Os Complexes Research Articles

A redox-active porous coordination network film based on a Ru complex as a building block on an ITO electrode

The combination of self-assembled monolayer (SAM) and layer-by-layer (LbL) growth methods for the construction of a surface porous film has the potential to incorporate a wide range of chemical functionalities on a solid surface. A novel redox-active Ru complex with 2,6-bis(N-pyridylbenzimidazolyl)-pyridine ligands (Ru complex 1), in which four peripheral pyridine groups act as coordination sites, was used as a building block for a porous coordination network film. By using (4-pyridyl)phenylphosphonic acid as a SAM primer layer on an ITO surface, the Ru complex 1 was immobilized by the successive reaction of PdCl2 on the ITO electrode in the LbL growth method. Multilayer growth was monitored by UV-vis spectra and cyclic voltammetry, in which the linear increases of both absorbance and the peak current were observed. This result indicated that the regular accumulation of Ru complex 1 onto the ITO surface took place. The permselectivity of the present porous coordination network structure was examined using redox-active molecular probes with different sizes and charges such as ferrocene, trimethylaminomethylferrocene, the Os bis(2,6-bis(N-methylbenzimidazolyl)-pyridine) complex, and tetrathiofulvarene (TTF). With the Os complex and cationic ferrocene, only the catalytic peak was observed as a prewave of the adsorbed Ru(II/III) peak at +0.73 V. On the other hand, the oxidation peak of ferrocene was observed around 0 V vs. Fc(+)/Fc even for nine-layered films in addition to the adsorbed Ru(II/III) peak. From these results, not only molecular size but also electrostatic interaction plays an important role in the permeation into the Ru complex 1 porous network film.

Near-infrared phosphorescence: materials and applications

Room-temperature phosphorescent materials that emit light in the visible (red, green, and blue; from 400 to 700 nm) have been a major focus of research and development during the past decades, due to their applications in organic light-emitting diodes (OLEDs), light-emitting electrochemical cells, photovoltaic cells, chemical sensors, and bio-imaging. In recent years, near-infrared (NIR) phosphorescence beyond the visible region (700-2500 nm) has emerged as a new, promising, and challenging research field with potential applications toward NIR OLEDs, telecommunications, night vision-readable displays. Moreover, NIR phosphorescence holds promise for in vivo imaging, because cells and tissues exhibit little absorption and auto-fluorescence in this spectral region. This review describes the overall progress made in the past ten years on NIR phosphorescent transition-metal complexes including Cu(I), Cu(II), Cr(III), Re(I), Re(III), Ru(II), Os(II), Ir(III), Pt(II), Pd(II), Au(I), and Au(III) complexes, with a primary focus on material design complemented with a selection of optical, electronic, sensory, and biologic applications. A critical comparison of various NIR phosphorescent materials reported in the literature and a blueprint for future development in this field are also provided.

Organometallic anticancer complexes of lapachol: metal centre-dependent formation of reactive oxygen species and correlation with cytotoxicity

Organometallic Ru(II), Os(II) and Rh(III) complexes of lapachol induce apoptosis in human tumour cell lines in the low μM range by a mode of action involving oxidative stress, especially in the case of the ruthenium compound.

Structural properties of trans hydrido–hydroxo M(H)(OH)(NH2CMe2CMe2NH2)(PPh3)2 (M = Ru, Os) complexes and their proton exchange behaviour with water in solution

We report the synthesis of Ru(II) and Os(II) trans hydrido-hydroxo complexes by reacting the unsaturated amido complexes MH(NHCMe2CMe2NH2)(PPh3)2 (M = Ru, Os) with stoichiometric amounts of water. Proton exchange is rapid at room temperature between the amine/water/hydroxide moieties which leads to signal averaging of the NMR properties which can be slowed at low temperature in order to see resonances of separate complexes. These compounds can also be cleanly converted back to their starting complexes by dehydration in the presence of 3 Å molecular sieves. X-ray crystal structures of these Ru(II) and Os(II) trans hydrido-hydroxo complexes reveal that the unit cell contains an additional molecule of water trapped in the crystal lattice which hydrogen bonds with a neighbouring hydroxo ligand, forming a water bridged dimer in the solid state. Although there are many cases of oxidative addition of water to transition metal complexes, relatively few cases are well characterized where water addition occurs via metal-ligand cooperation (bifunctional addition) without altering the oxidation state of the metal center.

