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Kerr WR, Squire MA, Fitchett CM. Synthesis and structural isomerism of sterically hindered isobornyl amide tethered N-heterocyclic carbene complexes. J Organomet Chem 2022. [DOI: 10.1016/j.jorganchem.2022.122519] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Pradhan RN, Irrera P, Romdhane F, Panda SK, Longo DL, Torres J, Kremer C, Assaiya A, Kumar J, Singh AK. Di-Pyridine-Containing Macrocyclic Triamide Fe(II) and Ni(II) Complexes as ParaCEST Agents. Inorg Chem 2022; 61:16650-16663. [PMID: 36205705 DOI: 10.1021/acs.inorgchem.2c02242] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Fe(II) and Ni(II) paraCEST contrast agents containing the di-pyridine macrocyclic ligand 2,2',2″-(3,7,10-triaza-1,5(2,6)-dipyridinacycloundecaphane-3,7,10-triyl)triacetamide (DETA) are reported here. Both [Fe(DETA)]2+ and [Ni(DETA)]2+ complexes were structurally characterized. Crystallographic data revealed the seven-coordinated distorted pentagonal bipyramidal geometry of the [Fe(DETA)]·(BF4)2·MeCN complex with five coordinated nitrogen atoms from the macrocyclic ring and two coordinated oxygen atoms from two amide pendant arms. The [Ni(DETA)]·Cl2·2H2O complex was six-coordinated in nature with a distorted octahedral geometry. Four coordinated nitrogen atoms were from the macrocyclic ring, and two coordinated oxygen atoms were from two amide pendant arms. [Fe(DETA)]2+ exhibited well-resolved sharp proton resonances, whereas very broad proton resonances were observed in the case of [Ni(DETA)]2+ due to the long electronic relaxation times. The CEST peaks for the [Fe(DETA)]2+ complex showed one highly downfield-shifted and intense peak at 84 ppm with another shifted but less intense peak at 28 ppm with good CEST contrast efficiency at body temperature, whereas [Ni(DETA)]2+ showed only one highly shifted intense peak at 78 ppm from the bulk water protons. Potentiometric titrations were performed to determine the protonation constants of the ligand and the thermodynamic stability constant of the [M(DETA)]2+ (M = Fe, Co, Ni, Cu, Zn) species at 25.0 °C and I = 0.15 mol·L-1 NaClO4. Metal exchange studies confirmed the stability of the complexes in acidic medium in the presence of physiologically relevant anions and an equimolar concentration of Zn(II) ions.
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Affiliation(s)
- Rabindra N Pradhan
- School of Basic Sciences, Indian Institute of Technology Bhubaneswar, Bhubaneswar752050, India
| | - Pietro Irrera
- University of Campania "Luigi Vanvitelli", Caserta81100, Italy
| | - Feriel Romdhane
- Institute of Biostructures and Bioimaging (IBB), National Research Council of Italy (CNR), Torino10126, Italy
| | - Suvam Kumar Panda
- School of Basic Sciences, Indian Institute of Technology Bhubaneswar, Bhubaneswar752050, India
| | - Dario Livio Longo
- Institute of Biostructures and Bioimaging (IBB), National Research Council of Italy (CNR), Torino10126, Italy
| | - Julia Torres
- Área Química Inorgánica, Departamento Estrella Campos, Facultad de Química, Universidad de la República, Montevideo11800, Uruguay
| | - Carlos Kremer
- Área Química Inorgánica, Departamento Estrella Campos, Facultad de Química, Universidad de la República, Montevideo11800, Uruguay
| | - Anshul Assaiya
- National Centre for Cell Science, NCCS Complex, Pune University Campus, Ganeshkhind, Pune411 007, India
| | - Janesh Kumar
- National Centre for Cell Science, NCCS Complex, Pune University Campus, Ganeshkhind, Pune411 007, India
| | - Akhilesh K Singh
- School of Basic Sciences, Indian Institute of Technology Bhubaneswar, Bhubaneswar752050, India
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Majumder A, Dutta N, Haldar S, Das A, Carrella L, Bera M. Aromatic dicarboxylate incorporated new di- and tetranuclear cobalt(II) complexes: Synthetic and structural aspects, and evaluation of properties and catalytic activity. Inorganica Chim Acta 2020. [DOI: 10.1016/j.ica.2020.119752] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Bond CJ, Cineus R, Nazarenko AY, Spernyak JA, Morrow JR. Isomeric Co(ii) paraCEST agents as pH responsive MRI probes. Dalton Trans 2020; 49:279-284. [PMID: 31833500 DOI: 10.1039/c9dt04558a] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
A newly discovered isomer of Co(ii) (1,4,8,11-tetrakis(carbamoylmethyl)-1,4,8,11-tetraazacyclotetradecane = CCRM) produces four highly paramagnetically shifted chemical exchange saturation transfer (CEST) peaks. The 1,8-pendants of the complex are bound in a trans-arrangement to produce a Co(ii) complex of increased kinetic inertness. The isomers have a stabilized Co(ii) center (E1/2 of 540 to 550 mV versus SHE). Both the 1,8 and the 1,4-isomer are excellent pH probes in solution and in tissue homogenate by virtue of their highly paramagnetically shifted amide protons. These isomers produce both a ratiometric pH readout as well as amide proton exchange rate constants that correlate to pH.
