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The reactivities of Fe(iv) oxido complexes of two pentadentate ligands are related to steric and electronic properties of the ligands.

Converting biomass into value-added chemicals is of significant interest and we report an efficient hydrosilylation to convert levulinic acid to γ-valerolactone using cost-effective silanes such as PMHS and TMDS with B(C6F5)3 as catalyst. This metal free methodology works at room temperature reaching TONs and TOFs up to 16000 and 2000 h−1. Insights into the reaction mechanism are reported.

New PCNPy pincer nickel complexes have been synthesized through a short synthetic route. Incorporating pyridine as the nitrogen side arm facilitated the C–H activation in the PCN ligand and allowed the cyclometallation with nickel to take place at room temperature. Pyridine also enhanced the stability of β-hydrogen-containing alkyl complexes. Also, the symmetric NCN nickel complex with pyridine side arms was successfully obtained giving a rare example of such type of complexes to be prepared through direct C–H activation. Furthermore, preliminary results showed that the (PCNPy)Ni–Br is active in Kumada coupling reactions particularly the coupling of aryl halides with aryl Grignard reagents.

To enable the large-scale use of hydrogen fuel cells for mobility applications, convenient methods for on-board hydrogen storage and release are required. A promising approach is liquid organic hydrogen carriers (LOHCs), since these are safe, available on a large scale, and compatible with existing refueling infrastructure. Usually, LOHC dehydrogenation is carried out in batch-type reactors by transition metals and their complexes and suffers from slow H

The synthesis of a new unsymmetrical PCN ligand bearing tert-butyl groups on the phosphorus atom and isopropyl groups on the nitrogen donor atom is presented. It reacts with the commercially availa...

Plasmamedizin hat sich zu einem innovativen Forschungsgebiet mit diversen Anwendungsmoglichkeiten insbesondere in der Dermatologie entwickelt. Kaltes Atmospharendruckplasma (KAP) kann sowohl gewebeschonend als auch zur Destruktion von malignem Gewebe eingesetzt werden. KAP besteht aus einer komplexen Mixtur aus verschiedenen biologisch aktiven Agenzien, die zum Teil synergistisch auf das zu behandelnde Material oder Gewebe wirken. Dargestellt werden die Anwendungsgebiete fur KAP in der Dermatologie sowie der aktuelle Stand der Forschung. Literatur zur Anwendung von KAP in der Dermatologie wurde gesichtet und als Ubersichtsarbeit zusammengefasst. Mit einer KAP-Behandlung konnen beispielsweise antimikrobielle, gewebestimulierende, durchblutungsfordernde, aber auch proapoptotische Effekte erreicht werden. Unter Ausnutzung dieser Effekte kommt KAP in der Dermatologie erfolgreich zur Desinfektion und Wundbehandlung zum Einsatz. Des Weiteren zeigen Untersuchungen zur Anwendung von KAP bei der Behandlung von Tumoren, aktinischen Keratosen, Narben, Ichthyose, atopischen Ekzemen sowie zur Linderung von Schmerz und Juckreiz positive Effekte. Wahrend die Anwendung von KAP zur Desinfektion und zur Wundbehandlung vereinzelt bereits den Einzug in die klinische Praxis gefunden hat, befindet sich die Anwendung in weiteren Bereichen, beispielsweise zur Tumortherapie, noch im Forschungskontext.

From the reaction of 2-hydroxy-6-methylpyridine (L) with iron(II) tetrafluoroborate, a new mononuclear iron(III) octahedral complex [FeL6](BF4)3 has been isolated. The color of the complex reversibly changed from red at room temperature to yellow-orange at the liquid nitrogen temperature. Magnetization measurements indicate that iron(III) in [FeL6](BF4)3 is in a high-spin state S = 5/2, from room temperature to 1.8 K. The high-spin ground state of iron(III) is also confirmed by DFT calculations. Although the spin-crossover of the complex is not observed, X-band and multifrequency high-field/high-frequency electron spin resonance (ESR) spectroscopy shows rather uncommon iron(III) spectra at room temperature and an unusual change with cooling. Spectral simulations reveal that the S = 5/2 ground state multiplet of the complex can be characterized by the temperature independent axial zero-field splitting parameter of |D| = +2 GHz (0.067 cm−1) while the value of the rhombic parameter E of the order of some tenths MHz increases on lowering the temperature. Single crystal X-ray diffraction (SCXRD) shows that the iron(III) coordination geometry does not change with temperature while supramolecular interactions are temperature dependent, influencing the iron(III) rhombicity. Additionally, the DFT calculations show temperature variation of the HOMO–LUMO gap, in agreement with the changes of color and ESR-spectra of the iron(III) complex with temperature.

