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The ruthenium(II) compounds cis-[Ru(bpy) 2 (4-bzpy)(CO)](PF 6 ) 2 (I) and cis-[Ru(bpy) 2 (4-bzpy)(Cl)](PF 6 ) (II) (4-bzpy=4-benzoylpyridine, bpy=2,2'-bipyridine) were synthesized and characterized by spectroscopic and electrochemical techniques. The crystal structure of II was determined by X-ray diffraction. The photochemical behavior of I in aqueous solution shows that irradiation with ultraviolet light (365nm) releases both CO and 4-bzpy leading to the formation of the cis-[Ru(bpy) 2 (H 2 O) 2 ] 2+ ion as identified by NMR and electronic spectroscopy. Carbon monoxide release was confirmed with the myoglobin method and by gas chromatographic analysis of the headspace. CO release was not observed when aqueous I was irradiated with blue light (453nm). Changes in the electronic and 1 H NMR spectra indicate that I undergoes photoaquation of 4-bzpy to form cis-[Ru(bpy) 2 (CO)(H 2 O)] 2+ . Blue light irradiation of aqueous II released the coordinated 4-bzpy to give the cis-[Ru(bpy) 2 (H 2 O)(Cl)] 2+ ion. When the latter reaction was carried out in the presence of the nucleobase guanine, Ru-guanine adducts were formed, indicating that the metal containing photoproduct may also participate in biologically relevant reactions. The photochemical behavior of I indicates that it can release either CO or 4-bzpy depending on the wavelength chosen, a feature that may have therapeutic application., (Copyright © 2017 Elsevier Inc. All rights reserved.)

The selective formation of dialkyl formamides through photochemical CO2 reduction was developed as a means of utilizing CO2 as a C1 building block. Photochemical CO2 reduction catalyzed by a [Ru(bpy)2(CO)2](2+) (bpy: 2,2'-bipyridyl)/[Ru(bpy)3](2+)/Me2NH/Me2NH2(+) system in CH3CN selectively produced dimethylformamide. In this process a ruthenium carbamoyl complex ([Ru(bpy)2(CO)(CONMe2)](+)) formed by the nucleophilic attack of Me2NH on [Ru(bpy)2(CO)2](2+) worked as the precursor to DMF. Thus Me2NH acted as both the sacrificial electron donor and the substrate, while Me2NH2(+) functioned as the proton source. Similar photochemical CO2 reductions using R2NH and R2NH2(+) (R = Et, nPr, or nBu) also afforded the corresponding dialkyl formamides (R2NCHO) together with HCOOH as a by-product. The main product from the CO2 reduction transitioned from R2NCHO to HCOOH with increases in the alkyl chain length of the R2NH. The selectivity between R2NCHO and HCOOH was found to depend on the rate of [Ru(bpy)2(CO)(CONR2)](+) formation., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Luminescence quenching of the metallopolymers [Ru(bpy)(2)(PVP)(10)](2+) and [Ru(bpy)(2)(PVP)(10)Os(bpy)(2)](4+), both in solution and as thin films, is reported, where bpy is 2,2'-bipyridyl and PVP is poly(4-vinylpyridine). When the metallopolymer is dissolved in ethanol, quenching of the ruthenium excited state, Ru(2+*), within [Ru(bpy)(2)(PVP)(10)](2+) by [Os(bpy)(3)](2+) proceeds by a dynamic quenching mechanism and the rate constant is (1.1 +/- 0.1) x 10(11) M(-1) s(-1). This quenching rate is nearly two orders of magnitude larger than that found for quenching of monomeric [Ru(bpy)(3)](2+) under the same conditions. This observation is interpreted in terms of an energy transfer quenching mechanism in which the high local concentration of ruthenium luminophores leads to a single [Os(bpy)(3)](2+) centre quenching the emission of several ruthenium luminophores. Amplifications of this kind will lead to the development of more sensitive sensors based on emission quenching. Quenching by both [Os(bpy)(3)](2+) and molecular oxygen is significantly reduced within a thin film of the metallopolymer. Significantly, in both optically driven emission and electrogenerated chemiluminescence, emission is observed from both ruthenium and osmium centres within [Ru(bpy)(2)(PVP)(10)Os(bpy)(2)](4+) films, i.e. the ruthenium emission is not quenched by the coordinated [Os(bpy)(2)](2+) units. This observation opens up new possibilities in multi-analyte sensing since each luminophore can be used to detect separate analytes, e.g. guanine and oxoguanine.

