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Svítok A, Blahut J, Urbanovský P, Hermann P. Dynamics of Coordinated Phosphonate Group Directly Observed by 17O-NMR in Lanthanide(iii) Complexes of a Mono(ethyl phosphonate) DOTA Analogue. Chemistry 2024; 30:e202400970. [PMID: 38624256 DOI: 10.1002/chem.202400970] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2024] [Revised: 04/15/2024] [Accepted: 04/16/2024] [Indexed: 04/17/2024]
Abstract
Biological phosphates can coordinate metal ions and their complexes are common in living systems. Dynamics of mutual oxygen atom exchange in the tetrahedral group in complexes has not been investigated. Here, we present a direct experimental proof of exchange ("phosphonate rotation") in model Ln(III) complexes of monophosphonate H4dota analogue which alters phosphorus atom chirality of coordinated phosphonate monoester. Combination of macrocycle-based isomerism with P-based chirality leads to several diastereoisomers. (Non)-coordinated oxygen atoms were distinguished through 17O-labelled phosphonate group and their mutual exchange was followed by various NMR techniques and DFT calculations. The process is sterically demanding and occurs through bulky bidentate (κ2-PO2)- coordination and was observed only in twisted-square antiprism (TSA) diastereoisomer of large Ln(III) ions. Its energy demands increase for smaller Ln(III) ions (298ΔG≠(exp./DFT)=51.8/52.1 and 61.0/71.5 kJ mol-1 for La(III) and Eu(III), respectively). These results are helpful in design of such complexes as MRI CA and for protein paramagnetic NMR probes. It demonstrates usefulness of 17O NMR to study solution dynamics in complexes involving phosphorus acid derivatives and it may inspire use of this method to study dynamics of phosphoric acid derivatives (as e. g. phosphorus acid-based inhibitors of metalloenzymes) in different areas of chemistry.
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Affiliation(s)
- Adam Svítok
- Department Department of Inorganic Chemistry, Faculty of Science, Charles University, Hlavova 2030, 12843, Prague 2, Czech Republic
| | - Jan Blahut
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Science, Flemingovo náměstí 2, 16000, Prague 6, Czech Republic
| | - Peter Urbanovský
- Department Department of Inorganic Chemistry, Faculty of Science, Charles University, Hlavova 2030, 12843, Prague 2, Czech Republic
| | - Petr Hermann
- Department Department of Inorganic Chemistry, Faculty of Science, Charles University, Hlavova 2030, 12843, Prague 2, Czech Republic
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2
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Abstract
Structures, electron spectroscopy and theoretical (DFT and TD DFT) analyses of two complexes of Eu(ii) with phosphonate and phosphinate ligands based on cyclen ring are presented.
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Ratnakar SJ, Chirayil S, Funk AM, Zhang S, Queiró JF, Geraldes CFGC, Kovacs Z, Sherry AD. A Frequency-Selective pH-Responsive paraCEST Agent. Angew Chem Int Ed Engl 2020; 59:21671-21676. [PMID: 32726500 DOI: 10.1002/anie.202008888] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Indexed: 01/01/2023]
Abstract
Paramagnetic chemical exchange saturation transfer (paraCEST) agents are well-suited for imaging tissue pH because the basis of CEST, chemical exchange, is inherently sensitive to pH. Several previous pH-sensitive paraCEST agents were based on an exchanging Ln3+ -bound water molecule as the CEST antenna but this design often added additional line-broadening to the bulk water signal due to T2 exchange. We report herein a pH-sensitive paraCEST agent that lacks an inner-sphere water molecule but contains one Ln-bound -OH group for CEST activation. The Yb3+ complex, Yb(1), displayed a single, highly shifted CEST peak originating from the exchangeable Yb-OH proton, the frequency of which changed over the biologically relevant pH range. CEST images of phantoms ranging in pH from 6 to 8 demonstrate the potential of this agent for imaging pH. Initial rodent imaging studies showed that Gd(1) remains in the vascular system much longer than anticipated but is cleared slowly via renal filtration.
