This chapter discusses visible light photocatalysis by a titania transition metal complex. Hexachloroplatinic acid in solution only induces a stoichiometric visible light photooxidation of the ubiquitous water pollutant 4-chlorophenol (4-CP), whereas, the reaction becomes photocatalytic when the complex is supported onto titania. It was found that the most active catalyst was obtained when the complex was covalently attached to titania. Different from a single crystal electrode, it is more difficult to measure the flatband potential of a semiconductor powder, which is necessary to estimate the absolute positions of the valence and conduction band edges. The degradation of atrazine in general affords cyanuric acid as the final product when the photocatalyst is an unmodified titania material. In the photodegradation with sunlight, a significant difference between the photocatalysts prepared by adsorption from solution and by grinding becomes apparent.