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1.

001-es BibID:BIBFORM067453
Első szerző:Baranyai Zsolt (vegyész)
Cím:Equilibrium and NMR Relaxometric Studies on the s-Triazine-Based Heptadentate Ligand PTDITA Showing High Selectivity for Gd3+ Ions / Zsolt Baranyai, Lorenzo Tei, Giovanni B. Giovenzana, Ferenc K. Kálmán, Mauro Botta
Dátum:2012
ISSN:0020-1669
Megjegyzések:A complete potentiometric and NMR relaxometric solution study on the heptadentate 2,2·,2ı,2·ı-[(6-piperidinyl-1,3,5-triazine-2,4-diyl)dihydrazin-2-yl-1-ylidene]tetraacetic acid (PTDITA) ligand has been carried out. This ligand is based on the 1,3,5-triazine ring with two hydrazine-N,N-diacetate groups in positions 2 and 4 and a piperidine moiety in position 6. The introduction of the triazine ring into the ligand backbone is expected to modify its flexibility and then to affect the stability of the corresponding complexes with transition-metal and lanthanide ions. Thermodynamic stabilities have been determined by pH potentiometry, UV spectrophotometry, and 1H NMR spectroscopy for formation of the complexes with Mg2+, Ca2+, Cu2+, Zn2+, La3+, Gd3+, and Lu3+ ions. PTDITA shows a good binding affinity for Gd3+ (logK = 18.49, pGd = 18.6) and an optimal selectivity for Gd3+ over the endogenous Ca2+, Zn2+, and Cu2+ (Ksel = 6.78 ? 107), which is 3 orders of magnitude higher that that reported for Gd(DTPA) (Ksel = 2.85 ? 104). This is mainly due to the lower stability of the CuII- and ZnII(PTDITA) complexes compared to the corresponding DTPA complexes, which suggests an important role of the triazine ring on the selectivity for the Gd3+ ion. The relaxometric properties of Gd(PTDITA) have been investigated in aqueous solution by measuring the 1H relaxivity as a function of the pH, temperature, and magnetic field strength (nuclear magnetic relaxation dispersion profile). Variable-temperature 17O NMR data have provided direct information on the kinetic parameters for exchange of the coordinated water molecules. A simultaneous fit of the data suggests that the high relaxivity value (r1 = 10.2 mM?1 s?1) is a result of the presence of two inner-sphere water molecules along with the occurrence of relatively slow rotation and electronic relaxation. The water residence lifetime, 298?M = 299 ns, is quite comparable to that of clinically approved magnetic resonance imaging contrast agents. The displacement of the inner-sphere water molecules by bidentate endogeneous anions (citrate, phosphate, and carbonate) has also been evaluated by 1H relaxometry. In general, the binding interaction is markedly weak, and only in the case of citrate, a ca. 35% decrease in relaxivity was observed in the presence of 60 equiv of the anion. Phosphate and carbonate also interact with the paramagnetic ion, likely as monodentate ligands, but formation of the ternary complex is accompanied by a modest increase of r1 due to the contribution of second-sphere water molecules.
Tárgyszavak:Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
Heptadentate Ligand
Equilibrium
NMR Relaxometry
gadolinium
Molekulatudomány
Megjelenés:Inorganic Chemistry 51 : 4 (2012), p. 2597-2607. -
További szerzők:Tei, Lorenzo Giovenzana, Giovanni Battista Kálmán Ferenc K. (1978-) (vegyész) Botta, Mauro
Pályázati támogatás:OTKA-83253
OTKA
EU FP6 European Imaging Laboratories
Egyéb
TÁMOP-4.2.1/B-09/1/KONV-2010-0007
TÁMOP
Kémiai vizsgálatok az orvosi képalkotó diagnosztikában használt fémkomplexek fejlesztésére
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2.