The nature of the binding of several ruthenium polypyridyl complexes containing 2,2'-bipyridine (bipy), 4,4'-dimethyl-2,2'-bipyridine (DMB), 1,10-phenanthroline (phen), 4,7-diphenyl-1,10-phenanthroline (DPP), 2,2',2"-terpyridine (terpy), 2,2'-biquinoline (biq), 1,4,5,8-tetraazaphenanthrene (TAP) and 1,4,5,8,9,12-hexaazatriphenylene (HAT), with calf thymus DNA, poly[d(A-T)] and poly[d(G-C)] were studied by absorption and emission spectroscopy, DNA melting techniques, and emission lifetime measurements. In low ionic strength phosphate buffer, spectroscopic changes and DNA stabilization depended on the polypyridyl ligands present, and indicated binding that varied from substantially electrostatic to intercalative. Ru(bipy)2(HAT)2+ and Ru(phen)3(2+), which bind by partial intercalation, also show a strong preference for poly[d(A-T)]. The emission quantum yields for most complexes were increased in the presence of DNA. An exception was Ru(TAP)3(2+) which has a markedly reduced emission quantum yield and lifetime in the presence of poly[d(G-C)] or CT-DNA, due to photoredox interaction with quanines. Emission decays of the complexes generally showed multiexponential behaviour. The ability of the ruthenium complexes to sensitise DNA cleavage was determined using pBR322 plasmid DNA. Ru(TAP)3(2+) is the most efficient sensitiser while uncharged complexes and complexes with very short-lived excited states do not cleave DNA.

In this work, we used DFT and TD‐DFT in the investigation of the structural parameters and photophysics of the complex [Ru(bpy)2dppn]2+ (dppn=benzo[i]‐dipyrido[3,2‐a:2’,3’‐c]phenazine) in water, and its suitability as a photosensitizer (PS) in photodynamic therapy (PDT). For that, the thermodynamics of electron transfer (ET) and energy transfer (ENT) reactions in the excited state with molecular oxygen and guanosine‐5’‐monophosphate (GMP) were investigated. The overall intersystem crossing (ISC) rate constant was approximately 1012 s−1, indicating that this process is highly favorable, and the triplet excited states are populated. The triplet excited states are known to lead to photoreactions between the PS and species of the medium or directly with nucleobases. Here, we show that the Ru‐dppn complex can react favorably to oxidize the GMP and generate singlet oxygen. Furthermore, this complex can also act as an intercalator between DNA base pairs and undergo dual‐channel reactions. It has been proposed that the T2 excited state is responsible for oxidizing the GMP, but we show that T1 is thermodynamically capable of undergoing the same reaction. In this sense, docking simulations were carried out to investigate further the interactions of the Ru‐dppn complex with a DNA fragment. [ABSTRACT FROM AUTHOR]

The one‐pot synthesis of a total of 32 ruthenium(II) and osmium(II) photosensitizers bearing substituted 2,2’‐bipyridines, 1,10‐phenanthrolines, and diaza ligands is reported. Whereas most of these photosensitizers were already reported in the literature, the present study offers extensive datasets of ground‐ and excited‐state properties highly desirable for future development in e. g., machine learning, artificial intelligence, and photoredox catalysis. All photosensitizers absorbed light intensely in the visible part of the spectrum, with the Os(II) photosensitizers absorbing further into the red part. Excited‐state lifetimes and photoluminescence quantum yields were generally larger for Ru(II) photosensitizers than for Os(II) analogs, which agrees with the energy gap law. The excited‐state redox potentials were determined for all investigated photosensitizers covering a range of −0.21 to −1.35 V vs. SCE for excited‐state oxidation and 0.14 to 1.48 V vs. SCE for excited‐state reduction. A procedure for counterion exchange to generate the corresponding PF6−, Cl−, BF4−, NO3−, OTf−, ClO4−, and BArF− is reported for six photosensitizers. The synthetic ease, detailed report of fundamental photophysical properties, and a broad range of excited‐state redox potentials open opportunities for systematic investigations in several applications and further streamline developments in photoredox catalysis. [ABSTRACT FROM AUTHOR]

Photoinduced nitric oxide (NO) release for complexes [RuNO(L)2(NO2)2OH], where L=methyl isonicotinate (1), ethyl isonicotinate (2), methyl nicotinate (3) and ethyl nicotinate (4) was studied in DMSO, MeCN and water solutions (PBS, CTAB) using spectroscopic methods (UV‐vis, IR, EPR) and spectrometric techniques (ESI‐MS). Additionally, we present methodological evidence for improving the calculation of the quantum yield (QY) of NO release through the utilization of a combined IR‐UV‐vis‐spectroscopy flow‐through setup. According to DFT calculations, the production of nitric oxide occurs through the photoinduced cleavage of the Ru−NO bond, triggered by irradiation at 445 or 532 nm. This cleavage is a consequence of charge transfer from the orbitals of the Ru−OH group and the equatorial ligands (HOMO, HOMO‐1) to the Ru−NO antibonding orbital (LUMO). The cytotoxicity and photoinduced cytotoxicity of the investigated compounds were assessed against the breast adenocarcinoma cell line MCF‐7. Moreover, the investigation of the lipophilic properties of compounds 1–4 unveiled a significant influence of their lipophilicity on cytotoxic behavior, allowing for the modification of cytotoxicity through changes in the ligand L or by light irradiation. [ABSTRACT FROM AUTHOR]

