Intermolecular bonds bridging two anthracene molecules in a gamma-cyclodextrin

The most preferable state of the two neutral anthracene molecules in a cyli ndrical molecule of gamma-cyclodextrin is assigned as a face-to-face (copla nar, S-shape) configuration that is distinguished from the gas phase, where anthracenes form a face-to-edge (T-shape) configuration. Their faces are s lightly tilted and twisted, thus the nearest sites are 9 and 9' and the sec ond nearest sites are 10 and 10' between them, Excitation (300-400 nm) form s intermolecular bonds between two anthracenes in a gamma-cyclodextrin. Abs orption spectra were obtained from the reflection spectra of the powder sam ple 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, The ab initio and molecular dynamics simulatio n reveal that the most probable bonds between them are the intermolecular b onds formed at the middle of them, namely, one between 9 and 9' and the oth er between 10 and 10' sites. (C) 1999 Academic Press.