Ruthenium(II) Terpyridyl complexes featuring donor and acceptor moieties
In the last decades, tremendous research has been focused on the conversion of solar energy into chemical energy (i.e., photocatalysis). Hereby, scientists tried to mimic the fundamental processes in natural photosynthesis (i.e., light-harvesting, photoinduced charge separation, charge accumulation and multielectron catalysis), in order to prepare artificial photosynthetic devices. The thesis describes the synthesis and characterization of photoactive assemblies based on ruthenium(II) 2,2':6',2''-terpyridyl complexes that are capable of light-harvesting and photoinduced charge separation. It is shown that the remarkable customizability of terpyridine ligands in 4'-position and readily coordination to ruthenium centers enables a rapid access to highly functionalized complexes. The latter are equipped with organosulfurs as electron donors and fullerenes or polyoxometalates as electron acceptors and the donor-acceptor distance was varied by incorporation of spacer units. The systems can be considered as linear molecular triads with the complex as central light absorbing photosensitizer. Upon visible light excitation, two electron transfer processes involving the donor and acceptor units are observed and result in a long-ranged charge separated state. The lifetime of the charge separation increases with the donor-acceptor distance and is multiple times higher than the lifetime of the excited state, which reflects the effectivity of the photosensitizer. Furthermore, it is demonstrated that light-harvesting antennae systems can be obtained via linkage of iridium(III) and ruthenium(II) complexes. The dinuclear complexes feature enhanced absorptivity and in addition, the light which is absorbed by iridium complex is efficiently transferred to the ruthenium complex.
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