Synthesis and characterization of a polyoxovanadate cluster representing a new topology

A new type of mixed-valence polyoxoanionic cluster, [V(V)13V(IV)3O42(Cl)]8-, composed of 14 {VO5} square pyramids and 2 {VO4} tetrahedral units, hosting a chloride ion has been synthesized and characterized.     

New series of asymmetrically substituted Bis(1,2-dithiolato)-nickel(III) complexes exhibiting near IR absorption and structural diversity

The synthesis, structural characterization, and properties of a new series of asymmetrically substituted bis(dithiolene) nickel(III) compounds [Bu4N][Ni(Phdt)2] (1) (Phdt = 2-Phenyl-1,2-dithiolate), [Bu4N][Ni(NO2Phdt)2] (2) (NO2Phdt = 2-( p-nitrophenyl)-1,2-dithiolate), [Bu4N][Ni(FPhdt)2] (3) (FPhdt = 2-( p-fluorophenyl)-1,2-dithiolate), [Bu4N][Ni(ClPhdt)2] (4) (ClPhdt = 2-( p-chlorophenyl)-1,2-dithiolate), and [Bu4N][Ni(BrPhdt)2] (5) (BrPhdt = 2-( p-bromophenyl)-1,2-dithiolate) have been described. All complexes 1- 5 exhibit absorptions in the near-infrared region; the shift of these absorption bands can be tuned by the choice of the substituents on the relevant dithiolene moieties. The substituents on the dithiolene moiety are also responsible for their structural diversities. The nature of the substituents on the dithiolene moiety play an important role in tuning the redox potentials along this series. The nitro derivative (compound 2) exhibits several redox couples in its cyclic voltammogram in contrast to the other compounds in this series. The synthesis and characterization of two asymmetrically halogen substituted tetrathiafulvalene (TTF) derivatives 4,4'-bis(4-chlorophenyl)-tetrathiafulvalene ClPhTTF (6) and 4,4'-bis(4-bromophenyl)-tetrathiafulvalene (BrPhTTF) (7) have been described. One of these compounds has been structurally characterized. Iodine treatment of the monoanionic Ni(III) compound [Bu4N][Ni(ClPhdt)2] (4) results in the formation of a neutral Ni(IV) complex [Ni(ClPhdt)2] (8). All monoanionic compounds 1- 5 are Ni(III) complexes, as evidenced by electron spin resonance spectroscopy. Interestingly, strong Cl...Cl interactions are observed in the solid state structures of the chlorinated compounds 6 and 8. Finally, the structural features of compound [Ni(ClPhdt)2] (8) and the TTF derivative ClPhTTF (6) are compared based on their enormous structural similarities, and the neutral compound [Ni(ClPhdt)2] (8) is classed as the "an inorganic counterpart of TTF".     

When Metathesis Reactions Go Wrong: Novel Structural Consequences

The complex [Yb(Ph₂pz)₃(LiOBu)]₂ ( 1 ) (Ph₂pz = 3,5‐diphenylpyrazolate), fortuitously obtained from reaction of Yb metal with a lithium containing sample of [SnMe₃(Ph₂pz)] at elevated temperatures forms a centrosymmetric butoxy‐ and pyrazolate‐bridged open box structure. Each ytterbium atom is eight coordinate with one chelating Ph₂pz ligand, one μ‐η²:η² bridging pyrazolate, one μ‐η²(Yb):η⁴(Li) Ph₂pz group and two bridging butoxide ligands. Each lithium atom is unsymmetrically chelated by an η²‐Ph₂pz group, η⁴(N,C(pz)C₂(Ph)) bonded by another pyazolate group, and bridged through a butoxide oxygen atom to two ytterbium atoms. The type of η⁴‐pyrazolate coordination is unprecedented and is the first observation of interactions to a metal by the Ph rings of the Ph₂pz ligand. The complex [Li(dme)₃][Eu(Ph₂pz)₃(dme)] ( 2 ) obtained from reaction of Eu metal with the same sample of [SnMe₃(Ph₂pz)] in dme at room temperature is a charged separated species with the first anionic pyrazolatolanthanoidate(II) complex in which europium is eight coordinate with three chelating Ph₂pz ligands and a chelating dme.     

Thermal stability of CR/CSM rubber blends filled with nano- and micro-silica particles

The properties of filled polymers depend on the properties of the matrix and the filler, the concentration of the components and their interactions. In this research we investigated the rheological and mechanical properties and thermal stability of polychloroprene/chlorosulfonated polyethylene (CR/CSM) rubber blends filled with nano- and micro-silica particles. The density of the nano-silica filled CR/CSM rubber blends was lower than that of the micro-silica filled samples but the tensile strength and elongation at break were much higher. The nano-silica filled CR/CSM rubber blend has higher V _r0/V _rf values than micro-silica composites and show better polymer–filler interaction according to Kraus equation. The nano-silica filled CR/CSM rubber blends were transparent at all filler concentration, and have higher glass transition values than micro-silica filled compounds. The higher values of the glass transition temperatures for the nano- than the micro-filled cross-linked systems are indicated by DMA analysis. The nano-filled cross-linked systems have a larger number of SiO–C links than micro-filled cross-linked systems and hence increased stability.     