001-es BibID:BIBFORM099677
035-os BibID:(WoS)000739859300001 (Scopus)85123404452
Első szerző:Botár Richárd (vegyész)
Cím:Synthesis and characterization of a stable and inert Mn-II-based Zn-II responsive MRI probe for molecular imaging of glucose stimulated zinc secretion (GSZS) / Botár Richárd, Molnár Enikő, Garda Zoltán, Madarasi Enikő, Trencsényi György, Kiss János, Kálmán Ferenc K., Tircsó Gyula
Dátum:2022
ISSN:2052-1553
Tárgyszavak:Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
Megjelenés:Inorganic Chemistry Frontiers. - 9 : 3 (2022), p. 577-583. -
További szerzők:Molnár Enikő (1991-) (vegyész) Garda Zoltán (1989-) (vegyész) Madarasi Enikő Trencsényi György (1978-) (biológus, biokémikus, molekuláris biológus) Kiss János (1992-) (fizikus) Kálmán Ferenc K. (1978-) (vegyész) Tircsó Gyula (1977-) (vegyész, kémia tanár)
Pályázati támogatás:GINOP-2.3.2-15-2016-00008
GINOP
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3.

001-es BibID:BIBFORM099978
035-os BibID:(WoS)000753087700001 (Scopus)85127854797
Első szerző:Csupász Tibor (1991-)
Cím:Exceptionally fast formation of stable rigidified cross-bridged complexes formed with Cu(II) isotopes for Molecular Imaging / Csupász Tibor, Lihi Norbert, Fekete Zsuzsa, Nagy Antónia, Botár Richárd, Forgács Viktória, Szikra Dezső, May Nóra Veronika, Tircsó Gyula, Kálmán Ferenc Krisztián
Dátum:2022
ISSN:2052-1553
Tárgyszavak:Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
Megjelenés:Inorganic Chemistry Frontiers. - 9 : 6 (2022), p. 1217-1223. -
További szerzők:Lihi Norbert (1990-) (vegyész) Fekete Zsuzsa Nagy Antónia Botár Richárd (1992-) (vegyész) Forgács Viktória (1991-) (vegyész) Szikra Dezső Péter (1983-) (vegyész) May Nóra Veronika Tircsó Gyula (1977-) (vegyész, kémia tanár) Kálmán Ferenc K. (1978-) (vegyész)
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4.

001-es BibID:BIBFORM106980
035-os BibID:(WoS)000643574200067 (Scopus)85100045839
Első szerző:Garda Zoltán (vegyész)
Cím:Complexation of Mn(II) by Rigid Pyclen Diacetates: Equilibrium, Kinetic, Relaxometric, Density Functional Theory, and Superoxide Dismutase Activity Studies / Zoltán Garda, Enikő Molnár, Nadège Hamon, José Luis Barriada, David Esteban-Gómez, Balázs Váradi, Viktória Nagy, Kristof Pota, Ferenc Krisztián Kálmán, Imre Tóth, Norbert Lihi, Carlos Platas-Iglesias, Éva Tóth, Raphaël Tripier, Gyula Tircsó
Dátum:2021
ISSN:0020-1669 1520-510X
Megjegyzések:We report the Mn(II) complexes with two pyclen-based ligands (pyclen = 3,6,9,15-tetraazabicyclo[9.3.1]pentadeca-1(15),11,13-triene) functionalized with acetate pendant arms at either positions 3,6 (3,6-PC2A) or 3,9 (3,9-PC2A) of the macrocyclic fragment. The 3,6-PC2A ligand was synthesized in five steps from pyclen oxalate by protecting one of the secondary amine groups of pyclen using Alloc protecting chemistry. The complex with 3,9-PC2A is characterized by a higher thermodynamic stability [log K-MnL = 17.09(2)] than the 3,6-PC2A analogue [log K-MnL = 15.53(1); 0.15 M NaCl]. Both complexes contain a water molecule