Aminopolycarboxylate Complexes Research Articles

Electrosynthesis of highly transparent cobalt oxide water oxidation catalyst films from cobalt aminopolycarboxylate complexes.

Efficient catalysis of water oxidation represents one of the major challenges en route to efficient sunlight-driven water splitting. Cobalt oxides (CoOx ) have been widely investigated as water oxidation catalysts, although the incorporation of these materials into photoelectrochemical devices has been hindered by a lack of transparency. Herein, the electrosynthesis of transparent CoOx catalyst films is described by utilizing cobalt(II) aminopolycarboxylate complexes as precursors to the oxide. These complexes allow control over the deposition rate and morphology to enable the production of thin, catalytic CoOx films on a conductive substrate, which can be exploited in integrated photoelectrochemical devices. Notably, under a bias of 1.0 V (vs. Ag/AgCl), the film deposited from [Co(NTA)(OH2 )2 ](-) (NTA=nitrilotriacetate) decreased the transmission by only 10 % at λ=500 nm, but still generated >80 % of the water oxidation current produced by a [Co(OH2 )6 ](2+) -derived oxide film whose transmission was only 40 % at λ=500 nm.

Electrospray Ionization Mass Spectrometry for the Quantification of Inorganic Cations and Anions

Recent studies from our laboratory on electrospray ionization mass spectrometry (ESI-MS) for the quantification of inorganic cations and anions are reviewed. Metal ions were determined by ESI-MS in negative-ion mode as monovalent negative ions of their aminopolycarboxylate (APC) complexes, where excess amounts of the APC agents were added to sample solutions. Among the APCs studied, we found trans-1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid (CyDTA, the chemical forms in a complex were expressed as H(n)cydta(n-4)) as the best chelating agent. A size exclusion column was used for on-line separation of the metal-APC complexes from matrix salts in samples. Total amounts of Al, Ni, Cu, Zn, and Pb in the biological certified reference materials (CRM), Olive Leaves (BCR-062) and Plankton (BCR-414), and in a soil CRM (JSAC-0401) were successfully determined by the proposed method. Halide ions (X(-) = F(-), Cl(-), Br(-) and I(-)) and cyanide (CN(-)) were determined by ESI-MS based on the formation of ternary complexes of metals, chelating agents and the analyte anions. Negative ions of the ternary complexes of group 13 elements, nitrilotriacetic acid (NTA, H(n)nta(n-3)), and halides, i.e., [AlF(nta)](-) for F(-), and [InX(nta)](-) for other halides, were measured; the limits of detection (LODs) were 10 nmol dm(-3) for F(-), 0.31 μmol dm(-3) for Cl(-), 3.8 nmol dm(-3) for Br(-), and 1.6 nmol dm(-3) for I(-), respectively. In the case of CN(-), an LOD of 20 nmol dm(-3) was obtained based on measurements of the ternary complex of Cu(II), CN(-) and 4-(2-pyridylazo)resorcinol (PAR, Hnpar(n-2)), i.e., [(63)Cu(II)(CN)(par)](-) (m/z 302). Moreover, quantitative methods for Cr(VI) and Cr(III) by ESI-MS were developed, where HCrO4(-) (m/z 117) for Cr(VI) and [Cr(III)(cydta)](-) for Cr(III) were used for measurements.

