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Uzal-Varela R, Rodríguez-Rodríguez A, Wang H, Esteban-Gómez D, Brandariz I, Gale EM, Caravan P, Platas-Iglesias C. Prediction of Gd(III) complex thermodynamic stability. Coord Chem Rev 2022. [DOI: 10.1016/j.ccr.2022.214606] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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2
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Farkas E, Fodor T, Kálmán FK, Tircsó G, Tóth I. Equilibrium and dissociation kinetics of the [Al(NOTA)] complex (NOTA = 1,4,7-triazacyclononane-1,4,7-triacetate). REACTION KINETICS MECHANISMS AND CATALYSIS 2015. [DOI: 10.1007/s11144-015-0892-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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Notni J, Šimeček J, Wester HJ. Phosphinic Acid Functionalized Polyazacycloalkane Chelators for Radiodiagnostics and Radiotherapeutics: Unique Characteristics and Applications. ChemMedChem 2014; 9:1107-15. [DOI: 10.1002/cmdc.201400055] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2014] [Indexed: 11/11/2022]
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4
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Morfin JF, Tóth É. Kinetics of Ga(NOTA) formation from weak Ga-citrate complexes. Inorg Chem 2011; 50:10371-8. [PMID: 21902283 DOI: 10.1021/ic201445e] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Gallium complexes are gaining increasing importance in biomedical imaging thanks to the practical advantages of the (68)Ga isotope in Positron Emission Tomography (PET) applications. (68)Ga has a short half-time (t(1/2) = 68 min); thus the (68)Ga complexes have to be prepared in a limited time frame. The acceleration of the formation reaction of gallium complexes with macrocyclic ligands for application in PET imaging represents a significant coordination chemistry challenge. Here we report a detailed kinetic study of the formation reaction of the highly stable Ga(NOTA) from the weak citrate complex (H(3)NOTA = 1,4,7-triazacyclononane-1,4,7- triacetic acid). The transmetalation has been studied using (71)Ga NMR over a large pH range (pH = 2.01-6.00). The formation of Ga(NOTA) is a two-step process. First, a monoprotonated intermediate containing coordinated citrate, GaHNOTA(citrate)*, forms in a rapid equilibrium step. The rate-determining step of the reaction is the deprotonation and slow rearrangement of the intermediate accompanied by the citrate release. The observed reaction rate shows an unusual pH dependency with a minimum at pH 5.17. In contrast to the typical formation reactions of poly(amino carboxylate) complexes, the Ga(NOTA) formation from the weak citrate complex becomes considerably faster with increasing proton concentration below pH 5.17. We explain this unexpected tendency by the role of protons in the decomposition of the GaHNOTA(citrate)* intermediate which proceeds via the protonation of the coordinated citrate ion and its subsequent decoordination to yield the final product Ga(NOTA). The stability constant of this intermediate, log K(GaHNOTA(citrate)*) = 15.6, is remarkably high compared to the corresponding values reported for the formation of macrocyclic lanthanide(III)-poly(amino carboxylates). These kinetic data do not only give mechanistic insight into the formation reaction of Ga(NOTA), but might also contribute to establish optimal experimental conditions for the rapid preparation of Ga(NOTA)-based radiopharmaceuticals for PET applications.
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Affiliation(s)
- Jean-François Morfin
- Centre de Biophysique Moléculaire, Centre National pour la Recherche Scientifique (CNRS), rue Charles, Sadron, 45071 Orléans, France
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Tircsó G, Benyó ET, Suh EH, Jurek P, Kiefer GE, Sherry AD, Kovács Z. (S)-5-(p-nitrobenzyl)-PCTA, a promising bifunctional ligand with advantageous metal ion complexation kinetics. Bioconjug Chem 2010; 20:565-75. [PMID: 19220012 DOI: 10.1021/bc8004914] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A bifunctional version of PCTA (3,6,9,15-tetraazabicyclo[9.3.1]pentadeca-1(15),11,13-triene-3,6,9,-triacetic acid) that exhibits fast complexation kinetics with the trivalent lanthanide(III) ions was synthesized in reasonable yields starting from N,N',N''-tristosyl-(S)-2-(p-nitrobenzyl)-diethylenetriamine. pH-potentiometric studies showed that the basicities of p-nitrobenzyl-PCTA and the parent ligand PCTA were similar. The stability of M(NO(2)-Bn-PCTA) (M = Mg(2+), Ca(2+), Cu(2+), Zn(2+)) complexes was similar to that of the corresponding PCTA complexes, while the stability of Ln(3+) complexes of the bifunctional ligand is somewhat lower than that of PCTA chelates. The rate of complex formation of Ln(NO(2)-Bn-PCTA) complexes was found to be quite similar to that of PCTA, a ligand known to exhibit the fastest formation rates among all lanthanide macrocyclic ligand complexes studied to date. The acid-catalyzed decomplexation kinetic studies of the selected Ln(NO(2)-Bn-PCTA) complexes showed that the kinetic inertness of the complexes was comparable to that of Ln(DOTA) chelates making the bifunctional ligand NO(2)-Bn-PCTA suitable for labeling biological vectors with radioisotopes for nuclear medicine applications.
