From a humorous post to a detailed quantum-chemical study: isocyanate synthesis revisited.

Isocyanates play an essential role in modern manufacturing processes, especially in polyurethane production. There are numerous synthesis strategies for isocyanates both under industrial and laboratory conditions, which do not prevent searching for alternative highly efficient synthetic protocols. Here, we report a detailed theoretical investigation of the mechanism of sulfur dioxide-catalyzed rearrangement of phenylnitrile oxide into phenyl isocyanate, which was first reported in 1977.

3-Halo-5,6-dihydro-4-1,2-oxazine -oxides as synthetic equivalents of unsaturated nitrile oxides in the [3 + 2]-cycloaddition with arynes: synthesis of substituted 3-vinyl-1,2-benzisoxazoles.

The reaction of 3-halo-5,6-dihydro-4-1,2-oxazine -oxides with arynes was studied. Arynes were generated from -silylaryl triflates and underwent consecutive [3 + 2]-cycloaddition/[4 + 2]-cycloreversion with -oxides leading to substituted 3-vinyl-benzisoxazoles in high yields. In the presented sequence, 1,2-oxazine -oxides act as surrogates of rarely employed unsaturated nitrile oxides.

Luminescent Ln-based silsesquioxanes with a β-diketonate antenna ligand: toward the design of efficient temperature sensors.

We report the synthesis and single-crystal X-ray diffraction, magnetic, and luminescence measurements of a novel family of luminescent cage-like tetranuclear silsesquioxanes (PhSiO)(LnO)(O)(CHO)(EtOH)(CHCN)⋅2CHCN (where Ln = Tb, ; Tb/Eu, ; and Gd, ), featuring seven-coordinated lanthanide ions arranged in a one-capped trigonal prism geometry. Compounds and exhibit characteristic Tb and Tb/Eu-related emissions, respectively, sensitized by the chelating antenna acetylacetonate (acac) ligands upon excitation in the UV and visible spectral regions. Compound is used to assess the energies of the triplet states of the ligand.

Synthesis of new representatives of AB-type carboranylporphyrins based on -tetra(pentafluorophenyl)porphyrin transformations.

A carboranylporphyrin of AB-type bearing a single pentafluorophenyl ring was prepared through the regioselective nucleophilic aromatic substitution reaction of the -fluorine atoms in 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin with 9-mercapto--carborane. The reaction of this porphyrin with sodium azide led to the selective substitution of the -fluorine atom in the pentafluorophenyl substituent with an azide functionality which upon reduction with SnCl resulted in the formation of the corresponding porphyrin with an amino group. Pentafluorophenyl-substituted AB-porphyrins were studied and transformed to thiol and amino-substituted compounds allowing for the preparation of porphyrins with different reactive groups such as hydroxy and amino derivatives capable for further functionalization and conjugation of these porphyrins to other substrates.

Tungsten Oxide Dispersed on Silica as Robust and Readily Available Oxo/Imido Heterometathesis Catalyst.

Continuing our investigation of catalytic oxo/imido heterometathesis as novel water-free method for C=N bond construction, we report here the application of classical transition metal oxides dispersed on silica (MO/SiO, M=V, Mo, W) as cheap, robust and readily available alternative to the catalysts prepared via Surface Organometallic Chemistry (SOMC). The oxide materials demonstrated activity in heterometathetical imidation of ketones, WO/SiO being the most efficient. We also describe a new well-defined supported W imido complex (≡SiO)W(=NMes)(MePyr) (Mes=2,4,6-MeCH, MePyr=2,5-dimethylpyrrolyl) and characterize it with SOMC protocols, which allowed us to identify the position of W on the oxo/imido heterometathesis activity scale (Mo View Article and Find Full Text PDF

Planar-chiral arene ruthenium complexes: synthesis, separation of enantiomers, and application for catalytic C-H activation.

Heating -butyl-tetraline with [(-cymene)RuCl] produces the racemic complex [(arene)RuCl], which can be separated into enantiomers by chromatography of its diastereomeric adducts with chiral phosphine ligand. The resolved chiral complex catalyzes C-H activation of -methoxy-benzamides and their annulation with -vinyl-pivaloyl amide giving dihydroisoquinolones in 50-80% yields and with 40-80% enantiomeric excess.

