Continuing our development of artificial models for photosystem II in green plants, a series of compounds have been prepared in which a Ru(bpy)32+ photosensitizer is covalently linked to a manganese(II) electron donor. In addition to a trispicolylamine ligand, two other manganese ligands, dipicolylamine and aminodiacetic acid, have been introduced in order to study ligands that are appropriate for the construction of manganese dimers with open coordination sites for the binding of water. Coordination equilibria of the manganese ions were monitored by EPR. The interactions between the ruthenium and manganese moieties were probed by flash photolysis, cyclic voltammetry and steady-state and time-resolved emission measurements. The quenching of the RuII excited state by MnII was found to be rapid in complexes with short Ru-Mn distances. Nevertheless, each RuII species could be photo-oxidized by bimolecular quenching with methylviologen, and the subsequent electron transfer from MnII to RuIII could be monitored.
- N ligands
- Electron transfer