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Affiliation(s)
- Gyula Tircsó
- Department of Chemistry, University of Texas at Dallas, Richardson, TX 75080, USA
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Rojas-Quijano FA, Benyó ET, Tircsó G, Kálmán FK, Baranyai Z, Aime S, Sherry AD, Kovács Z. Lanthanide(III) complexes of tris(amide) PCTA derivatives as potential bimodal magnetic resonance and optical imaging agents. Chemistry 2009; 15:13188-200. [PMID: 19882595 PMCID: PMC2907668 DOI: 10.1002/chem.200901095] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Lanthanide complexes of two tris(amide) derivatives of PCTA were synthesized and characterized. The relaxometric and luminescence properties of their lanthanide complexes were investigated as bimodal magnetic resonance (MR) and optical imaging agents. Luminescence studies show that one of the Tb(III) complexes dimerizes in solution at low millimolar concentrations, whereas the other may have a higher than expected coordination number in solution. The corresponding Gd(III) complexes display unusually high T(1) relaxivities and enhanced kinetic inertness compared to GdPCTA. These features suggest that these new chelates may be suitable for in vivo applications. The fast water-exchange rates observed for these complexes make them unsuitable as paramagnetic chemical exchange saturation transfer (PARACEST) agents.
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Affiliation(s)
- Federico A. Rojas-Quijano
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas 75390 (USA)
| | - Enikő Tircsóné Benyó
- Department of Inorganic and Analytical Chemistry, University of Debrecen, 4010, Debrecen, Egyetem tér 1. (Hungary)
| | - Gyula Tircsó
- Department of Inorganic and Analytical Chemistry, University of Debrecen, 4010, Debrecen, Egyetem tér 1. (Hungary)
| | - Ferenc K. Kálmán
- Department of Chemistry IFM & Molecular Imaging Center, Università degli Studi di Torino, Via P. Giuria 7, 10125 Torino (Italy)
| | - Zsolt Baranyai
- Department of Inorganic and Analytical Chemistry, University of Debrecen, 4010, Debrecen, Egyetem tér 1. (Hungary)
- Department of Chemistry IFM & Molecular Imaging Center, Università degli Studi di Torino, Via P. Giuria 7, 10125 Torino (Italy)
| | - Silvio Aime
- Department of Chemistry IFM & Molecular Imaging Center, Università degli Studi di Torino, Via P. Giuria 7, 10125 Torino (Italy)
| | - A. Dean Sherry
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas 75390 (USA)
| | - Zoltán Kovács
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas 75390 (USA)
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Notni J, Pohle K, Peters JA, Görls H, Platas-Iglesias C. Structural Study of Ga(III), In(III), and Fe(III) Complexes of Triaza-Macrocycle Based Ligands with N3S3 Donor Set. Inorg Chem 2009; 48:3257-67. [DOI: 10.1021/ic900119a] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Johannes Notni
- Department of Nuclear Medicine, Technische Universität München, Ismaninger Strasse 22, D-81675 München, Germany, Laboratory of Biocatalysis and Organic Chemistry, Department of Biotechnology, Delft University of Technology, Julianalaan 136, 2628 BL Delft, The Netherlands, Institut für Anorganische and Analytische Chemie, Friedrich-Schiller-Universität Jena, Lessingstrasse 8, D-07743 Jena, Germany, and Departamento de Química Fundamental, Campus da Zapateira, Universidade da Coruña, Alejandro de la Sota 1
| | - Karolin Pohle
- Department of Nuclear Medicine, Technische Universität München, Ismaninger Strasse 22, D-81675 München, Germany, Laboratory of Biocatalysis and Organic Chemistry, Department of Biotechnology, Delft University of Technology, Julianalaan 136, 2628 BL Delft, The Netherlands, Institut für Anorganische and Analytische Chemie, Friedrich-Schiller-Universität Jena, Lessingstrasse 8, D-07743 Jena, Germany, and Departamento de Química Fundamental, Campus da Zapateira, Universidade da Coruña, Alejandro de la Sota 1
| | - Joop A. Peters
- Department of Nuclear Medicine, Technische Universität München, Ismaninger Strasse 22, D-81675 München, Germany, Laboratory of Biocatalysis and Organic Chemistry, Department of Biotechnology, Delft University of Technology, Julianalaan 136, 2628 BL Delft, The Netherlands, Institut für Anorganische and Analytische Chemie, Friedrich-Schiller-Universität Jena, Lessingstrasse 8, D-07743 Jena, Germany, and Departamento de Química Fundamental, Campus da Zapateira, Universidade da Coruña, Alejandro de la Sota 1