coordinated to the metal ion, which results in relatively high H-1 relaxivities (r(1p) = 2.72 and 2.91 mM(-1) s(-1) for the complexes with 3,6-PC2A and 3,9-PC2A, respectively, at 25 degrees C and 0.49 T). The coordinated water molecule displays fast exchange kinetics with the bulk in both cases; the rates (k(ex)(298)) are 140 x 10(6) and 126 x 10(6) s(-1) for [Mn(3,6-PC2A)(H2O)] and [Mn(3,9-PC2A)(H2O)], respectively. The two complexes were found to be remarkably inert with respect to their dissociation, with half-lives of 63 and 21 h, respectively, at pH = 7.4 in the presence of excess Cu(II). The r(1p) values recorded in blood serum remain constant at least over a period of 120 h. Cyclic voltammetry experiments show irreversible oxidation features shifted to higher potentials with respect to [Mn(EDTA)(H2O)](2-) (H(4)EDTA = ethylenediaminetetraacetic acid) and [Mn(PhDTA)(H2O)](2-) (H(4)PhDTA = phenylenediamine-N,N,N',N'-tetraacetic acid), indicating that the PC2A complexes reported here have a lower tendency to stabilize Mn(III). The superoxide dismutase activity of the Mn(II) complexes was tested using the xanthine/xanthine oxidase/p-nitro blue tetrazolium chloride assay at pH = 7.8. The Mn(II) complexes of 3,6-PC2A and 3,9-PC2A are capable of assisting decomposition of the superoxide anion radical. The kinetic rate constant of the complex of 3,9-PC2A is smaller by 1 order of magnitude than that of 3,6-PC2A.
Tárgyszavak:Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
Megjelenés:Inorganic Chemistry. - 60 : 2 (2021), p. 1133-1148. -
További szerzők:Molnár Enikő (1991-) (vegyész) Hamon, Nadège Barriada, José Luis Esteban-Gómez, David Váradi Balázs (1990-) (vegyész) Nagy Viktória Póta Kristóf Kálmán Ferenc K. (1978-) (vegyész) Tóth Imre (1950-) (vegyész) Lihi Norbert (1990-) (vegyész) Platas-Iglesias, Carlos Tóth Éva (1967-) (koordinációs kémia) Tripier, Raphaël Tircsó Gyula (1977-) (vegyész, kémia tanár)
Pályázati támogatás:K-120224
OTKA
128201
OTKA
134694
OTKA
PD-128326
OTKA
2019-2.1.11- 1179 TET-2019-00084
Egyéb
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5.

001-es BibID:BIBFORM103530
035-os BibID:(WOS)000541873600033 (Scopus)85084399701
Első szerző:Garda Zoltán (vegyész)
Cím:Unexpected Trends in the Stability and Dissociation Kinetics of Lanthanide(III) Complexes with Cyclen-Based Ligands across the Lanthanide Series / Zoltán Garda, Viktoria Nagy, Aurora Rodríguez-Rodríguez, Rosa Pujales-Paradela, Véronique Patinec, Goran Angelovski, Éva Tóth, Ferenc K. Kálmán, David Esteban-Gómez, Raphaël Tripier, Carlos Platas-Iglesias, Gyula Tircsó
Dátum:2020
ISSN:0020-1669 1520-510X
