Ruthenium complexes containing the pentapyridyl ligand 6,6′′‐(methoxy(pyridin‐2‐yl)methylene)di‐2,2′‐bipyridine (L‐OMe) of general formula trans‐[RuII(X)(L‐OMe‐κ‐N5)]n+ (X=Cl, n=1, trans‐1+; X=H2O, n=2, trans‐22+) have been isolated and characterized in solution (by NMR and UV/Vis spectroscopy) and in the solid state by XRD. Both complexes undergo a series of substitution reactions at oxidation state RuII and RuIII when dissolved in aqueous triflic acid–trifluoroethanol solutions as monitored by UV/Vis spectroscopy, and the corresponding rate constants were determined. In particular, aqueous solutions of the RuIII‐Cl complex trans‐[RuIII(Cl)(L‐OMe‐κ‐N5)]2+ (trans‐12+) generates a family of Ru aquo complexes, namely trans‐[RuIII(H2O)(L‐OMe‐κ‐N5)]3+ (trans‐23+), [RuIII(H2O)2(L‐OMe‐κ‐N4)]3+ (trans‐33+), and [RuIII(Cl)(H2O)(L‐OMe‐κ‐N4)]2+ (trans‐42+). Although complex trans‐42+ is a powerful water oxidation catalyst, complex trans‐23+ has only a moderate activity and trans‐33+ shows no activity. A parallel study with related complexes containing the methyl‐substituted ligand 6,6′′‐(1‐pyridin‐2‐yl)ethane‐1,1‐diyl)di‐2,2′‐bipyridine (L‐Me) was carried out. The behavior of all of these catalysts has been rationalized based on substitution kinetics, oxygen evolution kinetics, electrochemical properties, and density functional theory calculations. The best catalyst, trans‐42+, reaches turnover frequencies of 0.71 s−1 using CeIV as a sacrificial oxidant, with oxidative efficiencies above 95 %.

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optimize these pathways and thus to guarantee their maximum chance of survival, cells produce enzymes at precise and constant rates. [4] However, because of cellular complexity, determination of optimal enzyme levels is still unclear, in particular because specific enzymatic functions are strongly interconnected with their cascade effects. [5] A smart manner to study the behavior of enzymes, when involved in complex reactions, consists of taking advantage of synthetic micrometer-sized compartments shaped into spherical architectural bodies. [6-8] Though these idealized models favor even partitioning of membrane proteins and simplify diffusion gradients, similarly to cells, they provide the desired membrane selectivity and permeability. [9,10] Single specific functions have been presented by combining enzymes (the catalytic compounds) with synthetic supramolecular assemblies, either intrinsically semipermeable, such as lipid-coated porous silica particles, [11] protein cages, [12] layer-by-layer capsules, [13-15] and polydopamine capsules, [16,17] or rendered permeable by the insertion of biopores/membrane proteins (acting as "gates" for the passage of molecules), as in lipid-based [7,18,19] or polymer-based [8,20-22] giant unilamellar vesicles (GUVs). At present, GUVs formed with amphiphilic block copolymers are particularly appealing because they provide enhanced structural membrane properties compared to lipids, since they possess compartments with higher chemical versatility, controlled permeability, robustness, and stability. [23] Nevertheless, common approaches to form polymer GUVs by self-assembly, as electroformation [24] and film-rehydration, [25] rely on the statistical process of encapsulation of biomolecules with a probability of finding the designed amount of one type of enzyme inside the compartments ranging from 12-57%. In the context of elementary biochemical pathways where at least two enzymes are present, this scenario is even more unsatisfactory, with co-encapsulation of two enzymes inside one compartment as low as 10-22%. [26,27] These shortcomings are worsened by the fact that these probabilities have a large uncertainty induced by specific properties of enzymes (e.g., solubility and stability). To date, scientists have struggled to work with stateof-the-art average values for number/mass of enzymes that are vastly non-representative (limited by a small sample size) Cells rely upon producing enzymes at precise rates and stoichiometry for maximizing functionalities. The reasons for this optimal control are unknown, primarily because of the interconnectivity of the enzymatic cascade effects within multi-step pathways. Here, an elegant strategy for studying such behavior, by controlling segregation/combination of enzymes/ metabolites in synthetic cell-sized compartments, while preserving vital cellular elements is presented. Therefore, compartments shaped into polymer GUVs are developed, producing via high-precision double-emulsion microfluidics that enable: i) tight control over the absolute and...

Two ruthenium complexes containing the tetradentate ligand [1,1'-biisoquinoline]-3,3'-dicarboxylic acid, and 4-picoline or 6-bromoisoquinoline as axial ligands have been prepared. The complexes have been fully characterised and initial studies on their potential to function as molecular water oxidation catalysts have been performed. Both complexes catalyse the oxidation of water in acidic media with Ce as a stoichiometric chemical oxidant, although turnover numbers and turnover frequencies are modest when compared with the closely related Ru-bda and Ru-pda analogues. Barriers for the water nucleophilic attack and intermolecular coupling pathways were obtained from density functional theory calculations and the crucial influence of the ligand framework in determining the most favourable reaction pathway was elucidated from a combined analysis of the theoretical and experimental results.