| | - Helmar Görls
- Department of Nuclear Medicine, Technische Universität München, Ismaninger Strasse 22, D-81675 München, Germany, Laboratory of Biocatalysis and Organic Chemistry, Department of Biotechnology, Delft University of Technology, Julianalaan 136, 2628 BL Delft, The Netherlands, Institut für Anorganische and Analytische Chemie, Friedrich-Schiller-Universität Jena, Lessingstrasse 8, D-07743 Jena, Germany, and Departamento de Química Fundamental, Campus da Zapateira, Universidade da Coruña, Alejandro de la Sota 1
| | - Carlos Platas-Iglesias
- Department of Nuclear Medicine, Technische Universität München, Ismaninger Strasse 22, D-81675 München, Germany, Laboratory of Biocatalysis and Organic Chemistry, Department of Biotechnology, Delft University of Technology, Julianalaan 136, 2628 BL Delft, The Netherlands, Institut für Anorganische and Analytische Chemie, Friedrich-Schiller-Universität Jena, Lessingstrasse 8, D-07743 Jena, Germany, and Departamento de Química Fundamental, Campus da Zapateira, Universidade da Coruña, Alejandro de la Sota 1
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Guo H, Shao XJ, Li J, Wang C, Yang GM, Duan MY, Zhang FX. Synthesis, structures and properties of cobalt(III) and iron(III) complexes with a new triazamacrocycle, 1,4-diacetate-1,4,7-triazacyclodecane. J COORD CHEM 2008. [DOI: 10.1080/00958970802090148] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Affiliation(s)
- Hui Guo
- a Shaanxi Key Laboratory of Physico-Inorganic Chemistry, Department of Chemistry , Northwest University , Xi’an Shaanxi 710069, China
| | | | - Jun Li
- a Shaanxi Key Laboratory of Physico-Inorganic Chemistry, Department of Chemistry , Northwest University , Xi’an Shaanxi 710069, China
| | - Chen Wang
- a Shaanxi Key Laboratory of Physico-Inorganic Chemistry, Department of Chemistry , Northwest University , Xi’an Shaanxi 710069, China
| | - Gao-Mai Yang
- a Shaanxi Key Laboratory of Physico-Inorganic Chemistry, Department of Chemistry , Northwest University , Xi’an Shaanxi 710069, China
| | - Min-Yue Duan
- a Shaanxi Key Laboratory of Physico-Inorganic Chemistry, Department of Chemistry , Northwest University , Xi’an Shaanxi 710069, China
| | - Feng-Xing Zhang
- a Shaanxi Key Laboratory of Physico-Inorganic Chemistry, Department of Chemistry , Northwest University , Xi’an Shaanxi 710069, China
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Saito S, Suzuki R, Danzaka N, Hikichi A, Yoshimoto K, Maeda M, Aoyama M. Direct fluorometric detection of paramagnetic and heavy metal ions at sub-amol level using an aromatic polyaminocarboxylate by CZE: Combination of pre- and on-capillary complexation technique. Electrophoresis 2007; 28:2448-57. [PMID: 17577884 DOI: 10.1002/elps.200600516] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The low sensitivity of simple CZE for detecting metal ions is a long-standing problem even when an LIF detection system is employed. We have successfully achieved an ultrasensitive CE-LIF using a simple CZE mode (typical detection limit: 10(-11)-10(-10) mol/dm(3)). Both the design of a newly synthesized ligand and the combination of a precapillary derivatizing technique with an on-capillary ternary complexing technique have enabled us to achieve this extremely low LOD and high resolution of large metal complexes. The direct fluorescent detection of the paramagnetic metal ions was achieved for the first time despite their intrinsic fluorescent quenching nature. The fluorescent ligand (L) consists of a polyaminocarboxylate chelating moiety, a strongly emissive fluorescein moiety and a spacer connecting the two portions. The migration behavior of various metal-L complexes was investigated. The resolution among the complexes was improved by the introduction of a ternary complex equilibrium of the kinetically stable mother complexes with OH(-) ion. The analytical potential of our simple system was examined, and it was proved that the system was one of the most sensitive methods without the need for any preconcentration process.
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Affiliation(s)
- Shingo Saito
- Graduate School of Science, and Engineering, Saitama University, Saitama City, Japan.