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Affiliation(s)
- Christopher J Bond
- Department of Chemistry, Natural Sciences Complex, University at Buffalo, the State University of New York, Amherst, NY 14260, USA.
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Gupta A, Caravan P, Price WS, Platas-Iglesias C, Gale EM. Applications for Transition-Metal Chemistry in Contrast-Enhanced Magnetic Resonance Imaging. Inorg Chem 2020; 59:6648-6678. [PMID: 32367714 DOI: 10.1021/acs.inorgchem.0c00510] [Citation(s) in RCA: 60] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Contrast-enhanced magnetic resonance imaging (MRI) is an indispensable tool for diagnostic medicine. However, safety concerns related to gadolinium in commercial MRI contrast agents have emerged in recent years. For patients suffering from severe renal impairment, there is an important unmet medical need to perform contrast-enhanced MRI without gadolinium. There are also concerns over the long-term effects of retained gadolinium within the general patient population. Demand for gadolinium-free MRI contrast agents is driving a new wave of inorganic chemistry innovation as researchers explore paramagnetic transition-metal complexes as potential alternatives. Furthermore, advances in personalized care making use of molecular-level information have motivated inorganic chemists to develop MRI contrast agents that can detect pathologic changes at the molecular level. Recent studies have highlighted how reaction-based modulation of transition-metal paramagnetism offers a highly effective mechanism to achieve MRI contrast enhancement that is specific to biochemical processes. This Viewpoint highlights how recent advances in transition-metal chemistry are leading the way for a new generation of MRI contrast agents.
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Affiliation(s)
- Abhishek Gupta
- Nanoscale Organisation and Dynamics Group, School of Science and Health, Western Sydney University, Penrith, New South Wales 2751, Australia.,Ingham Institute of Applied Medical Research, Liverpool, New South Wales 2170, Australia
| | | | - William S Price
- Nanoscale Organisation and Dynamics Group, School of Science and Health, Western Sydney University, Penrith, New South Wales 2751, Australia.,Ingham Institute of Applied Medical Research, Liverpool, New South Wales 2170, Australia
| | - Carlos Platas-Iglesias
- Centro de Investigacións Científicas Avanzadas and Departamento de Química, Facultade de Ciencias, Universidade da Coruña, A Coruña, Galicia 15071, Spain
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Yu M, Bouley BS, Xie D, Que EL. Highly fluorinated metal complexes as dual 19F and PARACEST imaging agents. Dalton Trans 2019; 48:9337-9341. [PMID: 31168527 PMCID: PMC6626988 DOI: 10.1039/c9dt01852b] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We reported a set of water-soluble transition metal complexes that can serve as both 19F and PARACEST magnetic resonance imaging agents. The high number of equivalent fluorine atoms and the paramagnetic effect of metals offer these complexes high 19F sensitivity as demonstrated by in vitro19F MRI experiments. The complexes contain carboxamide groups appended onto a cyclen macrocycle, which provide 1H CEST peaks well differentiated from bulk water. The Co(ii) agent displays two CEST peaks that can be utilized for ratiometric pH determination and the concept of combining 19F MR and PARACEST as complementary imaging techniques was demonstrated with the Fe(ii) complex.
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Affiliation(s)
- Meng Yu
- Department of Chemistry, The University of Texas at Austin, 105 E. 24th St Stop A5300, Austin, Texas 78712, USA.
