Complexation properties of 1,4,10,13-tetraoxa-7,16-diazacyclooctadecane-7-malonate, -7,16-bis(malonate) and -7,16-bis(α-methylacetate)

Brücher, Ernő; Győri, Béla; Emri, J.; Jakab, Sándor; Solymosi, P.; Tóth, I.

doi:10.1039/dt9950003353

Cited by 9 publications

(10 citation statements)

References 27 publications

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“…[21] For the preparation of Eu(O 3 SCF 3 ) 3 , EuCl 3 , and SrCl 2 solutions, we used the salts of the highest analytical grade (Fluka and Alfa Aesar). The concentration of ligand solutions was determined from the pH potentiometric titration curves obtained in the absence and presence of an excess of CaCl 2 .…”

Section: Methodsmentioning

confidence: 99%

“…Due to the relatively large cavity of the 18membered macrocycle, its derivatives form especially stable complexes with the divalent and trivalent ions of large ionic radius, and with the rare-earth ions. [21] These observations urged us to investigate the thermodynamic and redox stability as well as the water exchange rate of the Eu II complexes of two [18]aneN 2 O 4carboxylate derivatives, namely the 1,4,10,13-tetraoxa-7,16diaza-cyclooctadecane-7,16-diacetate (ODDA 2À ), and -dimalonate (ODDM 4À ) (chemical structure of the ligands in Scheme 1.). [21] These observations urged us to investigate the thermodynamic and redox stability as well as the water exchange rate of the Eu II complexes of two [18]aneN 2 O 4carboxylate derivatives, namely the 1,4,10,13-tetraoxa-7,16diaza-cyclooctadecane-7,16-diacetate (ODDA 2À ), and -dimalonate (ODDM 4À ) (chemical structure of the ligands in Scheme 1.).…”

Section: Introductionmentioning

confidence: 99%

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Solution and Solid-State Characterization of EuII Chelates: A Possible Route Towards Redox Responsive MRI Contrast Agents

et al. 2000

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We report the first solid state X-ray crystal structure for a Eu(II) chelate, [C(NH2)3]3[Eu(II)(DTPA)(H2O)].8H2O, in comparison with those for the corresponding Sr analogue, [C(NH2)3]3[Sr(DTPA)(H2O).8H2O and for [Sr(ODDA)].8H2O (DTPA5 = diethylenetriamine-N,N,N',N",N"-pentaacetate, ODDA2- =1,4,10,13-tetraoxa-7,16-diazacyclooctadecane-7,16-diacetate ). The two DTPA complexes are isostructural due to the similar ionic size and charge of Sr(2+) and Eu(2+). The redox stability of [Eu(II)(ODDA)(H2O)] and [Eu(II)(ODDM)]2- complexes has been investigated by cyclovoltammetry and UV/Vis spectrophotometry (ODDM4- =1,4,10,13-tetraoxa-7,16-diaza-cyclooctadecane-7,16-++ +dimalonate). The macrocyclic complexes are much more stable against oxidation than [Eu(II)(DTPA)(H2O)]3- (the redox potentials are E1/2 =-0.82 V, -0.92 V, and -1.35 V versus Ag/AgCl electrode for [Eu(III/II)(ODDA)(H2O)],[Eu(III/II)(ODDM)], and [Eu(III/II)(DTPA)(H2O)], respectively, compared with -0.63 V for Eu(III/II) aqua). The thermodynamic stability constants of [Eu(II)(ODDA)(H2O)], [Eu(II)(ODDM)]2-, [Sr(ODDA)(H2O)], and [Sr(ODDM)]2- were also determined by pH potentiometry. They are slightly higher for the EuII complexes than those for the corresponding Sr analogues (logK(ML)=9.85, 13.07, 8.66, and 11.34 for [Eu(II)(ODDA)(H2O)], [Eu(II)(ODDM)]2-, [Sr(ODDA)(H2O)], and [Sr(ODDM)]2-, respectively, 0.1M (CH3)4NCl). The increased thermodynamic and redox stability of the Eu(II) complex formed with ODDA as compared with the traditional ligand DTPA can be of importance when biomedical application is concerned. A variable-temperature 17O-NMR and 1H-nuclear magnetic relaxation dispersion (NMRD) study has been performed on [Eu(II)(ODDA)(H2O)] and [Eu(II)(ODDM)]2- in aqueous solution. [Eu(II)(ODDM)]2- has no inner-sphere water molecule which allowed us to use it as an outer-sphere model for [Eu(II)(ODDA)(H2O)]. The water exchange rate (k298(ex)= 0.43 x 10(9)s(-1)) is one third of that obtained for [Eu(II)(DTPA)(H2O)]3-. The variable pressure 17O-NMR study yielded a negative activation volume, deltaV (not=) = -3.9cm3mol(-1); this indicates associatively activated water exchange. This water exchange rate is in the optimal range to attain maximum proton relaxivities, which are, however, strongly limited by the fast rotation of the small molecular weight complex.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Solution and Solid-State Characterization of EuII Chelates: A Possible Route Towards Redox Responsive MRI Contrast Agents