Megjegyzések:We report a detailed study of the thermodynamic stability and dissociation kinetics of lanthanide complexes with two ligands containing a cyclen unit, a methyl group, a picolinate arm, and two acetate pendant arms linked to two nitrogen atoms of the macrocycle in either cis (1,4-H(3)DO2APA) or trans (1,7-H(3)DO2APA) positions. The stability constants of the Gd3+ complexes with these two ligands are very similar, with log K-GdL values of 16.98 and 16.33 for the complexes of 1,4-H(3)DO2APA and 1,7-H(3)DO2APA, respectively. The stability constants of complexes with 1,4-H(3)DO2APA follow the usual trend, increasing from log K-LaL = 15.96 to log K-LuL = 19.21. However, the stability of [Ln(1,7-DO2APA)] complexes decreases from log K = 16.33 for Gd3+ to 14.24 for Lu3+. The acid-catalyzed dissociation rates of the Gd3+ complexes differ by a factor of similar to 15, with rate constants (k(1)) of 1.42 and 23.5 M(-1)s(-1) for [Gd(1,4-DO2APA)] and [Gd(1,7DO2APA)], respectively. This difference is magnified across the lanthanide series to reach a 5 orders of magnitude higher k(1) for [Yb(1,7-DO2APA)] (1475 M(-1)s(-1)) than for [Yb(1,4-DO2APA)] (5.79 x 10(-3)M(-1)s(-1)).The acid catalyzed mechanism involves the protonation of a carboxylate group, followed by a cascade of proton-transfer events that result in the protonation of a nitrogen atom of the cyclen unit. Density functional theory calculations suggest a correlation between the strength of the Ln-O-carboxylate bonds and the kinetic inertness of the complex, with stronger bonds providing more inert complexes. The H-1 NMR resonance of the coordinated water molecule in the [Yb(1,7-DO2APA)] complex at 176 ppm provides a sizable chemical exchange saturation transfer effect thanks to a slow water exchange rate of (15.9 +/- 1.6) x 10(3) s(-1).
Tárgyszavak:Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
Megjelenés:Inorganic Chemistry. - 59 : 12 (2020), p. 8184-8195. -
További szerzők:Nagy Viktória Rodríguez-Rodríguez, Aurora Pujales-Paradela, Rosa Patinec, Véronique Angelovski, Goran Tóth Éva Kálmán Ferenc K. (1978-) (vegyész) Esteban-Gómez, David Tripier, Raphaël Platas-Iglesias, Carlos Tircsó Gyula (1977-) (vegyész, kémia tanár)
Pályázati támogatás:GINOP-2.3.2-15-2016-00008
GINOP
NKFIH-K-120224
Egyéb
NKFIH-K-128201
Egyéb
2019-2.1.11-TÉT-2019-00084
Egyéb
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6.

001-es BibID:BIBFORM084932
035-os BibID:(cikkazonosító)1721713
Első szerző:Garda Zoltán (vegyész)
Cím:Thermodynamic and kinetic properties of Mn2+cyclododecane derivative complexes: fine-tuning by the nature of donor atoms / Garda Zoltán, Fodor Tamás, Molnár Enikő, Botár Richárd, Kálmán Ferenc Krisztián, Tóth Imre, Tircsó Gyula, Kovacs Zoltán
Dátum:2014
ISSN:0949-8257
Tárgyszavak:Természettudományok Kémiai tudományok idézhető absztrakt
folyóiratcikk
kémia
biokémia és molekuláris biológia
Megjelenés:Journal of Biological Inorganic Chemistry. - 19 : S1 (2014), p. S686. -
További szerzők:Fodor Tamás (1987-) (vegyész) Molnár Enikő (1991-) (vegyész) Botár Richárd (1992-) (vegyész) Kálmán Ferenc K. (1978-) (vegyész) Tóth Imre (1950-) (vegyész) Tircsó Gyula (1977-) (vegyész, kémia tanár) Kovács Zoltán
Pályázati támogatás:TÁMOP-4.2.2.A-11/1/KONV-2012-0043
TÁMOP
TÁMOP-4.2.2/B-10/1-2010-0024
TÁMOP
TÁMOP 4.2.4. A/1-11-1-2012-0001
TÁMOP
OTKA-84291
OTKA
TÉT_11-2-2012-0010
Egyéb
PD-83253
Egyéb
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7.

