Models of molecular photocatalysts for water oxidation: Strategies for conjugating the Ru(bda) fragment (bda=2,2′-bipyridine-6,6′-dicarboxylate) to porphyrin photosensitizers

Model dyads, in which the Ru(bda) water oxidation catalyst (WOC) is connected to a porphyrin, were prepared following two different modular strategies: i) the direct linkage approach, in which porphyrins bearing peripheral pyridyl rings are bound to the {Ru(bda)} fragment as axial ligands, and the metal-containing ligand approach, in which symmetrical trans-[Ru(bda)(L)(2)] or unsymmetrical trans- [Ru(bda)(L)(pic)] compounds (L = bifunctional pyridyl linker), are axially bound to metalloporphyrins. Both synthetic strategies are modular and thus rather flexible in nature. As proofs of principle, the following Ru(bda) - porphyrin dyads are described: trans-[Ru(bda)(4'-MPyP)(2)] (2, 4'-MPyP = 5-(4'-pyridyl)-10,15,20-phenylporphyrin), and the sandwich compounds [trans-Ru(bda)(4,4'-bpy)(2) {Ru(CO)(TPP)}(2)] (5) and [trans-Ru(bda)(4,4'-bpy)(2) (6Zn)](2) (7), where 6Zn is the porphyrin metallacycle [trans,cis,cis-RuCl2(CO2)(2)(Zn.4' -cisDPyP)](2) (4'-cisDPyP = 5,10-(4'-pyridyl)-15,20-(phenyl)-porphyrin.

Automated summary

This study demonstrates the connection between the Ru(bda) water oxidation catalyst and porphyrin through two different modular strategies, showing a highly flexible synthetic approach.