Cyclams with Ambidentate Methylthiazolyl Pendants for Stable, Inert, and Selective Cu(II) Coordination - Université de Bretagne Occidentale Access content directly
Journal Articles Inorganic Chemistry Year : 2016

Cyclams with Ambidentate Methylthiazolyl Pendants for Stable, Inert, and Selective Cu(II) Coordination

Abstract

Aiming to develop new copper chelates for application in nuclear medicine we report two new chelators, te1th and te2th, based on a cyclam backbone mono-N- or di-N1,N8-functionalized by methylthiazolyl arms. The acid–base properties of both ligands were investigated as well as their coordination chemistry, especially with Cu2+, when possible in aqueous solution and in the solid state. Single-crystal X-ray diffraction structures of complexes were determined. Stability constants of the copper(II) and zinc(II) complexes showed that the complexes of both ligands with Cu2+ are thermodynamically very stable, and they exhibit an important selectivity for Cu2+ over Zn2+. The kinetic inertness in acidic medium of both copper(II) complexes was evaluated revealing a quite good resistance to dissociation (the half-life times of complexes with te1th and te2th are 50.8 and 5.8 min, respectively, in 5 M HCl and 30 °C). The coordination geometry of the metal center in the complexes was established in aqueous solution based on UV–visible, electron paramagnetic resonance (EPR) spectroscopy, DFT studies, and NMR by using the zinc(II) complex analogues. The [Cu(te1th)]2+ and [Cu(te2th)]2+ complexes adopt trans-I and trans-III configurations both in the solid state and in solution, while the [Zn(te2th)]2+ complex crystallizes as the cis-V isomer but exists in solution as a mixture of trans-III and cis-V forms. Cyclic voltammetry experiments in acetonitrile point to a relatively easy reduction of [Cu(te2th)]2+ in acetonitrile solution (Epc = −0.41 V vs NHE), but the reduced complex does not undergo dissociation in the time scale of our electrochemical experiments. The results obtained in these studies revealed that despite the limited solubility of its copper(II) chelate, te2th is an attractive chelator for Cu2+ that provides a fast complexation process while forming a complex with a rather high thermodynamic stability and kinetic inertness with respect to dissociation even upon electrochemical reduction.
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Dates and versions

hal-01517782 , version 1 (03-05-2017)

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Aurora Rodríguez-Rodríguez, Zakaria Halime, Luís M. P. Lima, Maryline Beyler, David Deniaud, et al.. Cyclams with Ambidentate Methylthiazolyl Pendants for Stable, Inert, and Selective Cu(II) Coordination. Inorganic Chemistry, 2016, 55 (2), pp.619-632. ⟨10.1021/acs.inorgchem.5b01779⟩. ⟨hal-01517782⟩
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