001-es BibID:BIBFORM016465
Első szerző:Gianolio, Eliana
Cím:Improving the relaxivity by dimerizing Gd-AAZTA : Insights for enhancing the sensitivity of MRI contrast agents / Eliana Gianolio, Kondareddiar Ramalingam, Bo Song, Ferenc Kalman, Silvio Aime, Rolf Swenson
Dátum:2010
ISSN:1387-7003
Megjegyzések:The synthesis of a dimeric derivative of Gd-AAZTA is reported. It retains the basic properties of the parent complex (q = 2, high stability) and displays a relaxivity of 14.0 mM(-1) s(-1) at 20 MHz and 298 K. The outstanding relaxivity is the result of the increased molecular reorientational time and of the contribution arising from 4 to 5 water molecules in the second coordination sphere of the Gd(III) ions. (C) 2010 Elsevier B.V. All rights reserved.
Tárgyszavak:Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
Gadolinium chelate
MRI imaging
Relaxivity
water exchange
o-17 nmr
variable-temperature
complexes
relaxation
dynamics
Megjelenés:Inorganic Chemistry Communications. - 13 : 5 (2010), p. 663-665. -
További szerzők:Ramalingam, Kondareddiar Song, Bo Kálmán Ferenc K. (1978-) (vegyész) Aime, Silvio Swenson, Rolf
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8.

001-es BibID:BIBFORM076226
035-os BibID:(WoS)000433013600028 (Scopus)85047315800
Első szerző:Gündüz, Serhat
Cím:Coordination Properties of GdDO3A-Based Model Compounds of Bioresponsive MRI Contrast Agents / Serhat Gündüz, Sandip Vibhute, Richard Botár, Ferenc K. Kálmán, Imre Tóth, Gyula Tircsó, Martín Regueiro-Figueroa, David Esteban-Gómez, Carlos Platas-Iglesias, Goran Angelovski
Dátum:2018
ISSN:0020-1669 1520-510X
Megjegyzések:We report a detailed characterization of the thermodynamic stability and dissociation kinetics of Gd3+ complexes with DO3A derivatives containing a (methylethylcarbamoylmethylamino)acetic acid (L1), (methylpropylcarbamoylmethylamino)acetic acid (L2), 2-dimethylamino-N-ethylacetamide (L3), or 2-dimethylamino-N-propylacetamide (L4) group attached to the fourth nitrogen atom of the macrocyclic unit. These ligands are model systems of Ca2+- and Zn2+-responsive contrast agents (CA) for application in magnetic resonance imaging (MRI). The results of the potentiometric studies (I = 0.15 M NaCl) provide stability constants with log KGdL values in the range 13.9?14.8. The complex speciation in solution was found to be quite complicated due to the formation of protonated species at low pH, hydroxido complexes at high pH, and stable dinuclear complexes in the case of L1,2. At neutral pH significant fractions of the complexes are protonated at the amine group of the amide side chain (log KGdL?H = 7.2?8.1). These ligands form rather weak complexes with Mg2+ and Ca2+ but very stable complexes with Cu2+ (log KCuL = 20.4?22.3) and Zn2+ (log KZnL = 15.5?17.6). Structural studies using a combination of 1H NMR and luminescence spectroscopy show that the amide group of the ligand is coordinated to the metal ion at pH ?8.5, while protonation of the amine group provokes the decoordination of the amide O atom and a concomitant increase in the hydration number and proton relaxivity. The dissociation of the complexes occurs mainly through a rather efficient proton-assisted pathway, which results in kinetic inertness comparable to that of nonmacrocyclic ligands such as DTPA rather than DOTA-like complexes.
Tárgyszavak:Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
Megjelenés:Inorganic Chemistry. - 57 : 10 (2018), p. 5973-5986. -
További szerzők:Vibhute, Sandip Botár Richárd (1992-) (vegyész) Kálmán Ferenc K. (1978-) (vegyész) Tóth Imre (1950-) (vegyész) Tircsó Gyula (1977-) (vegyész, kémia tanár) Regueiro-Figueroa, Martín Esteban-Gómez, David Platas-Iglesias, Carlos Angelovski, Goran
Pályázati támogatás:GINOP-2.3.2-15-2016-00008
GINOP
GINOP-2.3.3-15-2016-00004
GINOP
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9.

