What type of study is this?

This is a DFT calculations study (also classified as: Cyclic Voltammetry, NMR, HR-MS, Electron Spin Resonance).

September 10, 2025ACS Omega1 citationsOpen Access

Dimer of the DPPH Stable Radical

ADAdela F. DobreUniversity of Bucharest CLCecilia LeteRomanian Academy VKV. KuncserNational Institute of Materials Physics

Key Points

Dimerization of DPPH radical was achieved through an alternative synthesis, leading to new structural insights.
Oxidation of the DPPH-dimer generated a diradical that retained properties similar to the original DPPH radical.
Analyses like NMR and electron spin resonance confirmed the structures and characteristics of the synthesized compounds.
DFT calculations indicated an open-shell singlet ground state with significant diradical character.

Abstract

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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