Spectral studies, cyclic voltammetry and synthesis of cobalt(II) and ruthenium(III) complexes with symmetric and asymmetric ring containing membered N2S2, N4, and N5 donor macrocyclic ligands

Reaction of divalent cobalt(II) and trivalent ruthenium(III) salts (NO3, SCN and SO4) with macrocyclic ligands L1, L2 and L3 having N2S2, N4 and N5 core, have been designed and carry out. All these three macrocyclic ligands and their complexes were obtained in pure form. Their structures were investigated by using microanalytical analyses, IR, mass, magnetic moments, electronic and EPR spectral studies. The redox properties of the complexes were also examined by cyclic voltammetry. An interesting feature of complexes is that the relatively large rings of macrocyclic ligands prevent the macrocyclic rings from approaching the metal center as closely as they would, if they were not constrained. So the Ru-N distances are longer than expected due to ring size. Electrochemical studies show that the macrocyclic ligand L1 is more effective electron donors to ruthenium than of L2 and L3. Electronic spectral properties also show that the sulphur donor atom of L1 weakens the ligand field with respect to ligand-to-metal charge-transfer band. However it is expected that second-row transition metal-ligand bonds tend to be weaker than third-row transition metal-ligand bonds. There are well-established examples of reactions in which decreased of reactivity down a triad of transition metals is not observed. These novelties are usually attributed to pi-bonding effects for ligands such as carbon monoxide, solvent effects, or a change in mechanism.     

Quantitative estimations of ferric iron by phosphoric acid in aqueous-alcoholic medium

Summary The only method recommended for the direct estimation of ferric iron in presence of HCl is to reduce the ferric iron to ferrous iron and then to titrate against KMnO₄ solution by adding Reinhardt-Zimmermann reagent (MnSO₄ + H₂SO₄ + H₃PO₄). The solubility of the phosphato complexes of ferric chloride and phosphoric acid is much reduced by adding a nonaqueous solvent, ethyl alcohol or acetone. This property has been availed of to find out a method of estimating ferric iron directly against standard solution of phosphoric acid in aqueous-nonaqueous medium using K₄Fe(CN)₆ or cupferron as external indicators. A slight discrepancy at the end point, however, exists in the direct titration but it can be removed by applying a correction factor determined from the estimated results.     

Über triterpene—XXIX : Zur struktur des avenacins

From the roots of oat (Avena sativa) a second antibiotic active glycoside, avenacine B, was isolated in addition to the main glycoside avenacine A. In the aglycone of A the double bond could not be established contrary to the statement in the literature but an aldehyde group in addition to the keto group was identified and therefore the proposed structure has to be revised. In the aglycone of B the —CH₂OH-group of A has been substituted by CH₃. The structures of the sugar chains in both glycosides have been determined, in avenacine A as [β-d-gluco-pyranosyl(1 → 4)-[β-d-glucopyranosyl (1 → 2)]-α-l-arabinosyl (1)- and in B as [β-d-glucopyranosyl (1 → 4)]-β-d-glucopyranosyl (1)-.     

Photometric determination of trivalent gallium,indium and thallium with Xylenol orange

Summary Xylenol orange reacts very sensitively with gallium(III), indium (III) and thallium(III) to form reddish violet colored chelates having _max 560 nm in case of Ga and In and _max 590 nm in case of Ti at P_H 4.0. The molar ratio for all the chelates is 1 1 (metal reagent). Optimum conditions including the range for adherence to Beer's law, effect of P_H on the color intensity, effect of excess reagent, and sensitivity are reported for the photometric determination of these metal ions using Xylenol orange.

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Zusammenfassung Xylenolorange reagiert sehr empfindlich mit Gallium(III), Indium(III) und Thallium(III) unter Bildung rötlich-violetter Chelate mit einem Absorptionsmaximum bei 560 nm im Falle von Ga und In bzw. 590 nm für Tl bei p_H 4,0. Das Molverhältnis ist in jedem Fall 11. Die besten Arbeitsbedingungen, der Gültigkeitsbereich des Beerschen Gesetzes, der Einfluß des P_H auf die Farbintensität und des Reagensüberschusses sowie die Empfindlichkeit werden für die photometrische Bestimmung der genannten Ionen angegeben.