001-es BibID:BIBFORM062902
Első szerző:Kálmán Ferenc K. (vegyész)
Cím:H4octapa: Highly Stable Complexation of Lanthanide(III) Ions and Copper(II) / Ferenc Krisztián Kálmán, Andrea Végh, Martín Regueiro-Figueroa, Éva Tóth, Carlos Platas-Iglesias, Gyula Tircsó
Dátum:2015
ISSN:0020-1669
Megjegyzések:The acyclic ligand octapa4 (H4octapa = 6,6'-((ethane-1,2-diylbis((carboxymethyl)azanediyl))bis(methylene))dipicolinic acid) forms stable complexes with the Ln3+ ions in aqueous solution. The stability constants determined for the complexes with La3+, Gd3+ and Lu3+ using relaxometric methods are logKLaL = 20.13(7), logKGdL = 20.23(4) and logKLuL = 20.49(5) (I = 0.15 M NaCl). High stability constants were also determined for the complexes formed with divalent metal ions such as Zn2+ and Cu2+ (logKZnL = 18.91(3) and logKCuL = 22.08(2)). A UV-Vis and NMR spectroscopic study and DFT calculations point to hexadentate binding of the ligand to Zn2+ and Cu2+, the donor atoms of the acetate groups of the ligand remaining uncoordinated. The complexes formed with the Ln3+ ions are nine-coordinated thanks to the octadentate binding of the ligand and the presence of a coordinated water molecule. The stability constants of the complexes formed with the Ln3+ ions do not change significantly across the lanthanide series. A DFT investigation shows that this is the result of a subtle balance between the increased binding energies across the 4f period, which contribute to an increasing complex stability, and the parallel increase of the absolute values of the hydration free energies of the Ln3+ ions. In the case of the [Ln(octapa)(H2O)] complexes the interaction between the amine nitrogen atoms of the ligand and the Ln3+ ions is weakened along the lanthanide series, and therefore the increased electrostatic interaction does not overcome the increasing hydration energies. A detailed kinetic study of the dissociation of the [Gd(octapa)(H2O)] complex in the presence of Cu2+ shows that the metal-assisted pathway is the main responsible for complex dissociation at pH 7.4 and physiological [Cu2+] concentration (1 uM).
Tárgyszavak:Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
Magnetic Resonance Imaging
Complexes
Equilibrium
Kinetics
DFT calculation
Megjelenés:Inorganic Chemistry. - 54 : 5 (2015), p. 2345-2356. -
További szerzők:Végh Andrea (vegyész) Regueiro-Figueroa, Martín Tóth Éva (1967-) (koordinációs kémia) Platas-Iglesias, Carlos Tircsó Gyula (1977-) (vegyész, kémia tanár)
Pályázati támogatás:Centro de Supercomputación de Galicia (CESGA)
Egyéb
COST Actions CM1006 "European F-Element Network (EuFen)" and TD1004 "Theragnostics Imaging and Therapy: An Action to Develop Novel Nanosized Systems for Imaging-Guided Drug Delivery"
Egyéb
K-84291
OTKA
K-109029
OTKA
Hungarian-French bilateral Scientific and Technological Cooperation (project # TÉT_11-2-2012-0010 and PHC Balaton)
Egyéb
János Bolyai Research Scholarship of the Hungarian Academy of Sciences.
MTA
TÁMOP 4.2.2.A-11/1/KONV-2012-0043
TÁMOP
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10.

001-es BibID:BIBFORM038395
Első szerző:Kálmán Ferenc K. (vegyész)
Cím:Kinetic Inertness of the Mn Complexes Formed with AAZTA and Some Open-Chain EDTA Derivatives / Ferenc K. Kálmán, Gyula Tircsó
Dátum:2012
ISSN:0020-1669
Megjegyzések:The results of systematic equilibrium, kinetic, and relaxometric investigations carried out on the Mn2+ complexes of open-chain and AAZTA ligands indicate that the [Mn(CDTA)]2- complex has satisfactorily high kinetic inertness (t1/2 = 12 h at pH = 7.4), which, in turn, may allow its use as a contrast agent in the field of magnetic resonance imaging (as a replacement for Gd3+-based agents).