Osmium–Germanium and Osmium–Germanium–Gold Carbonyl Cluster Complexes: Syntheses, Structures, Bonding, and Reactivity

Reactions of Os3(CO)10(NCMe)2 with HGePh3 have yielded the compounds Os3(CO)10(NCMe)(GePh3)(μ-H) (1) and Os3(CO)10(GePh3)2(μ-H)2 (2) by the sequential replacement of the NCMe ligands and the oxidative addition of the GeH bonds of one and two HGePh3 molecules, respectively, to the osmium atoms of the cluster. Compound 2 exists as two isomers in solution at low temperatures which interconvert rapidly on the 1H NMR time scale at room temperature. When it was heated, 1 was transformed into the pentaosmium complex Os5(CO)17(μ-GePh2) (3), which exhibits a planar raft structure with one bridging GePh2 ligand. Compound 1 reacts with the compound PhAu(PPh3) to yield the compound Os3(CO)8(μ-CO)(μ-O═CPh)(μ-GePh2)(μ-AuPPh3) (4), which contains a bridging O═CPh ligand and a Au(PPh3) group that bridges an Os–Ge bond. A minor product, Os(CO)4(GePh3)(AuPPh3) (5), was also obtained in this reaction. Compound 4 was also obtained from the reaction of 1 with CH3Au(PPh3). Compound 4 reacted with PhC2Ph to yield the complex Os...

Microwave Promoted Oxidative Addition Reactions of Os3(CO)12: Efficient Syntheses of Triosmium Clusters of the Type Os3(μ-X)2(CO)10 and Os3(μ-H)(μ-OR)(CO)10

Microwave heating allows for the high-yield, one-step synthesis of the known triosmium complexes Os3(μ-Br)2(CO)10 (1), Os3(μ-I)2(CO)10 (2), and Os3(μ-H)(μ-OR)(CO)10 with R = methyl (3), ethyl (4), isopropyl (5), n-butyl (6), and phenyl (7). In addition, the new clusters Os3(μ-H)(μ-OR)(CO)10 with R = n-propyl (8), sec-butyl (9), isobutyl (10), and tert-butyl (11) are synthesized in a microwave reactor. The preparation of these complexes is easily accomplished without the need to first prepare an activated derivative of Os3(CO)12, and without the need to exclude air from the reaction vessel. The syntheses of complexes 1 and 2 are carried out in less than 15 min by heating stoichiometric mixtures of Os3(CO)12 and the appropriate halogen in cyclohexane. Clusters 3–6 and 8–10 are prepared by the microwave irradiation of Os3(CO)12 in neat alcohols, while clusters 7 and 11 are prepared from mixtures of Os3(CO)12, alcohol and 1,2-dichlorobenzene. Structural characterization of clusters 2, 4, and 5 was carried out by X-ray crystallographic analysis. High resolution X-ray crystal structures of two other oxidative addition products, Os3(CO)12I2 (12) and Os3(μ-H)(μ-O2CC6H5)(CO)10 (13), are also presented.

Design and verification of a lightweight reliable virtual machine monitor for a many-core architecture

Virtual machine monitors (VMMs) play a central role in cloud computing. Their reliability and availability are critical for cloud computing. Virtualization and device emulation make the VMM code base large and the interface between OS and VMM complex. This results in a code base that is very hard to verify the security of the VMM. For example, a misuse of a VMM hyper-call by a malicious guest OS can corrupt the whole VMM. The complexity of the VMM also makes it hard to formally verify the correctness of the system's behavior. In this paper a new VMM, operating system virtualization (OSV), is proposed. The multiprocessor boot interface and memory configuration interface are virtualized in OSV at boot time in the Linux kernel. After booting, only inter-processor interrupt operations are intercepted by OSV, which makes the interface between OSV and OS simple. The interface is verified using formal model checking, which ensures a malicious OS cannot attack OSV through the interface. Currently, OSV is implemented based on the AMD Opteron multi-core server architecture. Evaluation results show that Linux running on OSV has a similar performance to native Linux. OSV has a performance improvement of 4%---13% over Xen.