     

Hydrophobic interaction chromatography coupled with atomic fluorescence spectrometric detection Effect of the denaturation on the determination of thiolic proteins

Hydrophobic interaction chromatography coupled online with chemical vapour atomic fluorescence spectrometry (HIC-CVGAFS) has been optimized for the analysis of thiolic proteins in denaturing conditions. Proteins are pre-column simultaneously denatured and derivatized in phosphate buffer solution containing 8.0 mol dm⁻³ urea and p-hydroxymercurybenzoate (PHMB) and the derivatized denatured proteins are separated on a silica HIC Eichrom Propyl column in the presence of 8.0 M urea in the mobile phase. Post-column online reaction of derivatized denatured proteins with bromine, generated in situ by KBr/KBrO₃ in HCl medium, allowed the fast conversion of the uncomplexed PHMB and of the PHMB bound to proteins to inorganic mercury also in presence of urea. Hg²⁺, present in solution as Hg²⁺-urea complex, is selectively detected by AFS in a Ar/H₂ miniaturized flame after sodium borohydride reduction to Hg. Under optimized conditions, online bromine treatment gives a 100±2% recovery of both free and protein-complexed PHMB. Denatured glyceraldehyde-3-phosphate dehydrogenase, aldolase, lactate dehydrogenase, trioso phosphate isomerase and β-lactoglobulin have been examined. As the sensitivity and limit of detection of proteins in the HIC-CVGAFS apparatus depends on number of SH groups reacting with PHMB, the denaturation process, which increases the number of PHMB-reactive thiolic groups in proteins, improves the analytical performances of the described system in protein analysis. The detection limit for the denatured proteins examined was found in the range of 10⁻¹⁰-10⁻¹² mol dm⁻³, depending on the considered protein, with linear calibration curves spanning over four decades of concentration.     

Ternary complexes of copper(II), nickel(II) and zinc(II) with nitrilotriacetic acid as a primary ligand and some phenolic acids as secondary ligands

Summary The formation of ternary complexes of the MAL^3– type [where M = Cu^II, Ni^II and Zn^II ; A = nitrilotriacetic acid (NTA); L = 1-hydroxy-2-naphthoic acid (1,2 HNA) and 2-hydroxy-1-naphthoic acid (2,1 HNA)] have been studied potentiometrically in 50% v/v aqueous — ethanol (25° and µ = 0.1). Under identical conditions the binary complexes of the 1,2- and 2,1-HNA ligands have also been examined. The values of mixed ligand formation constants K_MAL have been found to be lower than K_ML (first step formation constant of binary complexes) and even less than (second step formation constant of binary complexes).     

Spin crossover studies in tris(N,N′-dialkyldithiocarbamato)iron(III) complexes

A series of fifteen complexes of the type [Fe(RRNCS₂)₃] with symmetric (R=R=n- C₆H₁₃, n-C₈H₁₇, CH₂–CH=;CH₂, C₆H₅, C₆H₁₁ and C₆H₅CH₂), unsymmetric (R = CH₃; R = n-C₄H₉, C₆H₁₁, C₆H₅ and R = C₂H₅; R = n-C₄H₉, C₆H₁₁, C₆H₅ and i-C₃H₇) and ring substituents (RNR=pyrrolidyl and piperidyl) have been synthesized and their magnetic moments and Mössbauer spectra recorded from room temperature (RT) to liquid nitrogen temperature (LNT). Room temperature Mössbauer spectra of all the complexes exhibit an asymmetric doublet, which could be resolved into two doublets, each corresponding to low and high spin states in equilibrium. The crystal structure of tris(N, N-diallyldithiocarbamato)iron(III) shows it to be monoclinic with trigonally distorted octahedral geometry and space group C2/c. Fe–S stretching vibrations in the far i.r. region also show equilibria, HS LS. Depending on the nature of the alkyl group substituent, variable temperature magnetic moment and Mössbauer spectral studies, all the complexes may be divided into three groups; high spin complexes exhibiting spin-crossover (⁶A_1g ²T_2g), high spin complexes exhibiting spin transition (⁶A_1g ⁴T_1g) and intermediate spin complexes showing spin transition (⁴A_1g ²T_2g). On the basis of areas of the two doublets corresponding to high and low spin states, their percent contributions were calculated. Furthermore, magnetic moments of the equilibrium mixture calculated on the basis of respective areas compare well with the experimentally determined _eff values. E_Q values for both high and low spin states show linear decrease with increasing temperature.     

Kinetics and mechanism of oxidation of methanol by acid bromate

The kinetics of oxidation of methanol by bromate ion in hydrochloric acid medium has been investigated. A mechanism consistent with the experimental observations is suggested.

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Analysis of fragrances in cosmetics by gas chromatography–mass spectrometry

A gas chromatographic (GC)-mass spectrometric (GC-MS) method has been developed for the routine analysis of 11 fragrance substances in cosmetics: cinnamic alcohol, cinnamic aldehyde, eugenol, hydroxy citronellal, α-amyl cinnamic aldehyde, geraniol, isoeugenol, coumarin, dihydrocoumarin, citronellal and citral. Methods for sample preparation of various types of cosmetic products, prior to GC analysis, have also been developed and proved to be rugged. Detection limits of all of target fragrance substances were approximately 1 ppm. Calibration curves of the target fragrance substances analyzed by GC were found to be linear in the investigated concentration range, 0.005% – 0.50%. The recoveries of the target fragrances from various types of cosmetic products were 80% – 116% and the relative standard deviations of the quantitative analysis of the target fragrance substances were within 5%.