A Family of Hexacopper Phenylsilsesquioxane/Acetate Complexes: Synthesis, Solvent-Controlled Cage Structures, and Catalytic Activity.

Convenient self-assembly synthesis of copper(II) complexes via double (phenylsilsesquioxane and acetate) ligation allows to isolate a family of impressive sandwich-like cage compounds. An intriguing feature of these complexes is the difference in the structure of a pair of silsesquioxane ligands despite identical (Cu) nuclearity and number (four) of acetate fragments. Formation of particular combination of silsesquioxane ligands (cyclic/cyclic vs condensed/condensed vs cyclic/condensed) was found to be dependent on the synthesis/crystallization media.

New Hybrid Ethylenediurea (EDU) Derivatives and Their Phytoactivity.

Natural and synthetic phytohormones are widely used in agriculture. The synthetic cytokinin ethylenediurea (EDU) induces protection in plants against ozone phytotoxicity. In our study, new hybrid derivatives of EDU were synthesized and tested for phytoactivity.

Luminescent Er based single molecule magnets with fluorinated alkoxide or aryloxide ligands.

We report the synthesis, structures, and magnetic and luminescence properties of a series of new mono- and dinuclear Er complexes derived from sterically demanding aryloxide and fluorinated alkoxide ligands: [4-Bu-2,6-(PhCH)CHO]Er(THF) (1), [(CF)CO]Er(MeSiOH) (2), [(CF)CO]Er[(MeSi)NH] (3), [(CF)CO]Er(CHCH) (4), [(CF)CO]Er(-MeNCHCH) (5) and {[Ph(CF)CO]Er(μ-OC(CF)Ph)} (6). In compounds 1, 2, and 4, the Er ion is four-coordinated and adopts a distorted trigonal pyramidal geometry, while in 3, 5, and 6, the coordination geometry of Er is impacted by the presence of several relatively short Er⋯F distances, making them rather 6-coordinated. All compounds behave as field-induced Single Molecule Magnets (SMMs) and exhibit an Er characteristic near infrared (NIR) emission associated with the I → I transition with a remarkably long lifetime going up to 73 μs, which makes them multifunctional luminescent SMMs.

Cryostructuring of Polymeric Systems: 67 Properties and Microstructure of Poly(Vinyl Alcohol) Cryogels Formed in the Presence of Phenol or Bis-Phenols Introduced into the Aqueous Polymeric Solutions Prior to Their Freeze-Thaw Processing.

Poly(vinyl alcohol) (PVA) physical cryogels that contained the additives of -, -, and -bis-phenols or phenol were prepared, and their physico-chemical characteristics and macroporous morphology and the solute release dynamics were evaluated. These phenolic additives caused changes in the viscosity of initial PVA solutions before their freeze-thaw processing and facilitated the growth in the rigidity of the resultant cryogels, while their heat endurance decreased. The magnitude of the effects depended on the interposition of phenolic hydroxyls in the molecules of the used additives and was stipulated by their H-bonding with PVA OH-groups.

The Copper Reduction Potential Determines the Reductive Cytotoxicity: Relevance to the Design of Metal-Organic Antitumor Drugs.

Copper-organic compounds have gained momentum as potent antitumor drug candidates largely due to their ability to generate an oxidative burst upon the transition of Cu to Cu triggered by the exogenous-reducing agents. We have reported the differential potencies of a series of Cu(II)-organic complexes that produce reactive oxygen species (ROS) and cell death after incubation with -acetylcysteine (NAC). To get insight into the structural prerequisites for optimization of the organic ligands, we herein investigated the electrochemical properties and the cytotoxicity of Cu(II) complexes with pyridylmethylenethiohydantoins, pyridylbenzothiazole, pyridylbenzimidazole, thiosemicarbazones and porphyrins.

Readily available Ti-based catalytic system for oxo/imido heterometathesis.