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Tircsó G, Kovács Z, Sherry AD. Equilibrium and formation/dissociation kinetics of some Ln(III)PCTA complexes. Inorg Chem 2007; 45:9269-80. [PMID: 17083226 PMCID: PMC2597434 DOI: 10.1021/ic0608750] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The protonation constants () of 3,6,9,15-tetraazabicyclo[9.3.1]pentadeca-1(15),11,13-triene-3,6,9-triacetic acid (PCTA) and stability constants of complexes formed between this pyridine-containing macrocycle and several different metal ions have been determined in 1.0 M KCl at 25 degrees C and compared to previous literature values. The first protonation constant was found to be 0.5-0.6 log units higher than the value reported previously, and a total of five protonation steps were detected (log = 11.36, 7.35, 3.83, 2.12, and 1.29). The stability constants of complexes formed between PCTA and Mg2+, Ca2+, Cu2+, and Zn2+ were also somewhat higher than those previously reported, but this difference could be largely attributed to the higher first protonation constant of the ligand. Stability constants of complexes formed between PCTA and the Ln3+ series of ions and Y3+ were determined by using an "out-of-cell" potentiometric method. These values ranged from log K = 18.15 for Ce(PCTA) to log K = 20.63 for Yb(PCTA), increasing along the Ln series in proportion to decreasing Ln3+ cation size. The rates of complex formation for Ce(PCTA), Eu(PCTA), Y(PCTA), and Yb(PCTA) were followed by conventional UV-vis spectroscopy in the pH range 3.5-4.4. First-order rate constants (saturation kinetics) obtained for different ligand-to-metal ion ratios were consistent with the rapid formation of a diprotonated intermediate, Ln(H(2)PCTA)(2+). The stabilities of the intermediates as determined from the kinetic data were 2.81, 3.12, 2.97, and 2.69 log K units for Ce(H(2)PCTA), Eu(H(2)PCTA), Y(H(2)PCTA), and Yb(H(2)PCTA), respectively. Rearrangement of these intermediates to the fully chelated complexes was the rate-determining step, and the rate constant (k(r)) for this process was found to be inversely proportional to the proton concentration. The formation rates (k(OH)) increased with a decrease in the lanthanide ion size [9.68 x 10(7), 1.74 x 10(8), 1.13 x 10(8), and 1.11 x 10(9) M(-1) s(-1) for Ce(PCTA), Eu(PCTA), Y(PCTA), and Yb(PCTA), respectively]. These data indicate that the Ln(PCTA) complexes exhibit the fastest formation rates among all lanthanide macrocyclic ligand complexes studied to date. The acid-catalyzed dissociation rates (k1) varied with the cation from 9.61 x 10(-4), 5.08 x 10(-4), 1.07 x 10(-3), and 2.80 x 10(-4) M(-1) s(-1) for Ce(PCTA), Eu(PCTA), Y(PCTA), and Yb(PCTA), respectively.
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Affiliation(s)
- Gyula Tircsó
- Department of Chemistry, University of Texas at Dallas, P.O. Box 830660, Richardson, Texas, 75080
| | - Zoltán Kovács
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas, 75390
- Macrocyclics, 2110 Research Row, Suite 425, Dallas, Texas, 75235
| | - A. Dean Sherry
- Department of Chemistry, University of Texas at Dallas, P.O. Box 830660, Richardson, Texas, 75080
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas, 75390
- Department of Radiology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas, 75390
- Author to whom correspondence should be addressed. Phone: 214-645-2730, E-mail: or
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11
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Balogh E, He Z, Hsieh W, Liu S, Tóth E. Dinuclear complexes formed with the triazacyclononane derivative ENOTA4-: high-pressure 17O NMR evidence of an associative water exchange on [MnII2(ENOTA)(H2O)2]. Inorg Chem 2007; 46:238-50. [PMID: 17198433 DOI: 10.1021/ic0616582] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Mn2+ has five unpaired d-electrons, a long electronic relaxation time, and labile water exchange, all of which make it an attractive candidate for contrast agent application in medical magnetic resonance imaging. In the quest for stable and nonlabile Mn2+ complexes, we explored a novel dimeric triazacyclononane-based ligand bearing carboxylate functional groups, H4ENOTA. The protonation constants of the ligand and the stability constants of the complexes formed with some endogenously important metals (Ca2+, Cu2+, Zn2+), as well as with Mn2+ and Ce3+, have been assessed by NMR methods, potentiometry, and UV-vis spectrophotometry. Overall, the thermodynamic stability of the complexes is lower as compared to that of the corresponding NOTA analogues (H3NOTA, 1,4,7-triaazacyclononane-1,4,7-triacetic acid). The crystal structure of Mn2(ENOTA)(H2O) x 5H2O contains two six-coordinated Mn2+, in addition to the three amine nitrogens and the two oxygens from the pendent monodentate carboxylate groups, and one water (Mn2) or one bridging carboxylate oxygen (Mn1) completes the coordination sphere of the metal ion. In an aqueous solution, this bridging carboxylate is replaced by a water molecule, as evidenced by the 17O chemical shifts and proton relaxivity data that point to monohydration for both metal ions in the dinuclear complex. A variable-temperature and -pressure 17O NMR study has been performed on [Mn2(ENOTA)(H2O)2] to assess the rate and, for the first time on a Mn2+ chelate, also the mechanism of the water exchange. The inner sphere water is slightly more labile in [Mn2(ENOTA)(H2O)2] (k298ex = 5.5 x 107 s-1) than in the aqua ion (2.1 x 107 s-1, Merbach, A. E.; et al. Inorg. Chem. 1980, 19, 3696). The water exchange proceeds via an almost limiting associative mechanism, as evidenced by the large negative activation volume (deltaV = -10.7 cm3 mol-1). The proton relaxivities measured on [Mn2(ENOTA)(H2O)2] show a low-field dispersion at approximately 0.1 MHz arising from a contact interaction between the MnII electron spin and the water proton nuclear spins.
