Biomedical
Diazenium Betaines Derived from the Stable Free Radical DPPH with Diradicaloid Behavior
Adela F. Dobre,
Augustin M. Mădălan,
Anamaria Hanganu,
Petre Ionita
Peer Reviewed
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.
Key Questions and Answers
1. What are the key features that contribute to the stability of the DPPH free radical?
The stability of DPPH is largely attributed to its steric and electronic factors, such as the influence of the ortho-nitro groups that prevent dimerization, and the combination of electron-donating and electron-accepting groups creating a push-pull effect that stabilizes the radical.
2. How do the redox properties of DPPH relate to its applications in antioxidant measurements and ESR spectroscopy?
DPPH’s redox properties, especially its reaction to antioxidants, make it useful in antioxidant assays. Additionally, its behavior as a stable free radical makes it a reliable standard for electron spin resonance (ESR) spectroscopy.
3. What role do amino derivatives play in the synthesis of diazenium betaines from DPPH?
Amino derivatives react with DPPH to form diazenium betaines. This reaction creates stable zwitterionic compounds, which are characterized using various techniques such as NMR, IR, and UV-Vis spectroscopy.
4. How do the properties of diazenium betaines, including their potential diradicaloid behavior, influence their applications in organic materials?
Diazenium betaines exhibit diradicaloid behavior, which offers unique properties for organic materials, including applications in solar cells, photovoltaics, spintronics, and energy storage, due to their optical, electronic, and magnetic characteristics.
5. How does the study extend the scope of diazenium betaines synthesis and their potential for unique applications in photovoltaics, spintronics, and energy storage?
This study broadens the synthesis of diazenium betaines by exploring different substrates and revealing their interesting redox and diradicaloid behaviors, making them suitable for diverse applications in functional organic materials like photovoltaics and energy storage devices.
