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Updated: Sep 10, 2025

Isolating Free Carbenes, their Mixed Dimers and Organic Radicals
Published on: April 19, 2019
Dimer of the DPPH Stable Radical
Adela F Dobre1, Cecilia Lete2, Victor E Kuncser3
1Faculty of Chemistry, University of Bucharest, Panduri 90, Bucharest 050663, Romania.
None:
Although the DPPH (2,2-diphenyl-1-(2,4,6-trinitrophenyl)-hydrazyl) radical is known for its indefinite stability, both in solid and in solution, and therefore no dimerization reaction occurs, the DPPH-dimer has been obtained by an alternative synthesis. Oxidation of the DPPH-dimer led to the corresponding DPPH-diradical, practically exhibiting all of the known properties of the simple DPPH radical. The structures were confirmed using 1H and 13C NMR, IR, UV-vis, HR-MS, and electron spin resonance (for the diradical) analyses. Additionally, cyclic voltammetry and superconducting quantum interference device (SQUID) measurements were performed to investigate the electrochemical and magnetic properties of the DPPH-diradical. DFT calculations revealed that the ground state was an open-shell singlet. The diradical character y of the ground state and vertical S-T gap were 0.279 and -5.81 kcal mol-1, respectively.
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