigated by means of differential scanning calorimetry, dynamic mechanical analysis and scanning electron microscopy. Special emphasis was given to the role of LNR in inducing interactions between NR and LLDPE. It has been observed that increasing LNR content decreases T_m and ΔH_f which are indicators of the crystalline part of the blends. The decrease reflects a reduction in the degree of crystallinity which is due to the interference in the form of NR dissolution into the LLDPE phase. The phenomenon leads to a shift in T_g of the amorphous part of LLDPE to higher temperatures as observed by DMA thermograms. The dissolution effect creates better interactions between the phases leading to improvements in the compatibility of the blends. Further confirmation was obtained through SEM examination.     

Phosphoramidate-mediated conversion of carbonyl ligands into isocyanide ligands: a new approach to chiral isocyanide ligands

Metal isocyanides have been used and studied by organometallic chemists for many years and, as a result, they have a rich and interesting chemistry. The nature of metal-free isocyanides and the methods of making isocyanide complexes, however, has resulted in the vast majority of studies to date being performed with structurally simple isocyanides. We report here a new approach to the synthesis of isocyanide ligands that involves the reaction of a metal carbonyl ligand with the anion of a phosphoramidate. As phosphoramidates can be synthesised in one step from amines, our method means that the structural diversity of readily available amines, particularly chiral amines, can now be incorporated into isocyanide ligands.