Paramagnetic Re(I) complexes with azolyl-nitroxide ligands.

[Display omitted] A one-stage synthesis of paramagnetic Re(I) compounds based on the reaction of [Re(CO) 5 Br] with spin-labeled N -donor heterocycles was developed. Nitronyl nitroxide derivatives of 1 H- imidazole (L1), 1 H- pyrazole (L2), di(1 H -pyrazol-1-yl)methane (L3) and 4-methyl-2-(1 H -pyrazol-1-yl)quinoline (L4) can easily substitute two coordinated CO molecules in [Re(CO) 5 Br], resulting in a series of paramagnetic fac- [Re(CO) 3 (L i) n Br]· x Solv 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) 2 Br] (1), [Re(CO) 3 (L2) 2 Br] (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 (L i) n Br] valuable model objects for material design for theranostics purposes. [ABSTRACT FROM AUTHOR]