Room temperature anthracene excimer emission from self-assembled (aminomethyl)anthracene derivatives in plastic crystalline phase

A series of (aminomethyl)anthracene (AMA) derivatives with single alkyl chain substituent (octyl, dodecyl, octadecyl and p-butylaniline) were synthesized and self-assembly of the compounds was analyzed in dichloromethane and solid thin film. Upon heat treatment of the solid thin films, the AMA derivatives exhibit plastic crystalline phase which can be preserved in a glassy state through rapid cooling of the system to room temperature. In the glassy state, the AMA derivatives are arranged in rectangular discotic columnar fashion, where the face-to-face distance between two anthracene moieties is 3.9 Å. Steady state and time resolved fluorescence studies were carried out in dichloromethane, which indicate that a fraction of the AMA derivatives form anthracene excimer, upon excitation at 360 nm. Conversely, photoexcitation of the solid thin film at 360 nm leads to the exclusive formation of anthracene excimers due to the close proximity of anthracene units in the discotic columnar arrangement. Furthermore, the self-assembled AMA derivatives were utilized as effective templates for in situ prepared Ag nanoparticles. While the AMA derivatives stabilize the Ag nanoparticles effectively, the excimer emission intensity was quenched in the presence of silver nanoparticles. The experimental results from the present study provide a unique approach for generating anthracene excimer emission from solid thin films at room temperature, which is a rare observation.