Oxidative addition is the standard process for single-bond activation in transition metal catalysis and it is known to operate for many types of bonds, but challenging σ-bonds e. g. C(sp3)−F and C(sp3)−C(sp3) bonds are the exceptions in this respect. This short review aims at demonstrating how both α- and β-eliminations may be better options for activation of unstrained C−F and C−C single bonds. Selected examples of such eliminations are presented with a mechanistic focus indicating how unstrained and unactivated C−C and C−F bonds can be broken by employing α- and β-eliminations in transition metal hydrocarbyl ligands. Our examples show that the reaction barrier in β-eliminations is controlled by the s-character of the participating bonds where a higher s-character gives a better overlap in the multi-center transition state thereby increasing the reactivity; still β-aryl eliminations can compete with the classical β-hydrogen eliminations in certain cases. (Less)

A new generation of N-heterocyclic carbene palladium(II) complexes containing vinyl groups in different positions in the backbone of the N-heterocycle have been developed. The fully characterised monomers were copolymerised with divinylbenzene to fabricate robust polymer supported NHC-PdII complexes and these polymers were applied as heterogeneous catalysts in directed C-H halogenation of arenes with a pyridine-type directing group. The catalysts demonstrated medium-high catalytic activity with up to 90 % conversion and 100 % selectivity in chlorination. They are heterogeneous and recyclable (at least six times) with no significant leaching of palladium in batch mode catalysis. The best catalyst was also applied under continuous flow conditions where it disclosed an exceptional activity (90 % conversion) and 100 % selectivity for the mono-halogenated product for at least six days, with no leaching of palladium, no loss of activity and an ability to maintain the original oxidation state of PdII .

This work explores the use of water-in-supercritical carbon dioxide (scCO2) microemulsions for the extraction of polar metabolites from plants. Stevia rebaudiana Bertoni leaves and polyethylene glycol trimethylnonyl ether (TMN) surfactants were selected for a case study. A CO2-water-TMN 10 mixture at 35 °C and 30.0 MPa extracted 7 mg target analyte/g dry leaves. The extraction was proven to occur due to a water-surfactant liquid solution rather than a water-in-CO2 microemulsion. Using a modified extraction setup, the microemulsion was created prior to extraction. TMN 6 was able to dissolve enough water in CO2 to extract steviol glycosides, in detectable but very small amounts.

We report the first examples of the carbide ligand in (Cy3P)2Cl2Ru≡C (RuC) developing into a μ3 ligand toward metal centers. Conventionally, sterics exclude this coordination mode, but Fe2(CO)9 and Co2(CO)8 expel bridging CO ligands upon reaction with RuC to form trimetallic (Cy3P)2Cl2Ru═CFe2(CO)8 (RuCFe2) and (Cy3P)2Cl2Ru═CCo2(CO)7 (RuCCo2) complexes. Thus, the proximity offered by metal–metal associations in bimetallic carbonyl complexes allows the formation of trinuclear carbide complexes as verified by NMR, Mossbauer, and X-ray spectroscopic techniques.

A systematic study of the photophysical and electrochemical properties of triscyclometalated homoleptic iridium(III) complexes based on 2-(1-naphthyl)pyridine (npy) ligands is presented. A systematic investigation of ligand substitution patterns showed an influence on the lifetime of the excited state, with slight changes in the absorption and emission spectral features. Specifically, the emission lifetime of a complex of an npy ligand substituted with a strongly electron-withdrawing trifluoromethyl group was longer than that of the corresponding complex with the electronically nonperturbed ligand (3.7 μs versus 1.5 μs). Electronically complementary ligands and complexes with ­orthogonal configurations showed slightly shorter excited state lifetimes compared with unsubstituted npy (1.4–3.0 μs). All complexes displayed reversible or quasireversible redox-couple processes, with the complex of the trifluoromethylated ligand showing the highest ground-state oxidation potential E1/2 ox [Ir(III)/Ir(IV) = 0.95 V vs. SCE in CH2Cl2]. This study showed that these complexes can be used as efficient photoredox catalysts, as demonstrated by their application in a regioselective methoxytrifluoromethylation in which the npy complexes showed equal or better performance compared with the archetypical photo­redox catalyst tris[2-phenylpyridinato]iridium(III).