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Affiliation(s)
- Edina Balogh
- Laboratoire de chimie inorganique et bioinorganique, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
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Choi KY, Kang SH, Kim DW, Chung YS, Kim CS, Oh JJ, Hong CP, Lee YI. Formation kinetics of triaza-crown-alkanoic acid complexes of first-row transition metal(II) ions. Supramol Chem 2006. [DOI: 10.1080/10610279608054992] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Ki-Young Choi
- a Department of Chemistry , Mokwon University , Taejeon , 301-729 , Korea
| | | | | | | | - Chang Suk Kim
- c Chemical Education , Chungbuk National University , Cheongju , 360-763 , Korea
| | - Je Jik Oh
- d Department of Chemical Education , Kongju National University , Kongju , 314-701 , Korea
| | - Choon Pyo Hong
- d Department of Chemical Education , Kongju National University , Kongju , 314-701 , Korea
| | - Yong Ill Lee
- e Department of Chemistry , Keonyang University , Nonsan , 320-800 , Korea
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13
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Picraux LB, Smeigh AL, Guo D, McCusker JK. Intramolecular Energy Transfer Involving Heisenberg Spin-Coupled Dinuclear Iron−Oxo Complexes. Inorg Chem 2005; 44:7846-59. [PMID: 16241134 DOI: 10.1021/ic0506761] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The synthesis, structure, and physical properties of a series of oxo-bridged dinuclear Fe(III) complexes containing pendant naphthalene groups are described. The compounds [Fe(2)O(O(2)CCH(2)-C(10)H(7))(tren)(2)](BPh(4))(NO(3))(2) (8), [Fe(2)O(O(2)CCH(2)-C(10)H(7))(TPA)(2)](ClO(4))(3) (9), Fe(2)O(O(2)CCH(2)-C(10)H(7))(2)(Tp)(2) (10), and Fe(2)O((O(2)CCH(2)CH(2))(2)-C(10)H(6))(Tp)(2) (11) (where tren is tris(2-aminoethyl)amine, TPA is tris(2-pyridyl)amine, and Tp is hydrotrispyrazolylborate) have been characterized in terms of their structural, spectroscopic, magnetic, and photophysical properties. All four complexes exhibit moderately strong intramolecular antiferromagnetic exchange between the high-spin ferric ions (ca. -130 cm(-)(1) for H = -2JS(1).S(2)). Room-temperature steady-state emission spectra for compounds 8-11 in deoxygenated CH(3)CN solution reveal spectral profiles similar to methyl-2-naphthyl acetate and [Zn(2)(OH)(O(2)CCH(2)-C(10)H(7))(2)(TACN-Me(3))(2)](ClO(4)) (13, where TACN-Me(3) is N,N,N-1,4,7-trimethyltriazacyclononane) but are significantly weaker in intensity relative to these latter two compounds. Time-resolved emission data for the iron complexes following excitation at 280 nm can be fit to simple exponential decay models with tau(obs)(S)()1 = 36 +/- 2, 32 +/- 4, 30 +/- 5, and 39 +/- 3 ns for compounds 8-11, respectively. The decays are assigned to the S(1) --> S(0) fluorescence of naphthalene; all of the lifetimes are less than that of the zinc model complex (tau(obs)(S)()1 = 45 +/- 2 ns), indicating quenching of the S(1) state by the iron-oxo core. Nanosecond time-resolved absorption data on [Zn(2)(OH)(O(2)CCH(2)-C(10)H(7))(2)(TACN-Me(3))(2)](ClO(4)) reveal a feature at lambda(max) = 420 nm that can be assigned as the T(1) --> T(n) absorption of the naphthalene triplet; the rise time of 50 +/- 10 ns corresponds to an intersystem crossing rate of 2 x 10(7) s(-1). A similar feature (though much weaker in intensity) is also observed for compound 8. The order-of-magnitude reduction in the T(1) lifetime of the pendant naphthalene for all of the iron-oxo complexes (tau(obs)(T)1 = 5 +/- 2 micros vs 90 +/- 10 micros for [Zn(2)(OH)(O(2)CCH(2)-C(10)H(7))(2)(TACN-Me(3))(2)](ClO(4))) indicates quenching of the naphthalene triplet with an efficiency of >90%. Neither the naphthalene radical cation nor the reduced Fe(II)Fe(III) species were observed by transient absorption spectroscopy, implying that energy transfer is the most likely origin for the quenching of both the S(1) and T(1) states. Spectral overlap considerations strongly support a Förster (i.e., dipolar) mechanism for energy transfer from the S(1) state, whereas the lack of phosphorescence from either the free naphthyl ester or the Zn model complex suggests Dexter transfer to the diiron(III) core as the principal mechanism of triplet quenching. The notion of whether spin exchange within the diiron(III) core is in part responsible for the unusual ability of the iron-oxo core to engage in energy transfer from both the singlet and triplet manifolds of naphthalene is discussed.
