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Chromophore–catalyst assemblies are interesting benchmark molecules for photocatalysis. We have prepared two examples of these assemblies and characterized their behaviour as catalysts for the water oxidation reaction. In the bimetallic complexes [Ru(tpy)(4,4′-X2-bpy)(μ-CN)Ru(bda)(DMSO)](PF6) (X = –H (1), –OCH3 (2), tpy = 2,2′:6′,2′′-terpyridine, bpy = 2,2′-bipyridine, H2bda = 2,2′-bipyridine-6,6′-dicarboxylic acid and DMSO = (CH3)2SO), a Ru(II)-polypiridine chromophore {Ru(tpy)(4,4′-X2-bpy)} is linked by a cyanide bridge to a {Ru(bda)} water oxidation catalyst. Both complexes catalyze water oxidation both chemically, using Ce(IV) as the terminal oxidant, and electrochemically. Electrochemical and spectroelectrochemical studies, aided with (TD)DFT calculations, allowed us to study the different species involved in the catalytic cycle. For the RuIIRuIII, an intense MMCT (metal-to-metal charge transfer) band suggests a geometrical reorganization during the oxidation process. The wave associated with oxidation to the RuIIIRuIV species shows an increased current that suggests that it may be a catalyst for the water oxidation reaction. Further oxidation results in the RuIIIRuV redox state which is an active catalyst for the water oxidation reaction as demonstrated by the evolution of oxygen. [ABSTRACT FROM AUTHOR]

The interaction of metal complexes with ionic liquids, with a particular focus on the stability and surface concentration of the metal centers, is crucial in applications involving catalysts based on supported ionic liquids. In this study, we synthesized the complexes [Ru(tpy)(bpy)Cl][PF6] and [Ru(tpy)(dcb)Cl][PF6] (tpy = 2,2′,2′′-terpyridine, bpy = 2,2′-bipyridine, dcb = 4,4′-dicarboxy-2,2′-bipyridine) and we prepared solutions using the ionic liquids (ILs) 1-ethyl-3-methylimidazolium acetate [C2C1Im][OAc] and 1-butyl-3-methylimidazolium hexafluorophosphate [C4C1Im][PF6]. The chemical environment of the Ru(II) metal center and the interfacial behavior of the complexes in the different IL solutions were determined using angle-resolved X-ray photoelectron spectroscopy (ARXPS). In [C4C1Im][PF6], [Ru(tpy)(bpy)Cl][PF6] maintains its chemical structure, while in [C2C1Im][OAc], partial changes in the chemical environment of the Ru center are indicated by XPS, likely due to ligand exchange. The presence of carboxylic acid functional groups in the bipyridyl ligand seems to inhibit this ligand exchange. The investigated complexes do not exhibit surface activity but are depleted from the IL/gas interface. These findings hold significance for the design of new supported ionic liquid phase catalysts based on Ru complexes. [ABSTRACT FROM AUTHOR]

The preparation of nanomaterials for energy applications such as intercalation batteries and materials that can act as substrates for water oxidation is a subject of major interest nowadays. In this work, we report the deposition of Prussian blue (PB) and its cobalt analogue (CoPBA) on mesoporous titania thin films (MTTF) using the successive ionic layer adsorption reaction (SILAR) technique under soft conditions. A bifunctional ligand, 1,10‐phenanthroline‐5,6‐dione (pd), was used to functionalize the titania surface and promote the growth of PB and CoPBA. The resulting PB@MTTF and CoPBA@MTTF nanocomposites were characterized using several techniques and it was determined that PB and CoPBA grow in a controlled and sequential manner, maintaining the mesoporous architecture. Both PB@MTTF and CoPBA@MTTF demonstrated very good electroactive properties, while CoPBA@MTTF exhibited water oxidation capabilities. The flexibility of this PBA@MTTF platform allows the incorporation of any labile transition metal ion or fragment into the structure of the coordination polymer embedded into a mesoporous matrix, opening the door for (photo)electrochemical devices and catalysts. [ABSTRACT FROM AUTHOR]

The synthesis, characterization, and spectroscopic properties of a family of trinuclear cyano-bridged mixed-valent compounds, trans-[Ru(super II)L4{NCFe(super III)(CN)5}2](super 4-), trans-[Ru(super II)L4{CNFe(super III)(CN)5}2](super 4-), and cis[Ru(super II)(bpy)(sub 2-){NCFe(super III)(CN)5}2](super 4-) (L = pyridine, 4-tert-butylpyridine, and 4-methoxypyridine).