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Pradhan RN, Chakraborty S, Bharti P, Kumar J, Ghosh A, Singh AK. Seven coordinate Co(ii) and six coordinate Ni(ii) complexes of an aromatic macrocyclic triamide ligand as paraCEST agents for MRI. Dalton Trans 2019; 48:8899-8910. [PMID: 31140528 DOI: 10.1039/c9dt00747d] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
We are reporting Co(ii) and Ni(ii) complexes of a pyridine containing aromatic macrocyclic triamide ligand, 3,6,9,15-tetraazabicyclo(9.3.1)pentadeca-1(15),11,13-triene-3,6,9-triacetamide (TPTA), as paramagnetic chemical exchange saturation transfer (paraCEST) MRI contrast agents. The synthesis and characterization of TPTA and its complexes are reported. The solution chemistry and solid-state structure of Co(ii) and Ni(ii) complexes are studied. Crystallographic data show that the [Co(TPTA)]·Cl2·2H2O complex (seven-coordinate, all four N atoms of ring and three amide O atoms) has a distorted pentagonal bipyramidal geometry, however the [Ni(TPTA)Cl]·Cl·0.25H2O complex (six-coordinate, all four N atoms of the ring, one amide O and one chloride ion) adopts a distorted octahedral geometry. Notably the two pendent amide arms are not coordinated in the [Ni(TPTA)Cl]+ complex and one chloride ion fulfils its sixth coordination. The CEST effect of [Co(TPTA)]2+ and [Ni(TPTA)Cl]+ amide protons is observed at 57 ppm and 78 ppm downfield of the bulk water proton respectively in a buffer solution containing 20 mM N-(2-hydroxyethyl)piperazine-N'-ethanesulfonic acid and 100 mM NaCl at pH 7.4 at 37 °C on a 9.4 T NMR spectrometer. The effects of CEST intensity and exchange rate constant with variation of pH of the solution were studied. The CEST effect and exchange rate constant for the amide protons of the [Co(TPTA)]2+ complex have been monitored in HEPES buffer, fetal bovine serum (FBS), rabbit serum and 4% agarose gel (w/w). The stability of the [Co(TPTA)]2+ complex in aqueous solution towards oxidation was verified by cyclic voltammetry measurement. The stability of [Co(TPTA)]2+ has further been monitored in the presence of biologically relevant ions including HPO42-, CO32-, and Zn2+ and under acidic conditions.
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Affiliation(s)
- Rabindra N Pradhan
- School of Basic Sciences, Indian Institute of Technology Bhubaneswar, Bhubaneswar, 752050, India.
| | - Subhayan Chakraborty
- School of Chemical Sciences, National Institute of Science Education and Research (HBNI) Bhubaneswar, 752050, India.
| | - Pratibha Bharti
- National Centre for Cell Science, NCCS Complex, Pune University Campus, Ganeshkhind, Pune 411 007, India
| | - Janesh Kumar
- National Centre for Cell Science, NCCS Complex, Pune University Campus, Ganeshkhind, Pune 411 007, India
| | - Arindam Ghosh
- School of Chemical Sciences, National Institute of Science Education and Research (HBNI) Bhubaneswar, 752050, India.
| | - Akhilesh K Singh
- School of Basic Sciences, Indian Institute of Technology Bhubaneswar, Bhubaneswar, 752050, India.
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Du K, Thorarinsdottir AE, Harris TD. Selective Binding and Quantitation of Calcium with a Cobalt-Based Magnetic Resonance Probe. J Am Chem Soc 2019; 141:7163-7172. [PMID: 30946580 DOI: 10.1021/jacs.9b02661] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
We report a cobalt-based paramagnetic chemical exchange saturation transfer (PARACEST) magnetic resonance (MR) probe that is able to selectively bind and quantitate the concentration of Ca2+ ions under physiological conditions. The parent LCo complex features CEST-active carboxamide groups and an uncoordinated crown ether moiety in close proximity to a high-spin pseudo-octahedral CoII center. Addition of Na+, Mg2+, K+, and Ca2+ leads to binding of these metal ions within the crown ether. Single-crystal X-ray diffraction and solid-state magnetic measurements reveal the presence of a cation-specific coordination environment and magnetic anisotropy of CoII, with axial zero-field splitting parameters for the Na+- and Ca2+-bound complexes differing by over 90%. Owing to these differences, solution-based measurements under physiological conditions indicate reversible binding of Na+ and Ca2+ to give well-separated CEST peaks at 69 and 80 ppm for [LCoNa]+ and [LCoCa]2+, respectively. Dissociation constants for different cation-bound complexes of LCo, as determined by 1H NMR spectroscopy, demonstrate high selectivity toward Ca2+. This finding, in conjunction with the large excess of Na+ in physiological environments, minimizes interference from related cations, such as Mg2+ and K+. Finally, variable-[Ca2+] CEST spectra establish the ratio between the CEST peak intensities for the Ca2+- and Na+-bound probes (CEST80 ppm/CEST69 ppm) as a measure of [Ca2+], providing the first example of a ratiometric quantitation of Ca2+ concentration using PARACEST. Taken together, these results demonstrate the ability of transition metal PARACEST probes to afford a concentration-independent measure of [Ca2+] and provide a new approach for designing MR probes for cation sensing.
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Affiliation(s)
- Kang Du
- Department of Chemistry , Northwestern University , Evanston , Illinois 60208-3113 , United States
| | - Agnes E Thorarinsdottir
- Department of Chemistry , Northwestern University , Evanston , Illinois 60208-3113 , United States
| | - T David Harris
- Department of Chemistry , Northwestern University , Evanston , Illinois 60208-3113 , United States
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Thorarinsdottir AE, Harris TD. Dramatic enhancement in pH sensitivity and signal intensity through ligand modification of a dicobalt PARACEST probe. Chem Commun (Camb) 2019; 55:794-797. [DOI: 10.1039/c8cc09520e] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
A ratiometric dicobalt PARACEST pH probe that exhibits dramatic enhancements in sensitivity and signal intensity over analogous probes is reported.
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