Dimer formation of a stilbenesulphonic acid salt in aqueous solution

The steady-state and time-resolved fluorescence and H-1 NMR spectra of a st ilbenesulphonic acid salt, commonly used as an optical brightening agent, w as studied as a function of concentration in aqueous solution. The aggregat es, formed at higher concentrations, were shown to be predominantly dimers with the central stilbene moieties of the molecules stacked plane-parallel. The equilibrium constant for the dimer formation at 25 degrees C was obtai ned from both NMR and fluorescence measurements. Copyright (C) 1999 John Wi ley & Sons, Ltd.