Spectrophotometric Determination of Acidity Constants of 4‐(2‐Pyridylazo) Resorcinol in Various Micellar Media Solutions

Dissociation equilibria of 4‐(2‐pyridylazo) resorcinol (PAR) in aqueous micellar solutions were determined spectrophotometrically at 25 °C and at the constant ionic strength I = 0.1 M KNO₃. For this purpose, the effect of nonionic (Brij‐35, Triton X‐100, Triton X‐114, Triton X‐405), and anionic (SDS) surfactants on the absorption spectra of PAR at different pH values was studied. Results show that the pK_a values and pure spectra of each species of PAR are influenced by percentages of a neutral and an anionic surfactant such as Brij‐35, Triton X‐100, Triton X‐114, Triton X‐405 and SDS, respectively, added to the solution of this reagent.     

Pyrazine Complexes of Octacyanometallates of Mo(IV) and W(IV) With 8-hydroxyquinoline: Synthesis,characterisation and thermal studies

The complexes formed by photosubstitution of pyrazine (Pz) in octacyanomolybdate(IV) and -tungstate(IV) with 8-hydroxyquinoline have been assigned the formulae [Mo(CN)₂(OH)₂(Pz)₂(OX)] and [W(CN)₂(OH)₂(Pz)₂(OX)·1.5H₂O]. Coordination of Pz as an unidentate ligand by donating a lone pair of electron from nitrogen is shown by an absorption peak between 8–11 µ. Mechanism for the thermal decomposition of the complexes has been given. The formation of tungsten metal as residue in case of II has been confirmed by XRD analysis. The kinetic and thermodynamic parameters like activation energy (E _a), pre-exponential factor (A) and entropy of activation (S ^#) were calculated employing different integral methods of Doyle, Coats and Redfern and Arrhenius.H for each stage of decomposition was obtained from DSC.This revised version was published online in November 2005 with corrections to the Cover Date.     

Synthesis and Antibacterial Activity of Some Substituted 3-(Aryl)- and 3-(Heteroaryl)indoles

Summary. A synthesis of 3-(4-methoxycarbonyl-2,6-dinitrophenyl)indole, its 2,6-diamino analog, and 3-(2-amino-4-trifluoromethyl-6-nitrophenyl)indole is described. 4-(Trifluoromethyl)phenyl derivatives exhibit higher antibacterial potency than the former 4-(methoxycarbonyl)phenyl homologs, while 3-(4-trifluoromethyl-2-nitrophenyl)indole was the most active agent in the series, with MIC ≈ 7 μg/cm³ against E. coli and S. aureus.     

Synergistic extraction of Ce(III), Eu(III) and Tm(III) with a mixture of picrolonic acid and benzo-15-crown-5 in chloroform

Summary The synergistic mixture comprising picrolonic acid (HPA) and benzo-15-crown-5 (B15C5) in chloroform has been used for the extraction of Ce(III), Eu(III) and Tm(III) as representatives of lanthanide(III) ions from pH 1-2 solutions having ionic strength of 0.1 mol^. dm^-3(K⁺/H⁺, Cl^-). The composition of the extracted species has been determined as M(PA)₃^. nB15C5 where M is Ce, Eu and Tm and n=1 or 2. The influence of various anions and cations on the extraction of these ions has also been studied and only oxalate, cyanide and tartrate have some deleterious effect. The extraction equilibrium constants have been evaluated and discussed.     

New computer program to calculate the symmetry of molecules

In this paper we, present some MATLAB and GAP programs and use them to find the automorphism group of the Euclidean graph of the C₈₀ fullerence with connectivity and geometry of I _h symmetry point group. It is proved that this group has order 120 and is isomorphic to I _h ≊Z₂×A₅, where Z₂ is, a cyclic group of order 2 and A₅ is the alternating group on five symbols.     