We simulate a simple nanocomposite consisting of a single spherical nanoparticle surrounded by coarse-grained polymer chains that are composed of two monomer types differing only in their interactions with the nanoparticle. We measure the atomic stress fluctuations and use them to estimate the local stress autocorrelation as a function of distance from the nanoparticle. This local stress autocorrelation is substituted into the well-known relationship between the bulk stress autocorrelation and the bulk (frequency-dependent) dynamic modulus, and the result is treated as an estimate of the local dynamic modulus. This allows us to examine the effect of adjusting copolymer sequence on estimations of local storage and loss modulus as a function of distance from the nanoparticle. Notably, we find certain blocky copolymer sequences can lead to a higher tan(δ) (hysteresis) in the interphase than either homopolymer system, suggesting that tuning the copolymer sequence could allow for significant control over nanoc...

In situ X-ray absorption spectroscopy (XAS) investigations have been performed to provide insights into the reaction mechanism of a palladium(II) catalyzed undirected C–H acetoxylation reaction in the presence of an oxidant. A Pd(II) N-heterocyclic carbene complex π-stacked onto reduced graphene oxide (rGO) was used as the catalyst. The Pd speciation during the catalytic process was examined by XAS, which revealed a possible mechanism over the course of the reaction. Pd(II) complexes in the as-synthesized catalyst first go through a gradual ligand substitution where chloride ions bound to Pd(II) are replaced by other ligands with a mean bond distance to Pd matching Pd–C/N/O. Parallel to this the mean oxidation state of Pd increases indicating the formation of Pd(IV) species. At a later stage, a fraction of the Pd complexes start to slowly transform into Pd nanoclusters. The mean average oxidation state of Pd decreases to the initial state at the end of the experiment which means that comparable amounts of Pd(0) and Pd(IV) are present. These observations from heterogeneous catalysis are in good agreement with its homogeneous analog and they support a Pd(II)–Pd(IV)–Pd(II) reaction mechanism.

An N-heterocyclic carbene palladium(II) complex containing two anthracene side arms was immobilized on the surface of reduced graphene oxide (rGO) by π-stacking. The activity of the homogeneous analogue and the supported complex in undirected C–H acetoxylation reaction of arenes was studied. The results show that the catalytic efficiency in acetoxylation of benzene is improved in the immobilized materials compared to the homogeneous analogue. According to XPS analysis, the immobilized catalyst maintains the original oxidation state of PdII after the catalytic reaction.

We report an efficient process for the oxidation of benzyl alcohols using molecular oxygen as the oxidant catalyzed by Ag-Cu catalysts supported on polyoxometalates (Ag-Cu/POM). The Ag-Cu/POM catalyst was prepared by galvanic displacement in the presence of polyvinyl pyrrolidone and polyethylene glycol. The catalysts were characterized using Fourier transform infrared spectroscopy (FTIR), ultraviolet–visible spectroscopy (UV–Vis), powder X-ray diffraction (PXRD), X-ray fluorescence (XRF), Brunauer-Emmett-Teller (BET) surface analysis, transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS) and thermogravimetric analysis (TGA). The oxidation reaction was carried out using a Schlenk– line setup, under ambient atmospheric pressure. Reaction products were identified by GC–MS and quantified with GC using an internal standard method. The Ag-Cu/POM catalyst gave close to 100% benzyl alcohol conversion in 5 h with >99% selectivity to benzaldehyde. When tested on various benzyl alcohol derivatives the Ag-Cu catalysts showed good conversions and >99% selectivity to the corresponding aldehydes. The Ag-Cu catalysts supported on the POM are highly stable, and don’t show tendency to leach or deactivate. The catalysts are heterogeneous in nature and easy to recover after reactions, and could be reused at least 5 times without significant loss in activity and selectivity.

