Paramagnetic Re(I) complexes with azolyl-nitroxide ligands

• Published in: Polyhedron 2023-10, Vol.243, p.116524, Article 116524
• Main Authors: Chernavin, Platon, Maryunina, Kseniya, Letyagin, Gleb, Romanenko, Galina, Tumanov, Sergey, Veber, Sergey, Fedin, Matvey, Bogomyakov, Artem, Ovcharenko, Victor
• Format: Article
• Language: English
• Subjects: Heterocyclic ligands; Nitroxide radicals; Paramagnets; Rhenium(I) complexes
• ISSN: 0277-5387
• DOI: 10.1016/j.poly.2023.116524

[Display omitted] A one-stage synthesis of paramagnetic Re(I) compounds based on the reaction of [Re(CO)5Br] with spin-labeled N-donor heterocycles was developed. Nitronyl nitroxide derivatives of 1H-imidazole (L1), 1H-pyrazole (L2), di(1H-pyrazol-1-yl)methane (L3) and 4-methyl-2-(1H-pyrazol-1-yl)quinoline (L4) can easily substitute two coordinated CO molecules in [Re(CO)5Br], resulting in a series of paramagnetic fac-[Re(CO)3(Li)nBr]·xSolv complexes. Single crystal XRD studies showed that the paramagnetic L1-L4 ligands are coordinated by Re(I) through the imine atoms N of the heterocycles. According to SQUID measurements and EPR spectroscopy data, magnetic behavior of [Re(CO)3(L1)2Br] (1), [Re(CO)3(L2)2Br] (2), and [Re(CO)3(L3)Br] (3) complexes are typical for biradicals, while [Re(CO)3(L4)Br] (4) is typical for monoradical. The combination of Re(I) therapeutic properties and contrasting characteristics of nitroxide radicals in diagnostic magnetic resonance imaging, stability and simplicity of synthesis make [Re(CO)3(Li)nBr] valuable model objects for material design for theranostics purposes.