We investigate Ti(NEt) supported on silica dehydroxylated at 700 °C as an easily accessible pre-catalyst for oxo/imido heterometathesis reactions. Being activated with TolNH, the supported Ti amide (SiO)Ti(NEt) (1) demonstrates catalytic activity in the imidation of ketones with -sulfinylamines comparable with the most active previously described well-defined imido catalyst (SiO)Ti(NBu)(MePyr)(py) (2) (MePyr = 2,5-dimethylpyrrolyl), which implies the formation of surface imido species in this system. The materials obtained treatment of 1 with anilines (TolNH (1a) and -MeOCHNH (1b)) were studied with IR, EA and H, C, N and 2D solid-state NMR, although the proposed imido intermediate has not been detected, pointing towards tris-amides (SiO)Ti(NHCHX) (X = Me, OMe) being the major surface species in the isolated materials 1a and 1b.

Assessing the effectiveness of fenbendazole supramolecular complexes against schistosomiasis, monieziosis and parabronemosis in sheep.

Helminth infections pose a significant economic threat to livestock production, causing productivity declines and, in severe cases, mortality. Conventional anthelmintics, exemplified by fenbendazole, face challenges related to low solubility and the necessity for high doses. This study explores the potential of supramolecular complexes, created through mechanochemical modifications, to address these limitations.

Activity of zinc oxide and zinc borate nanoparticles against resistant bacteria in an experimental lung cancer model.

Background: Recent research indicates a prevalence of typical lung infections, such as pneumonia, in lung cancer patients. Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii stand out as antibiotic-resistant pathogens. Given this, there is a growing interest in alternative therapeutic avenues.

Magnetic field dependence of the para-ortho conversion rate of molecular hydrogen in SABRE experiments.

The use of parahydrogen - the isomer of molecular hydrogen with zero nuclear spin - is important for promising and actively developing methods for spin hyperpolarization of nuclei called parahydrogen induced polarization (PHIP). However, the dissolved parahydrogen in PHIP experiments quickly loses its spin order, resulting in the formation of orthohydrogen and reduction of the overall nuclear polarization of the substrate. This process is due to the difference of chemical shifts of hydride protons, as well as spin-spin couplings between nuclei, in the intermediate catalytic complexes, and it has not been rigorously explained so far.

Preparation, X-ray Characterization, and Reactivity of the Rod-like and Angular Germanium- and Titanium(IV)-Capped Iron(II) Bis-Clathrochelates and Their Mono- and Bis-Capped (Semi)clathrochelate Precursors.

Transmetalation of the bis{triethylantimony(V)}-capped iron(II) tris-α-dioximate with -butylboronic acid afforded the mixed antimony, boron cross-linked clathrochelate with single reactive antimony(V)-based apical fragment. This macrobicyclic precursor easily underwent the transmetalation reactions with germanium and titanium(IV) alkoxides to give the rod-like and angular FeM-trinuclear bis-clathrochelates. Those of the aforementioned diantimony(V)-capped complex with 3- and 4-carboxyphenylboronic acids afforded the monoboron-capped iron(II) semiclathrochelates, undergoing a double-cyclization (macrobicyclization) with germanium- and titanium(IV)-based capping agents.

Simplified Version of the Eschweiler-Clarke Reaction.

The traditional Eschweiler-Clarke reaction is a three-component process involving formaldehyde, amine, and formic acid. In this work, we showed that the reductive potential of formaldehyde was sufficient to provide methylation of secondary amines in the absence of acidic additives. Various acid-sensitive moieties remain intact under developed conditions.

The permeability of diamond and other microphase-separated morphologies in copolymer films.

A method is proposed for the theoretical assessment of potential membrane properties in materials based on microphase-separated block copolymer films subjected to the etching of one of the components. The concepts of topological permeability and connectivity contrast introduced by the authors are used to compare the percolation characteristics of simple cubic, diamond, and diamond-like morphologies compatible with the slit geometry and specified by a given distribution of the order parameter. The diamond-like morphology, which has the most promising transport characteristics, can be formed in a thin film of diblock copolymer AB placed on a chemically structured substrate.

Impact of the Methylene Bridge Substitution in Chelating NHC-Phosphine Mn(I) Catalyst for Ketone Hydrogenation.