Ruthenium(II) complexes with chelating polypyridine ligands are among the most frequently investigated compounds in photophysics and photochemistry, owing to their favorable luminescence and photoredox properties. Equally good photoluminescence performance and attractive photocatalytic behavior is now achievable with isoelectronic molybdenum(0) complexes. The zero‐valent oxidation state of molybdenum is stabilized by carbonyl or isocyanide ligands, and metal‐to‐ligand charge transfer (MLCT) excited states analogous to those in ruthenium(II) complexes can be established. Microsecond MLCT excited‐state lifetimes and photoluminescence quantum yields up to 0.2 have been achieved in solution at room temperature, and the emission wavelength has become tunable over a large range. The molybdenum(0) complexes are stronger photoreductants than ruthenium(II) polypyridines and can therefore perform more challenging chemical reductions. The triplet nature of their luminescent MLCT states allows sensitization of photon upconversion via triplet‐triplet annihilation, to convert low‐energy input radiation into higher‐energy output fluorescence. This review summarizes the current state of the art concerning luminescent molybdenum(0) complexes and highlights their application potential. Molybdenum is roughly 140 times more abundant and far cheaper than ruthenium, hence this research is relevant in the greater context of finding more sustainable alternatives to using precious and rare transition metals in photophysics and photochemistry. [ABSTRACT FROM AUTHOR]

Optical storage and photon quantification systems based on sensitive photoreactions have numerous applications. Herein, we report a highly efficient photocatalytic reaction, in which ruthenium photoredox catalysis is combined with a 1,2‐dioxetane from which chemiluminescence can be triggered. In this system, blue light irradiation as optical input enables a defined inverse correlation with base‐triggered, blue light emission as optical output. Comparison of readout by 1H NMR and chemiluminescence, relative to previous optical input, underlines the reliability and usefulness of the ruthenium‐dioxetane system for optical storage, sensing and ruthenium detection. [ABSTRACT FROM AUTHOR]

Two ruthenium(II) polypyridyl complexes were prepared with the {Ru(phen)2}2+ moiety and a third sterically non-hindering bidentate ligand, namely 2,2′-dipyridylamine (dpa) and N-benzyl-2,2′-dipyridylamine (Bndpa). Hence, complexes [Ru(phen)2(dpa)](PF6)2 (1) and [Ru(phen)2(Bndpa)](PF6)2 (2) were characterized and their photochemical behaviour in solution (acetonitrile and water) was subsequently investigated. Compounds 1 and 2, which do not exhibit notably distorted octahedral coordination environments, contrarily to the homoleptic "parent" compound [Ru(phen)3](PF6)2, experience two-step photoejection of the dpa and Bndpa ligand upon irradiation (1050–430 nm) for several hours. DNA-binding studies revealed that compounds 1 and 2 affect the biomolecule differently upon irradiation; while 2 solely modifies its electrophoretic mobility, complex 1 is also capable of cleaving it. In vitro cytotoxicity studies with two cancer-cell lines, namely A549 (lung adenocarcinoma) and A375 (melanoma), showed that both 1 and 2 are not toxic in the dark, while only 1 is significantly cytotoxic if irradiated, 2 remaining non-toxic under these conditions. Light irradiation of the complex cation [Ru(phen)2(dpa)]2+ leads to the generation of transient Ru species that is present in the solution medium for several hours, and that is significantly cytotoxic, ultimately producing non-toxic free dpa and [Ru(phen)(OH2)2]2+. [ABSTRACT FROM AUTHOR]

Iridium(III) and ruthenium(II) polypyridyl based photocatalysts have been prepared and their structure determined using 1H NMR, HR‐MS and single crystal XRD. Their spectroscopic and electrochemical properties have been studied by UV‐vis absorption, emission spectroscopy and cyclic voltammetry. These complexes have been used as photoredox homogeneous catalysts in an intramolecular cyclization model reaction in which they show high activity. They have been covalently anchored on graphene oxide (GO) via an esterification reaction and non‐covalently fixed on reduced graphene oxide (rGO) via pyrene moieties. Heterogenized complexes exhibit good photocatalytic activities and, interestingly, the use of a pyrene‐derivatized Ir(III) terpyridine‐based complex highlights an unexpected "on/off" effect of the photocatalytic activity triggered by the presence or absence of rGO. [ABSTRACT FROM AUTHOR]

One monometallic and three bimetallic ruthenium nitrosyl (RuNO) complexes are presented and fully characterized in reference to a parent monometallic complex of formula [FTRu(bpy)(NO)]3+, where FT is a fluorenyl‐substituted terpyridine ligand, and bpy the 2,2'‐bipyridine. These new complexes are built with the new ligands FFT, TFT, TFFT, and TF‐CC‐TF (where an alkyne C≡C group is inserted between two fluorenes). The crystal structures of the bis‐RuNO2 and bis‐RuNO complexes built from the TFT ligand are presented. The evolution of the spectroscopic features (intensities and energies) along the series, at one‐photon absorption (OPA) correlates well with the TD‐DFT computations. A spectacular effect is observed at two‐photon absorption (TPA) with a large enhancement of the molecular cross‐section (σTPA), in the bimetallic species. In the best case, σTPA is equal to 1523±98 GM at 700 nm, in the therapeutic window of transparency of biological tissues. All compounds are capable of releasing NO⋅ under irradiation, which leads to promising applications in TPA‐based drug delivery. [ABSTRACT FROM AUTHOR]