The Chemistry of TALSPEAK: A Review of the Science

The TALSPEAK Process (Trivalent Actinide Lanthanide Separation with Phosphorus-Reagent Extraction from Aqueous Komplexes) was originally developed at Oak Ridge National Laboratory by B. Weaver and F.A. Kappelmann in the 1960s. It was envisioned initially as an alternative to the TRAMEX process (selective extraction of trivalent actinides by tertiary or quaternary amines over fission product lanthanides from concentrated LiCl solutions). TALSPEAK proposed the selective extraction of trivalent lanthanides away from the actinides, which are retained in the aqueous phase as aminopolycarboxylate complexes. After several decades of research and development, the conventional TALSPEAK process (based on di-(2-ethylhexyl) phosphoric acid (extractant) in 1,4-di-isopropylbenzene (diluent) and a concentrated lactate buffer containing diethylenetriamine-N,N,N’,N”,N”-pentaacetic acid (actinide-selective holdback reagent)) has become a widely recognized benchmark for advanced aqueous partitioning of the trivalent 4f/5f elements. TALSPEAK aqueous chemistry has also been utilized to selectively strip actinides (Reverse TALSPEAK) with some notable success. Under ideal conditions, conventional TALSPEAK separates Am3+ from Nd3+ (the usual limiting pair) with a single-stage separation factor of about 100; both lighter and heavier lanthanides are more completely separated from Am3+. Despite this apparent efficiency, TALSPEAK has not seen enthusiastic adoption for advanced partitioning of nuclear fuels at process scale for two principle reasons: first, all adaptations of TALSPEAK chemistry to process scale applications require rigid pH control within a narrow range of pH, and second, phase-transfer kinetics are often slower than ideal. To compensate for these effects, high concentrations of the buffer (0.5–2 M H/Na lactate) are required. Acknowledgement of these complications in TALSPEAK process development has inspired significant research activities dedicated to improving understanding of the basic chemistry that controls TALSPEAK (and related processes based on the application of actinide-selective holdback reagents). In the following report, advances in understanding of the fundamental chemistry of TALSPEAK that have been reported during the past decade will be reviewed and discussed.

Dissociation Kinetics of Open‐Chain and Macrocyclic Gadolinium(III)‐Aminopolycarboxylate Complexes Related to Magnetic Resonance Imaging: Catalytic Effect of Endogenous Ligands

The kinetics of the metal exchange reactions between open-chain Gd(DTPA)(2-) and Gd(DTPA-BMA), macrocyclic Gd(DOTA)(-) and Gd(HP-DO3A) complexes, and Cu(2+) ions were investigated in the presence of endogenous citrate, phosphate, carbonate and histidinate ligands in the pH range 6-8 in NaCl (0.15 M) at 25 °C. The rates of the exchange reactions of Gd(DTPA)(2-) and Gd(DTPA-BMA) are independent of the Cu(2+) concentration in the presence of citrate and the reactions occur via the dissociation of Gd(3+) complexes catalyzed by the citrate ions. The HCO(3)(-)/CO(3)(2-) and H(2)PO(4)(-) ions also catalyze the dissociation of complexes. The rates of the dissociation of Gd(DTPA-BMA), catalyzed by the endogenous ligands, are about two orders of magnitude higher than those of the Gd(DTPA)(2-). In fact near to physiological conditions the bicarbonate and carbonate ions show the largest catalytic effect, that significantly increase the dissociation rate of Gd(DTPA-BMA) and make the higher pH values (when the carbonate ion concentration is higher) a risk-factor for the dissociation of complexes in body fluids. The exchange reactions of Gd(DOTA)(-) and Gd(HP-DO3A) with Cu(2+) occur through the proton assisted dissociation of complexes in the pH range 3.5-5 and the endogenous ligands do not affect the dissociation rates of complexes. More insights into the interaction scheme between Gd(DTPA-BMA) and Gd(DTPA)(2-) and endogenous ligands have been obtained by acquiring the (13)C NMR spectra of the corresponding diamagnetic Y(III)-complexes, indicating the increase of the rates of the intramolecular rearrangements in the presence of carbonate and citrate ions. The herein reported results may have implications in the understanding of the etiology of nephrogenic systemic fibrosis, a rare disease that has been associated to the administration of Gd-containing agents to patients with impaired renal function.

