Biological water oxidation is the basis of higher life on Earth and has become the blue-print for developing artificial water oxidation catalysts made of cheap and sustainable base metals. While tremendous progress has been achieved over the last decades in understanding biological water oxidation, important aspects are not yet known at a level required for successful translation into artificial systems. In this project we will study both biological and synthetic catalysts capable of water oxidation. To meet this challenge, we combine our local strong expertise in experimental probes of water oxidation with electronic structure calculations to provide an integrated view of water-splitting catalysts. We have previously shown the effectiveness of our approach by showing how electronic properties are affected both by the choice of metal and the ligand design ligand. This includes temperature-dependent spin-crossover behavior, magnetic anisotropy, oxidation potential as well as catalytic performance in water oxidation. Calculations will be performed using a combination of density-functional theory and molecular mechanics methods, both stand-alone and combined in multi-scale methods.