Re(i)-nitroxide complexes.

Spin-labeled cyrhetrenes [(NNCp)Re(CO) 3 ] and [(INCp)Re(CO) 3 ], where NNCp is nitronyl nitroxide 2-(η 5 -cyclopentadienyl)-4,4,5,5-tetramethyl-4,5-dihydro-1 H -imidazole-3-oxide-1-oxyl and INCp is the corresponding imino nitroxide, were synthesized and characterized by EPR, CV, XRD, magnetochemistry and quantum chemistry methods. The correlations between different arrangements of paramagnetic centers and the magnetic exchange interactions for three polymorphs of [(NNCp)Re(CO) 3 ] were studied. It was concluded that high kinetic stability of nitroxide-substituted cyrhetrenes is a promising feature of compounds for the creation of multifunctional contrast agents.