A series of ligands containing a 1,4‐disubstituted 1,2,3‐triazole unit have been used for the formation of triple‐stranded dinuclear Ru(II) complexes. In contrast to the previously reported complexes of labile metals, the use of inert Ru(II) enabled stereoisomeric mixtures of triple‐stranded diruthenium(II) complexes to be accessed. The chromatographic resolution of the enantiomers of a reported helicate containing a more rigid 1,4‐xylyl spacer was carried out on cellulose. The ligand spacer was modified and as the flexibility increased the production of isomeric mixtures was detected; the mesocate and helicate forms were separated when an n‐propyl spacer was used. This pair of diastereomers was found to exhibit photoconversion, a unique observation for Ru(II) compounds of this type. Partial separation via chromatographic resolution was achieved for compounds containing an n‐butyl spacer, and the presence of a mesocate/helicate pair confirmed. [ABSTRACT FROM AUTHOR]

The ruthenium(II) compounds cis-[Ru(bpy)2(4-bzpy)(CO)](PF6)2 (I) and cis-[Ru(bpy)2(4-bzpy)(Cl)](PF6) (II) (4-bzpy=4-benzoylpyridine, bpy=2,2'-bipyridine) were synthesized and characterized by spectroscopic and electrochemical techniques. The crystal structure of II was determined by X-ray diffraction. The photochemical behavior of I in aqueous solution shows that irradiation with ultraviolet light (365nm) releases both CO and 4-bzpy leading to the formation of the cis-[Ru(bpy)2(H2O)2]2+ ion as identified by NMR and electronic spectroscopy. Carbon monoxide release was confirmed with the myoglobin method and by gas chromatographic analysis of the headspace. CO release was not observed when aqueous I was irradiated with blue light (453nm). Changes in the electronic and 1H NMR spectra indicate that I undergoes photoaquation of 4-bzpy to form cis-[Ru(bpy)2(CO)(H2O)]2+. Blue light irradiation of aqueous II released the coordinated 4-bzpy to give the cis-[Ru(bpy)2(H2O)(Cl)]2+ ion. When the latter reaction was carried out in the presence of the nucleobase guanine, Ru-guanine adducts were formed, indicating that the metal containing photoproduct may also participate in biologically relevant reactions. The photochemical behavior of I indicates that it can release either CO or 4-bzpy depending on the wavelength chosen, a feature that may have therapeutic application.

This study describes the synthesis and characterization of the photoluminescent and water‐soluble complex cis‐[Ru(phen)2(2Apy)]2+ (Ru2Apy, phen=1,10‐phenanthroline and 2Apy=2‐aminopyridine), which exhibits spectroscopic and physicochemical properties favorable for biological applications. 1H‐NMR, photoluminescence, and UV‐vis spectroscopy experiments show bidentate coordination of the 2Apy ligand, which leads to a blue shift in the emission spectrum and places the 3MLCT in proximity to the 3MC excited states, thus enabling a photochemical pathway. Under continuous light irradiation at 450 nm, Ru2Apy opens the coordinating site of the NH2 group in 2Apy to form the monoacetonitrile complex cis‐[Ru(phen)2(2Apy)(CH3CN))2+, with a quantum yield of 0.457. Further irradiation leads to a second photoprocess to form the bis‐acetonitrile cis‐[Ru(phen)2(CH3CN)2]2+ complex, with a quantum yield of 0.002. Ru2Apy binds to human serum albumin via non‐covalent interactions with Kb=4.63×10−9 mol L−1, ΔH=−3.4×10−3 kcal mol−1, and ΔS=8.7 kcal mol−1K−1, and displays a moderate inhibition of AChE with an IC50 of 13.2±2.0 μmol L−1. The complex also exhibited high uptake into HeLa cells with no cytotoxicity. Furthermore, the emissive response of Ru2Apy was be used to assess, in real‐time, the aggregation of Aβ1–40 in a dose‐dependent manner. [ABSTRACT FROM AUTHOR]

A series of ruthenium(II) polypyridine complexes of the type [Ru(tpy)((CH3O)2bpy)(4-R-py)]2+, where tpy = 2,2′;6′,2″-terpyridine, (CH3O)2bpy = 4,4′-dimethoxy-2,2′-bipyridine, and 4-R-py = pyridine (py, 2), 4-methoxypyridine (4-CH3O-py, 3), 4-aminopyridine (4-NH2-py, 4), were synthesized and their crystal structures, electronic absorption, luminescence, and electrochemical properties were investigated. The effect of adding electron-donating groups to the bidentate and monodentate ligand was investigated and compared with [Ru(tpy)(bpy)(py)]2+ (1) where bpy = 2,2′-bipyridine. While anticipated trends were not observed for the Ru-N(6) bond length as 4-R-py was varied, noticeable modifications of the measured photophysical properties were observed. A red-shift of the metal-to-ligand charge transfer (1MLCT) is observed from 466 nm in 1 to 474 nm, 478 nm, and 485 nm for 2–4, respectively. Additionally, a red-shift in the luminescence maxima is observed in 2–4 as compared to 1, with 4 exhibiting the greatest shift of more than 100 nm. Complexes 2–4 exhibited luminescence quantum yields of 2.7 × 10−4, 7.2 × 10−4, and 7.4 × 10−4, respectively, which are increased compared to the quantum yield of 2.0 × 10−4 in 1. These findings demonstrate systematic tuning of absorbance and luminescence properties of ruthenium polypyridine complexes by addition of π-donating substituents to the monodentate and bidentate ligand. [ABSTRACT FROM AUTHOR]

