Design of pincer complexes based on (methylsulfanyl)acetic/propionic acid amides with ancillary S‐ and N‐donors as potential catalysts and cytotoxic agents

Pincer complexes featuring readily tunable tridentate ligand frameworks comprise one of the most actively studied classes of organometallic and metal–organic compounds and find extensive use in catalysis, organic synthesis, materials science, and other fields of chemistry and allied disciplines. Currently growing attention is devoted to non‐classical ligand scaffolds, such as functionalized carboxamides, which offer multiple options for directed structural modifications. In this study, the reactions of (methylsulfanyl)acetyl and propanoyl chlorides with 2‐(aminomethyl)pyridine, 2‐(2‐aminoethyl)pyridine, 8‐aminoquinoline and 2‐(diphenylthiophosphoryl)aniline afford a series of new pincer‐type ligands based on functionalized carboxamides. The ligands obtained readily undergo direct cyclopalladation under the action of PdCl₂(NCPh)₂ in dichloromethane at room temperature, resulting in Pd(II) pincer complexes with N,N,S‐ and S,N,S‐donor sets. Importantly, some of the cyclopalladated derivatives can also be produced efficiently under solvent‐free conditions according to the approach recently developed by our group. The complexes obtained have been tested for cytotoxicity against several human cancer cell lines and catalytic activity in the model Suzuki reaction. The results have been compared to those for the related Pd(II) pincer complexes to define the main structure–activity relationships and to outline the most promising structures for further investigations.     

Physicochemical and adsorption properties of hypercross‐linked polystyrene with ultimate cross‐linking density

The paper describes unexpected properties of hypercross‐linked polystyrenes with ultimate cross‐linking degrees of 300, 400, and 500%, where three, four, or five methylene links, respectively, could bind each polystyrene phenyl ring to its spacious neighbors. The polymers exhibit a strong electron spin resonance signal, unusual spectra in IR, UV, and visible ranges, and they are not typical dielectrics. The nonfunctionalized hypercross‐linked polymers absorb significant amounts of inorganic acids, salts, and bases due to interactions of protons or other cations with electron‐donating fragments of the aromatic network with the high extent of mutual connectivity and also due to dispersion interactions of anions with the polymer matrix.     

Synthesis and Complexing Properties of Phosphorus-Substituted Pyridine-2-Carboxylic Acid Anilides

Abstract

Novel phosphorus-containing ligands have been synthesized by the condensation of 2-(thio)phosphorylated anilines with 2,6-dichloro- and 4-chloropyridine-2-carbonyl chlorides in the presence of Et₃N and unsubstituted pyridine-2-carboxylic acid using P(OPh)₃ as a coupling agent. The compounds derived readily form complexes with a range of transition metals (M=Re(I), Pd(II), and Cu(II)), serving as bi- or tridentate monoanionic ligands. The composition and structure of the resulting metallocycles depend both on the presence/amount of the Cl atoms in the pyridine ring and on the nature of the donor atom X in the P=X moiety. The novel compounds were characterized by multinuclear NMR and IR spectroscopy as well as X-ray crystallography.     

Reactions of 2-phenylpyrrole with bromobenzoylacetylene on metal oxides active surfaces

The solvent-free interaction of 2-phenylpyrrole with bromobenzoylacetylene (room temperature) upon their grinding with solid metal oxides (MgO, CaO, ZnO, BaO, Al₂O₃, TiO₂, ZrO₂) and salts (CaCO₃, ZrSiO₄) leads to either the cross-coupling product or the adduct of pyrrole addition to the riple bond of acetylene. The ethynylation is accompanied by the formation of intermediate and side products: E-2-(1-bromo-2-benzoylethenyl)-5-phenylpyrrole and 1,1-di(5-phenylpyrrol-2-yl)-2-benzoylethene. The activity of the metal oxides in the ethynylation reaction falls in the order (in the brackets, the content of 2-benzoylethynyl-5-phenylpyrrole in the reaction mixture is given): ZnO (81%), BaO (73%), Al₂O₃ (71%), MgO (69%), CaO (50%). The oxides, SiO₂, TiO₂, ZrO₂, and the salts, CaCO₃ and ZrSiO₄, are inactive in the ethynylation reaction affording only the intermediate adduct, with ZrO₂ the isolated yield of the bromoethenylpyrrole reaching 60%. ESR monitoring shows the reaction to start from one electron transfer from pyrrole to acetylene mediated by the oxide surface. The adduct is readily converted on Al₂O₃ to 2-(benzoylethynyl)-5-phenylpyrrole crystallized mostly as cis-rotamer (X-ray data).     