Heterobimetallic Ba–Co aminopolycarboxylate complexes as precursors for BaCoO3-δ oxides; towards a one-stage-deposition of cobaltite films

Aminopolycarboxylate (APC) ligands have been selected to prepare seven new heterobimetallic barium-cobalt complexes as molecular precursors for BaCoO3-δ oxide materials. The use of APC = nitrilotriacetate (nta3−), ethylenediaminetetraacetate (edta4−), cyclohexane-1,2-diaminetetraacetate (cdta4−) and diethylenetriaminepentaacetate (dtpa5−) polydentate chelating agents enables the possible incorporation of Ba and CoII or CoIII in a 1 : 1 ratio. The crystal structure of the new BaCoII(nta)CH3COO·2H2O and BaCo(cdta)·5H2O have been refined from single crystal X-ray diffraction data. Our choice for the barium-cobalt system is based on the existence of a number of distinct BaCoO3-δ hexagonal perovskite polytypes, depending on the oxygen stoichiometry. It yields an easy probing of the cobalt oxidation state after thermal treatments. Temperature controlled X-ray diffraction (TCXRD) technique has been used to characterize the phases in competition upon thermal cycles of the precursors. The influences of the nature of ligands, initial cobalt oxidation state, temperature and working atmosphere on the process of formation of the mixed-oxide have been investigated. All the APC-precursors show appearance of a mixture of crystallized barium carbonate and Co3O4 in various ratio during the degradation process under air or flowing oxygen at 350–450 °C. Further thermal treatment under flowing oxygen leads to pure submicronic 2H-BaCoO3-δ above 650 °C in the case of cdta complexes, i.e. in softer conditions compared to the solid state route performed under high oxygen pressure. No essential influence of the cobalt valence in the precuror complexes was observed regarding the target BaCoO3-δ oxygen non stoichiometry. Finally, with a view to access porous electrodes for SOFCs, we demonstrated the possibility of one-stage-deposition of BaCoO3-δ layers on dense YSZ substrates, with a relatively good adherence, via the high temperature degradation of these complexes.

On‐column titration and investigation of metal complex formation for aminopolycarboxylate functionalised monoliths using scanning contactless conductivity detection

The application of scanning capacitively coupled contactless conductivity detection (SC(4)D) for the determination of pH dependant behaviour of two aminopolycarboxylates immobilised onto the surface of a monolithic capillary column is described. The use of SC(4)D to visualise changes in conductivity of the discrete zones of functional groups within monolithic capillary columns allows for the effects of immobilisation on the physicochemical properties of zones to be compared to that of the functional group in solution. The perturbation of the pK(a) values of the functional groups can be attributed to the change in chemical environment experienced by the functional group through the presence of local hydrogen bonding and surface induced effects. These bonds, both between adjacent functional groups and with the monolithic polymethacrylate scaffold, result in a modification of the electron density on the functional group and therefore a change in pK(a). Changes in the pK(a) of N-(2-acetamido)iminodiacetic acid (ADA) from 2.48 to 5.2 for one of the acidic protons, with little change in the pK(a) of the amine group, were observed, which correlates to similar changes in aggregated systems of aminopolycarboxylates. Similar results were obtained for the iminodiacetic acid (IDA) once immobilised onto the surface of the monolith. Furthermore, the ability to measure changes in the charge of such discrete zones of functional groups allows for the visualisation of complexation events occurring directly on-column, where such complexes result in a change in charge of the functional group. This potentially useful technique is illustrated within for the formation of aminopolycarboxylate complexes with a selection of metal ions.

Quantification of Trace Elements in Natural Samples by Electrospray Ionization Mass Spectrometry with a Size-Exclusion Column Based on the Formation of Metal−Aminopolycarboxylate Complexes

Metal ions were determined by ESI-MS in the negative ion mode as monovalent negative ions of their aminopolycarboxylic acid (APC) complexes, e.g., [Al(cydta)](-), [Pb(Hcydta)](-), where excess amounts of the APC agents were added to sample solutions. Among several APCs studied, we chose trans-1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid (CyDTA) as the best chelating agent because of higher stabilities and higher sensitivities of the complexes. The ionization efficiency of these metal complexes was strongly affected by the presence of matrix salts, e.g., NaCl, KNO(3), and etc. Thus, a size exclusion column (Sephadex G-10) was used for the online separation of the metal-APC complexes from other matrix salts. This method was successfully applied to the quantitative analyses for total amounts of Al, Ni, Cu, Zn, and Pb in the biological certified reference materials, olive leaves (BCR-062) and plankton (BCR-414). The detection limits of the present methods for these elements were several to several ten nanomolar levels. Moreover, this approach was extended to determine ultratraces of fluoride based on the formation of the ternary complex of aluminum, fluoride and nitrilotriacetic acid (NTA), i.e., [AlF(nta)](-). Its detection limit was 10 nM and was 2 orders of magnitude better than that of a fluoride ion selective electrode method. This method was applied to determine fluoride in tap water, river water, and green tea samples.

