New isoindoline aminoxyl based polyradicals for spin probes and molecular magnetic materials

Abstract

The synthesis of a range of aminoxyl polyradicals based on the isoindoline aminoxyl moiety is described. Friedel–Crafts alkylation reactions between 1,1,3,3-tetramethylisoindolin-2-yloxyl (1) and suitable haloalkanes were used to prepare three new biradicals and one new triradical. Standard methods for the synthesis of nitronyl aminoxyls and iminyl aminoxyls were employed to prepare two novel tridentate biradical derivatives of 1. Also a novel isoindoline-like fused biradical was prepared. The room temperature solution EPR spectra of all radicals are reported and reveal a wide range of exchange coupling constants. The crystal structure determinations of two of these compounds, 1,1-bis(1′,1′,3′,3′-tetramethylisoindolin-2′-yloxyl-5′-yl)ethane (3) and 1,2,3,5,6,7-hexahydro-1,1,3,3,5,5,7,7-octamethylbenzo[1,2-c:4,5-c′]dipyrrol-2,6-diyloxyl (15), are reported.