Biomedical
Diazenium Betaines Derived from the Stable Free Radical DPPH with Diradicaloid Behavior
Adela F. Dobre,
Augustin M. Mădălan,
Anamaria Hanganu,
Abstract
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.
