A new approach to the synthesis of verdazyls, stable organic radicals, has been developed at the ZIOC
The creation of new functional organic materials remains one of the urgent tasks of modern science and technology. In this context, stable organic radicals, which are used as spin labels in supramolecular chemistry, as well as components of magnetic and conductive materials, are quite promising. One of the best known stable organic radicals is verdazyl, a structure containing a partially saturated tetrazine ring. The first verdazyls were synthesized by Richard Kuhn in the 1960s. Similar structures are currently called Kuhn verdazyls. The existing method for the synthesis of Kuhn verdazyls is applicable only to a narrow range of starting materials and requires laborious isolation of intermediate compounds. The development of a general and simple method for the synthesis of Kuhn verdazils is an urgent task.
Researchers from the Laboratory of Nitrogen-Containing Compounds of the ZIOC have proposed a new improved method for the preparation of Kuhn verdazyls. The synthesis involves the reaction of readily available hydrazones with arenediazonium salts, followed by base-catalyzed cyclization of the intermediate formazans with formalin. The mechanistic studies showed that, contrary to the previous hypotheses, the formation of verdazyl occurs through the intermediate formation of verdazilium cations. As part of the study, the spectroscopic and electrochemical behavior of the synthesized verdazyls was also studied in detail. The results obtained make a great contribution to the development of stable organic radicals for use in materials science.
Fedor E. Teslenko and Leonid L. Fershtat Unlocking Kuhn Verdazyls: New Synthetic Approach and Useful Mechanistic Insights // Int. J. Mol. Sci. 2023, 24, 2693. DOI: 10.3390/ijms24032693.