Synthetic investigation for spiro-junctioned biradical compounds

Biradical compounds are expected as promising building blocks for molecular magnetic materials, especially when they have a ground triplet state. We focused on spiro-junctioned D2d biradicals, 9,9’(10H,10H’)-spirobiacridine-10,10’-dioxyls. tert-Butylation would suppress intermolecular interaction and facilitate analysis on the intramolecular exchange coupling. During attempted preparation of a precursory diamine 2,2’,7,7’-tetra-tert-butyl-9,9’(10H,10’H)-spirobiacridine, 2,7-di-tert-butyl-9-{3-tert-butyl-6-(4-tert-butylphenylamino)phenyl}acridine was isolated as an isomeric byproduct and characterized by means of spectroscopic methods including 2D NMR. Fast aromatization is assumed to occur before intramolecular Friedel-Crafts cyclization.Biradical compounds are expected as promising building blocks for molecular magnetic materials, especially when they have a ground triplet state. We focused on spiro-junctioned D2d biradicals, 9,9’(10H,10H’)-spirobiacridine-10,10’-dioxyls. tert-Butylation would suppress intermolecular interaction and facilitate analysis on the intramolecular exchange coupling. During attempted preparation of a precursory diamine 2,2’,7,7’-tetra-tert-butyl-9,9’(10H,10’H)-spirobiacridine, 2,7-di-tert-butyl-9-{3-tert-butyl-6-(4-tert-butylphenylamino)phenyl}acridine was isolated as an isomeric byproduct and characterized by means of spectroscopic methods including 2D NMR. Fast aromatization is assumed to occur before intramolecular Friedel-Crafts cyclization.