Tracer diffusion of viologen dications in aqueous NaCl, KBr, NaDS, and DTABr solutions

Diffusion coefficients have been measured for five viologen halides, i.e., 1,1′-dimethyl-, diethyl-, dipropyl-, dibutyl-, and diphenyl-4,4′-bipyridinium chlorides or bromides, whose concentrations are less than 2 × 10− 4 M (1 M = 1 mol dm− 3), in aqueous solutions of 0.1 M NaCl, 0.1 M KBr, 0.04 M sodium dodecyl sulfate (NaDS), and 0.04 M dodecyltrimethylammonium bromide (DTABr) at 298.15 K. The values obtained can be taken as tracer diffusion coefficients of the viologen dications and those in the NaCl and KBr solutions are found to be very close to those of tetraalkylammonium ions in water when compared at the same ionic radius. The degree of association of the viologen dications to the micelles were calculated to be 100% for 0.04 M NaDS in water, larger than 97% for 0.04 M NaDS + 0.1 M NaCl, and less than 6% for 0.04 M DTABr. Some discussions are made for the results with those obtained from the analyses of photoinduced electron-transfer reactions.