Synthesis, Characterization, and Water Oxidation Activity of Isomeric Ru Complexes

Abstract

The synthesis and characterization of the isomeric ruthenium complexes with the general formula cis- and trans-[Ru­(trpy)­(qc)­X] n+ (trpy is 2,2′:6′,2″-terpyridine, qc is 8-quinolinecarboxylate, cis - 1 and trans- 1, X = Cl, n = 0; cis - 2 and trans- 2, X=OH2, n = 1) with respect to the relative disposition of the carboxylate and X ligands are reported. For comparison purposes, another set of ruthenium complexes with general formula cis- and trans-[Ru­(trpy)­(pic)­(OH2)]+ (pic is 2-picolinate (cis-3, trans-3)) have been prepared. The complexes with a qc ligand show a more distorted geometry compared to the complexes with a pic ligand. In all of the cases, the trans isomers show lower potential values for all of the redox couples relative to the cis isomers. Complexes cis - 2 and trans- 2 with six-member chelate rings show higher catalytic activity than cis - 3 and trans - 3. Overall, it was shown that the electronic perturbation to the metal center exerted by different orientation and geometry of the ligands significantly influences both redox properties and catalytic performance.

New ruthenium polypyridyl complexes as potential sensors of acetonitrile and catalysts for water oxidation

“…The diagram of Fig. 4 is almost identical to those found for the recently reported complexes cis - and trans -[Ru II (trpy)(qc)(OH 2 )] + , where qc = 8-quinoline-carboxylate, 32 which exhibit good performances as WOCs, thus evidencing that complex 2 is a promising candidate for catalysing one of the key steps in artificial photosynthesis. 18 …”

Dangling Carboxylic Group That Participates in O–O Bond Formation Reaction to Promote Water Oxidation Catalyzed by a Ruthenium Complex: Experimental Evidence of an Oxide Relay Pathway

“…During water oxidation reaction, removal of hydrogen atoms (H + + e – ) from a water molecule and the making of an O–O bond are two major aspects that a catalyst should execute effectively. − To develop an effective catalyst, the judicious design of a ligand is essential. In recent years, strategies are taken to design ligands that not only govern the primary coordination sphere but also fine-tune the secondary interactions. − In this regard, the design of molecular catalysts containing a carboxylate functional group in the ligand scaffold has gained much attention in order to develop efficient water oxidation catalysts (WOCs), particularly with ruthenium metal ions. − ,− In a natural oxygen-evolving complex of photosystem II, the manganese ions are surrounded by numerous negatively charged oxo and carboxylate ligands that provide a coordination environment as well as modulate the reactivity by forming a hydrogen bond with incoming water . The carboxylate moiety in a ligand can play diverse roles to control the catalytic performances of metal complexes.…”

Electrochemical ruthenium-catalysed C–H activation in water through heterogenization of a molecular catalyst

“…The complex is essentially isostructural to cis -[Ru II (tpy)(pic)Cl] described by Llobet and co-workers. 51 The trans -isomer, with the carboxylate moiety in the axial position, was only observed in small amounts and could be separated by preparative HPLC. This is consistent with previous reports of [Ru II (tpy)(pic)Cl] synthesised from ethanolic H 2 O, 43 whereas synthesis from EtOH lead to the formation of both isomers.…”

“…This is consistent with previous reports of [Ru II (tpy)(pic)Cl] synthesised from ethanolic H 2 O, 43 whereas synthesis from EtOH lead to the formation of both isomers. 51,52…”