Self-Assembled Anthracene Dimers Formed in Aqueous Solution in the Presence of γ-cyclodextrin

Abstract

We have studied the dimer formation of a series of mono- and disubstituted anthracenes (1-methylanthracene, 2-methylanthracene, 9-methylanthracene, and 9,10-dimethylanthracene) in the γ-cyclodextrin nanocavity, using electronic absorption and fluorescence spectroscopic techniques, as well as quantum chemical calculations. We have measured fluorescence spectra of anthracene derivatives in ethanol and γ-CD aqueous solution, and the excimer-like fluorescence was observed only in γ-CD aqueous solution. The fluorescence excitation spectra observed with the excimer-like fluorescence showed an exciton splitting in the S₃ ← S₀ electronic transition of anthracene π-electron system. This splitting indicates that a self-assembled dimer was formed in γ-CD. The structures of dimers were estimated from the exciton splitting energies with the help of Lennard-Jones potential calculations including coulombic interactions.

Keywords:

• anthracene
• cyclodextrin
• dimer
• fluorescence
• Lennard-Jones

Acknowledgment

This work was supported by a Grant-in-Aid for Scientific Research (C) (No. 20550001) from MEXT Japan to S.-i.S., and by Grant-in-Aid for JSPS Fellows (No. 20·2850) from JSPS to T.K.