The direct, one-step oxidation of aromatic C–H bonds is an important reaction, as the generated phenol products are important precursors for the synthesis of pharmaceuticals and functional polymers. Nevertheless, due to the inert character of aromatic C–H bonds and the low product selectivity usually obtained, the development of catalysts that can generate powerful and selective oxidants is needed in order to enable proficient aromatic oxidation reactions. In this respect, nature has been taken as inspiration, and bioinspired complexes have been explored for the development of novel methodologies in oxidation catalysis. The present thesis describes the direct hydroxylation of aromatic C–H bonds catalyzed by aminopyridine-based manganese and nickel complexes, employing aqueous hydrogen peroxide as benign oxidant. The thesis details the development of new catalysts systems based on first-row transition metal complexes and contributes to the current transition from noble metals to non-noble metals in catalysis.