Tárgyszavak:Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
Magnetic Resonance Imaging
Contrast Agents
Manganese Complexes
Thermodynamic Stability
Kinetic Interness
Relaxivity
Megjelenés:Inorganic Chemistry. - 51 : 19 (2012), p. 10065-10067. -
További szerzők:Tircsó Gyula (1977-) (vegyész, kémia tanár)
Pályázati támogatás:PD-83253
OTKA
K-84291
OTKA
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11.

001-es BibID:BIBFORM006199
Első szerző:Kálmán Ferenc K. (vegyész)
Cím:Stability constants and dissociation rates of the EDTMP complexes of Samarium(III) and Yttrium(III) / Kalman, F. K., Kiraly, R., Brucher, E.
Dátum:2008
Megjegyzések:The stability constants of Sm(EDTMP) (log K-ML = 20.71) and Y(EDTMP) (log K-ML = 19.19) were determined by a competition reaction between the Ln(3+) ion (Ln(3+) = Sm3+ or Y3+) and Cu2+ for the EDTMP ligand by spectrophotometry at pH approximate to 10, in the presence of an excess amount of citrate (0.15 M NaCl, 25 degrees C). For determining the stability constants of Cu(EDTMP) (log K-ML = 19.36) and Ca(EDTMP) (log K-ML = 8.71) pH-potentiometry was used. In the pH range 4-9 the EDTMP complexes are present in the form of nonprotonated and mono-, di- and triprotonated species. The Ca2+ ion forms a dinuclear complex with Ln(EDTMP). In a simplified blood plasma model consisting of Sm3+, Ca2+ and Zn2+ metal ions, EDTMP, citrate, cysteine and histidine ligands, Sm3+ is practically present in the form of [Sm(HEDTMP)Ca](2-), whereas Zn2+ predominantly forms [Zn(HEDTMP)](5-) and [Zn(H2EDTMP)](4-) complexes. For studying the dissociation rates of the complexes, the kinetics of the metal exchange (transmetallation) reactions between the Ln(EDTMP) complexes and Cu2+-citrate were investigated in the pH range 7-9 by the stopped-flow method. The rates of the exchange reactions are independent of the Cu2+ concentration and increase with the H+ concentration. The rate constants, characterizing the proton-assisted dissociation of the Ln(EDTMP) complexes, are several orders of magnitude higher than those of the similar Ln(EDTA) complexes, because the protonation constants of Ln(EDTMP) are high and the protonated Ln(HEDTMP) and Ln(H2EDTMP) species are present in higher concentration. The half-times of dissociation of Sm(EDTMP) and Y(EDTMP) at pH = 7.4 and 25 degrees C are 4.9 and 7.5 s, respectively. These relatively short dissociation half-time values do not predict the deposition of Ln(3+) ions in bones in the form of intact Ln(EDTMP) complexes. It is more probable that sorption of the EDTMP ligand and Sm3+ or Y3+ ions occurs independently after the dissociation of complexes.
Tárgyszavak:Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:European Journal Of Inorganic Chemistry. - 30 (2008), p. 4719-4727. -
További szerzők:Király Róbert (1947-) (vegyész) Brücher Ernő (1935-) (vegyész)
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12.

001-es BibID:BIBFORM006198
Első szerző:Kálmán Ferenc K. (vegyész)
Cím:Synthesis, potentiometric, kinetic, and NMR studies of 1,4,7,10-tetraazacyclododecane-1,7-bis(acetic acid)-4,10-bis(methylenephosphonic acid) (DO2A2P) and its complexes with Ca(II), Cu(II), Zn(II) and lanthanide(III) ions / Kalman, F. K., Baranyai, Z., Toth, I., Banyai, I., Kiraly, R., Brucher, E., Aime, S., Sun, X., Sherry, A. D., Kovacs, Z.
