Complexes of TiCl4, VCl4 and SnX4 (X = Cl or Br) with Schiff bases derived from 2-aminobenzimidazole

Summary The reactions of anhydrous titanium(IV), tin(IV) and vanadium(IV) halides with Schiff bases derived from 2-aminobenzimidazole and 4-methylbenzaldehyde (abimbz) and salicylaldehyde (abisal), yield hexacoordinated complexes M(abimbz)Cl₄ and M(abisal)₂X₄ (M = Ti, Sn or V; X = Cl or Br).The compounds have been characterized by elemental analyses, magnetic measurements, e.p.r., electronic and i.r. spectral studies. I.r. spectra suggest that the Schiff base (abimbz) is coordinated as a bidentate ligand with the metal ion and the (abisal) base acts as a monodentate ligand.     

Solvent and metal ion effects in condensation reactions between semicarbazides and pyridine derivatives and study of the complexes with metal chlorides

Co, Ni, Cu, Zn, Cd and Hg chloride complexes of 3-acetylpyridinesemicarbazone, 3-acetylpyridinethiosemicarbazone 4-pyridinesemicarbazone and 4-pyridinethiosemicarbazone have been obtained, and have the general formulae [MLCl₂], [ML₂Cl₂], [MLCl₂]H₂O, [ML₂Cl₂]-H₂O, [ML_xCl₂] (L=3-apsc, 3-aptsc, 4-psc or 4-ptsc). The reaction product of 4-pyridinecarbaldehyde with semicarbazide has properties consistent with 4-pyridinecarbaldehyde·semicarbazide, without condensation, but this condensation may be obtained by solvent or metal template effects using Cd or Hg. The products have been characterized by physicochemical and spectroscopic methods.     

The influence of the zwitterionic form on the C=N stretching frequency in nickel and copper complexes of a Schiff base

Summary The Schiff base derived from 2-aminobenzimidazole and salicylaldehyde has been used to prepare a series of nickel(II) and copper(II) complexes. I.r., electronic spectra, elemental analyses, conductivity measurements and magnetic data have been utilized to determine the nature of these complexes.The results show that the base acts as bidentate ligand through the phenolic oxygen and the azomethine nitrogen in the non-polar form of the ligand or the pyridine-like imine nitrogen of imidazole ring in its zwitterionic form.One of the more striking differences between these compounds and those of other Schiffs bases^(1,2) is the coordination spheres of the metal ions with this particular ligand.     

Complexes of chromium(III), cobalt(II) and copper(II) with sulphur or oxygen and nitrogen donors

Summary The synthesis and characterization of 4-acetyl-pyridinesemicarbazone (4-apsc) and 4-acetylpyridine-thiosemicarbazone (4-aptsc) and their complexes with CrCl₃, CoCl₂ and CuCl₂ are reported. These compounds were characterized on the basis of elemental analyses, electronic and i.r. spectra, magnetic moments and conductivities measurements. The compounds are nonconductors in dimethylformamide. Tentative structures for the complexes are suggested.     

Benzenocarbothioamide complexes of IIB metal halides

Summary Complexes having the empirical formula M(BCTA)₂X₂, (M=Zn or Hg; X=Cl, Br or I) and Cd(BCTA)X₂ (X=Cl, Br or I) are formed by reaction of benzenocarbothioamide (BCTA) with anhydrous zinc(II), cadmium(II) or mercury(II) halides and have been isolated and characterized by elemental analysis, conductance and molecular weight measurements, and by i.r., Raman and¹H n.m.r. spectral studies. They are not appreciably ionized in acetonitrile solvent. The i.r.v(CN) shift to higher a frequency andv(CS) shift to a lower frequency indicate that BCTA is bound to the metals through sulphur. A tetrahedral structure withC _2v symmetry is proposed for [M(BCTA)₂X₂] on the basis of the i.r. and Raman data, and a dimeric tetrahedral structure withC _2h skeletal symmetry for Cd(BCTA)X₂. The¹H n.m.r. spectral measurements also show coordination through the sulphur atom.     

Dispersion stability of a ceramic glaze achieved through ionic surfactant adsorption

The adsorption of cetylpyridinium chloride (CPC) and sodium dodecylbenzenesulfonate (SDBS) onto a ceramic glaze mixture composed of limestone, feldspar, quartz, and kaolin has been investigated. Both adsorption isotherms and the average particle zeta potential have been studied in order to understand the suspension stability as a function of pH, ionic strength, and surfactant concentration. The adsorption of small amounts of cationic CPC onto the primarily negatively charged surfaces of the particles at pH 7 and 9 results in strong attraction and flocculation due to hydrophobic interactions. At higher surfactant concentrations a zeta potential of more than +60 mV results from the bilayered adsorbed surfactant, providing stability at salt concentrations < or = 0.01 M. At 0.1 M salt poor stability results despite substantial zeta potential values. Three mechanisms for SDBS adsorption have been identified. When anionic SDBS monomers either adsorb by electrostatic interactions with the few positive surface sites at high pH or adsorb onto like charged negative surface sites due to dispersion or hydrophobic interactions, the magnitude of the negative zeta potential increases slightly. At pH 9 this increase is enough to promote stability with an average zeta potential of more than -55 mV, whereas at pH 7 the zeta potential is lower at about -45 mV. The stability of suspensions at pH 7 is additionally due to steric repulsion caused by the adsorption of thick layers of neutrally charged Ca(DBS)2 complexes created when the surfactant interacts with dissolved calcium ions from the calcium carbonate component.     

Adsorption and diffusion parameters of methane and nitrogen on microwave-synthesized ETS-4

ETS-4 is a titanium silicate developed by Engelhard Corporation, which possesses a small pore network, the size of which can be reduced by heat treatment to improve its kinetic selectivity in nitrogen/methane separation. Most of the reported studies about ETS-4 employ crystals synthesized with conventional heating. Furthermore, information available on the adsorption properties of ETS-4, especially the diffusion properties, is scarce. In this work, Na-ETS-4 crystals have been synthesized by microwave heating and have been exchanged with strontium to obtain Sr-ETS-4 using also microwave heating. This method for obtaining the strontium form of ETS-4 has not been reported before. Both materials have been dehydrated to reduce their pore size. The adsorption and diffusion parameters of nitrogen and methane on these materials, which have not been measured for microwave-synthesized ETS-4 up to the present date, have been estimated by modeling the desorption breakthrough curves of both gases using a fixed bed of ETS-4 crystals. The kinetic selectivity of nitrogen over methane at 298 K of microwave-synthesized Sr-ETS-4 is 26. This value is higher than the maxima reported in the literature for this material.     

Adsorption Behavior of Potassium Ion on Planting Materials

Characterization of planting materials used as adsorbent has been studied in order to compare potassium ion adsorption on two types of planting materials, which are a fired planting material （FPM） made from a mixture of 4 kinds of wastes （bottom ash, flue gas desulfurization （FGD） gypsum, paddy soil and sawdust） formed and fired at 850 ℃and the commercial planting material called ＂hydroball＂ （HDB） bought from Jatujak market, Bangkok. The physical characteristics of both types of planting materials indicate that the FPM has a larger specific surface area than the HDB. The factors affecting potassium adsorption on both the planting materials such as an equilibration time and some solid/solution ratios were investigated. The suitable equilibration time for the adsorption to reach an equilibrium on the FPM and HDB is one and two hours, respectively. The highest amounts of potassium ion adsorbed on both the planting materials were obtained when the solid/solution ratio was 1 ： 15. The adsorption behavior on both the planting materials tends to correspond with the Freundlich isotherm.