et al. 2000

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“…The ligand Na 4 oddm was chosen for its ability to bind Sr 2+ ions selectively over Ca 2+ ions. 13 In addition, the lariat arms containing charged functional groups on Na 4 oddm (Figure 1) may help prevent excessive leaching of the doped ligand through increased size and hydrogen-bonding interactions with the solgel framework. Leaching studies show that only 13 ( 3% of the doped ligand leached from within the sol-gel after the newly formed gel was placed in water for 72 h as monitored by 1 H NMR.…”

Section: Resultsmentioning

confidence: 99%

“…1,4,10, ligand (Na 4 oddm) (Figure 1) was prepared according to the literature procedure. 13 Sr 2+ concentrations were determined by atomic emission (AE) spectroscopy. Emission measurements were conducted at the 460.7-nm line on an upgraded Perkin-Elmer 5100 atomic absorption spectrophotometer.…”

Section: Methodsmentioning

confidence: 99%

Crown Ether-Doped Sol−Gel Materials for Strontium(II) Separation

et al. 2000

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Hybrid organic/inorganic sol-gel materials containing an encapsulated crown ether ligand were found to selectively remove 91.4 +/- 1.3% of Sr2+ from a solution containing excess of competing ions such as Ca2+. The crown ether ligand, 1,4,10,13-tetraoxa-7,16-diazacyclooctadecane-7,16-bis(malonate) ligand (Na4oddm), with known high affinity for Sr2+ was encapsulated in hydrophilic SiO2 through a simple sol-gel process. Washing the Sr(2+)-loaded gel with acid or ethylenediaminetetraacetic acid disodium salt recovered the Sr2+ from the sol-gel sorbent and regenerated the doped gel for subsequent Sr2+ intake. The approach reported here is a new alternative to the use of crown ethers in metal ion separation through, for example, solvent extraction or the use of sorbents containing chemically grafted crown ether ligands.

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“…One of the main driving forces behind the interest in them was to find more effective magnetic resonance imaging (MRI) contrast agents for medical diagnosis. [11Ϫ15] Now, however, other applications have also emerged; these include the fabrication of highly metal ion selective electrodes, [16] the removal of toxic and radioactive metal ions from the human body, [17] determination of intracellular metal ion concentrations, [18] potential applications of luminescent macrocyclic complexes in bioanalytics, [19Ϫ22] and others.…”

Section: Introductionmentioning

confidence: 99%

Synthesis, Conformation and Equilibrium Study of New Piperazine and Azamacrocyclic Ligands with N-(Tetrahydro-2-oxofuran-3-yl) and N-[(Carboxy)(2-hydroxyethyl)methyl] Pendant Arms

et al. 2002

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Complexation properties of 1,4,10,13-tetraoxa-7,16-diazacyclooctadecane-7-malonate, -7,16-bis(malonate) and -7,16-bis(α-methylacetate)

Cited by 9 publications

References 27 publications

Solution and Solid-State Characterization of EuII Chelates: A Possible Route Towards Redox Responsive MRI Contrast Agents

Solution and Solid-State Characterization of EuII Chelates: A Possible Route Towards Redox Responsive MRI Contrast Agents

Crown Ether-Doped Sol−Gel Materials for Strontium(II) Separation

Synthesis, Conformation and Equilibrium Study of New Piperazine and Azamacrocyclic Ligands with N-(Tetrahydro-2-oxofuran-3-yl) and N-[(Carboxy)(2-hydroxyethyl)methyl] Pendant Arms

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