Chemistry (Sep 2024)

Diazenium Betaines Derived from the Stable Free Radical DPPH with Diradicaloid Behavior

  • Adela F. Dobre,
  • Augustin M. Mădălan,
  • Anamaria Hanganu,
  • Petre Ionita

DOI
https://doi.org/10.3390/chemistry6050052
Journal volume & issue
Vol. 6, no. 5
pp. 899 – 910

Abstract

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Starting from the well known stable free radical DPPH (or its reduced counterpart, 2,2-diphenyl-1-picryl-hydrazine) and several amino derivatives, novel zwitterionic compounds (diazenium betaines) were obtained and characterized by different means, like NMR, IR, MS, and UV–Vis. These betaines are highly intense blue-colored compounds that can be easily reduced by ascorbic acid (vitamin C) or sodium ascorbate to their corresponding para-phenyl substituted derivatives of DPPH, which have a yellow color. Most of such redox processes were found to be reversible. However, the oxidation of 2-p-aminophenyl-2-phenyl-1-picryl-hydrazine led to an azo-derivative of DPPH diradical, and its structure was unveiled by X-ray monocrystal diffraction. Possible diradicaloid behavior is also discussed.

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