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Affiliation(s)
- S James Ratnakar
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Sara Chirayil
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Alexander M Funk
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Shanrong Zhang
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - João F Queiró
- CMUC, Department of Mathematics, University of Coimbra, Coimbra, Portugal
| | - Carlos F G C Geraldes
- Department of Life Sciences and Coimbra Chemistry Center, University of Coimbra, Coimbra, Portugal.,CIBIT- Coimbra Institute for Biomedical Imaging and Translational Research, University of Coimbra, Coimbra, Portugal
| | - Zoltan Kovacs
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - A Dean Sherry
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, USA.,Department of Chemistry and Biochemistry, University of Texas at Dallas, Richardson, TX, USA
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Ratnakar SJ, Chirayil S, Funk AM, Zhang S, Queiró JF, Geraldes CFGC, Kovacs Z, Sherry AD. A Frequency‐Selective pH‐Responsive paraCEST Agent. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202008888] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- S. James Ratnakar
- Advanced Imaging Research Center University of Texas Southwestern Medical Center Dallas TX USA
| | - Sara Chirayil
- Advanced Imaging Research Center University of Texas Southwestern Medical Center Dallas TX USA
| | - Alexander M. Funk
- Advanced Imaging Research Center University of Texas Southwestern Medical Center Dallas TX USA
| | - Shanrong Zhang
- Advanced Imaging Research Center University of Texas Southwestern Medical Center Dallas TX USA
| | - João F. Queiró
- CMUC, Department of Mathematics University of Coimbra Coimbra Portugal
| | - Carlos F. G. C. Geraldes
- Department of Life Sciences and Coimbra Chemistry Center University of Coimbra Coimbra Portugal
- CIBIT- Coimbra Institute for Biomedical Imaging and Translational Research University of Coimbra Coimbra Portugal
| | - Zoltan Kovacs
- Advanced Imaging Research Center University of Texas Southwestern Medical Center Dallas TX USA
| | - A. Dean Sherry
- Advanced Imaging Research Center University of Texas Southwestern Medical Center Dallas TX USA
- Department of Chemistry and Biochemistry University of Texas at Dallas Richardson TX USA
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5
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De S, Gottlieb HE, Hoz S. Quantification of the Interaction of SmI 2 with Substrates and Ligands. Chemistry 2020; 26:6846-6850. [PMID: 32045042 DOI: 10.1002/chem.201905233] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Revised: 02/10/2020] [Indexed: 12/31/2022]
Abstract
The method developed and introduced here enables for the first time (to the authors' knowledge), a quantitative assessment of the interaction of SmI2 with substrates prior to the electron transfer stage. As a proof of concept, equilibrium constants for some model substrates including carbonyl compounds and aromatic nuclei are reported here. In addition, the first equilibrium constants with some common ligands were also determined. The equilibrium constants range from approximately 0.07 m-1 for diisopropyl ketone to 2500 m-1 for hexamethylphosphoramide (HMPA). It is shown that the data acquired by this method, which is based on the concept of shift reagents, can shed light on the most intimate details of the reaction mechanism, and this method is a useful tool for planning a synthetic process.
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Affiliation(s)
- Suranjan De
- Department of Chemistry, Bar-Ilan University, Ramat Gan, 5290002, Israel
| | - Hugo E Gottlieb
- Department of Chemistry, Bar-Ilan University, Ramat Gan, 5290002, Israel
| | - Shmaryahu Hoz
- Department of Chemistry, Bar-Ilan University, Ramat Gan, 5290002, Israel
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Clough TJ, Jiang L, Wong KL, Long NJ. Ligand design strategies to increase stability of gadolinium-based magnetic resonance imaging contrast agents. Nat Commun 2019; 10:1420. [PMID: 30926784 PMCID: PMC6441101 DOI: 10.1038/s41467-019-09342-3] [Citation(s) in RCA: 167] [Impact Index Per Article: 33.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Accepted: 12/20/2018] [Indexed: 01/08/2023] Open
Abstract
Gadolinium(III) complexes have been widely utilised as magnetic resonance imaging (MRI) contrast agents for decades. In recent years however, concerns have developed about their toxicity, believed to derive from demetallation of the complexes in vivo, and the relatively large quantities of compound required for a successful scan. Recent efforts have sought to enhance the relaxivity of trivalent gadolinium complexes without sacrificing their stability. This review aims to examine the strategic design of ligands synthesised for this purpose, provide an overview of recent successes in gadolinium-based contrast agent development and assess the requirements for clinical translation.
