Covalent hybrids based on Re(i) tricarbonyl complexes and polypyridine-functionalized polyoxometalate: synthesis, characterization and electronic properties

Towards Covalent Photosensitizer-Polyoxometalate Dyads-Bipyridyl-Functionalized Polyoxometalates and Their Transition Metal Complexes

“…At positive voltages, three signals were identified (0.69, 0.43, and 0.09 V), which were correlated with oxidation processes involving the {V 3 } tris-vanadium cap of the POM fragment. These results agree with the data reported by Auvray et al elsewhere for related organo-functionalized Dawson-type POMs [26]. The same also holds true for the four reduction processes which were assigned to the cluster; the first two are expected to occur on the V(V) centers.…”

“…Detailed photophysical studies on the Ir(III)-containing dyads 9 and 11 with respect to the quenching mechanism are currently ongoing. However, the results line up with the observations already made for related POM-Re dyads, for which intramolecular electron-transfer processes were proposed [26]. Auvray et al pointed out that the luminescence quenching via such a pathway would be significantly more efficient in molecular dyads comprising a covalent linkage of the components; for the intermolecular electron transfer, as in the mixture of 3 and [Ir(ppy) 2 (bpy)] + , the diffusion rate will limit the quenching efficiency.…”

“…As described previously by the groups of Hasenknopf [26] and Streb [10], the bpy-equipped POMs represent versatile platforms for the coordination of transition metal complexes, such as biscyclometalated Rh(III) and Ir(III) or Re(I) tricarbonyl fragments. In line with these studies, the coordination of appropriate precursor complexes to the POM-bpy conjugates was investigated.…”

“…Similar signal patterns have been reported in the literature. However, no statement about their exact origin has been made [26,41]. Presumably, the intense signal at −1.34 V is due to a reduction of the tungsten centers.…”

“…The vacant amino groups of the TRIS-POM conjugated can be utilized for a subsequent attachment of additional functional molecules, such as Ir(III) photosensitizers, in Schiff-base reactions [18]. Hanan and Hasenknopf introduced an alternative approach in which polypyridyl ligands equipped with a triol anchor group were used to synthesize POMs with pending ligands for transition metal ion complexation [20,25,26]. Recently, aryl-substituted derivatives of tris(hydroxymethyl)methane have been suggested as tripodal ligands for the organo-functionalization of POMs [24].…”