Electrospray ionization mass spectrometry (ESI-MS) was used for the study of cyclization of organic chelating compounds (chelators). Four chelating compounds were studed: Symmetrical ethylenediaminediacetic acid (s-EDDA), Unsymmetrical ethylenediaminediacetic acid (u-EDDA), N-(2-hydroxyethyl) ethylenediaminetriacetic acid (HEDTA), and N-(2-hydroxyethyl)iminodiacetic acid (HEIDA). The chelators were cyclized with treatments of acids and heating. The open and cyclized form of the chelators were semi-quantified by both positive and negative ion modes ESI-MS. The kinetics of chelator cyclization was studied as a function of reaction temperature and the pH of the matrix. The cyclization of s-EDDA was found to be a pseudo-first order reaction in s-EDDA and overall second order. The cyclizations of HEIDA and HEDTA are reversible reactions. Higher temperature and lower pH favors cyclization.
Authors:Cs. Várhelyi Jr., G. Pokol, Á. Gömöry, A. Gănescu, P. Sohár, G. Liptay, and Cs. Várhelyi
chelates of the type [Ni(II)(Diox.H)2], ((Diox.H)2:
various α-dioximes) have been studied by means of FTIR, NMR, MS data
and various thermoanalytical methods (TG, DTA, DTG, DSC). In some cases kinetic
parameters of the thermal decomposition of the complexes were also calculated
using Zsak’s ‘nomogram method’. The mechanism of
the decomposition processes was characterised on the basis of mass spectra.
Authors:Luiza Arakaki, Josiane Diniz, A. Silva, Vera Augusto Filha, Maria Fonseca, J. Espínola, and T. Arakaki
The divalent copper, nickel, cobalt and trivalent chromium, molybdenium and iron chelate compounds derived from bis(acetylacetone)
ethylenediimine were grafted on activated silica gel using a batch process in methanolic solution. The sequence of the maximum
retention capacity was Cr(III)>Mo(III)>Fe(III)>Co(II)>Ni(II)>Cu(II). Calorimetric titration was employed to study the interaction
of activated silica gel with these series of metal chelate compounds. Exothermic enthalpic results were obtained throughout
all interactions process. The spontaneity of these systems was reflected in negative and positive free Gibbs energy from entropic
Authors:F. Macášek, V. Mikulaj, R. Kopunec, and P. Rajec
The specific phenomena accompanying the daughter nuclide formation by radioactive β-decay of complex parent compounds cause
certain deviations from a thermodynamic distribution of daughter elements in separation procedures (e.g. in radionuclidic
generators) and they are shown to complicate or, less probably, simplify their separation. A simple kinetic model has been
proposed to explain such processes as the distribution of some daughter nuclides of fission products by solvent extraction
with chelating compounds (systems of99Mo−99mTc and144Ce−144Pr with oxines).
Authors:Juan Zhang, Feng-Tian Hu, Qian-Qian Liu, Xin Zhao, and Shou-Qing Liu
A heterogeneous photo-Fenton catalyst was prepared using the complex tris(1,10)-phenanthroline iron(II) loaded on the NaY type of zeolite. The catalyst displayed a feature of the photo-Fenton degradation of methylene blue, and a linear relationship between ln(C0/Ct) and reaction time was obtained, indicating the kinetic characteristics of a pseudo first-order reaction. The repeated cyclic experiments showed that the heterogeneous catalyst was stable and recoverable. Compared with the traditional homogeneous Fenton reagent, the heterogeneous catalyst has the advantage in the neutral or weakly basic medium used because the active component tris(1,10)-phenanthroline iron(II) is a stable chelate compound. The photo-Fenton degradation pathway for methylene blue was given based on the mass spectral data.
Authors:S. Dutta, A. Kundu, M. R. Chakraborty, S. Ojha, J. Chakrabarti, and N. C. Chatterjee
Siderophores are low molecular weight
(<1000 D) iron chelating compounds produced by microorganisms. Production of
siderophore is a device of antagonism as by virtue of the capacity of
siderophore production, a microorganism competes for Fe (III) with the others.
Production of siderophores by 9 different soil fungi and wood-decay fungi was
studied following CAS - assay and CAS - agar plate assay. Optimization for the production of
siderophores was done by varying the levels of pH and Fe (III) concentrations
in the low nutrient medium. All the test fungi could produce siderophores,
though the degree of production recorded to be very low both in Botryodiplodia
theobromae and in Fusarium spp. On the other hand, all the species of
Trichoderma showed their excellency in siderophore production. The optimum pH
for production of siderophores remained at neutral pH level though the range
varied from pH 6.0-8.0. The optimum range of the
concentration of Fe (III) required for siderophore production was recorded to
be 1.5-21.0 µM. However, the stress condition of
iron might be a decisive factor for siderophore production.
Authors:M. Döring, J. Wuckelt, W. Ludwig, and H. Görls
Complexes of the type M(Pa)2(HAz)2 and M(QA)2(HAz)2 (M=cobalt(II) and nickel(II); HPa=picolinic acid, HQa=quinaldic acid; HAz=azoles like imidazole (Him), pyrazole (HPz), benzimidazole
(HBzIm) etc.) show a similar thermal behaviour. In the first step of decomposition the corresponding azolinium picolinates
or quinaldinates (H2AzPa, H2AzQa) are split off with formation of polymeric mixed ligand complexes M(Pa)(Az) or M(Qa)(Az). X-ray analysis of Co(Qa)2(HBzIm)2 XIIIa illustrates a proton transfer and a subsequent thermal removal of benzimidazolinium quinaldinate (H2BzImQa): Hydrogen bridges from pyrrole nitrogen of the benzimidazole to the non-coordinated oxygen of the quinaldinate predetermine
the thermal initiated proton transfer. The high volatility of the heterocyclic acids and the nitrogen coordination are responsible
for the formation of the mixed ligand complex Co(Qa)(BzIm) XIVa.
Exceptions are the complexes M(Pa)2(HPz)2 XIa-b and M(Qa)2(HIm)2 XVIIa-b. Pyrazole is eliminated from the complexes XIa-b with formation of the solvent-free inner complex M(Pa)2 XIIa-b. From compounds XVIIIa-b quinaldic acid or their decomposition products are split off and a high temperature modification
of M(Im)2 XVIIIa-b is formed at elevated temperature. XVIIIa-b are decomposed to the cyanides M(CN)2 similarly to the thermal behaviour of Cu(Im).
In the first step the thermal degradation of imidazole and pyrazole adducts of copper(II) picolinates and quinaldinates is
characterized by the elimination of azoles. The reason for this thermal behaviour is the weaker coordination of the azole
heterocycles in copper chelate compounds.
Authors:G. I. Zharkova, S. V. Sysoev, P. A. Stabnikov, V. A. Logvinenko, and I. K. Igumenov
representatives of chelatecompounds forming the molecular crystals with the molecules linked by the weak van der Waals forces [ 5 – 7 ], therefore the estimation of the interaction energy provides the basis for the prediction of the volatility in the compounds of