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Affiliation(s)
- Thomas J Clough
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, White City Campus, Wood Lane, London, W12 0BZ, UK
| | - Lijun Jiang
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, White City Campus, Wood Lane, London, W12 0BZ, UK
- Department of Chemistry, Hong Kong Baptist University, Kowloon Tong, Hong Kong SAR, China
| | - Ka-Leung Wong
- Department of Chemistry, Hong Kong Baptist University, Kowloon Tong, Hong Kong SAR, China.
| | - Nicholas J Long
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, White City Campus, Wood Lane, London, W12 0BZ, UK.
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Krchová T, Herynek V, Gálisová A, Blahut J, Hermann P, Kotek J. Eu(III) Complex with DO3A-amino-phosphonate Ligand as a Concentration-Independent pH-Responsive Contrast Agent for Magnetic Resonance Spectroscopy (MRS). Inorg Chem 2017; 56:2078-2091. [PMID: 28170242 DOI: 10.1021/acs.inorgchem.6b02749] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
A new DOTA-like ligand H5do3aNP with a 2-[amino(methylphosphonic acid)]ethyl-coordinating pendant arm was prepared, and its coordinating properties were studied by NMR spectroscopy and potentiometry. The study revealed a rare slow exchange (on the 1H and 31P NMR time scale) between protonated and unprotonated complex species with a corresponding acidity constant pKA ∼ 8.0. This unusually slow time scale associated with protonation is caused by a significant geometric change from square-antiprismatic (SA) arrangement observed for protonated complex SA-[Eu(Hdo3aNP)]- to twisted-square-antiprismatic (TSA) arrangement found for deprotonated complex TSA-[Eu(do3aNP)]2-. This behavior results in simultaneous occurrence of the signals of both species in the 31P NMR spectra at approximately -118 and +70 ppm, respectively. Such an unprecedented difference in the chemical shifts between species differing by a proton is caused by a significant movement of the principal magnetic axis and by a change of phosphorus atom position in the coordination sphere of the central Eu(III) ion (i.e., by relative movement of the phosphorus atom with respect to the principal magnetic axis). It changes the sign of the paramagnetic contribution to the 31P NMR chemical shift. The properties discovered can be employed in the measurement of pH by MRS techniques as presented by proof-of-principle experiments on phantoms.
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Affiliation(s)
- Tereza Krchová
- Department of Inorganic Chemistry, Faculty of Science, Charles University , Hlavova 2030, Prague 2 128 43, Czech Republic
| | - Vít Herynek
- Department of Radiodiagnostic and Interventional Radiology, Magnetic Resonance Unit, Institute for Clinical and Experimental Medicine , Vídeňská 1958/9, Prague 4 140 21, Czech Republic
| | - Andrea Gálisová
- Department of Radiodiagnostic and Interventional Radiology, Magnetic Resonance Unit, Institute for Clinical and Experimental Medicine , Vídeňská 1958/9, Prague 4 140 21, Czech Republic
| | - Jan Blahut
- Department of Inorganic Chemistry, Faculty of Science, Charles University , Hlavova 2030, Prague 2 128 43, Czech Republic
| | - Petr Hermann
- Department of Inorganic Chemistry, Faculty of Science, Charles University , Hlavova 2030, Prague 2 128 43, Czech Republic
| | - Jan Kotek
- Department of Inorganic Chemistry, Faculty of Science, Charles University , Hlavova 2030, Prague 2 128 43, Czech Republic
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Farashishiko A, Chacón KN, Blackburn NJ, Woods M. Nano assembly and encapsulation; a versatile platform for slowing the rotation of polyanionic Gd(3+) -based MRI contrast agents. CONTRAST MEDIA & MOLECULAR IMAGING 2016; 11:154-9. [PMID: 26708733 PMCID: PMC4864039 DOI: 10.1002/cmmi.1676] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2015] [Revised: 10/30/2015] [Accepted: 11/09/2015] [Indexed: 11/05/2022]
Abstract
Encapsulating discrete Gd(3+) chelates in nano-assembled capsules (NACs) is a simple and effective method of preparing an MRI contrast agent capable of delivering a large payload of high relaxivity imaging agent. The preparation of contrast agent containing NACs had previously focussed on preparations incorporating GdDOTP(5-) into the internal aggregate. In this report we demonstrate that other Gd(3+) chelates bearing overall charges as low as 2- can also be used to prepare NACs. This discovery opens up the possibility of using Gd(3+) chelates that have inner-sphere water molecules that could further increase the relaxivity enhancement associated with the long τR that arises from encapsulation. However, encapsulation of the q = 1 chelate GdDTPA(2-) did not give rise to a significant increase in relaxivity relative to encapsulation of the outer-sphere chelate GdTTHA(3-). This leads us to the conclusion that in the NAC interior proton transport is not mediated by movement of whole water molecules and the enhanced relaxivity of Gd(3+) chelate encapsulated within NACs arises primarily from second sphere effects.