1H NMR cryoporosimetry of swollen hypercrosslinked polymers

The porous structure of two laboratory samples of hypercrosslinked polystyrene networks with a crosslinking degree of 200%, the commercial hypercrosslinked sorbent MN-270 (Purolite Int.), and macroporous polystyrene sorbents Amberlite XAD-4 and Amberlite XAD-1600 were investigated by means of ¹H NMR cryoporosimetry. It was determined that the signal intensity of benzol, dioxane, dichloroethane and water protons previously frozen in polymer pores increases during solvent melt. Dependencies of the integral proton signal intensities on the sample temperature obtained in various solvents are discussed in terms of sample micropore accessibility and solvent—polystyrene interaction energy. Pore dimensions are estimated using the melting temperature value of ice according to the Gibbs—Thomson equation. We conclude that the obtained distribution curves reveal all hypercrosslinked polymers to be mainly microporous with diameter distribution maxima around 10 Å. It is shown that along with pores 120 Å in diameter, XAD-4 has a considerable amount of micropores. In contrast, XAD-1600 is ranged as a mesoporous sorbent.     

Novel Mechanism of Bioluminescence: Oxidative Decarboxylation of a Moiety Adjacent to the Light Emitter of Fridericia Luciferin

A novel luciferin from a bioluminescent Siberian earthworm Fridericia heliota was recently described. In this study, the Fridericia oxyluciferin was isolated and its structure elucidated. The results provide insight into a novel bioluminescence mechanism in nature. Oxidative decarboxylation of a lysine fragment of the luciferin supplies energy for light generation, while a fluorescent CompX moiety remains intact and serves as the light emitter.     

Dielectric characterization of samples showing the SmCPA/B7 transition

Dielectric measurements on samples consisting of banana-shaped molecules with a polymorphism I/SmCP_A/B₇ have been performed for the first time. The dielectric increment for the reorientation of the molecules about the long axis, and the corresponding relaxation time, surprisingly decrease at the SmCP_A/B₇ transition. This effect is discussed in terms of the undulated structure which partially destroys the ferroelectric short range order. Decreasing temperature gives an even stronger hindrance for this reorientation and could explain controversial results obtained in the B₇ phases of different samples. At lower temperatures a further mesophase was detected. This was additionally observed by calorimetric and atomic force microscopy methods.     

Hypercrosslinked Polycondensation Networks: Copolymers of <Emphasis Type="Italic">p</Emphasis>-Xylylene Dichloride

It was shown that self-condensation of p-xylylene dichloride (p-XDC) and its co-polycondensation with naphthalene, anthracene, benzyl alcohol, and benzhydrol in presence of the Lewis acids in solution leads to the formation of hypercrosslinked polymers characterized by developed porosity and ability to swell in nonpolar and polar media. Swelling and porosity of the polycondensed network do not depend on dilution of the initial monomer mixture or catalyst amount involved in the reaction as opposed to the properties of hypercrosslinked polymer. The similarities and differences of the regularities of formation of structures obtained at intense crosslinking of linear polymers (polystyrene) and polycondensed networks were examined. It was also estimated that copolymers with naphthalene and anthracene demonstrate perfect ability to extract furfural (which is able to participate in strong π–π interactions) even from methanol solution.     

Chemo- and regioselective ethynylation of 4,5,6,7-tetrahydroindoles with ethyl 3-halo-2-propynoates

4,5,6,7-Tetrahydroindoles undergo a rapid, facile (rt, 60 min) ethynylation with ethyl 3-halo-2-propynoates upon grinding with solid K₂CO₃ (without solvent) at C-2 of the tetrahydroindole ring to afford ethyl 3-(4,5,6,7-tetrahydroindol-2-yl)-2-propynoates in 62–90% yield.     

Quartz crystal microbalance immunosensor for the detection of antibodies to double-stranded DNA

We report the development of a novel quartz crystal microbalance immunosensor with the simultaneous measurement of resonance frequency and motional resistance for the detection of antibodies to double-stranded DNA (dsDNA). The immobilization of poly(l-lysine) and subsequent complexation with DNA resulted in formation of a sensitive dsDNA-containing nanofilm on the surface of a gold electrode. Atomic force microscopy has been applied for the characterization of a poly(l-lysine)–DNA film. After the blocking with bovine serum albumin, the immunosensor in flow-injection mode was used to detect the antibodies to dsDNA in purified protein solutions of antibodies to dsDNA and to single-stranded DNA, monoclonal human immunoglobulin G, DNase I and in blood serum of patients with bronchial asthma and systemic lupus erythematosus. Experimental results indicate high sensitivity and selectivity of the immunosensor. In memoriam Prof. Victor G. Vinter