Artificial photosynthesis aims to develop photocatalytic systems for light-driven water splitting. Promising structures are molecular assemblies combining a light-harvesting and a redox-active catalytic unit, which are chemically linked by a molecular bridge. Such molecularly defined systems offer the opportunity for detailed, mechanistic investigations upon structural modifications. From various studies, transition metal complexes, i.e., based on Ru II , Ir III , Os II or Re I emerged as efficient photosensitizer building-bocks. However, to strive for sustainable photocatalysis it is mandatory to replace noble-metal sensitizers by low-cost and easy to derivatize organic chromophores such as oligothiophene and rylene dyes.