Naturally occurring phyllosilicate minerals such as talc and vermiculite in conjunction with n-tetra butyl ammonium bromide (TBAB) co-catalyst were found to be efficient in the coupling of CO2 with epoxides to form cyclic carbonates. The reaction was carried out in a pressurized autoclave reactor at moderate pressures of 10–35 bars and temperatures of 100–150 °C. The optimized catalyst system exhibited > 90% conversion of the epoxides and > 90% selectivity for the desired cyclic carbonates, in the presence or absence of a solvent. The selectivity of the catalytic system could be improved with heat pre-treatment of the phyllosilicates albeit this resulted in slightly lower epoxide conversion. The results obtained using the heat treated phyllosilicates strongly support the hydrogen bond assisted mechanism for the cycloaddition of epoxides and CO2. The cycloaddition reaction could also be carried out in the absence of TBAB, although lower cyclic carbonate yields were observed. The phyllosilicate part of the catalyst system is heterogeneous, easy to separate after completion of reactions and reusable a number of runs without loss of activity.

Plasma medicine is gaining increasing interest and provides a multitude of dermatological applications. Cold atmospheric pressure plasma (CAP) can be used in clinical applications without harming the treated tissue or in a tissue destructive manner. It consists of a complex mixture of biologically active agents, which can act synergistically on the treated material or tissue.A summary of the current research findings regarding dermatological applications of CAP is provided.Literature on CAP applications in dermatology has been screened and summarized.CAP exerts antimicrobial, tissue-stimulating, blood-flow-stimulating but also pro-apoptotic effects. By exploiting these properties, CAP is successfully applied for disinfection and treatment of chronic ulcerations. Furthermore, positive effects of CAP have been shown for the treatment of tumors, actinic keratosis, scars, ichthyosis, atopic eczema as well as for alleviation of pain and itch.While the use of CAP for disinfection and wound treatment has already moved into clinical practice, further applications such as cancer treatment are still exploratory.

New diamagnetic nickel(II) complexes based on an unsymmetrical (1-(3-((ditert-butylphosphino)methyl)phenyl)-N,N-dimethyl-methanamine) (PCN) pincer ligand were synthesized and characterized by 1H, 31P{1H}, and 13C{1H} NMR spectroscopy. Their molecular structures were confirmed by X-ray diffraction. Oxidation to high-valent paramagnetic Ni(III) dihalide complexes was achieved through straightforward reaction of the corresponding diamagnetic halide complexes with anhydrous CuX2 (X = Cl, Br). In agreement with this, the complexes are active in Kharasch addition of CCl4 to olefins. The reaction of the hydroxo complex (8) and the amido complex (11) with CO2 produced the hydrogen carbonate and carbamate complexes, respectively. The hydrogen carbonate complex was converted to the dinuclear nickel carbonate complex (10). The methyl (13), phenyl (14), and p-tolylacetylide (15) complexes are also described in the current study providing the first example of the hydrocarbyl nickel complexes based on an unsymmetric ar...

Pincer complexes attract considerable attention both as interesting objects for fundamental studies and efficient catalysts. This review describes a relatively new offshoot of the field – namely, the chemistry of iridium complexes with aliphatic PCsp3P non-innocent pincer ligands. High flexibility, often combined with possibility to activate internal C–H bonds, offers several new patterns of metal-ligand cooperation; some of them were successfully used in catalysis of acceptorless alcohol dehydrogenation, olefin hydroformylation and deuterium exchange, others opened up for remarkable stoichiometric reactions.

A nickel(II) hydroxo complex (3) supported by a cyclohexyl based POCsp3OP pincer ligand (POCsp3OP = cis-1,3-Bis-(di-tert-butylphosphinito)cyclohexyl) is reported. Complex 3 reacts with CO to form the corresponding hydroxycarbonyl complex, (POCsp3OP)NiCOOH (4). Complex 3 is also reactive towards CO2, forming a bicarbonate species (5) that under reduced pressure loses ½ eq. of H2O and CO2 to give a binuclear, bridged carbonate complex (6). All compounds were characterized in the solid state by X-ray diffraction.

