A Diazaborolidine Nitronyl Nitroxide: Synthesis, Structure, and Electronic Properties

Abstract In this paper, we report the nitronyl nitroxide organoboron derivative, namely, 1,3-bis(2,6-diisopropylphenyl)-2-(4,4,5,5-tetramethyl-3-oxide-1-oxyl-4,5-dihydro-1H-imidazole-2-yl)-1,3,2-diazaborolidine. The paramagnet is stable under ambient conditions. It was characterized by electron spin resonance (ESR), cyclic voltammetry (CV), infrared (IR), and UV–vis spectroscopy, supported by quantum chemical calculations. The molecular and crystal structure of the diazaborolidine nitronyl nitroxide was determined by X-ray diffraction analysis. ESR spectroscopy combined with DFT calculations revealed spin density delocalization onto the boron atom. Cyclic voltammetry showed a reversible oxidation wave attributed to the nitronyl nitroxide moiety at E1/2 = 303 mV and an irreversible reduction process at Ep = −1815 mV (vs Fc/Fc+). This work expands the family of functional paramagnetic systems and opens new prospects for the design of high-spin organic magnets based on the chemistry of organoboron compounds.