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Affiliation(s)
- Annah Farashishiko
- Department of Chemistry, Portland State University, 1719 SW 10 Avenue, Portland, OR 97201, USA
| | - Kelly N. Chacón
- Institute of Environmental Health, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA
| | - Ninian J. Blackburn
- Institute of Environmental Health, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA
| | - Mark Woods
- Department of Chemistry, Portland State University, 1719 SW 10 Avenue, Portland, OR 97201, USA
- Advanced Imaging Research Center, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA
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Janicki R, Kędziorski A, Mondry A. The first example of ab initio calculations of f–f transitions for the case of [Eu(DOTP)]5− complex—experiment versus theory. Phys Chem Chem Phys 2016; 18:27808-27817. [DOI: 10.1039/c6cp05284c] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Structure, IR and UV-vis-NIR spectra of the [Eu(DOTP)]5− complex in single crystals were studied experimentally. Ab initio calculations of the excited states of the [Eu(DOTP)]5− complex provide new insights into the interpretation of the observed f–f electronic transitions spectra.
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Affiliation(s)
- Rafał Janicki
- University of Wrocław
- Faculty of Chemistry
- 50-383 Wrocław
- Poland
| | - Andrzej Kędziorski
- Nicolaus Copernicus University
- Faculty of Physics
- Astronomy and Informatics
- Address Toruń
- Institute of Physics
| | - Anna Mondry
- University of Wrocław
- Faculty of Chemistry
- 50-383 Wrocław
- Poland
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Wu X, Dawsey AC, Siriwardena-Mahanama BN, Allen MJ, Williams TJ. A (Fluoroalkyl)Guanidine Modulates the Relaxivity of a Phosphonate-Containing T1-Shortening Contrast Agent. J Fluor Chem 2014; 168:177-183. [PMID: 25431503 PMCID: PMC4241975 DOI: 10.1016/j.jfluchem.2014.09.018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Responsive magnetic resonance imaging (MRI) contrast agents, those that change their relaxivity according to environmental stimuli, have promise as next generation imaging probes in medicine. While several of these are known based on covalent modification of the contrast agents, fewer are known based on controlling non-covalent interactions. We demonstrate here accentuated relaxivity of a T1-shortening contrast agent, Gd-DOTP5- based on non-covalent, hydrogen bonding of Gd-DOTP5- with a novel fluorous amphiphile. By contrast to the phosphonate-containing Gd-DOTP5- system, the relaxivity of the analogous clinically approved contrast agent, Gd-DOTA- is unaffected by the same fluorous amphiphile under similar conditions. Mechanistic studies show that placing the fluorous amphiphile in proximity of the gadolinium center in Gd-DOTP5- caused an increase in τ m (bound-water residence lifetime or the inverse of water exchange rate, τ m = 1/kex) and an increase in τ R (rotational correlation time), with τ R being the factor driving enhanced relaxivity. Further, these effects were not observed when Gd-DOTA- was treated with the same fluorous amphiphile. Thus, Gd-DOTP5- and Gd-DOTA- respond to the fluorous amphiphile differently, presumably because the former binds to the amphiphile with higher affinity. (DOTP = 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraphosphonic acid; DOTA = 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid).
