Direct observation of excimer formation in anthracene and 9,9′-bianthryl

The existence of anthracene excimer in fluid solution was confirmed for the first time by observing the coincidence of the rise time of excimer fluorescence with the decay time of monomer fluorescence with the use of a picosecond laser, a streak camera, and a computer. The continuum model of diffusion theory is found to be applicable to the excimer formation and the encounter distance between anthracene in the excited state and that in the ground state is calculated to be 8 ± 2 Å. The anomalously broad featureless fluorescence observed for 9,9′-bianthryl in glycerol-methanol (9:1) solution was found to be emitted from the species formed only in the excited state and its rise time was found to be coincident with the decay time of fluorescence from anthracene moiety composing 9,9′-bianthryl, α,ω-9,9′-bianthrylpropane, -butane, -hexane, and -dodecane were found not to form excimer in the excited state.