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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]

Controlling the local concentration of metal complexes at the surface of ionic liquids (ILs) is a highly sought‐after objective due to its pivotal implications in supported ionic liquid phase (SILP) catalysis. Equally important is to avoid per‐ and polyfluorinated substances due to environmental concerns. Herein, we investigate the surface enrichment of Ru polypyridyl complexes with fluorine‐free alkylic side groups of varying lengths and shapes, using the hydrophilic IL [C2C1Im][OAc] as solvent. Additional charged carboxylate groups are included into the polypyridyl ligands to increase the solubility of the complex in the IL. When the ligand system is functionalized with long and hydrophobic alkyl side chains, the complex predominantly localizes at the IL/vacuum interface, as deduced from angle‐resolved X‐ray photoelectron spectroscopy. Conversely, in the presence of short or more bulky substituents, no surface enrichment is observed. This buoy‐like behaviour with fluorine‐free side groups is explored for 0.05 %mol to 1 %mol solutions. Intriguingly, surface saturation occurs at approximately 0.5 %mol, which is beneficial to the efficient operation of catalytic systems featuring high surface areas, such as SILP catalysts. [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]

We have prepared two trimetallic complexes [{Ru(bda)(DMSO)(μ-CN)}2Ru(L)4] (with bda = 2,2′-bipyridine-6,6′-dicarboxylate) where two {Ru(bda)} centers are bridged by a cyanide complex of the trans-Ru(L)4CN2 family (with L = pyridine and 4-tert-butylpyridine). The complex [{Ru(bda)(DMSO)(μ-CN)}2Ru(py)4] is fully soluble in aqueous solution and is a catalyst for the oxidation of water both chemically, using Ce(IV) at pH = 1 as the terminal oxidant, and electrochemically. Both reactions are first order in the complex and the resting state of the catalyst is the [RuVRuIII(py)4RuIV]2+ redox state. Electrochemical and spectroelectrochemical studies together with (TD)DFT calculations show that the coupling between the Ru(bda) fragments for the [RuIIIRuII(py)4RuIII]2+ and [RuIVRuII(py)4RuIV]2+ redox states is very weak, but significant for the [RuVRuII(py)4RuIV]2+ ion due to the orientation of the orbitals involved. This coupling affects the reactivity of the [RuVRuII(py)4RuIV]2+ redox state, making it a much slower catalyst towards the water oxidation reaction than [RuVRuIII(py)4RuIV]2+. [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 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]

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]

In this work, we present the preparation of a complex [(tpy)(bpy)Ru(μ-CN)Ru(py)4(OH2)](PF6)3 (tpy = 2,2′,6′,2′′-terpyridine; bpy = 2,2′-bipyridine; py = pyridine) that combines a ruthenium chromophore linked to another ruthenium ion that bears a labile position trans to the bridge. Substitution in this position is very attractive, as it allows us to place a quencher trans to the chromophore maximizing the separation between them. This complex allowed us to prepare a family of cyanide-bridged ruthenium polypyridines of general formula [Ru(tpy)(bpy)(μ-CN)Ru(py)4(L)]2/3+ (L = Cl−, NCS−, 4-dimethylaminopyridine or acetonitrile) and compare them with the related complexes [Ru(tpy)(bpy)(μ-CN)Ru(bpy)2(L)]2/3+ where the L ligand lies cis to the bridge. The mixed-valence form of these complexes shows evidence of strong coupling between the ruthenium ions and enhanced delocalization as the redox potential of the {Ru(py)4L} fragment increases. (TD)DFT calculations reproduce very well the experimental spectra of these complexes and indicate that when L = acetonitrile, the hole in the mixed-valence complex is almost equally distributed between both ruthenium ions. For L = DMAP and NCS− the π orbitals of the ligands are mixed with dπ orbitals of the Ru ions, resulting in partial delocalization of the charge on the ligands. The latter result illustrates that the trans configuration of these complexes is well-suited to extend the interaction beyond the bridged ruthenium ions. [ABSTRACT FROM AUTHOR]

