Neutron reflectometry has been employed to determine the structure of films adsorbed from aqueous solutions of[Ru(bipy)(2)(bipy')] [Cl](2) complexes where (bipy') = 5,5'-dialkyl- 2,2'-bipyridine. Surfactants with alkyl chains with carbon numbers of n = 13 and 19 have been studied for which both alkyl chains on each molecule have the same chain length. Measurements of solutions with concentrations below and in excess of the critical micelle concentration (cmc) have been made. For the complex with n = 13, an adsorbed film resides at the solution surface and the maximum surface coverage corresponds to an area per molecule of 100 +/- 2 Angstrom(2) molecule(-1), which is comparable with the expected headgroup area of the molecule. A different situation arises for complexes with n = 19. Here the measured reflectivity data are extremely time-dependent, with the solutions taking up to 12 h to form an equilibrium surface layer. From the equilibrium measurements, the values determined for the area per molecule indicate that for concentrations greater than the cmc there are approximately two headgroups associated with each monolayer adsorption site at the surface, suggesting that the monolayer is highly corrugated or a more complex surface structure exists.