A series of heterodinuclear complexes, M-1-PtX with M=H , Zn, Cu or Co, X=Cl or I, has been synthesized, and first results on their photocatalytic activity in visible light driven proton reduction are presented. The compounds are based on a phenanthroline extended meso-tetramesityl-porphyrin bridging ligand (H -1) incorporating different metal centers in the porphyrin moiety, which functions as a photosensitizer unit. The well-known catalytically active PtX fragment resides in the phenanthroline coordination pocket. The synthesis was optimized, compounds were fully characterized and a solid-state structure could be obtained for selected complexes. Photocatalytic studies in acetonitrile/water mixtures using triethylamine as sacrificial electron donor showed that the activity of the complexes depends strongly on the metal center in the porphyrin moiety as well as the halogen ions bound at the platinum(II) center.
Two synthetic approaches towards the mononuclear complex [(tbbpy) 2 Os II (tpphz)] 2+ (tbbpy = 4,4′-di-tert-butyl-2,2′bipyridine; tpphz = tetrapyrido[3,2-a:2′,3′-c:3′′,2′′-h:2′′′,3′′′j]phenazine) based on the precursor [(tbbpy) 2 Os II Cl 2 ] and its oxidized side product [(tbbpy) 2 Os III Cl 2 ] + are presented. The first route is analogous to that for the isostructural ruthenium complex, whereas the second strategy efficiently uses the oxidized Os III complex under reducing conditions to obtain so-called virtual dilution, which avoids the formation of the dinuclear complex [(tbbpy) 2 Os II (tpphz)Os II (tbbpy) 2 ]. Concentration-dependent [a]
The synthesis and characterization of a mixed metal ruthenium(II)/gold(III) complex bridged by tetrapyridophenazine (tpphz) are described. It is isostructural and isoelectronic to the well-known photocatalysts with palladium(II) or platinum(II). Concentration dependent 1 H-NMR spectroscopy and XRD studies show that the electrostatic repulsion between the gold(III) moieties exceeds the attractive π-stacking interaction.Theoretical calculations based on the new structural data confirm an increased positive charge on the bridging ligand as well as significantly altered orbital symmetry as compared to the previously investigated palladium(II) complex. This is the first example of a tpphz ruthenium(II) complex where π-stacking is completely inhibited. The detailed investigation of the solid-state structure showed for the first time in bimetallic tpphz bridged complexes no significant torsion within the bridging ligand itself. Although catalytic performance for proton reduction by gold(III) is naturally not observed, its photochemical decomposition in colloidal gold particles could be shown by TEM and DLS.
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