The thermal and photochemical reactivity of Ru(CO)3(dpae) (1) and Ru(CO)2(dpae)(PPh3) (2) towards H2 and diphenylacetylene is described. These reactions are monitored by NMR spectroscopy in conjunction with the parahydrogen induced polarisation (PHIP) effect, spatially resolved chemical shift imaging and the Only Parahydrogen Spectroscopy (OPSY) signal filtering method. The results are supported by DFT. The thermal and photochemical reactions of 1 with H2 proceed by CO loss and form Ru(H)2(CO)2(dpae) (3). 1 catalyses the formation of 1,2 diphenylethane, cis‐ and trans‐stilbene, and 1,2,3,4 tetraphenylbutadiene under 325 nm irradiation at 295 K in a reaction where Ru(CO)2(dpae)(η2‐CHPh=CPhCPh=CHPh) forms. When the same reaction is monitored under thermal conditions at 333 K the η2‐diene complex is no longer detected but hydride containing Ru(CHPhCH2Ph)(H)(CO)2(dpae) and Ru(CO)2(dpae)(trans‐stilbene) are seen. For 1, the photochemical promotion of hydrogenation through 325 nm irradiation results in an approximate 5.5‐fold increase in turnover at 333 K when compared to no irradiation. In contrast, 2 reacts thermally with H2 at 295 K through PPh3 and CO loss with both Ru(H)2(CO)(dpae)(solvent) and 3 being detected. Under irradiation, CO loss dominates and two isomers of Ru(H)2(CO)(dpae)(PPh3) form. While 2 forms the same 4 organic products at 295 K and a second isomer of Ru(CHPhCH2Ph)(H)(CO)2(dpae) alongside the diene complex no photochemical promotion of hydrogenation is observed. [ABSTRACT FROM AUTHOR]

A series of new Ruthenium(II) complexes based on the (1,10‐phenanthrolin‐5‐yl)diethyl phosphonate ligand L2 and their corresponding phosphonic acid along with reference compounds are synthesized in order to evaluate the influence of the phosphonate substitution on the catalytic performance of such molecules. UV‐vis absorption and emission spectroscopy show, that introduction of a phosphonate moiety into the periphery of the phenanthroline ligand does not alter the photophysical properties of the complex. In contrast, the electrochemical features of all compounds are affected upon respective functionalization compared to the reference molecule [Ru(bpy)3](PF6)2 in aqueous medium. Photostability tests in water or in water/persulfate show a dependency of the stability towards photodecomposition on quenching efficiency with persulfate anion. The lower quenching efficiency thus leads to increased stability based on the negative charge of the phosphonate moiety in 2 and P1 in aqueous medium following a quenching efficiency trend of [Ru(bpy)3](PF6)2>1>2>P1. Photocatalytic water oxidation using [Ru(dpp)(pic)2](PF6)2 reveals that compound 1 and [Ru(bpy)3](PF6)2 doe not exhibit any activity under the utilized conditions, P1 shows a negligible TON of 7, whereas compound 2 reaches a TON of 140 after 1 h. This fact highlights that the redox potential is not the sole driver in the catalytic cycle and accentuates the importance of different criteria determining the suitability of photosensitizers in light‐driven water oxidation, such as light absorption, redox potential of the RuIII/RuII event, photostability towards and quenching efficiency with the sacrificial agent. [ABSTRACT FROM AUTHOR]

A new heteroleptic ruthenium complex based on a 2,2′;6′,2′′‐terpyridine (tpy) and a thioether‐based tridentate ligand, btap (btap: 2,6‐bis(2‐thioanisyl)pyridine) was synthesized. Under visible light irradiation, this complex in solution in acetonitrile undergoes a photochemical ejection of the thioether ligand leading to [Ru(tpy)CH3CN)3]2+ and the free ligand. The reaction was monitored using NMR and UV‐Vis spectroscopies. This is very probably the first example of a tridentate ligand being expelled by the action of light. [ABSTRACT FROM AUTHOR]

Novel arene RuII complexes containing 2,2'‐azobispyridine ligands were synthesized and characterized by using 1H and 13C NMR spectroscopy, UV/vis spectroscopy, electrochemistry, DFT calculations and single‐crystal X‐ray diffraction. Z‐configured complexes featuring unprecedented seven‐membered chelate rings involving the nitrogen atom of both pyridines were isolated and were shown to undergo irreversible isomerization to the corresponding E‐configured five‐membered chelate complexes in response to light or electrochemical stimulus. [ABSTRACT FROM AUTHOR]