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Affiliation(s)
- Laura B Picraux
- Department of Chemistry, Michigan State University, East Lansing, 48824, USA
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14
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Weldon BT, Wheeler DE, Kirby JP, McCusker JK. Bimolecular electron and energy transfer reactivity of exchange-coupled dinuclear iron(III) complexes. Inorg Chem 2001; 40:6802-12. [PMID: 11735494 DOI: 10.1021/ic010659l] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Bimolecular quenching between photosensitizers and exchange-coupled transition metal complexes has been studied in an effort to experimentally establish a link between Heisenberg spin exchange and chemical reactivity. The acceptors are members of the oxo/hydroxo-biscarboxylato class of dinuclear Fe(III) compounds, where protonation of the oxo bridge provides a means for modulating the magnitude of spin exchange within the cluster. Photoexcitation of solutions containing Ru(II) polypyridyl sensitizers and the Fe(III) complexes results in quenching of emission from the (3)MLCT excited state of the Ru(II) chromophores; nanosecond time-resolved absorption measurements demonstrate that quenching occurs, in part, by electron transfer. Decoupling electron transfer driving force (DeltaG(0)(ET)) from changes in the magnitude of spin exchange was achieved by varying the bridging carboxylate to afford a series of complexes of the form [Fe(2)O(H)(O(2)CR)(2)(Tp)(2)](n)(+) (n = 0, 1, 2). Electrochemical measurements reveal a greater than 500 mV shift in cluster reduction potential across the series (i.e., R = CH(3) to CF(3)), whereas variable-temperature magnetic susceptibility measurements demonstrate a corresponding invariance in spin exchange between the metal centers (J(oxo) = -119 +/- 4 cm(-1) and J(hydroxo) = -18 +/- 2 cm(-1) for H = -2JS(1).S(2)). Structural analyses suggest that reorganization energies (lambda) associated with electron transfer should be identical for all molecules within a given series (i.e., oxo or hydroxo bridged); likewise Deltalambda between the series is expected to be small. A comparison of quenching rates for the two extended series firmly establishes that neither reorganization energy nor electron transfer driving force considerations can account for differences in reactivity between oxo-bridged (large spin exchange) and hydroxo-bridged (small spin exchange) quenchers. Upon consideration of energy transfer contributions, it is determined that reactivity differences between the oxo- and hydroxo-bridged quenchers must lie in the relative rates of Dexter energy transfer and/or electron transfer, with the origin of the latter linked to something other than DeltaG(0)(ET) or lambda. Finally, the extent to which spin exchange within the dinuclear Fe(III) quenchers can be identified as the key variable influencing these reactivity patterns is discussed.
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Affiliation(s)
- B T Weldon
- Department of Chemistry, University of California at Berkeley, Berkeley, California 94720, USA
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Chong HS, Garmestani K, Bryant LH, Brechbiel MW. Synthesis of DTPA analogues derived from piperidine and azepane: potential contrast enhancement agents for magnetic resonance imaging. J Org Chem 2001; 66:7745-50. [PMID: 11701031 DOI: 10.1021/jo0106344] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Two DTPA derivatives (PIP-DTPA and AZEP-DTPA) as potential contrast enhancement agents in MRI are synthesized. The T1 and T2 relaxivities of their corresponding Gd(III) complexes are reported. At clinically relevant field strengths, the relaxivities of the complexes are comparable to that of the contrast agent, Gd(DTPA) which is in clinical use. The serum stability of the (153)Gd-labeled complexes is assessed by measuring the release of (153)Gd from the ligands. The radiolabeled Gd chelates are found to be kinetically stable in human serum for up to at least 14 days without any measurable loss of radioactivity.
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Affiliation(s)
- H S Chong
- Chemistry Section, National Cancer Institute, NIH, Bethesda, Maryland, USA
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16
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O'Coinceanainn M, Hynes MJ. The kinetics and mechanisms of the reactions of aluminium(III) with gallic acid, gallic acid methyl ester and adrenaline. J Inorg Biochem 2001; 84:1-12. [PMID: 11330467 DOI: 10.1016/s0162-0134(00)00232-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
The kinetics and mechanisms of the reactions of gallic acid, gallic acid methyl ester and adrenaline with aluminium(III) have been investigated in aqueous solution at 25 degrees C and an ionic strength of 0.5 M. A mechanism has been proposed which accounts satisfactorily for the kinetic data. This is consistent with a mechanism in which complex formation takes place almost exclusively by reaction of [Al(H2O)5OH]2+ with the ligands. [Al(H2O)5OH]2+ reacts with gallic acid, gallic acid methyl ester and adrenaline with rate constants of 1145, 1330 and 316 M(-1) s(-1) respectively. These data together with the equilibrium data enable the rate constants for reaction of [Al(H2O)6]3+ with both gallic acid and gallic acid methyl ester to be calculated. In view of the dissociative nature of water exchange on [Al(H2O)6]3+ and [Al(H2O)5(OH)]2+ the complex formation rate constants are discussed in terms of the Eigen-Wilkins-Tamm mechanism. The overall mechanisms have been validated using global analysis. The results are compared with previously published data on the complex formation reactions of aluminium(III). In addition, the rate constants and mechanisms for replacement of maltol by gallic acid methyl ester and diethylenetriaminepentaacetic acid (dtpa) have been investigated.
