In todays science, one of the most challenging and demanding tasks is the development of new
materials that can be utilized to make renewable and clean energy from abundant and easily
accessible resources. Water and light afford an opportunity be converted as raw materials in
artificial photosynthesis, a process where water splitting is used electrochemically to generate
energy. One major obstacle is the development of robust and long-living water oxidation catalysts
that efficiently produce molecular oxygen. Works have been aimed on the development of
homogenous catalyst systems that can readily produce molecular oxygen via a defined pathway. The
major challenge is the evolution of highly stable systems that can be immobilized on anode surfaces
to drive water splitting catalysis in a controlled manner. Typical homogenous systems can suffer from
an oxidative degeneration of the ligand sphere triggered by rough oxidation conditions leading to the
decomposition of the complex. By introducing a special ligand sphere, several improvements in
comparison to conventionally applied systems will be expected. In this coherence, aza-arenes are
appealing ligands as a variation in number and position of the nitrogen-atoms can accomplish
multinuclear and macromolecular catalysts (linear polymers or toroidal systems). Primarily, the
formation of macromolecular structures will impinge positively on the thermodynamic stability of the
catalysts. Additionally, toroidal structures that are built up from six building blocks have their active
sites oriented inwards. The hole will act as size discriminator and only allows potential substrates to
penetrate inside the hole for the transformation. Moreover, potential (deactivating) interferences
between solvent molecules, counteranions or impurities and the WOC will be avoided. All in all, the
geometry of the WOC will improve the turnover number (TON) and frequency (TOF) of the catalyst
when generating elemental oxygen from water. This, in combination with an enhanced stability of
macromolecular WOCs, will be beneficial for an immobilization of the catalysts into solid supports
(anodes and photoanodes) that can be integrated in photo-electrochemical cells to successfully
achieve an artificial photosynthetic system.