We describe the synthesis, characterization, and photochemistry of a pair of Ru 2 (II,III) complexes featuring dibenzochalogen oxide ligands. Photolysis effects cleavage of the chalcogen–oxygen bond and oxygen atom transfer to phosphines is observed. These results expand the family of potential metal–oxo photoprecursors. [Display omitted] • Synthesis and characterization of O- bound chalcogen oxide ligands to Ru 2 (II,III) complexes. • Demonstration of E–O photoactivation and oxygen-atom transfer photochemistry. • Provides new platforms for tunable, predictable photogeneration of reaction metal–oxygen species. We describe the synthesis, characterization, and photochemistry of a pair of Ru 2 (II,III) complexes featuring dibenzochalogen oxide ligands, which were prepared as potential photoprecursors for Ru 2 oxo photochemistry. Treatment of [Ru 2 (chp) 4 H 2 O]BF 4 with either dibenzo[ b , d ]thiophene 5-oxide (DBTO) or dibenzo[ b , d ]selenophene 5-oxide (DBSeO) affords [Ru 2 (chp) 4 DBTO]BF 4 or [Ru 2 (chp) 4 DBSeO]BF 4 , respectively, in which the dibenzochalcogen oxide ligands display coordination through oxygen (chp = 6-chloro-2-oxypyridinate). Both dibenzochalcogen oxide complexes are characterized by NMR, UV-vis, and IR spectroscopies as well as X-ray crystallography. Photolysis (λ = 300 nm) of [Ru 2 (chp) 4 DBTO]BF 4 and [Ru 2 (chp) 4 DBSeO]BF 4 effects cleavage of the chalcogen–oxygen bond and oxygen atom transfer to phosphine additives is observed. These results expand the family of potential metal–oxo photoprecursors and demonstrate new opportunities in the photochemical synthesis of reactive metal–oxygen complexes. [ABSTRACT FROM AUTHOR]

Two novel homometallic Ru−Ru and heterometallic Ru−Os dimers and trimers, [MII(bpy)2(4‐tpy‐4′‐methyl‐2,2′‐bipyridine)MII(tpy)]4+ and [MII(bpy)2](4‐tpy‐4′‐tpy‐2,2′‐bipyridine)(MII(tpy))2]6+, have been first prepared and characterized. Electrochemical properties of the metal‐based reversible oxidation and ligand‐based reduction are measured. Spectroscopic analysis of these complexes exhibits for every Ru‐ or Os‐based subunit an individual intense absorption spectrum extended over the entire UV and visible region. The heteronuclear complexes [RuII(bpy)2(4‐tpy‐4′‐methyl‐2,2′‐bipyridine)OsII(tpy)]4+, [RuII(bpy)2](4‐tpy‐4′‐tpy‐2,2′‐bipyridine)(OsII(tpy))2]6+, and [OsII(bpy)2](4‐tpy‐4′‐tpy‐2,2′‐bipyridine)(RuII(tpy))2]6+ display a weak emission spectrum in the near‐infrared region (NIR). The luminescence of the polynuclear assemblies is quantitatively quenched, by intramolecular energy transfer to the lower‐lying metal‐to‐ligand charge transfer (3MLCT) and metal‐centered (3MC) state of the Os(II)‐based center or Ru(II)‐terpyridine moiety at room temperature. [ABSTRACT FROM AUTHOR]

Organelle‐targeting photosensitizers have attracted increasing attention in the development of drugs for photodynamic therapy because they can efficiently induce cellular functional disorder upon light irradiation. In this work, we reported a ruthenium(II) complex bearing two lipophilic carbon chains which specifically binds to the cell membrane. Light irradiation on the complex‐treated cells caused an increase of intracellular reactive oxygen species. The photocytotoxicity of the complex toward HeLa cells were evaluated via the 3‐(4,5‐dimethyl‐2‐thiazolyl)‐2,5‐diphenyltetrazolium bromide (MTT) assay. A high dose (3 µm) of the complex induced apoptotic cell death by photogeneration of intracellular reactive oxygen species. A low dose (0.25 µm) of the complex did not cause noticeable cell death but increased the permeability of the cell membrane upon light irradiation. [ABSTRACT FROM AUTHOR]

Ambient temperature ruthenium‐catalyzed C−H arylations were accomplished by visible light without additional photocatalysts. The robustness of the ruthenium‐catalyzed C−H functionalization protocol was reflected by a broad range of sensitive functional groups and synthetically useful pyrazoles, triazoles and sensitive nucleosides and nucleotides, as well as multifold C−H functionalizations. Biscyclometalated ruthenium complexes were identified as the key intermediates in the photoredox ruthenium catalysis by detailed computational and experimental mechanistic analysis. Calculations suggested that the in situ formed photoactive ruthenium species preferably underwent an inner‐sphere electron transfer. [ABSTRACT FROM AUTHOR]

