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Open AccessArticle

Synthesis of Organosilicon Ligands for Europium (III) and Gadolinium (III) as Potential Imaging Agents

1
School of Life Health and Chemical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK
2
School of Physical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK
*
Author to whom correspondence should be addressed.
Academic Editor: Eszter Borbas
Molecules 2020, 25(18), 4253; https://doi.org/10.3390/molecules25184253
Received: 6 August 2020 / Revised: 11 September 2020 / Accepted: 11 September 2020 / Published: 16 September 2020
(This article belongs to the Special Issue Luminescent Lanthanide Complexes)
The relaxivity of MRI contrast agents can be increased by increasing the size of the contrast agent and by increasing concentration of the bound gadolinium. Large multi-site ligands able to coordinate several metal centres show increased relaxivity as a result. In this paper, an “aza-type Michael” reaction is used to prepare cyclen derivatives that can be attached to organosilicon frameworks via hydrosilylation reactions. A range of organosilicon frameworks were tested including silsesquioxane cages and dimethylsilylbenzene derivatives. Michael donors with strong electron withdrawing groups could be used to alkylate cyclen on three amine centres in a single step. Hydrosilylation successfully attached these to mono-, di-, and tri-dimethylsilyl-substituted benzene derivatives. The europium and gadolinium complexes were formed and studied using luminescence spectroscopy and relaxometry. This showed the complexes to contain two bound water moles per lanthanide centre and T1 relaxation time measurements demonstrated an increase in relaxivity had been achieved, in particular for the trisubstituted scaffold 1,3,5-tris((pentane-sDO3A)dimethylsilyl)benzene-Gd3. This showed a marked increase in the relaxivity (13.1 r1p/mM−1s−1). View Full-Text
Keywords: lanthanide; luminescence; europium; gadolinium; relaxivity; organosilicon; silsesquioxane lanthanide; luminescence; europium; gadolinium; relaxivity; organosilicon; silsesquioxane
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MDPI and ACS Style

Bruce, J.I.; O’Connell, P.J.; Taylor, P.G.; Smith, D.P.T.; Adkin, R.C.; Pearson, V.K. Synthesis of Organosilicon Ligands for Europium (III) and Gadolinium (III) as Potential Imaging Agents. Molecules 2020, 25, 4253. https://doi.org/10.3390/molecules25184253

AMA Style

Bruce JI, O’Connell PJ, Taylor PG, Smith DPT, Adkin RC, Pearson VK. Synthesis of Organosilicon Ligands for Europium (III) and Gadolinium (III) as Potential Imaging Agents. Molecules. 2020; 25(18):4253. https://doi.org/10.3390/molecules25184253

Chicago/Turabian Style

Bruce, James I.; O’Connell, Patrick J.; Taylor, Peter G.; Smith, David P.T.; Adkin, Roy C.; Pearson, Victoria K. 2020. "Synthesis of Organosilicon Ligands for Europium (III) and Gadolinium (III) as Potential Imaging Agents" Molecules 25, no. 18: 4253. https://doi.org/10.3390/molecules25184253

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