Relative rates of reaction of Pt(en)Cl (NH2R)+ with guanosine monophosphate as a function of amino group substituent: Toward efficient labeling of DNA for TEM imaging

In an attempt to understand the factors that govern the rates of reaction of the complexes [Pt(en)Cl(NH2R)]+NO3− (en = ethylene diamine) with guanosine monophosphate (dGMP) a series of amine complexes, where RC8H9NO2 (benzo[d][1,3]dioxol-5-ylmethanamine) (1), C8H11N (phenethylamine) (2), C7H9N (benzylamine) (3), C6H7N (aniline) (4), C6H6IN (p-iodo-aniline) (5) C3H9NO (2-methoxy-ethylamine) (6) and C6H13N (cyclohexylamine) (7), were synthesized and their reactions with deoxyguanosine monophosphate (dGMP) were followed by 1H NMR. Compound 1 was initially chosen because it showed significant water solubility. Compound 1 reacted quantitatively but slowly with dGMP and a subsequent Transmission Electron Microscopy (TEM) study of the binding 1 to a GATC DNA repeat gave a TEM micrograph that showed selective labeling of DNA at guanine, using a technique that allowed the laying down of a straight single strand of DNA on a carbon platform. The TEM suggested a possible side reaction with adenine and so a study of the reaction of 1 with adenine was performed and showed slow and what appeared to be non-specific binding to deoxyadenosine monophosphate (dAMP). The reactions of compounds 2–7 with dGMP were then studied by 1H NMR and it was found that 2 reacted much faster than 1 with dGMP while the remaining complexes reacted more slowly. No reaction of 2 with dAMP was observed in the same time frame. The ultimate goal of the project was to bind a third row transition metal cluster to guanine and given the effective binding of 1 to DNA the synthesis of the complex [Os3(CO)11PPh2(CH2)2NH2(en)PtCl]NO3 (9) is also reported that contains Pt as a linker to label guanine. The synthesis was performed by reacting Os3(CO)10(CH3CN)2 with Ph2PCH2CH2NH2 which gave an η2 chelate complex Os3(CO)10PPh2(CH2)2NH2 (8). Complex 8 was reacted with [Pt(en)Cl(DMF)]NO3 in a CO atmosphere to give 9. 1H and 195Pt NMR indicate formation of an adduct with dGMP but too slowly to be of use in labeling DNA. The solid-state structure of 8 is also reported.

Direct electrochemistry and Os-polymer-mediated bioelectrocatalysis of NADH oxidation by Escherichia coli flavohemoglobin at graphiteelectrodes

Escherichia coli flavohemoglobin (HMP), which contains one heme and one FAD as prosthetic groups and is capable of reducing O2 by its heme at the expense of NADH oxidized at its FAD site, was electrochemically studied at graphite (Gr) electrodes. Two signals were observed in voltammograms of HMP adsorbed on Gr, at −477 and −171mV vs. Ag|AgCl, at pH 7.4, correlating with electrochemical responses from the FAD and heme domains, respectively. The electron transfer rate constant for ET reaction between FAD of HMP and the electrode was estimated to be 83s−1. Direct bioelectrocatalytic oxidation of NADH by HMP was not observed, presumably due to impeded substrate access to HMP orientated on Gr through the FAD-domain and/or partial denaturation of HMP. Bioelectrocatalysis was achieved when HMP was wired to Gr by the Os redox polymers, with the onset of NADH oxidation at the formal potential of the particular Os complex (+140mV or −195mV). Apparent Michaelis constants KMapp and jmax were determined, showing bioelectrocatalytic efficiency of NADH oxidation by HMP exceeding the one earlier shown with diaphorase, which makes HMP very attractive as a component of bioanalytical and bioenergetic devices.

