Synthesis and physicochemical properties of methoxy-substituted diphenyldihydroacridine and its Si and Ge bridged analogues and corresponding nitroxide radical derivatives

Three dihydroacridine analogues, 2,7-dimethoxy-9,10-dihydro-9,9-diphenylacridine (1-C), 2,8-dimethoxy-10,10-diphenyl-5,10-dihydrophenazasiline (1-Si), and 2,8-dimethoxy-10,10-diphenyl-5,10-dihydrophenazagermine (1-Ge), and corresponding nitroxide radical derivatives, 2,7-dimethoxy-9,10-dihydro-9,9-diphenylacridine-10-oxyl (2-C), 2,8-dimethoxy-10,10-diphenyl-5,10-dihydrophenazasiline-5-oxyl (2-Si), and 2,8-dimethoxy-10,10-diphenyl-5,10-dihydrophenazagermine-5-oxyl (2-Ge) were synthesized in order to study the effect of the Si and Ge bridging atoms on the physicochemical properties of the diaryl nitroxide radical derivatives. These derivatives were stable in non-halogenated solvents and in the solid state. Their structures were crystallographically analyzed and UV–vis, fluorescence, EPR, and cyclic voltammetry measurements were performed to investigate the physicochemical properties of the dihydroacridine analogues and nitroxide radical derivatives.