Radical Anions of Metallo-organic Diazines: Structural, Spectroscopic, and Theoretical Investigation of a Pyrazyl Radical Anion

The treatment of organomanganese triple-decker derivatives of pyrazine and pyrimidine with metallic potassium afforded paramagnetic radical anionic species in solution. Attempts to crystallize such species succeeded only in the case of one pyrazyl-containing triple-decker, which provided a rather air-resistant crystalline salt. X-ray diffraction analysis of a single crystal revealed the actual composition of this compound as a combined salt of Mn(CO)5− and of the bis(tricarbonylmanganese)pyrazyl triple-decker radical anion with two (222 kryptofix)-concealed potassium cations. The EPR signatures and behavior of this radical anion in the crystal state and in solution were acquired and compared to those of other organometallic radical anions possessing a triple-decker-type architecture. The spin density distribution and other spectroscopic properties were assessed by means of a computational investigation (density functional theory) of the paramagnetic properties.