N-Phenylfluorenylidene)acridane (Ph-FA) compounds with electron-withdrawing and -donating substituents (H, MeO,P h, NO 2 ,B r, F) at the para position of the phenyl group were successfully synthesized by Barton-Kellogg reactions of N-aryl thioacridones and diazofluorene.B yu sing the substituent on the nitrogen atom to alter the electronic properties,both the folded and twisted conformers of p-NO 2 -C 6 H 4 -FA could be crystallographically characterized, which enabled the charge transfer from the electron-donating acridane moiety to the electron-accepting fluorenylidene moiety to be understood. Ground-state mechanochromism, thermochromism, vapochromism, and proton-induced chromism were demonstrated between the folded and twisted conformations of the conformers.P rotonation and chemical oxidation of Ph-FAg ave two stable acridinium compounds,n amely,t he fluorenylacridinium and acridinium radical cations.T he present study will contribute to the development of functional dyes and organic semiconductors.