Excimer formation of cyanobiphenyls in calix[4]resorecinarene derivative probed by picosecond time-resolved fluorescence spectroscopy

Excimer formation kinetics of cyanobiphenyls (CB), which are linked in a parallel direction to a calix[4]resorecinarene (CRA), has been examined by means of a picosecond time-resolved fluorescence spectroscopy. From fluorescence decay analyses, the rate constant of excimer formation is estimated to be k3 = 1.9 × 109 s−1 and that of dissociation to be k4 = 4 × 107 s−1. These values are significantly smaller than those for a liquid crystal of 4-cyano-4′-octyloxybiphenyl (8OCB). The parallel orientation of CB groups in CRA may hinder the excimer formation, in contrast to those in the 8OCB liquid crystal in which the CBʹs form a weakly coupled antiparallel dimer in the ground state.