A study of aggregation of 9-(dicyano-vinyl)julolidine.

Di(cyano vinyl)julolidine (DCVJ) is a fluorescent probe which has been used to monitor the local mobility of its binding sites on proteins. It shows a concentration dependence of its emission spectrum in water. At higher DCVJ concentrations, a longer wavelength band appears. The latter increases relative to the shorter wavelength band as a function of increased DCVJ concentration. Absorption and excitation spectra indicate that the concentration dependent emission in the longer wavelength is a consequence of association in the ground state and subsequent excimer formation. DCVJ forms two types of complexes with gamma-cyclodextrin, one of which shows the longer wavelength emission band. Analysis of stoichiometry of association also suggests that longer wavelength emission band may be a consequence of association of two molecules of DCVJ in the gamma-cyclodextrin cavity. Possible uses of such excimer formation in biological systems have also been discussed.