The use of color tests for the presumptive identification of illicit substances has been an important tool used by law enforcement to establish probable cause for decades. However, recently color tests have received negative media attention due to their inconsistent and subjective results that can sometimes lead to wrongful arrests. Although they have been fairly effective in testing common drugs, current color tests cannot combat the constant influx of novel psychoactive substances due to their failure to clearly distinguish similarly-structured compounds from one another. Common commercially available color tests can yield false positives for cocaine when testing diphenhydramine, indistinguishable results between cocaine and phencyclidine (PCP), and cannot easily detect benzylpiperazine (BZP). Here, we report the use of copper(I) iodide as a feasible drug-indicating agent for criminalistics and law enforcement use. Photoluminescent organometallic clusters formed with copper(I) iodide (CuI) and cyclic amines have been investigated for around 40 years, but with no known application toward forensic science. This work shows the practical implementation of copper(I) iodide to detect and identify various substances of forensic interest by photoluminescence spectral analysis of the resulting organometallic clusters. This novel method provides an innovative route for the presumptive identification of BZP, cocaine, PCP, fentanyl, opiates, piperazine-based designer drugs, and other heterocyclic alkaloids.

A heterogeneous catalyst system for Suzuki and Heck coupling reactions was developed using polyoxometalates as supports for palladium. The catalyst system was synthesized in a one step process using sodium phosphotungstate and palladium acetate. We used the supported catalyst in organic media without the need for special ligands. Substantial activity was observed after several recycles. The catalyst showed high product selectivity with yields up to > 95 % in both Suzuki and Heck reactions.

A series of complexes with oxathiacrown ethers appended to a [Ru(bpy)2]2+ moiety have been synthesized and characterised using 1H NMR, 13C NMR, IR, electronic absorption and emission spectroscopies, mass spectrometry and elemental analyses. The complexes exhibit strong MLCT luminescence bands in the range 608–611 nm and one reversible metal centred oxidation potential in the range 1.00–1.02 V. Their selectivity and sensitivity towards Hg2+, Cd2+ and Pb2+ metal ions have been investigated using electronic absorption, luminescence, cyclic and differential pulse voltammetry titrations. Their responses towards selected cations and anions have also been investigated using electronic absorption and luminescence. While the complexes are selective towards Hg2+ and Cd2+ ions, none of them is selective towards Pb2+ ions. In particular, complex 2 gives a selective change in the UV/Vis absorbance with Hg2+ making it possible to detect mercury down to a detection limit of 68 ppm. The binding constants and limits of detection of the complexes have been calculated, with values ranging from 4.37 to 5.38 and 1.4 × 10−3 to 6.8 × 10−5 for log Ks and LOD respectively.

We simulate a simple nanocomposite consisting of a single spherical nanoparticle surrounded by coarse-grained polymer chains. The polymers are composed of two different monomer types that differ only in their interaction strengths with the nanoparticle. We examine the effect of adjusting copolymer sequence on the structure as well as the end-to-end vector autocorrelation, bond vector autocorrelation, and self-intermediate scattering function relaxation times as a function of distance from the nanoparticle surface. We show how the range and magnitude of the interphase of slowed dynamics surrounding the nanoparticle depend strongly on sequence blockiness. We find that, depending on block length, blocky copolymers can have faster or slower dynamics than a random copolymer. Certain blocky copolymer sequences lead to relaxation times near the nanoparticle surface that are slower than those of either homopolymer system. Thus, tuning copolymer sequence could allow for significant control over the nanocomposite behavior.

Aqueous coordination of cyanide and verification of the composition of the resulting coordination compound is important to ensure confidence in its coordination. Isothiocyanato compounds 1–7 were synthesized employing different synthetic routes and the complex, [Mo2O2(μ-S)2(SCN)5(CH3CN)]3−, 4, was structurally characterized. Ligand exchange reaction of 4 with cyanide forms 8, a cyano complex. Complex 8 was isolated as an organosoluble salt and fully characterized and confirmed as the major product formed in the aqueous ligand exchange reaction of 4–7 with cyanide. The crystal structure of 8 revealed the unusual [Mo2O2(μ-S)2(CN)5]3− anion where the two molybdenum(V) centers are unsymmetrically coordinated. A second unsymmetric cyano complex [Mo2O3(μ-S)2(CN)2]2− 9, presumed hydrolysis product from an aqueous reaction, was isolated and structurally characterized revealing one square pyramidal Mo center and one tetrahedral Mo center in the binuclear core. Attempts to quantify the first order dissociative ligand substitution rate of thiocyanate in 4 to form 8 using the stopped-flow method gave an estimated minimum rate constant of 70 s−1. This confirms that the exchange reaction is sufficiently fast to be useful in aqueous coordination of cyanide.