A Dimorphic Os(IV) Complex with Pyramidal Sulfur Inversion in a Sulfanyl Chelating Ligand

Coordination compound [Os(SC6F4H-4)2(SC6F3H-4(SC6F4H)-2)(C6H5)] is obtained during the thermolysis of [Os(SC6F4H-4)4(PPh3)] in non-dried toluene, as a product of C–F bond cleavage. The complex presents the expected trigonal–bipyramidal coordination geometry, with a thiolate-sulfanyl κ2 S,S’-ligand chelating the metal center in axial and equatorial sites. The complex was crystallized in the centrosymmetric space group C2/c and in the non-centrosymmetric space group Pna21. In both forms, the crystal is a RS racemate, with the chiral center being the axially coordinated sulfanyl S atom. In the case of the non centrosymmetric space group, the asymmetric unit retained for the refinement consists of two independent molecules related by a pyramidal sulfur inversion at the stereogenic center. Cell parameters: form I, C2/c, a = 20.8459(14) A, b = 12.2646(12) A, c = 25.253(3) A, β = 91.582(7)°; form II, Pna21, a = 16.208(2) A, b = 16.500(3) A, c = 23.604(3) A. An Os(IV) coordination complex bearing a thiolate-sulfanyl κ2 S,S’-ligand was crystallized in two spaces groups, C2/c with one molecule in the asymmetric unit, and Pna21 with two enantiomeric molecules in the asymmetric unit.

Reactions of Os3(CO)12 with carboxylic acids in a microwave reactor; synthesis of Os2(benzoate)2(CO)6, a dinuclear osmium(I) compound with aromatic carboxylate ligands

Microwave heating is used to synthesize compounds of the type Os2(μ-O2CR)2(CO)6, including the first example with aromatic carboxylate ligands. The one-step preparation of these complexes is straightforward and does not require an air-free reaction environment. The compounds for which R = Me (1) or Et (2) are produced in higher yield than previously reported by the microwave irradiation of Os3(CO)12 for less than 15 min in acetic or propionic acid, respectively. This method may also be used to prepare the new compound Os2(μ-O2CH)2(CO)6 (3) by reaction with formic acid, but a higher yield is obtained when 1,2-dichlorobenzene is used as a co-solvent. Irradiating a mixture of Os3(CO)12 and excess benzoic acid in 1,2-dichlorobenzene gives another new complex Os2(μ-O2CC6H5)2(CO)6 (4). X-ray crystallographic analyses of 3 and 4 reveal molecular structures similar to that of 1 with approximate C2v symmetry. When the molar ratio of benzoic acid to Os3(CO)12 is 1:1, then the major product is the trinuclear cluster Os3(μ-H)(μ-O2CC6H5)(CO)10 (5) instead of a dinuclear compound. This represents the first instance in which a cluster of this type has been produced directly from Os3(CO)12 instead of through a multi-step procedure.

Organic Light‐Emitting Diodes: Os(II) Based Green to Red Phosphors: A Great Prospect for Solution‐Processed, Highly Efficient Organic Light‐Emitting Diodes (Adv. Funct. Mater. 16/2012)

Preparation and characterization of a new class of emissive Os(II) complexes is reported by Hao-Wu Lin, Yun Chi, Pi-Tai Chou, and co-workers on page 3491. The complexes all show bright emission spanning the visible region from green to saturated red and a series of solution-processed organic light-emitting diodes (OLEDs) using the complexes as the dopant are successfully fabricated, demonstrating excellent device performance with an external quantum efficiency of 15% and power efficiency of up to 50 lm W−1.