Systematic modification of the chelating NHC-phosphine ligand (NHC = N-heterocyclic carbene) in highly efficient ketone hydrogenation Mn(I) catalyst fac-[(PhPCHNHC)Mn(CO)Br] has been performed and the catalytic activity of the resulting complexes was evaluated using acetophenone as a benchmark substrate. While the variation of phosphine and NHC moieties led to inferior results than for a parent system, the incorporation of a phenyl substituent into the ligand methylene bridge improved catalytic performance by ca. 3 times providing maximal TON values in the range of 15000-20000.

Photoswitchable Photochromic Chelating Spironaphthoxazines: Synthesis, Photophysical Properties, Quantum-Chemical Calculations, and Complexation Ability.

The stable and efficient photochromic and photoswitchable molecular systems designed from spirooxazines are of increasing scientific and practical interest because of their present and future applications in advanced technologies. Among these compounds, chelating spironaphthoxazines have received widespread attention due to their efficient optical response after complexation with some metal ions being of biomedical interest and environmental importance, as well as their good cycle performance and high reliability, especially by metal ion sensing. In this mini-review, we summarize our results in the design of novel photoswitchable chelating spironaphthoxazines with specific substituents in their naphthoxazine or indoline ring systems in view of recent progress in the development of such molecular systems and their applications as metal ion sensors.

Two active species from a single metal halide precursor: a case study of highly productive Mn-catalyzed dehydrogenation of amine-boranes intermolecular bimetallic cooperation.

Metal-metal cooperation for inert bond activation is a ubiquitous concept in coordination chemistry and catalysis. While the great majority of such transformations proceed intramolecular mode in binuclear complexes, to date only a few examples of intermolecular small molecule activation using usually bimetallic frustrated Lewis pairs (M⋯M') have been reported. We introduce herein an alternative approach for the intermolecular bimetallic cooperativity observed in the catalytic dehydrogenation of amine-boranes, in which the concomitant activation of N-H and B-H bonds of the substrate the synergetic action of Lewis acidic (M) and basic hydride (M-H) metal species derived from the same mononuclear complex (M-Br).

Charge-compensated -carborane derivatives in the synthesis of iron(II) bis(dicarbollide) complexes.

A series of stable iron(II) bis(dicarbollide) derivatives [8,8'-(RNHC(Et)HN)-3,3'-Fe(1,2-CBH)] (R = Pr, R = Ph, (CH)OH, (CH)OH, (CH)NMe) was prepared starting from FeCl or [FeCl(dppe)] and the corresponding -carboranyl amidines [10-RNHC(Et)HN-7,8-CBH]. In a similar way, the reactions of the oxonium derivatives of -carborane with FeCl in tetrahydrofuran in the presence of -BuOK lead to the corresponding stable oxonium derivatives iron(II) bis(dicarbollide) [8,8'-(RR'O)-3,3'-Fe(1,2-CBH)] (RR' = (CH), (CH)O(CH), (CH); R = R' = Et), which can be alternatively prepared by the reaction of the parent iron(II) bis(dicarbollide) with tetrahydrofuran or 1,4-dioxane in the presence of MeSO. The cyclic voltammetry studies of the synthesized iron(II) bis(dicarbollide) derivatives revealed that the introduction of amidinium and oxonium substituents leads to a significant increase in the Fe/Fe redox potential relative to the parent iron(II) bis(dicarbollide).

The Domain and Structural Characteristics of Ferroelectric Copolymers Based on Vinylidene Fluoride Copolymer with Tetrafluoroethylene Composition (94/6).

This paper presents data on the macroscopic polarization of copolymer films of vinylidene fluoride with tetrafluoroethylene obtained with a modified apparatus assembled according to the Sawyer-Tower Circuit. The kinetics of the polarization process were analyzed taking into consideration the contributions of both bound and quasi-free (impurity) charges. It was shown that an "abnormal" decrease in conductivity was observed in fields near the coercive fields.

Synthesis and Biological Evaluation of Chalconesulfonamides: En Route to Proapoptotic Agents with Antiestrogenic Potency.

Breast and other estrogen receptor α-positive cancers tend to develop resistance to existing drugs. Chalcone derivatives possess anticancer activity based on their ability to form covalent bonds with targets acting as Michael acceptors. This study aimed to evaluate the anticancer properties of a series of chalcones (-) with a sulfonamide group attached to the vinyl ketone moiety.