The preparation and characterization of mono- and bis-chelated cadmium(II) complexes of the di-2-pyridylketone Schiff base of S-methyldithiocarbazate (Hdpksme) and the X-ray crystal structure of the [Cd(dpksme)2] · 0.5 MeOH complex

New cadmium(II) complexes of empirical formulae, [Cd(dpksme)X] (dpksme = anionic form of the Schiff base; X = NCS^–, Cl^–, I^–) and [Cd(dpksme)₂] · 0.5MeOH, respectively have been prepared and characterized. The mono-ligated cadmium(II) complexes, [Cd(dpksme)X] are four-coordinate and tetrahedral but the bis-ligand complex, [Cd(dpksme)₂] · 0.5MeOH is six-coordinate and octahedral. The crystal and molecular structure of [Cd(dpksme)₂] · 0.5MeOH has been determined by X-ray diffraction. The complex has a distorted mer-octahedral structure in which the ligands are coordinated as uninegatively charged tridentate chelating agents via the pyridine nitrogen atoms, the azomethine nitrogen atoms and the thiolate sulfur atoms. The distortion from regular octahedral geometry is ascribed to the restricted bite angles of the ligands. The Schiff base and its cadmium(II) complexes exhibit mild antibacterial activities against Shigella dysenteriae, Bacillus cereus, Staphylococcus aureus and Escherichia coli. They are also mildly fungitoxic against the phytopathogenic fungi, Alternaria alternata and Macrophomina phaseolina.     

Die Reaktion von Tellurhexafluorid mit Trimethylamin,Strukturen der TeF5−- und SeF5−-Anionen

Reaction of Telluriumhexafluoride and Trimethylamine, Structures of the TeF₅^? and SeF₅^? Anions The reaction of TeF₆ and (CH₃)₃N is of the redox kind, resulting in reduction of tellurium: X-ray single crystal analysis reveals the compounds (CH₃)₂N? CH₂? N(CH₃)₂⁺TeF₅^? and [(CH₃)₃NH⁺]₅(TeF₅^?)₃(HF₂^?)₂. By comparison with published data it can be shown that this mixture is identical to previously published [(CH₃)₃N]₂TeF₆. The latter was supposed to be one of the few examples of tellurium in a coordination state of eight. (CH₃)₄N⁺TeF₅^? and (CH₃)₄N⁴SeF₅^? are obtained and their structure is investigated by single crystal x-ray methods also. The anions SF₅^?, SeF₅^? and TeF₅^? are discussed in terms of weak interactions.     

Synthesis and Characterization of Diphenyltin(IV) Dicarboxylates Containing Germanium

Twelve new germanium substituted diphenyltin dipropionates with the general formula (R¹GeCHR²‐CHR³COO)₂SnPh₂ where R¹ = N(CH₂CH₂O)₃, (C₆H₅)₃ and (CH₃C₆H₄)₃, R² = H, CH₃, C₆H₅, p‐CH₃C₆H₄, p‐CH₃OC₆H₄, p‐ClC₆H₄, and R³ = H, CH₃ have been synthesized by the reaction of diphenyltin oxide with a germanium substituted propionic acid. All the compounds were characterized by elemental analysis, IR, multi‐nuclear (¹H, ¹³C, ¹¹⁹Sn) NMR and Mössbauer spectroscopies as well as mass spectrometry. The in vitro antibacterial activity of selected compounds is also reported.     

A novel one-pot synthesis of some new interesting pyrrole derivatives

[reaction: see text] 11-(1H-Pyrrol-1-yl)-11H-indeno[1,2-b]quinoxaline and 3-(1H-pyrrol-1-yl)indolin-2-one derivatives have been synthesized in good yields in a novel, one-pot, and efficient process by condensation of 11H-indeno[1,2-b]quinoxalin-11-one or isatin derivatives with 4-hydroxyproline on solid-support montmorillonite K10 under microwave irradiation.     

Preconcentration and Determination of Chromium Species Using Octadecyl Silica Membrane Disks and Flame Atomic Absorption Spectrometry

A novel and selective method for the fast determination of trace amounts of chromium species in water samples has been developed. The procedure is based on the selective formation of chromium diethyldithiocarbamate complexes at different pH in the presence of Mn(II) as an enhancement agent of chromium signals followed by elution with organic eluents and determination by atomic flame absorption spectrometry. The maximum capacity of the employed disks was found to be (396±3) µg and (376±2) µg for Cr(III) and Cr(VI), respectively. The detection limit of the proposed method is 49 and 43 ng·L^?1 for Cr(III) and Cr(VI), respectively. The proposed method was successfully applied for determination of chromium species Cr(III) and Cr(VI) in different water samples.