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Bianchi A, Calabi L, Corana F, Fontana S, Losi P, Maiocchi A, Paleari L, Valtancoli B. Thermodynamic and structural properties of Gd(III) complexes with polyamino-polycarboxylic ligands: basic compounds for the development of MRI contrast agents. Coord Chem Rev 2000. [DOI: 10.1016/s0010-8545(99)00237-4] [Citation(s) in RCA: 141] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Singh B, Singh VL. Mono and trinuclear lanthanide complexes of 13-membered tetraaza macrocycle: Synthesis and characterization. J CHEM SCI 1999. [DOI: 10.1007/bf02869119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Geraldes CF, Marques MPM, Sherry AD. NMR conformational study of diamagnetic complexes of some triazatriacetate macrocycles. Inorganica Chim Acta 1998. [DOI: 10.1016/s0020-1693(97)06004-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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20
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Mizoguchi TJ, Lippard SJ. (&mgr;-Oxo)bis(&mgr;-carboxylato)bis(2,2'-bipyridyl)bis(X)diiron(III) Complexes, X = NCS(-), NCSe(-), and N(3)(-): Synthetic Models of Pseudohalide Derivatives of Carboxylate-Bridged Diiron Proteins. Inorg Chem 1997; 36:4526-4533. [PMID: 11670117 DOI: 10.1021/ic970397g] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The neutral (&mgr;-oxo)bis(&mgr;-carboxylato)diiron(III) complexes [Fe(2)O(&mgr;-XDK)(bpy)(2)(NCS)(2)] (1), [Fe(2)O(&mgr;-XDK)(bpy)(2)((15)NCS)(2)] (1a), [Fe(2)O(&mgr;-XDK)(bpy)(2)(NCSe)(2)] (2), [Fe(2)O(&mgr;-XDK)(bpy)(2)(N(3))(2)] (3), and [Fe(2)O(&mgr;-XDK)(bpy)(2)((15)NNN)(2)] (3a), where XDK is the doubly deprotonated form of m-xylylenediamine bis(Kemp's triacid imide) and bpy is 2,2'-bipyridyl, have been synthesized. The octahedrally coordinated iron centers are triply bridged by an oxo group and the two carboxylate groups of XDK. In the X-ray crystal structures of 1 and 2, the diiron centers have C(2) symmetry, whereas in 3 the coordinated azide ligands are also anti with respect to the Fe-O-Fe plane but in different rotational conformations with respect to the Fe-N(3) bond. The optical spectra of these highly colored compounds are characterized by broad ligand-field bands centered approximately 650 nm and a more intense combination of ligand-field and ligand-to-metal charge-transfer bands between 350 and 500 nm. Compounds 1-3 exhibit intense IR bands ( approximately 2050 cm(-)(1)) which are characteristic of terminally bound isothiocyanate, isoselenocyanate, and azide ligands, respectively. These bands shift to lower energies upon substitution with (15)NCS(-) in 1a (Deltanu = 24 cm(-)(1)) and (15)NNN(-) in 3a (Deltanu = 8 cm(-)(1)), and the failure of the latter to reveal two resolved features indicates a need for caution in interpreting analogous data from isotopically substituted protein adducts. Resonance Raman experiments on 1-3 revealed bands ( approximately 520 cm(-)(1)) attributable to the symmetric FeOFe stretching frequency. The Mössbauer spectra of 1-3 at 77 K display symmetric quadrupole doublets with isomer shifts ( approximately 0.5 mm s(-)(1)) and quadrupole splittings ( approximately 1.7 mm s(-)(1)) typical of (&mgr;-oxo)diiron(III) compounds. Crystal data: 1.2C(6)H(6), monoclinic, P2(1)/n, a = 19.6692(2) Å, b = 14.3069(1) Å, c = 22.6502(3) Å, beta = 96.922(1) degrees, V = 6327.4(1) Å(3), Z = 4, T = -90 degrees C; 2.2C(6)H(6), monoclinic, C2/c, a = 22.6834(3) Å, b = 14.4315(2) Å, c = 19.7013(4) Å, beta = 97.837(1) degrees, V = 6389.1(2) Å(3), Z = 4, T = -85 degrees C; 3.CH(2)Cl(2).C(6)H(3)(CH(3))(3), triclinic, P&onemacr;, a = 12.1645(2) Å, b = 14.9196(3) Å, c = 18.0690(3) Å, alpha = 79.688(1) degrees, beta = 78.611(1) degrees, gamma = 83.453(1) degrees, V = 3152.3(1) Å(3), Z = 2, T = -85 degrees C.