Estimation of the association and dissociation rate constants of Cd complexes with various aminopolycarboxylic acids by an exchange method

Environmental context. Phytoremediation is a potential way to remove cadmium from polluted soils. The process of plant uptake of cadmium can be enhanced by the addition of chelating compounds. The ability of roots to effectively take up Cd when bound to these complexes is dependent on the speed at which the Cd is associated or dissociated (bound or unbound) from the complex. An exchange method is used here to estimate these association and dissociation rates for a series of Cd–aminopolycarboxylate complexes (some of which have been tested elsewhere in phytoextraction studies). The results of these studies may make it possible to better model the bioavailability of Cd to plant roots. Abstract. Plant uptake of Cd depends not only on the concentration of Cd2+ in the soil solution but also on Cd complexes, the contribution of the latter depending on their association (ka) and dissociation (kd) rate constants. We used a previously designed exchange method to estimate ka and kd constants of Cd complexed with chelates of the aminopolycarboxylic acid series, i.e. ethylenediamine-N,N′-diacetic acid (EDDA), nitrilotriacetic acid (NTA), N-(2-hydroxyethyl)ethylene-diamine-N,N′,N′-triacetic acid (HEDTA), ethylenediaminetetraacetic acid (EDTA), ethylene glycol-bis(2-aminoethyl)-N,N,N′,N′-tetraacetic acid (EGTA), and trans-1,2-diaminocyclohexane-N,N,N′,N′-tetraacetic acid (CDTA) for future mechanistic modelling of Cd bioavailability including the lability of complexes. The precision of ka and kd estimates depended on the stability of the complexes. For the chelates with the highest stability, HEDTA, EDTA, EGTA and CDTA, the constants were estimated with a good precision. The knowledge of these constants enables improved modelling of bioavailability of Cd to plant roots by considering the contribution of Cd-complexes.

Influence of Fluoride on the Reversible Binding of NO by [FeII(EDTA)(H2O)]2−. Inhibition of Autoxidation of [FeII(EDTA)(H2O)]2−

The promising BioDeNO(x) process for NO removal from gaseous effluents suffers from an unsolved problem that results from the oxygen sensitivity of the Fe(II)-aminopolycarboxylate complexes used in the absorber unit to bind NO(g). The utilized [Fe(II)(EDTA)(H2O)](2-) complex is extremely oxygen sensitive and easily oxidized to give a totally inactive [Fe(III)(EDTA)(H2O)](-) species toward the binding of NO(g). We found that an in situ formed, less-oxygen-sensitive mixed-ligand complex, [Fe(II)(EDTA)(F)](3-), still reacts quantitatively with NO(g). The formation constant for the mixed ligand complex was determined spectrophotometrically. For [Fe(III)(EDTA)(F)](2-) we found log K(MLF)(F) = 1.7 +/- 0.1. The [Fe(II)(EDTA)(F)](3-) complex has a smaller value of log K(MLF)(F) = 1.3 +/- 0.2. The presence of fluoride does not affect the reversible binding of NO(g). Even over extended periods of time and fluoride concentrations of up to 1.0 M, the nitrosyl complex does not undergo any significant decomposition. The [Fe(III)(EDTA)(NO(-))](2-) complex releases bound NO on passing nitrogen through the solution to form [Fe(II)(EDTA)(H2O)](2-) almost completely. A reaction cycle is feasible in which fluoride inhibits the autoxidation of [Fe(II)(EDTA)(H2O)](2-) during the reversible binding of NO(g).