Infrared Spectra of the Complexes Os←NCCH3, Re←NCCH3, CH3–ReNC, CH2═Re(H)NC, and CH≡Re(H)2NC and their Mn Counterparts Prepared by Reactions of Laser-Ablated Os, Re, and Mn Atoms with Acetonitrile in Excess Argon

Acetonitrile forms primarily N-coordination complexes (M←NCCH3) with Os and Re metal atoms, but these metal atoms produce exclusively methylidyne complexes (HC≡MH2X) in similar previous reactions with small alkanes and halomethanes. The Os complex increases on visible photolysis and dissociates partially on UV irradiation without the generation of other new products, whereas the Re complex converts to other products (CH3–ReNC, CH2═Re(H)NC, and CH≡Re(H)2NC) on photolysis. The primary formation of the N-coordination complex originates from its stability relative to that of the nitrile π-complex in these systems. The agostic interaction in the methylidene complex is apparently insignificant, and this rare observation of a methylidyne product with Re reflects that H migration in the isocyanide system is less favorable than those in the hydride and halide analogues. Experiments with Mn gave weaker counterpart product absorptions.

Preparation of Germyl Complexes of Osmium(II)

AbstractThe germyl complex Os[Ge3Cl6(OH)2]P4 (1) [P = P(OEt)3] was prepared by allowing dihydride OsH2P4 to react with GeCl2·dioxane. Treatment of OsH2P4 with GeCl2·dioxane and then with SnCl2·2H2O in ethanol yielded the mixed‐ligand derivative Os[Ge3Cl6(OEt)(OH)4](SnCl3)P4 (2). Both complexes were characterised spectroscopically (IR, NMR) and by X‐ray crystal structure determination.

Calorimetric and vibrational spectroscopic investigations of phase transitions in crystalline [Cr(OS(CH3)2)6](BF4)3

Two phase transitions – one sharp at T1=247.4K and the other very broad at T2∼135K – were observed for [Cr(OS(CH3)2)6](BF4)3 by adiabatic calorimetry. They are of the order–disorder type, and their transition entropies are 28.4 and 8.3JK−1mol−1, respectively. IR absorption and Raman scattering spectroscopy measurements revealed distinct changes in the molecular dynamics of both CH3 groups and BF4− anions at T1 and reduced symmetry of the [Cr(OS(CH3)2)6]3+ complex cations and OS(CH3)2 ligands below T2. The spectral width of an IR and Raman active band associated with the δas(FBF)F2 mode yielded an activation energy (Ea)∼9kJmol−1 for the reorientation of BF4− anions, which is comparable with that obtained for other coordination compounds with BF4− anions.

Incorporation of Polymerizable Osmium(II) Bis-terpyridine Complexes into PMMA Backbones

For the first time, an Os(II) bis-terpyridine complex bearing a polymerizable methacryloyl function was synthesized and subsequently copolymerized with MMA using the RAFT polymerization technique. The well-defined polymer was analyzed by SEC, ESI-TOF MS, 1H NMR spectroscopy as well as UV–Vis absorption and emission spectroscopy. The lifetime as well as redox potentials of the complex and the corresponding polymer were also determined. Additionally, the film forming properties of the polymer were investigated and preliminary UV–Vis absorption as well as emission experiments were carried out with a second donor pendant polymer revealing energy transfer from the donor to the Os(II) complex. The synthesis and subsequent polymerization of a methacrylate functionalized Os(II) bis-terpyridine complex is described. The copolymerization with MMA resulted in a polymer that features the well-defined optical and electrochemical properties of the complex combined with typical polymer properties.

Tunable Energy Transfer Rates via Control of Primary, Secondary, and Tertiary Structure of a Coiled Coil Peptide Scaffold

Herein we report energy transfer studies in a series of Ru(II) and Os(II) linked coiled-coil peptides in which the supramolecular scaffold controls the functional properties of the assembly. A general and convergent method for the site-specific incorporation of bipyridyl Ru(II) and Os(II) complexes using solid-phase peptide synthesis and the copper-catalyzed azide-alkyne cycloaddition is reported. Supramolecular assembly positions the chromophores for energy transfer. Using time-resolved emission spectroscopy we measured position-dependent energy transfer that can be varied through changes in the sequence of the peptide scaffold. High level molecular dynamics simulations were used in conjunction with the spectroscopic techniques to gain molecular-level insight into the observed trends in energy transfer. The most efficient pair of Ru(II) and Os(II) linked peptides as predicted by molecular modeling also exhibited the fastest rate of energy transfer (with k(EnT) = 2.3 × 10(7) s(-1) (42 ns)). Additionally, the emission quenching for the Ru(II) and Os(II) peptides can be fit to binding models that agree with the dissociation constants determined for the peptides via chemical denaturation.

