title: 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 Cu(2+), 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 Cu(2+) are thermodynamically very stable, and they exhibit an important selectivity for Cu(2+) over Zn(2+). 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 Cu(2+) 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.
authors.affiliation: UFR des Sciences et Techniques, Université de Bretagne Occidentale , UMR-CNRS 6521, 6 avenue Victor le Gorgeu, C.S. 93837, 29238 Brest Cedex 3, France.
authors.forename: Aurora
authors.initials: A
authors.lastname: Rodríguez-Rodríguez
authors.affiliation: UFR des Sciences et Techniques, Université de Bretagne Occidentale , UMR-CNRS 6521, 6 avenue Victor le Gorgeu, C.S. 93837, 29238 Brest Cedex 3, France.
authors.forename: Zakaria
authors.initials: Z
authors.lastname: Halime
authors.affiliation: Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa , Av. da República, 2780-157 Oeiras, Portugal.
authors.forename: Luís M P
authors.initials: LM
authors.lastname: Lima
authors.affiliation: UFR des Sciences et Techniques, Université de Bretagne Occidentale , UMR-CNRS 6521, 6 avenue Victor le Gorgeu, C.S. 93837, 29238 Brest Cedex 3, France.
authors.forename: Maryline
authors.initials: M
authors.lastname: Beyler
authors.affiliation: UFR Sciences et Techniques, Université de Nantes , UMR-CNRS 6230, 2, rue de la Houssinière, BP 92208, 44322 Nantes Cedex 3, France.
authors.forename: David
authors.initials: D
authors.lastname: Deniaud
authors.affiliation: UFR des Sciences et Techniques, Université de Bretagne Occidentale , UMR-CNRS 6521, 6 avenue Victor le Gorgeu, C.S. 93837, 29238 Brest Cedex 3, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Le Poul
authors.affiliation: Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa , Av. da República, 2780-157 Oeiras, Portugal.
authors.forename: Rita
authors.initials: R
authors.lastname: Delgado
authors.affiliation: Grupo QUICOOR, Centro de Investigaciones Científicas Avanzadas (CICA) and Departamento de Química Fundamental, Facultade de Ciencias, Universidade da Coruña , Campus da Zapateira-Rúa da Fraga 10, 15008 A Coruña, Spain.
authors.forename: Carlos
authors.initials: C
authors.lastname: Platas-Iglesias
authors.affiliation: UFR des Sciences et Techniques, Université de Bretagne Occidentale , UMR-CNRS 6521, 6 avenue Victor le Gorgeu, C.S. 93837, 29238 Brest Cedex 3, France.
authors.forename: Véronique
authors.initials: V
authors.lastname: Patinec
authors.affiliation: UFR des Sciences et Techniques, Université de Bretagne Occidentale , UMR-CNRS 6521, 6 avenue Victor le Gorgeu, C.S. 93837, 29238 Brest Cedex 3, France.
authors.forename: Raphaël
authors.initials: R
authors.lastname: Tripier
mesh_terms: D003300:Copper / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004563:Electrochemistry; D004578:Electron Spin Resonance Spectroscopy; D047029:Lactams, Macrocyclic / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D013056:Spectrophotometry, Ultraviolet; D013844:Thiazoles / Q000737:chemistry*
chemical_list: D047029:Lactams, Macrocyclic; D013844:Thiazoles; D003300:Copper