Effect of Chelate Dynamics on Water Exchange Reactions of Paramagnetic Aminopolycarboxylate Complexes

Because of our interest in evaluating a possible relationship between complex dynamics and water exchange reactivity, we performed (1)H NMR studies on the paramagnetic aminopolycarboxylate complexes Fe (II)-TMDTA and Fe (II)-CyDTA and their diamagnetic analogues Zn (II)-TMDTA and Zn (II)-CyDTA. Whereas a fast Delta-Lambda isomerization was observed for the TMDTA species, no acetate scrambling between in-plane and out-of-plane positions is accessible for any of the CyDTA complexes because the rigid ligand backbone prevents any configurational changes in the chelate system. In variable-temperature (1)H NMR studies, no evidence of spectral coalescence due to nitrogen inversion was found for any of the complexes in the available temperature range. The TMDTA complexes exhibit the known solution behavior of EDTA, whereas the CyDTA complexes adopt static solution structures. Comparing the exchange kinetics of flexible EDTA-type complexes and static CyDTA complexes appears to be a suitable method for evaluating the effect of ligand dynamics on the overall reactivity. In order to assess information concerning the rates and mechanism of water exchange, we performed variable-temperature and -pressure (17)O NMR studies of Ni (II)-CyDTA, Fe (II)-CyDTA, and Mn (II)-CyDTA. For Ni (II)-CyDTA, no significant effects on line widths or chemical shifts were apparent, indicating either the absence of any chemical exchange or the existence of a very small amount of the water-coordinated complex in solution. For [Fe (II)(CyDTA)(H 2O)] (2-) and [Mn (II)(CyDTA)(H 2O)] (2-), exchange rate constant values of (1.1 +/- 0.3) x 10 (6) and (1.4 +/- 0.2) x 10 (8) s (-1), respectively, at 298 K were determined from fits to resonance-shift and line-broadening data. A relationship between chelate dynamics and reactivity seems to be operative, since the CyDTA complexes exhibited significantly slower reactions than their EDTA counterparts. The variable-pressure (17)O NMR measurements for [Mn (II)(CyDTA)(H 2O)] (2-) yielded an activation volume of +9.4 +/- 0.9 cm (3) mol (-1). The mechanism is reliably assigned as a dissociative interchange (I d) mechanism with a pronounced dissociation of the leaving water molecule in the transition state. In the case of [Fe (II)(CyDTA)(H 2O)] (2-), no suitable experimental conditions for variable-pressure measurements were accessible.

Pulse Radiolysis Study on Reactions of a Hydrated Electron with Europium(III)−Aminopolycarboxylate Complexes in Aqueous Perchlorate Media

Pulse radiolysis of 1:1 complexes of europium(III)-aminopolycarboxylates was studied in aqueous perchlorate solutions to understand relations of the reduction rate of Eu(III) with hydration state and stability of the complex. The rate constant for the reaction of a hydrated electron (e aq - ) with the complex was determined in the temperature range of 278.15 to 333.15 K and the ionic strength range of 0.05 to 1.0 mol kg -1 . The rate constant was linearly related not only with the residual hydration number of the complex representing the hydration state but also with the stability constant and redox potential as equilibrium constants. The reaction of eaq - with the complex was described by diffusive encounter and successive electron-transfer processes between eaq - and the complex. Gibbs free energy, enthalpy, and entropy of activation for the reaction were obtained from the effect of temperature on the rate constant, and the entropy term was found to be a dominant factor for the electron-transfer process after the diffusion process. These indicated that the entropy term, reflecting ionic interaction of Eu(III) -carboxylate groups and dehydration of aquo Eu(III) ion on the complexation, caused the difference in the rate constant between the complexes, and linear correlation between the rate constant and hydration number. The effect of ionic strength on the rate constant was examined by

Carbon[sbnd]carbon bond formation in neutral aqueous medium by modification of the Nozaki–Hiyama reaction

A carboncarbon bond forming reaction has been developed by modifying the Nozaki–Hiyama reaction using a chromium(II)-aminopolycarboxylate complexes in a neutral aqueous medium at room temperature. Aldehydes and ketones can be coupled with aralkyl and aryl halides in good yields.