Complex Förster Energy Transfer Interactions between Semiconductor Quantum Dots and a Redox-Active Osmium Assembly

The ability of luminescent semiconductor quantum dots (QDs) to engage in diverse energy transfer processes with organic dyes, light-harvesting proteins, metal complexes, and redox-active labels continues to stimulate interest in developing them for biosensing and light-harvesting applications. Within biosensing configurations, changes in the rate of energy transfer between the QD and the proximal donor, or acceptor, based upon some external (biological) event form the principle basis for signal transduction. However, designing QD sensors to function optimally is predicated on a full understanding of all relevant energy transfer mechanisms. In this report, we examine energy transfer between a range of CdSe-ZnS core-shell QDs and a redox-active osmium(II) polypyridyl complex. To facilitate this, the Os complex was synthesized as a reactive isothiocyanate and used to label a hexahistidine-terminated peptide. The Os-labeled peptide was ratiometrically self-assembled to the QDs via metal affinity coordination, bringing the Os complex into close proximity of the nanocrystal surface. QDs displaying different emission maxima were assembled with increasing ratios of Os-peptide complex and subjected to detailed steady-state, ultrafast transient absorption, and luminescence lifetime decay analyses. Although the possibility exists for charge transfer quenching interactions, we find that the QD donors engage in relatively efficient Förster resonance energy transfer with the Os complex acceptor despite relatively low overall spectral overlap. These results are in contrast to other similar QD donor-redox-active acceptor systems with similar separation distances, but displaying far higher spectral overlap, where charge transfer processes were reported to be the dominant QD quenching mechanism.

Rapid Synthesis of Radioactive Transition-Metal Carbonyl Complexes at Ambient Conditions

Carbonyl complexes of radioactive transition metals can be easily synthesized with high yields by stopping nuclear fission or fusion products in a gas volume containing CO. Here, we focus on Mo, W, and Os complexes. The reaction takes place at pressures of around 1 bar at room temperature, i.e., at conditions that are easy to accommodate. The formed complexes are highly volatile. They can thus be transported within a gas stream without major losses to setups for their further investigation or direct use. The rapid synthesis holds promise for radiochemical purposes and will be useful for studying, e.g., chemical properties of superheavy elements.

Nucleophilic Attack on an Electronically Unsaturated Triosmium Cluster Complex of 2-Methylbenzoxazole: An Unusual Oxidative Ring Opening

In the course of our studies of nucleophilic attack on electronically unsaturated benzoheterocycle triosmium clusters we have studied the reaction of the 2-methylbenzoxazole complex (μ-H)Os3(CO)9(μ3-η2-2-CH3–C7H3NO) (1) with hydride followed by protonation with acid. In sharp contrast to our previous studies with related benzoheterocycle triosmium clusters, where the nature of the heterocycle controls the regiochemistry of nucleophilic attack, we observe here an unusual ring opening of the heterocyclic ring, coupled with rearrangement of the carbocyclic ring to a 2-imino-ethyl-phenol complex (μ-H)Os3(CO)9(μ3-η3-N=CHCH3–C6H3(OH)) (2). Deuterium labeling experiments verify initial attack by hydride at the 2-position followed by protonation at oxygen. Reaction of 1 with two equivalents of hydride followed by two equivalents of acid results in reduction of the C=N bond in 2 and on standing in air, oxidation of the carbocyclic ring occurs to give the 2-ethyl-amino hydroquinolyl derivative (μ-H)Os3(CO)9(μ3-η3-NHCH2CH3–C6H3(2-O)(5-OH)) (3). The solid-state structure of 3 is reported and a plausible mechanism, supported by deuterium labeling experiments, is presented, for the formation of 2 and 3.