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Affiliation(s)
- Xinping Wu
- Loker Hydrocarbon Research Institute, Department of Chemistry, University of Southern California, Los Angeles, California 90089-1661
| | - Anna C. Dawsey
- Loker Hydrocarbon Research Institute, Department of Chemistry, University of Southern California, Los Angeles, California 90089-1661
| | | | - Matthew J. Allen
- Department of Chemistry, Wayne State University, 5101 Cass Ave, Detroit, MI 48202
| | - Travis J. Williams
- Loker Hydrocarbon Research Institute, Department of Chemistry, University of Southern California, Los Angeles, California 90089-1661
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Martins AF, Eliseeva SV, Carvalho HF, Teixeira JMC, Paula CTB, Hermann P, Platas-Iglesias C, Petoud S, Tóth E, Geraldes CFGC. A bis(pyridine N-oxide) analogue of DOTA: relaxometric properties of the Gd(III) complex and efficient sensitization of visible and NIR-emitting lanthanide(III) cations including Pr(III) and Ho(III). Chemistry 2014; 20:14834-45. [PMID: 25236257 DOI: 10.1002/chem.201403856] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Indexed: 11/07/2022]
Abstract
We report the synthesis of a cyclen-based ligand (4,10-bis[(1-oxidopyridin-2-yl)methyl]-1,4,7,10-tetraazacyclododecane-1,7-diacetic acid=L1) containing two acetate and two 2-methylpyridine N-oxide arms anchored on the nitrogen atoms of the cyclen platform, which has been designed for stable complexation of lanthanide(III) ions in aqueous solution. Relaxometric studies suggest that the thermodynamic stability and kinetic inertness of the Gd(III) complex may be sufficient for biological applications. A detailed structural study of the complexes by (1) H NMR spectroscopy and DFT calculations indicates that they adopt an anti-Δ(λλλλ) conformation in aqueous solution, that is, an anti-square antiprismatic (anti-SAP) isomeric form, as demonstrated by analysis of the (1) H NMR paramagnetic shifts induced by Yb(III) . The water-exchange rate of the Gd(III) complex is ${k{{298\hfill \atop {\rm ex}\hfill}}}$=6.7×10(6) s(-1) , about a quarter of that for the mono-oxidopyridine analogue, but still about 50 % higher than the ${k{{298\hfill \atop {\rm ex}\hfill}}}$ of GdDOTA (DOTA=1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid). The 2-methylpyridine N-oxide chromophores can be used to sensitize a wide range of Ln(III) ions emitting in both the visible (Eu(III) and Tb(III) ) and NIR (Pr(III) , Nd(III) , Ho(III) , Yb(III) ) spectral regions. The emission quantum yield determined for the Yb(III) complex (${Q{{{\rm L}\hfill \atop {\rm Yb}\hfill}}}$=7.3(1)×10(-3) ) is among the highest ever reported for complexes of this metal ion in aqueous solution. The sensitization ability of the ligand, together with the spectroscopic and relaxometric properties of its complexes, constitute a useful step forward on the way to efficient dual probes for optical imaging (OI) and MRI.
