Metal-organic complexes are of particular interest for studying photoinduced electron transfer as primary step for conversion and storage of solar energy. For vectorial electron transfer and rapid charge delocalization dyads have been made by chemically linking different complexes with a common ligand. Organized monolayers formed at the air-water interface by co-spreading the dyad with appropriate lipids provide excellent possibilities for well-defined deposition of such elaborate molecules on a solid surface. We studied the behavior of a Ru-Rh dyad with four COOH groups at the Rh ligands and having a net charge of + 1 (if all COOH groups are dissociated) by measuring pi-A and Delta V-A isotherms and reflection spectra. The water-soluble dyad remains at the interface when co-spread with negatively charged dimyristoylphosphatidic acid. Surprisingly, the dyad is also present at the interface after co-spreading with eicosylamine. We attribute this to strong interactions between the COO- groups and the protonated NH3+ groups overcompensating the repulsion by the more remote positive charge.