Chiral eniminium salts, prepared from α,β‐unsaturated aldehydes and a chiral proline derived secondary amine, underwent, upon irradiation with visible light, a ruthenium‐catalyzed (2.5 mol %) intermolecular [2+2] photocycloaddition to olefins, which after hydrolysis led to chiral cyclobutanecarbaldehydes (17 examples, 49–74 % yield), with high diastereo‐ and enantioselectivities. Ru(bpz)3(PF6)2 was utilized as the ruthenium catalyst and laser flash photolysis studies show that the catalyst operates exclusively by triplet‐energy transfer (sensitization). A catalytic system was devised with a chiral secondary amine co‐catalyst. In the catalytic reactions, Ru(bpy)3(PF6)2 was employed, and laser flash photolysis experiments suggest it undergoes both electron and energy transfer. However, experimental evidence supports the hypothesis that energy transfer is the only productive quenching mechanism. Control experiments using Ir(ppy)3 showed no catalysis for the intermolecular [2+2] photocycloaddition of an eniminium ion. [ABSTRACT FROM AUTHOR]

Synthesis, characterization, electrochemistry, and photophysics of homo‐ and heteroleptic ruthenium(II) complexes [Ru(cpmp)2]2+ (22+) and [Ru(cpmp)(ddpd)]2+ (32+) bearing the tridentate ligands 6,2"‐carboxypyridyl‐2,2'‐methylamine‐pyridyl‐pyridine (cpmp) and N,N'‐dimethyl‐N,N'‐dipyridin‐2‐ylpyridine‐2,6‐diamine (ddpd) are reported. The complexes possess one (32+) or two (22+) electron‐deficient dipyridyl ketone fragments as electron‐accepting sites enabling intraligand charge transfer (ILCT), ligand‐to‐ligand charge transfer (LL'CT) and low‐energy metal‐to‐ligand charge transfer (MLCT) absorptions. The latter peak around 544 nm (green light). Complex 22+ shows 3MLCT phosphorescence in the red to near‐infrared spectral region at room temperature in deaerated acetonitrile solution with an emission quantum yield of 1.3 % and a 3MLCT lifetime of 477 ns, whereas 32+ is much less luminescent. This different behavior is ascribed to the energy gap law and the shape of the parasitic excited 3MC state potential energy surface. This study highlights the importance of the excited‐state energies and geometries for the actual excited‐state dynamics. Aromatic and aliphatic amines reductively quench the excited state of 22+ paving the way to photocatalytic applications using low‐energy green light as exemplified with the green‐light‐sensitized thiol–ene click reaction. [ABSTRACT FROM AUTHOR]

Detailed studies on hydrogen evolution by decamethylruthenocene ([Cp*2RuII]) highlighted that metallocenes are capable of photoreducing hydrogen without the need for an additional sensitizer. Electrochemical, gas chromatographic, and spectroscopic (UV/Vis, 1H and 13C NMR) measurements corroborated by DFT calculations indicated that the production of hydrogen occurs by a two‐step process. First, decamethylruthenocene hydride [Cp*2RuIV(H)]+ is formed in the presence of an organic acid. Subsequently, [Cp*2RuIV(H)]+ is reversibly reduced in a heterolytic reaction with one‐photon excitation leading to a first release of hydrogen. Thereafter, the resultant decamethylruthenocenium ion [Cp*2RuIII]+ is further reduced with a second release of hydrogen by deprotonation of a methyl group of [Cp*2RuIII]+. Experimental and computational data show spontaneous conversion of [Cp*2RuII] to [Cp*2RuIV(H)]+ in the presence of protons. Calculations highlight that the first reduction is endergonic (ΔG0=108 kJ mol−1) and needs an input of energy by light for the reaction to occur. The hydricity of the methyl protons of [Cp*2RuII] was also considered. [ABSTRACT FROM AUTHOR]

Complementary to classical treatment methods used against cancer, photodynamic therapy (PDT) has received increasing attention over the last years. PDT relies on the generation of reactive oxygen species (ROS) upon light irradiation to trigger cell death. As the wavelength employed during such treatments directly influences the light penetration depth and therefore the possibility to treat deep seated tumors or large tumors, research efforts have been made towards the development of photosensitizers (PSs) with an absorption in the phototherapeutic window (600–900 nm). To tackle this drawback, we report herein the preparation and characterization of new RuII‐containing PDT PSs, that are based on a [Ru(bipy)3]2+ core (1; bipy: 2,2′‐bipyridine) and that are extended with methyl groups (2) or vinyl dimethylamino groups (3). As anticipated with our design, we found a red‐shift of 65 nm of the maximum absorption of complex 3 in comparison to complex 1. In addition, we report on the in‐depth photophysical properties as well as (photo‐)cytotoxicity against cervical cancerous HeLa cells of the investigated compounds. [ABSTRACT FROM AUTHOR]

Ruthenium‐catalyzed meta‐C−H activation of arenes at room temperature is reported to proceed under blue‐light irradiation. A variety of heteroarenes are compatible with this photochemical process, which leads to the corresponding meta C−C coupling products in good to very good yields. Initial mechanistic studies suggest a single‐electron transfer process occurs between a photoexcited RuII‐cyclometalated complex and alkyl halides, enabling meta‐C−H functionalization reaction via carbon‐centered radicals. [ABSTRACT FROM AUTHOR]