Upon MLCT photoexcitation, {(tpy)Ru} becomes the electron acceptor in the mixed valence {(tpyṖ−)RuIII−δ-NC-MII+δ} moiety, reversing its role as the electron donor in the ground-state mixed valence analogue. Photoinduced mixed valence interactions can be tuned to obtain extended lifetimes and higher emission quantum yields, beneficial in supramolecular energy conversion schemes. [ABSTRACT FROM AUTHOR]

In this work, we report the evolution of the properties of the inter-valence charge transfer (IVCT) transition in a family of cyanide-bridged ruthenium polypyridines of general formula [RuII(tpy)(bpy)(μ-CN)RuIII(bpy)2(L)]3/4+ (tpy = 2,2′,6′,2′′-terpyridine; bpy = 2,2′-bipyridine; L = Cl−, NCS−, 4-dimethylaminopyridine or acetonitrile). In these complexes, the redox potential difference between both ruthenium centers (ΔE) is systematically modified. A decrease in ΔE causes a red shift of the energy and an intensity enhancement of the observed IVCT transitions. For L = acetonitrile, the IVCT band becomes narrower and asymmetrical, and shows very little dependence on the nature of the solvent, suggesting a delocalized configuration, although a non-symmetrical one. Also, additional electronic transitions of low energy are clearly resolved in this complex. The observed variation in the properties of the IVCT transitions can be understood on the basis of DFT calculations, that point to increasing mixing between the dπ orbitals of both Ru ions. [ABSTRACT FROM AUTHOR]

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]

Multi-metallic complexes based on {Ru–Cr}, {Ru–Ru} and {Ru–Ru–Cr} fragments are investigated for their light-harvesting and long-range energy transfer properties. We report the synthesis and characterization of [Ru(tpy)(bpy)(μ-CN)Ru(py)4Cl]2+ and [Ru(tpy)(bpy)(μ-CN)Ru(py)4(μ-NC)Cr(CN)5]. The intercalation of {RuII(py)4} linked by cyanide bridges between {Ru(tpy)(bpy)} and {Cr(CN)5} results in efficient, distant energy transfer followed by emission from the Cr moiety. Characterization of the energy transfer process based on photophysical and ultrafast time-resolved absorption suggests the delocalization of holes in the excited state, providing a pathway for energy transfer between the end moieties. The proposed mechanism opens the door to utilize this family of complexes as an appealing platform for the design of antenna compounds as the properties of the fragments could be tuned independently. [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]

Here we describe the use of Ru polypyridine compounds as caging agents for a variety of molecules. The pholorelease of the caged molecule can be triggered using visible light (450-500 nm) with a high quantum yield. These caged compounds are very stable in aqueous environments and yield the molecule of interest intact in a single step without secondary reactions. The affinity of the Ru polypyridine for amine groups allows the caging of a variety of molecules, including neurochemicals and neurotransmitters like 4-aminopyridine, glutamate, gamma aminobutyric acid, glycine, serotonin, dopamine, and nicotine. These caged molecules have been used to elicit the response of neurons, both in vitro and in vivo experiments. Besides neurotransmitters other types of molecules, like antiproliferative drugs, can also be caged. In addition, sulfur-containing molecules, such as methylthiogalactose, can also be caged by this fragment. Another interesting application of the Ru polypyridine fragment is the caging of fluorescent dyes which can be uncaged using visible light. All of these applications can also be implemented using infrared light, as one of the distinctive advantages of Ru polypyridines as caging agents is their ability to be triggered in a two-photon regime, allowing the use of high power IR pulses to uncage the desired molecule. [ABSTRACT FROM AUTHOR]

The NIR and IR spectroscopic properties of the cyanide-bridged complex, trans-[Ru(dmap)4{(μ-CN)Ru(py)4Cl}2]3+ (py=pyridine, dmap=4-dimethylaminopyridine) provide strong evidence that this trimetallic ion behaves as a Class III mixed-valence species, the first example reported of a cyanide-bridged system. This has been accomplished by tuning the energy of the fragments in the trimetallic complex to compensate for the intrinsic asymmetry of the cyanide bridge. Moreover, (TD)DFT calculations accurately predict the spectra of the trans-[Ru(dmap)4{(μ-CN)Ru(py)4Cl}2]3+ ion and confirms its delocalized nature. [ABSTRACT FROM AUTHOR]

