This work comprises a redox-chemical investigation of a pyrazole-containing expanded porphyrin - the so-called Siamese-twin porphyrin. It includes synthetic organic and inorganic work and applies a series of analytical techniques. Repeated periphery-to-core fusion reactions of the ligand framework upon oxidation were studied in detail. Further, communication of the porphyrin-like hemi-macrocycles in a monopalladium(II) complex were revealed. Redox investigations and complementary calculations were performed to uncover the importance of a metalation-induced tautomerism on the electronic structure of the expanded porphyrin. Additional cooperative effects of the non-innocent ligands system and its central ion in bimetallic manganese(III) complexes were examined.
