Air-stable Curved pi-Radical Based on Corannulene: Dynamic Electronic-spin Structure Induced by Temperature-dependent Conformational Changes

A new corannulene-based curved neutral pi-radical bearing a tert-butylnitroxide moiety has been synthesized and isolated as an air-stable solid. Direct attachment of the spin centre to the corannulene skeleton gives rise to an extensive spin-delocalization onto the curved pi-conjugated system from the nitroxide moiety. This salient electronic feature in the curved neutral radical system and its high stability have allowed us to find a dynamic electronic-spin behaviour induced by the temperature-dependent conformational change of the nitroxide moiety, as studied by liquid-phase variable-temperature electron spin resonance and H-1 electron-nuclear double resonance and electron-nuclear-nuclear triple resonance spectroscopies with the help of density functional theory calculations.