The conditions for the photogeneration of NO linkage isomers at room temperature are studied. By pulsed laser irradiation in the blue spectral range, the long‐lived Ru−ON isomer can be generated at room temperature, which is crucial for potential applications, such as holography and data storage. By using static and time‐resolved spectroscopy (UV/Vis and IR), we give evidence that the liftime of the Ru−(η2‐(NO)) isomer is a decisive parameter for the formation of the Ru−ON isomer at high temperature owing to a two‐step isomerization mechanism Ru−NO→Ru−(η2‐(NO))→Ru−ON. Furthermore, we report the low‐temperature structures for each isomer, which were revealed by photocrystallography. [ABSTRACT FROM AUTHOR]

Calcium‐modified titania supported Ru catalysts were synthesized and evaluated for the hydrogenation of levulinic acid with formic acid as an internal hydrogen source and water as a green solvent. A new elegant photoassisted method was developed for the synthesis of uniform‐size and evenly distributed Ru particles on the titania surface. Compared with the counterpart catalysts prepared by classical wet impregnation, enhanced levulinic acid conversion and γ‐valerolactone yield were obtained and further improved through modification of the support by introduction of calcium into the titania support. This synthesis approach resulted in a change of the surface and bulk properties of the support, namely a decrease in the anatase crystallite size and the formation of a new calcium titanate phase. As a consequence, the properties of the catalysts were modified, and smaller ruthenium particles that had stronger interactions with the support were obtained. This affected the strength of the CO adsorption on the catalyst surface and facilitated the reaction performance. The optimum size of Ru particles that allowed for most efficient levulinic acid conversion was established. A new elegant photoassisted method was developed for the synthesis of uniform‐size and evenly distributed Ru particles on a titania surface. An enhanced catalytic performance for the synthesis of γ‐valerolactone was obtained compared with that of the catalysts prepared by classical wet impregnation, and further improved by modification of the titania support by the introduction of calcium. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Tissue adhesives are desired with low cytotoxicity and high tissue adhesion. • Catechol- and phenol-modified gelatin were synthesized respectively. • Adhesives were prepared via photochemistry or mussel-inspired chemistry. • Adhesives were evaluated by mechanical properties, tissue adhesion and toxicity. Abstract Tissue adhesives have been developed to overcome the difficulties of conventional wound closure techniques (e.g. sutures and staples), such as the potential for collateral damage and difficulty of stopping body fluid and gas. At the same time, it provides advantages such as simpler implementation, less painful, and does not require removal. However, representative adhesives such as cyanoacrylates and fibrin glues are plagued by cytotoxicity and low adhesion. In this study, we choose instead gelatin as the backbone of adhesive, due to its biocompatibility, biodegradability, and low cost. Firstly, catechol-modified gelatin and phenol-modified gelatin were synthesized via an EDC/NHS chemistry. Then, gelatin-based adhesives were prepared via ruthenium-based photochemistry, including photo-crosslinked gelatin (PG), phenol-modified gelatin (PPG), and catechol-modified gelatin (PCG). We also compared the photo-crosslinked adhesives to the recently reported ion-crosslinked catechol-modified gelatin. Our results indicate that gelatin-based adhesives demonstrate lower swelling index, great degradability, and low cytotoxicity. This shows that gelatin-based adhesives demonstrate great potential for wound closure and healing. [ABSTRACT FROM AUTHOR]

The photochemical properties of the complexes cis -[Ru(phen) 2 (SO 3)(H 2 O)], cis -Na 2 [Ru(phen) 2 (SO 3) 2 ] and cis-[Ru(phen) 2 (SO 3)(CO)] were investigated, where we noticed only cis -[Ru(phen) 2 (SO 3)(H 2 O)] did not show any photoreaction. However, cis -Na 2 [Ru(phen) 2 (SO 3) 2 ] and cis -[Ru(phen) 2 (SO 3)(CO)], after light irradiation (λ irr =453 and 350 nm), released SO 3 2- and CO, respectively, originating the same final photoproduct (cis -[Ru(phen) 2 (SO 3)(H 2 O)]. At least three species with biological activities can emerge from the use of light: CO, SO 3 2- and aqua ruthenium complex that might be further explored. [Display omitted] There is a need for new antimicrobial compounds to combat the growing threat of widespread antibiotic resistance. Recently, metal complexes have been recognized as promising sources for new antibiotics. In this context, Ru(II) complexes have shown good antimicrobial activity. Also, CO and SO 3 2- ligands can exhibit interesting modulatory effects, since they show promising antibacterial properties. So, here, we synthesized and characterized three new compounds of the type cis -[Ru(phen) 2 (SO 3)L]0/2-, where L = CO, H 2 O or SO 3 2-. Their photochemical properties were also investigated, where we noticed that cis- [Ru(phen) 2 (SO 3)(H 2 O)] complex did not show any photoreaction. However, cis -Na 2 [Ru(phen) 2 (SO 3) 2 ] and cis- [Ru(phen) 2 (SO 3)(CO)], after light irradiation, release SO 3 2- and CO, respectively, originating the same final photoproduct, cis- [Ru(phen) 2 (SO 3)(H 2 O)]. At least three species with biological activities can emerge from the use of light: CO, SO 3 2- and aqua ruthenium complex. Altogether, these results are encouraging and further biological studies might be explored. [ABSTRACT FROM AUTHOR]