Synthesis and properties of dinitrobenzamido-TEMPO derivatives

Abstract

4-Chloro-3,5-dinitrobenzoic acid (1a) and 2-chloro-3,5-dinitrobenzoic acid (1b) were converted into the corresponding acid chlorides (2a and 2b) and these were reacted first with an equimolar amount of 4-amino-2,2,6,6-tetramethylpiperidine-N-oxyl radical (4-amino-TEMPO) to afford monoradicals 3a, 3b, 5a, and 5b and then either (i) with methoxyamine to yield hetero-diradicals 6a and 6b, or (ii) with a second mole of 4-amino-TEMPO to afford homo-diradicals 4a and 4b. The reaction of 3a with 1,3-bis(aminooxy)propane gave the homo-diradical 7a. These reaction products are stable mono-or di-radicals as evidenced by their ESR spectra at various temperatures. The above reaction products can participate as oxidizers in redox reactions, and they afford deep-colored anions with inorganic or organic bases.Keywords: Dinitrobenzamido-TEMPO derivatives, mono-and diradicals (homo-and heterodiradicals), paramagnetic-chromogenic derivatives, RES, oxidizing properties