Photophysics of cis- and trans-1-(1-indanylidene)indane. Spectroscopic evidence for aggregation of the trans isomer

Abstract

From the temperature and concentration dependence of UV-vis absorption, fluorescence emission and excitation spectra of both trans- and cis-1-(1-indanylidene)indane it is concluded that at concentrations as low as 10 −4 M, aggregation can occur in solutions of the trans isomer. Since the emission is the superposition of the fluorescence of the monomer and an aggregated species, its spectrum is excitation wavelength dependent. The kinetic parameters of teh excited states derived in the past from experiments with solute concentrations larger than 10 −4 M must therefore be used with discretion. The unexpected formation of aggregates of trans-1-(1-indanylidene)indane is discussed on the basis of thermodynamic considerations.