Research has been conducted on the trans-[NCRu(py) (sub)4 (CN)Ru(py) (sub)4 NO](PF (sub)6) (sub)3 complex. The synthesis of this complex has been carried out in investigating the factors controlling NO (super)+ reactivity and the details are presented.

Research has been conducted on the pentacyano-L-osmate(II) complexes with L as N-heterocyclic ligands. The characterization of the complexes has been performed and the results of the mechanistic and kinetic study of the formation and dissociation reactions of a selected group of osmium complexes are reported.

Research has been conducted on the nitric oxide radical. The experimental and theoretical results demonstrating a comprehensive EPR picture of the ions [(NC) (sub)5 M(NO)] (super)3- where M=Fe, Ru, Os are discussed.

The spectra and reactivity of 4- and 3-cyanopyridine-bridged mixed-valence binuclear complexes, ((NC)5Fe(pyCN)Ru(NH3)5)n, featuring nitrile-N and pyridine-N binding to Ru and Fe, respectively, were investigated. The solid compounds, which were obtained via oxidation of the fully reduced Na-(NC)5Fe(pyCN)Ru(NH3)5.nH2O with peroxydisulfate, were found to be unstable towards dissociation. Thus, it decomposes via hydrolysis within minutes.

Ultraviolet-visible and infrared spectra and redox potentials for the different Os(super III,II) couples were obtained in the synthesis of the (Os(super II)(CN)5L)(super n-) complexes, where L = pyridinic or pyrazinic ligands, in aqueous solution and in the solid state. Results showed that the Os(II) complexes result in stable Os(III) species upon chemical or electrochemical oxidation.

The mixed-valence (Mi), fully oxidized, and fully reduced forms of the binuclear complex ( NC 5Fe-Im-Ru NH3 5)n are synthesized from (Fe CN 5H2O)3- and (Ru NH3 5Im)2+. The Mi species has FeII and RuIII localized site. Its visible bands, which are assigned by metal-to-ligand charge-transfer transitions, are observed to be on the lower energy levels than those of the mononuclear Ru(NH3)5Im2+ ion. The infrared spectrum shows bands at 2039 and 1327 cm-1 for the Fe(II) and Ru(III), respectively.

The gradient corrected density functional theory is used in conjunction with a continuum model to examine the effects of the solvent on the chemical structure and infrared spectrum of the Fe(CN)5NO2-ion. Results indicate that specific interactions are operative between the ion's donor cyanide ligands and the acceptor solvents. The data also suggest that metal-NO carriers are susceptible to nucleophilic attacks by several bases under physiological conditions.

The catalytic activity towards water oxidation of a strongly coupled bimetallic ruthenium complex, trans‐[Ru(tpy)(bpy)(μ‐CN)Ru(py)4(OH2)]3+ (RuIIRuIIOH2), where tpy=2,2′:6′,2"‐terpyridine, bpy=2,2′‐bipyridine and py=pyridine are presented. At pH 1 the first two oxidation reactions are centred at the aquo fragment and result in the RuIIRuIIIOH2 and RuIIRuIVO redox states as confirmed by its spectroscopy and DFT calculations. Oxidation by an additional electron is followed by an irreversible step and a catalytic wave associated with the water oxidation reaction. At pH 1 the reaction with an excess of Ce(IV) results in the generation of an stoichiometric amount of oxygen based on molar amounts of the added Ce(IV). The dominant species during the catalytic cycle is the three‐electron oxidized product, RuIIIRuIVO. The reduction of the concentration of Ce(IV) monitored at 370 nm follow the rate equation, −d[Ce(IV)]/dt=kox[Ce(IV)][RuIIRuIIOH2] with a kox=82±3 M−1s−1 at T=298 K. The RuIIIRuIVO species is not stable and reacts to give RuIIRuIVO. [ABSTRACT FROM AUTHOR]

Single-crystal x-ray diffraction studies reveal that sodium pentacyanonitrosylosmate(II) dihydrate is isostructural with the iron and ruthenium analogues. Spectroscopic studies reveal the presence of significant sigma- and back-bonding Pi-interaction from Os toward cyanides and nitrosyl groups. Mechanistic and kinetic studies of the reactions of this electrophilically reactive complex with various bases enable the determination of equilibrium constants. Various factors including radius, charge and energy of the pi*(NO) level influence the nucleophilic rate.