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Affiliation(s)
- André F Martins
- Department of Life Sciences, Faculty of Science and Technology, University of Coimbra, P. O. Box 3046, 3001-401 Coimbra (Portugal); Coimbra Chemistry Center, Rua Larga, University of Coimbra, 3004-535 Coimbra (Portugal); Centre de Biophysique Moléculaire, CNRS, Rue Charles Sadron, 45071 Orléans (France)
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12
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Di Bari L, Salvadori P. Static and Dynamic Stereochemistry of Chiral Ln DOTA Analogues. Chemphyschem 2011; 12:1490-7. [DOI: 10.1002/cphc.201100017] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2011] [Revised: 03/18/2011] [Indexed: 11/11/2022]
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Kubíček V, Vitha T, Kotek J, Hermann P, Vander Elst L, Muller RN, Lukeš I, Peters JA. Towards MRI contrast agents responsive to Ca(II) and Mg(II) ions: metal-induced oligomerization of dota-bisphosphonate conjugates. CONTRAST MEDIA & MOLECULAR IMAGING 2011; 5:294-6. [PMID: 20973114 DOI: 10.1002/cmmi.386] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
In magnetic resonance imaging (MRI), paramagnetic complexes are utilized as contrast agents. Much attention has been paid to the development of new contrast agents responsive to pH, temperature or concentration of various components of body liquids. We report a new type of MRI probe sensing the concentrations of calcium and magnesium in biological media. The ligand do3ap(BP) combines a dota-like chelator with a bisphosphonate group. In the complex, the Gd(III) ion is entrapped in the macrocyclic cavity whereas the bisphosphonate group is not coordinated and therefore is available for coordination with endogenous metal ions. In the presence of metal ions, Gd-do3ap(BP) appears to show formation of coordination oligomers leading to an unprecedented increase in r(1) up to 200-500%. The extremely high relaxivity response makes this type of compound interesting for further studies as MRI ion-responsive probes for biomedical research.
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Affiliation(s)
- Vojtěch Kubíček
- Department of Inorganic Chemistry, Faculty of Science, Charles University in Prague, Prague, Czech Republic.
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14
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Campello MPC, Lacerda S, Santos IC, Pereira GA, Geraldes CFGC, Kotek J, Hermann P, Vanek J, Lubal P, Kubícek V, Tóth E, Santos I. Lanthanide(III) complexes of 4,10-bis(phosphonomethyl)-1,4,7,10-tetraazacyclododecane-1,7-diacetic acid (trans-H6do2a2p) in solution and in the solid state: structural studies along the series. Chemistry 2010; 16:8446-65. [PMID: 20540046 DOI: 10.1002/chem.201000320] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Complexes of 4,10-bis(phosphonomethyl)-1,4,7,10-tetraazacyclododecane-1,7-diacetic acid (trans-H(6)do2a2p, H(6)L) with transition metal and lanthanide(III) ions were investigated. The stability constant values of the divalent and trivalent metal-ion complexes are between the corresponding values of H(4)dota and H(8)dotp complexes, as a consequence of the ligand basicity. The solid-state structures of the ligand and of nine lanthanide(III) complexes were determined by X-ray diffraction. All the complexes are present as twisted-square-antiprismatic isomers and their structures can be divided into two series. The first one involves nona-coordinated complexes of the large lanthanide(III) ions (Ce, Nd, Sm) with a coordinated water molecule. In the series of Sm, Eu, Tb, Dy, Er, Yb, the complexes are octa-coordinated only by the ligand donor atoms and their coordination cages are more irregular. The formation kinetics and the acid-assisted dissociation of several Ln(III)-H(6)L complexes were investigated at different temperatures and compared with analogous data for complexes of other dota-like ligands. The [Ce(L)(H(2)O)](3-) complex is the most kinetically inert among complexes of the investigated lanthanide(III) ions (Ce, Eu, Gd, Yb). Among mixed phosphonate-acetate dota analogues, kinetic inertness of the cerium(III) complexes is increased with a higher number of phosphonate arms in the ligand, whereas the opposite is true for europium(III) complexes. According to the (1)H NMR spectroscopic pseudo-contact shifts for the Ce-Eu and Tb-Yb series, the solution structures of the complexes reflect the structures of the [Ce(HL)(H(2)O)](2-) and [Yb(HL)](2-) anions, respectively, found in the solid state. However, these solution NMR spectroscopic studies showed that there is no unambiguous relation between (31)P/(1)H lanthanide-induced shift (LIS) values and coordination of water in the complexes; the values rather express a relative position of the central ions between the N(4) and O(4) planes.
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Affiliation(s)
- M Paula C Campello
- Departamento de Química, Instituto Tecnológico e Nuclear, Estrada Nacional 10, 2686-953 Sacavém, Portugal
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