Photochemistry of Amino-Linked Bichromophoric Anthracenes. Efficient Cyclomerization of 9-(1-Naphthylmethylaminomethyl)anthracene and Adiabatic Cycloreversion of the Cyclomer

Abstract

Abstract The spectral and photochemical properties of the title compound 1 and bis(9-anthrylmethyl)amine (2) have been investigated. The fluorescence spectrum of 1 in methylcyclohexane showed an emission from the locally excited state of the anthracene part and a weak broad emission at 410—550 nm from the intramolecular exciplex. The fluorescence quantum yields of 1 and 2 decreased along with an increase in the solvent polarity. Both 1 and 2 underwent intramolecular [4+4] cycloaddition. The quantum yield of the cyclomerization of 1 was 0.24 in acidic methanol, while in MeCN the reaction was completely quenched by an intramolecular electron transfer from the amino group to the excited anthracene moiety. Excitation of the cyclomer from 1 at 285 nm brought about fluorescene from both the locally excited anthracene and the exciplex state, indicating that adiabatic cycloreversion took place on the S1 potential surface. To investigate the conformations, the crystal structures of 1 and 2 were determined and PM3 calculations were performed for 1–H+. The calculations indicate that a conformer in which the two chromophores are located close to each other has a higher energy then other stable conformers.