The cover feature shows a ruthenium(II) polypyridine complex dissolved in 1‐ethyl‐3‐methylimidazolium acetate under X‐ray irradiation. The long hydrophobic alkyl chains of the complex act as buoys, pulling it towards the liquid/vacuum interface, as proven by ARXPS measurements. More details can be found in the Research Article by Hans‐Peter Steinrück, Federico J. Williams, and co‐workers (DOI: 10.1002/open.202400092)...By Luciano Sanchez Merlinsky; Daniel Hemmeter; Luis M. Baraldo; Florian Maier; Hans‐Peter Steinrück and Federico J. WilliamsReported by Author; Author; Author; Author; Author; Author [Extracted from the article]

Binuclear cyanopyridine-bridged complexes with pentacyanoruthenate(II) and pentaammineruthenium(II) were synthesized by the reaction of Ru(CN)5H2O3- with Ru(NH3)5(4-NCpy)2+. The oxidation of the different binuclear cyanopyridine-bridged complexes with peroxydisulfate exhibited the large differences in the reactivity between the Ru(II) species and peroxydisulfate. Furthermore, the cyanopyridine-bridged complexes exhibited strong IV transition bands due to the efficient orbital overlap of cyanopyridine.

The crystal and molecular structure of [Ru[(DMAP).sub.6]][Cl.sub.2].6[C.sub.3]C[H.sub.2]OH (DMAP = 4-dimethylaminopyridine) is studied by using X-ray diffraction method. The density functional theory (DFT) calculations have shown that in {[Ru.sup.II][(DMAP).sub.5]} the DMAP ligands have competed for the [pi] electron density of the ruthenium making the fragment a weaker [pi]-donor.

The NIR donor-acceptor charge transfer (DACT) bands of the series of trinuclear complexes are analyzed in terms of a simplified molecular orbital picture that reflects the interaction between the donor and acceptor fragments. The results have suggested that superexchange and hopping might become competitive paths, depending on the substituents in the bridging fragment, considering the finding that the species reveal a similar degree of electronic mixing, but the potential energy surface (PES) shows three minima.

The [Os(super III)(CN)6](super 3-)anion is prepared by chemical oxidation in aqueous solution and isolated as yellow prisms of [PH4P]3[Os(super III)(CN)6].6H2O. Spin-orbit-coupling splitting of the ground-state term dominates the NIR region of its electronic spectrum and magnetic behavior [Ph4P]3[Os(super III)(CN)6].6H2O.

We report the photophysical and photochemical properties of RuII–polypyridine complexes [Ru(bpy)(dcbpy)py2]2+ (1)2+ and [Ru(dcbpy)2py2]2+ (2)2+ (bpy = 2,2′‐bipyridine, dcbpy = 4,4′‐dicarboxy‐2,2′‐bipyridine, py = pyridine). These complexes combine a monodentate ligand with a chelate bipyridine substituted with carboxylate groups. At low pH, both complexes present metal‐to‐ligand charge transfer absorption bands in the visible region and room‐temperature photoluminescence with long excited‐state lifetimes (τ > 200 ns). At physiological pH, their absorption and emission maxima are displaced to higher energies, with a significant reduction of their emission lifetime. These species show photosubstitution of the monodentate pyridine upon irradiation at 450 nm. At low pH, the quantum yield for this process is very low, but at physiological pH, they are very active, with a φPS,450 value of 0.14 for (1)2+ and of 0.17 for (2)2+. The products of photosubstitution were identified as monoaquo complexes. Both the reactants and the products of the photosubstitution show photoluminescence, but with very different lifetimes, making it possible to monitor the reaction by the time constant of their decay. The ability of complexes (1)2+ and (2)2+ to photorelease monodentate ligands at physiological pH makes them attractive candidates for the delivery of biomolecules linked to more complex structures through the carboxylate functional group. [ABSTRACT FROM AUTHOR]

Ligand field (LF) states have been present in discussions on the photophysics and photochemistry of ruthenium-iminic chromophores for decades, although there is very little documented direct evidence of them. We studied the picosecond transient absorption (TA) spectroscopy of four {RuII(imine)} complexes that respond to the formula trans-[Ru(L)4(X)2], where L is either pyridine (py) or 4-methoxypyridine (MeOpy) and X is either cyanide or thiocyanate. Dicyano compounds behave as most ruthenium polypyridines and their LF states remain silent. In contrast, in the dithiocyanate complexes we found clear spectroscopic evidence of the participation of LF states in the MLCT decay pathway. These states are of donor and acceptor character simultaneously and this is manifested in the presence of MLCT and LMCT transient absorption bands of similar energy. Spectroelectrochemical techniques supported the interpretation of the absorption features of MLCT states, and DFT methods helped to assign their spectroscopic signatures and provided strong evidence on the nature of LF states. [ABSTRACT FROM AUTHOR]