A series of cyanide-bridged bimetallic compounds of the general formula [Ru(L)(bpy)(μ-NC)(M)]2−/−/2+ (L = tpy, 2,2′-6′,2′′-terpyridine, or tpm, tris(1-pyrazolyl)methane, bpy = 2,2′-bipyridine, M = RuII(CN)5, OsIII(CN)5, OsII(CN)5, RuII(py)4(CN), py = pyridine) have been synthesized and fully characterized. Most of them present MLCT emission (λ = 690–730 nm, Φ = 10−3–10−4) and their photophysical properties resemble the ones of the respective mononuclear Ru(L)(bpy) species. The exception is when M is OsIII(CN)5, where an intramolecular electron transfer quenching mechanism is proposed. The conditions that should be met for avoiding the reductive or oxidative quenching of the excited state are also discussed. [ABSTRACT FROM AUTHOR]

Examines the synthesis of nitrosyl dinuclear compound. Photoinduced release of nitrogen oxide during irradiation; Observation of strong electronic coupling after the Hush model application; Difference between the optical absorption energy and redox potentials.

Studies the synthesis and electronic structure of pentacyanoosmate(II) complexes with n-heterocyclic ligands. Materials and preparations of the complexes in aqueous solutions; Visible-UV spectra of the Os(II) complexes; Electrochemical measurements; Infrared spectra of the Os(II) compounds.

Focuses on the preparation of the mixed-valence imidazole-bridged compound [(NC)5FeII-Im-RuIII(NH3)5]- in solution and as a solid sodium salt from pentacyanoferrate and pentaamineruthenium. Spectral and electrochemical characterization of the imidazole-bridged complexes; Kinetics and mechanism of the formation and dissociation reactions; Thermodynamics.

Investigates the influence of the solvent on the structure and IR spectrum of the [Fe(CN)5NO]2- ion. Structural parameters; Computational methodology; Experimental procedure.

Reports on the molecular and electronic structure of the nitrosyl derivative. Synthesis of single crystals of soluble sodium salt; Comparison with bonding properties of iron and ruthenium pentacyanonitrosyl analogues.

Visible‐light excitation of a family of bimetallic ruthenium polypyridines with the formula [RuII(tpy)(bpy)(‐CN)RuII(py)4L]n+ (RuRuLn+), where L=Cl−, NCS−, DMAP and ACN, was used to prepare photoinduced mixed‐valence (PI‐MV) MLCT states as models of the photosynthetic reaction center. Ultrafast transient absorption spectroscopy allowed to monitor photoinduced IVCT bands between 6000 and 11000 cm−1. Mulliken spin densities resulting from DFT and (TD)DFT computations revealed the modulation of the charge density distribution depending on the ligand substitution pattern. Results are consistent with PI‐MV systems ranging from non‐degenerate Class II to degenerate Class III or II/III, with electronic couplings between 1000 and 3500 cm−1. These findings guide the control electron localization‐delocalization in charge‐transfer/charge‐separated excited states, like those involved in the photosynthetic reaction center. [ABSTRACT FROM AUTHOR]

Studies the bond cleavage of nitrous oxide N-N by a three-coordinate molybdenum(III) complexes. Chemical behavior of nitrous oxide (NO); Triple bond dissociation energy of nitrido derivative; Formation of Bradley's nitrosyl by post-rate determining NO capture.

Abstract: Here we report the derivatization of mesoporous TiO2 thin films for the preparation of H2O2 amperometric sensors. The coordination of the bifunctional ligand 1,10 phenantroline, 5,6 dione on the surface Ti(IV) ions provides open coordination sites for Fe(II) cations which are the starting point for the growth of a layer of Prussian blue polymer. The porous structure of the mesoporous TiO2 allows the growth, ion by ion of the coordination polymer. Up to four layer of Prussian blue can be deposit without losing the porous structure of the film, which results in an enhanced response of these materials as H2O2 sensors. These porous confined PB modified electrodes are robust sensors that exhibit good reproducibility, environmental stability and high sensitivity towards H2O2 detection. [ABSTRACT FROM AUTHOR]