Circularly polarized luminescence and intermolecular energy transfer from terbium(III) to neodymium(III) aminopolycarboxylate complexes

Total luminescence (TL), circularly polarized luminescence (CPL) and luminescence decay measurements have been used to investigate the chiroptical structures and energy transfer processes of mixtures of Tb 3+ and Nd 3+ complexes in solution with ( S,S)-ethylenediamine- N,N-disuccinate (edds) and L-alaninediacetate (alada) ligands. The decay and quenching profiles of the terbium luminescence reveal the energy transfer from Tb 3+ to Nd 3+ complexes with a quadratic dependence on acceptor concentration. The emission dissymmetry factor g em, which is in the order of −0.03 near 18400 cm −1 in absence of neodymium complexes, is also quenched with increase of the neodymium concentration. In case of edds complexes the quenching of both luminescence and dissymmetry factors is significantly more pronounced than in case of alada complexes. Critical distances of 7.4 nm and 3.7 nm were obtained for edds and alada complexes, respectively.

The Hydrolysis of Trimetaphosphate Catalyzed by Lanthanide(III) Aminopolycarboxylate Complexes: Coordination, Stability, and Reactivity of Intermediate Complexes

The Hydrolysis of Trimetaphosphate Catalyzed by Lanthanide(III) Aminopolycarboxylate Complexes: Coordination, Stability, and Reactivity of Intermediate Complexes

Determination of stability constants of metal complexes from NMR chemical shifts and relaxation rates using a spreadsheet computer program

The versatility of multinuclear magnetic resonance techniques in the determination of stability constants of metal complexes is demonstrated for three cases in which potentiometry is impossible or less suitable. The complexation of cyclo-trimetaphosphate to lanthanide aminopolycarboxylate complexes was investigated in a dilution experiment using 31P NMR shifts. The stabilities of CdL and CdL2 [L = 1-(2-aminoethylamino)-1-deoxy-D-galactitol] were determined by 113Cd NMR speciation, in which the occurring species were in slow exchange. Competition experiments using both 31P NMR shifts and 13C and 31P relaxation rate enhancements were performed to determine the stabilities of Nd(NTA)(PPP) and Nd(PPP)2 (PPP = tripolyphosphate). Where possible, the results were compared with potentiometric data and found to be in good agreement.

Structure and thermodynamic properties of aminopoly-phosphonate complexes of the alkaline-earth metal lons

The formation equilibria and thermodynamic properties of the alkaline-earth metal (M = Mg2+, Ca2+, Sr2+ or Ba2+) complexes of nitrilotris(methylenephosphonic acid)(H6ntmp) and ethylenediamine-tetrakis(methylenephosphonic acid)(H8edtmp) have been studied by means of potentiometry, NMR spectroscopy and calorimetry at 25.0 °C and at an ionic strength of 0.1 mol dm–3(KNO3). The complex formation constants and the protonation constants of the complexes were determined from the potentiometric titration data. Thermodynamic parameters of the protonation of the ligand, and the formation and protonation of the metal complexes of ntmp and edtmp were evaluated from the calorimetric titration data. The first protonation on the nitrogen atom of ntmp is significantly exothermic and it is followed by the endothermic protonation on the phosphonate O–. The protonations of edtmp are exothermic up to the third step. The formation of magnesium complexes of ntmp and edmp is endothermic and entropy driven, whereas that of the complexes of Ca2+, Sr2+ and Ba2+ is weakly exothermic. This behaviour is analogous to that of aminopolycarboxylate complexes. The results of calorimetric measurements of ntmp complexes support the structure of protonated alkaline-earth metal–ntmp complexes predicted from the stability and NMR data, i.e. the first protonation of the metal complexes occurs on the nitrogen atom of the ligand, rupturing the M–N bond. The thermodynamic behaviour of the edtmp complexes is considerably complicated. In the analysis of the pH dependence of the 31P NMR signals, the chemical shift of each species of ligand and its metal complexes was evaluated by using the formation constants obtained by potentiometry. The change in the chemical shift of the complexes upon protonation supports the structures of the alkaline-earth metal complexes predicted from the thermodynamic parameters.