Dátum:2008
ISSN:0020-1669
Megjegyzések:A cyclen-based ligand containing trans-acetate and trans-methylenephosphonate pendant groups, H(6)DO2A2P, was synthesized and its protonation constants (12.6, 11.43, 5.95, 6.15, 2.88, and 2.77) were determined by pH-potentiometry and H-1 NMR spectroscopy. The first two protonations were shown to occur at the two macrocyclic ring N-CH2-PO32- nitrogens while the third and fourth protonations occur at the two phosphonate groups. In parallel with protonation of the two -PO32- groups, the protons from the NH+-CH2-PO32- are transferred to the N-CH2-COO- nitrogens. The stability constants of the Ca2+, Cu2+, and Zn2+ (ML, MHL, MH2L, and M2L) complexes were determined by direct pH-potentiometry. Lanthanide(III) ions (Ln(3+)) form similar species, but the formation of complexes is slow; so, "out-of-cell" pH-potentiometry (La3+, Eu3+, Gd3+, Y3+) and competitive spectrophotometry with Cu(II) ion (Lu3+) were used to determine the stability constants. By comparing the log K-ML values with those of the corresponding DOTA (H(4)DOTA = 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) and DOTP (H8DOTP = 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetramethylenephosphonic acid) complexes, the order DOTA < DO2A2P < DOTP was found for all the metal ion complexes examined here with the exception of the Ca2+ complexes, for which the order is reversed. The relaxivity of Gd(DO2A2P) decreases between pH 2 and 7 but remains constant in the pH range of 7 < pH < 12 (r(1) = 3.6 mM(-1) s(-1)). The linewiths of the O-17 NMR signals of water in the absence and presence of Gd(DO2A2P) (at pH = 3.45 and 8.5) between 274 and 350 K are practically the same, characteristic of a q = 0 complex. Detailed kinetic studies of the Ce3+ and Gd3+ complexes with DO2A2P showed that complex formation is slow and involves a high stability diprotonated intermediate Ln(H(2)DO2A2P)*. Rearrangement of the diprotonated intermediate into the final complex is an OH- assisted process but, unlike formation of Ln(DOTA) complexes, rearrangement of Ln(H(2)DO2A2P)* also takes place spontaneously likely as a result of transfer of one of the protons from a ring nitrogen to a phosphonate group. The order of the OH- assisted formation rates of complexes is DOTA > DO2A2P > DOTP while the order of the proton assisted dissociation rates of the Gd3+ complexes is reversed, DOTP > DO2A2P > DOTA. H-1 and C-13 NMR spectra of Eu(DO2A2P) and Lu(DO2A2P) were assigned using two-dimensional correlation spectroscopy (2D COSY), heteronuclear multiple quantum coherence (HMQC), heteronuclear chemical shift correlation (HETCOR), and exchange spectroscopy (EXSY) NMR methods. Two sets of H-1 NMR signals were observed for Eu(DO2A2P) characteristic of the presence of two coordination isomers in solution, a twisted square antiprism (TSAP) and a square antiprism (SAP), in the ratio of 93% and 7%, respectively. Line shape analysis of the H-1 NMR spectra of Lu(DO2A2P) gave lower activation parameters compared to La(DOTP) for interconversion between coordination isomers. This indicates that the Ln(DO2A2P) complexes are less rigid probably due to the different size and spatial requireents of the carboxylate and phosphonate groups.
Tárgyszavak:Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:Inorganic Chemistry. - 47 : 9 (2008), p. 3851-3862. -
További szerzők:Baranyai Zsolt (1977-) (vegyész) Tóth Imre (1950-) (vegyész) Bányai István (1953-) (vegyész) Király Róbert Brücher Ernő (1935-) (vegyész) Aime, Silvio Sun, Xiankai Sherry, A. Dean Kovács Zoltán
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