Intermolecular Bonds Bridging Two Anthracene Molecules inA γ-Cyclodextrin

The most preferable state of the two neutral anthracene molecules in a cylindrical molecule ofγ-cyclodextrin is assigned as a face-to-face (coplanar, S-shape) configuration that is distinguished from the gas phase, where anthracenes form a face-to-edge (T-shape) configuration. Their faces are slightly tilted and twisted, thus the nearest sites are 9 and 9' and the second nearest sites are 10 and 10' between them. Excitation (300-400 nm) forms intermolecular bonds between two anthracenes in aγ-cyclodextrin. Absorption spectra were obtained from the reflection spectra of the powder sample using the Kubelka-Munk formula. Differential spectra of samples before and after irradiation (300- 400 nm) show a broad absorption band. This band corresponds to the transition from the ground state to the excited state of the supramolecular complex. Theab initioand molecular dynamics simulation reveal that the most probable bonds between them are the intermolecular bonds formed at the middle of them, namely, one between 9 and 9' and the other between 10 and 10' sites.