Oxidation of cobalt(II) aminopolycarboxylate complexes by peroxomonophosphoric acid in acetate buffers. A kinetic study

The kinetics of oxidation of the CoII complexes [Co(edta)]2− and [Co(hedta)]− [H4edta=ethylenediamine tetraacetic acid and H3hedta=N′-(2-hydroxyethyl)ethylenediamineN, N′, N′ triacetic acid] by peroxomonophosphoric acid (PMPA) in acetate buffer were investigated spectrophotometrically. The reactions exhibit first order behaviour in each reactant and are markedly in hibited by H+. A plausible mechanism consistent with the observed results is proposed.

Molecular structure, dynamics and stabilities of di-gadolinium aminopolycarboxylate complexes

The molecular structures, energies and dynamics of 2,3,5,6-tetrakis[ N,N-bis(carboxymethyl)aminomethyl]piperazine- N,N′-diacetic acid (DIMER A), 1,5-bis[1,1,4-tris(carboxymethyl)-1,4-diazabutyl]-2,4-bis[[ N,N-bis(carboxymethyl)]amino]cyclohexane (DIMER B) and 1,4-bis[1,1,4-tris(carboxymethyl)-1,4-diazabutyl]-2,5-bis[[ N,N-bis(carboxymethyl)]amino]cyclohexane (DIMER C) and their diGd-complexes were examined by molecular mechanical calculations and molecular dynamics simulations using the AMBER force field. The results indicate that DIMER A would form the most stable binuclear complex among the 3 ligands, mainly because the energy needed for the ligand to obtain the conformation in the complex is less in DIMER A than in DIMER B and DIMER C. The ( RSRS), ( RRSS), ( RRRS), ( SRRS) and ( SSSS) isomers of DIMER A had similar complex stabilities in these calculations. The ( SSRR), ( RSSR) and ( SSSR) isomers of DIMER B and of DIMER C also had similar stabilities. Steric and electrostatic interactions with neighbouring groups determined the conformations of N-substituents in the ligands.

Effect of Cu(II)-aminopolycarboxylates on the radiosensitivity of thymine

Relative degradation of thymine (T) on radiolysis was found to be enhanced appreciably in the presence of Cu(II)-aminopolycarboxylate complexes. However the role of Cu(II) complexes in affecting the radiosensitivity of thymine was found to be markedly different than when copper was used as a simple salt, e.g. copper sulphate. A probable reaction mechanism relating the formation of products and the degradation of thymine in these systems has been proposed.

ChemInform Abstract: Gadolinium(III)‐Aminopolycarboxylate Complexes as Potential Enhancing Agents for NMR Imaging.

ChemInformVolume 21, Issue 7 Physical Organic Chemistry ChemInform Abstract: Gadolinium(III)-Aminopolycarboxylate Complexes as Potential Enhancing Agents for NMR Imaging. E. + BRUECHER, E. + BRUECHER Kossuth L. Todomanyeg., Szervet. Analit. Kem. Tanszek, 4010 Debrecen, HungarySearch for more papers by this authorR. KIRALY, R. KIRALY Kossuth L. Todomanyeg., Szervet. Analit. Kem. Tanszek, 4010 Debrecen, HungarySearch for more papers by this author E. + BRUECHER, E. + BRUECHER Kossuth L. Todomanyeg., Szervet. Analit. Kem. Tanszek, 4010 Debrecen, HungarySearch for more papers by this authorR. KIRALY, R. KIRALY Kossuth L. Todomanyeg., Szervet. Analit. Kem. Tanszek, 4010 Debrecen, HungarySearch for more papers by this author First published: February 13, 1990 https://doi.org/10.1002/chin.199007064AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume21, Issue7February 13, 1990 RelatedInformation