Experimental and Theoretical Examination of the Radical Cations Obtained from the Chemical and Electrochemical Oxidation of 5‐Aminothiazoles. Issue 2 (15th March 2017)

• Record Type: Journal Article
• Authors: Yamaguchi, Kirara; Murai, Toshiaki; Kutsumizu, Shoichi; Miwa, Yohei; Ebihara, Masahiro; Guo, Jing‐Dong; Tokitoh, Norihiro
• Is Part Of: ChemistryOpen. Volume 6:Issue 2(2017)
• Page Start: 282
• Page End: 287
• Publication Date: 2017-03-15
• Subjects: absorption spectroscopy -- electron paramagnetic resonance -- heterocycles -- oxidation -- radical ions; Chemistry -- Periodicals; 540; 540.5
• DOI: 10.1002/open.201700016
• Languages: English
• ISSNs: 2191-1363

Abstract

Abstract: Chemical or electrochemical one‐electron oxidation of 5‐ N ‐arylaminothiazoles was found to afford stable radical cations. For chemical oxidation, 1 equivalent of [(4‐BrC6 H4 )3 N][SbCl6 ] (Magic Blue, MB) was added to CH2 Cl2 solutions of the thiazoles, and the thus‐obtained radicals showed light absorption in the near‐infrared region. Electrochemical oxidation also led to bathochromic shifts in the absorption bands, and the obtained spectra were similar to those derived from the chemically oxidized species. These radicals afforded electron paramagnetic resonance (EPR) spectra that are consistent with the notion of stable nitrogen radicals (half‐life≤385 h). The EPR spectrum of a thiazole containing 4‐dimethylaminophenyl groups on the nitrogen atom at the 5‐position changed significantly upon adding >3 equivalents of MB. Details of the electronic structures of the experimentally obtained radical cations were generated from theoretical calculations. Abstract : A little bit of magic : 5‐Aminothiazoles are subjected to chemical and electrochemical oxidation to afford the corresponding radical cations. These radicals show broad absorption spectra and half‐life times of up to several days. DFT calculations support the experimentally observed substantial bathochromic shifts in the maximum absorption wavelengths of the 5‐aminothiazoles upon oxidation.