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Affiliation(s)
- Tadashi J. Mizoguchi
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
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Reichert DE, Hancock RD, Welch MJ. Molecular Mechanics Investigation of Gadolinium(III) Complexes. Inorg Chem 1996; 35:7013-7020. [PMID: 11666881 DOI: 10.1021/ic960495m] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Parameters for the commercially available modeling package SYBYL have been developed for Gd(3+) complexes allowing these to be studied with molecular mechanics. With these parameters and a technique termed the "coordination scan", the coordination numbers of Gd(III) based complexes can be predicted, and thus the hydration number q determined. Knowledge of q has allowed the prediction of molar relaxivities based on correlations to literature values. In addition, the calculated value DeltaE(coord) was found to successfully predict the thermodynamic stability constants for polyamino carboxylate ligands with Gd(3+). Gadolinium complexes are commonly utilized as MRI contrast agents, and thus the techniques utilized in this work should aid in the development of new contrast agents.
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Affiliation(s)
- David E. Reichert
- Mallinckrodt Institute of Radiology, Washington University School of Medicine, 510 S. Kingshighway, St. Louis, Missouri 63110
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Miao L, Bell D, Rothremel GL, Bryant LH, Fitzsimmons PM, Jackels SC. Design and synthesis of an “ultrachelating” ligand based on an 18-membered ring hexaaza macrocycle. Supramol Chem 1996. [DOI: 10.1080/10610279608032556] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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23
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Kinetics of formation and dissociation of triaza-crown-alkanoic acid complexes of cerium(III) and europium(III). Polyhedron 1995. [DOI: 10.1016/0277-5387(94)00404-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Reddy KB, Cao S, Orr EC, Fábián I, van Eldik R, Eyring EM. Mechanistic information on ligand-substitution reactions of gadolinium(III) in aqueous solution from high-pressure stopped-flow experiments. ACTA ACUST UNITED AC 1994. [DOI: 10.1039/dt9940002497] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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25
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Choi KY, Sung Kim K, Chang Kim J. Dissociation kinetics of cerium(III) and gadolinium(III) complexes of macrocyclic DTPA bis(amide) ligands. Polyhedron 1994. [DOI: 10.1016/s0277-5387(00)84733-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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26
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Brunner U, Neuburger M, Zehnder M, Kaden TA. Cu2+complexes of tetraazacyclododecanes functionalized with benzyl side chains carrying carboxylic or phenolic groups. Supramol Chem 1993. [DOI: 10.1080/10610279308038304] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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28
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Syntheses of new 15-membered and 16-membered macrocyclic ligands with three pendant acetato groups and the structures of the gadolinium(III) complexes. Inorganica Chim Acta 1993. [DOI: 10.1016/s0020-1693(00)84976-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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29
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Inoue MB, Inoue M, Fernando Q. Capped trigonal prism coordination geometry in a cobalt(II) chelate with a 24-membered macrocyclic ligand in which two ethylenediaminetetraacetato and two ethylenediamine groups are linked by amide bonds. Inorganica Chim Acta 1993. [DOI: 10.1016/s0020-1693(00)84977-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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30
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Geraldes CF, Brown RD, Brucher E, Koenig SH, Sherry AD, Spiller M. Nuclear magnetic relaxation dispersion profiles of aqueous solutions of a series of Gd(NOTA) analogs. Magn Reson Med 1992; 27:284-95. [PMID: 1334203 DOI: 10.1002/mrm.1910270208] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Nuclear magnetic relaxation dispersion (NMRD) profiles and ESR linewidths have been measured for a series of neutral Gd(3+)-triazamacrocyclic complexes and compared with previous data for the simplest member of the macrocyclic triaza series, Gd(NOTA), and for the widely studied linear triaza complex, Gd(DTPA)2-. Water proton relaxivities and their temperature dependence were found to vary widely with the size of the triaza macrocycle and the identity of the side-chain chelating groups. The number of rapidly exchanging water molecules directly coordinated to the Gd3+ ion (q) was found to vary from 2 to 4 for eight of the ten complexes examined and a linear relationship between the 50-MHz relaxivity value and integral values of q is presented for this series of complexes. tau s values derived from ESR linewidths for some of the complexes are in reasonable agreement with those derived from their NMRD profiles; however, those complexes which either tended to form aggregates in solution or gave evidence for multiple averaged solution structures showed broad, near Lorentzian linewidths which were clearly not dominated by the electron spin relaxation time (tau s).
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Affiliation(s)
- C F Geraldes
- Department of Chemistry, University of Texas at Dallas, Richardson 75083-0688
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Potentiometric, calorimetric and nuclear magnetic resonance studies of the protonation in aqueous solution of 1-thia-4,7-diazacyclononane-N,N′-diacetic acid, 1-thia-4,8-diazacyclodecane-N,N′-diacetic acid and related open-chain diaminocarboxylic acids. Polyhedron 1992. [DOI: 10.1016/s0277-5387(00)83359-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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32
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Brechbiel MW, Gansow OA. Synthesis of C-functionalized trans-cyclohexyldiethylenetriaminepenta-acetic acids for labelling of monoclonal antibodies with the bismuth-212 α-particle emitter. ACTA ACUST UNITED AC 1992. [DOI: 10.1039/p19920001173] [Citation(s) in RCA: 92] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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