Isolation and structural characterization of 1,5-benzodiazepinium cation in an inorganic–organic hybrid compound [C12H17N2]3[Bi2Cl9]·2EtOH

The compound [C₁₂H₁₇N₂]₃[Bi₂Cl₉]·2EtOH (1) has been synthesized from bismuth trichloride and o-phenylenediamine (opda) in ethanol at an aerial ambient condition. This preparation includes the conversion of opda to 2,3-dihydro-1H-1,5-benzodiazepinium cation through its reaction with acetone that is formed in situ from aerial ethanol oxidation. Compound 1 crystallizes in triclinic system (space group P−1). In the crystal structure of 1, the supramolecular hydrogen bonding interactions between [Bi₂C₉]³⁻ and [C₁₂H₁₇N₂]⁺ play an important role in the stabilization of cationic form of 2,3-dihydro-1H-1,5-benzodiazepine and in obtaining emission signals of the organic moiety, which is otherwise not emissive. Compound [C₁₂H₁₇N₂]₃[Bi₂Cl₉]·2(2-PrOH) (2), that has been isolated from 2-propanol (instead of ethanol), is isostructural with compound 1.     

Influence of the aryl substituent identity in 4-arylamino-3-nitrocoumarins on their thermal behavior

Thermal behavior of structurally similar 4-arylamino-3-nitrocoumarin derivatives substituted with different electron-donor and electron-acceptor substituents on the aryl side group was investigated. The thermal stability of these compounds was studied by non-isothermal thermo-gravimetric analysis, differential thermo-gravimetry, differential thermal analysis, and pyrolysis–gas chromatography–mass spectrometry. The thermal degradation of the three synthesized 4-arylamino-3-nitrocoumarins, possessing an iodine atom, a nitro or a methyl group, proceeds in three steps. The thermal stability of the coumarin derivative with the electron-donating methyl substituent is lower than that of the compounds with the electron-accepting nitro group or iodine atom. This least stable compound (4-[(4-methylphenyl)amino]-3-nitro-2H-chromen-2-one) was also characterized with the greatest loss in mass that accompanied the degradation, and all of the three degradation steps of this compound began at the lowest temperature in comparison to the other two.     

Thermal behavior of modified urea–formaldehyde resins

The thermal stability of pure urea–formaldehyde resin (PR) and modified urea–formaldehyde (UF) resins with hexamethylenetetramine-HMTA (Resin 1), melamine-M (Resin 2), and ethylene urea (EU, Resin 3) including nano-SiO₂ was investigated by non-isothermal thermo-gravimetric analysis (TG), differential thermal gravimetry (DTG), and differential thermal analysis (DTA) supported by data from IR spectroscopy. Possibility of combining inorganic filler in a form of silicon dioxide with UF resins was found investigated and percentage of free formaldehyde was determined. The shift of DTG peaks to a high temperature indicates the increase of thermal stability of modified UF resin with EU (Resin 3) which is confirmed by data obtained from the FTIR study. The minimum percentage (6%) of free formaldehyde was obtained in Resin 3.     

Rapid CE‐UV binding tests of environmentally hazardous compounds with polymer‐modified magnetic nanoparticles

Hazardous compounds and bacteria in water have an adverse impact on human health and environmental ecology. Polydopamine (or polypyrrole)‐coated magnetic nanoparticles and polymethacrylic acid‐co‐ethylene glycol dimethacrylate submicron particles were investigated for their fast binding kinetics with bisphenol A, proflavine, naphthalene acetic acid, and Escherichia coli. A new method was developed for the rapid determination of % binding by sequential injection of particles first and compounds (or E. coli) next into a fused‐silica capillary for overlap binding during electrophoretic migration. Only nanolitre volumes of compounds and particles were sufficient to complete a rapid binding test. After heterogeneous binding, separation of the compounds from the particles was afforded by capillary electrophoresis. % binding was influenced by applied voltage but not current flow. In‐capillary coating of particles affected the % binding of compounds.     

Design,synthesis, and antimicrobial activity of fluorophore 1,2,3-triazoles linked nicotinonitrile derivatives

The synthesis and investigation of fluorescence and antimicrobial properties of a new series of 1,2,3-triazoles were described. Acetylenes 4a–c were resulted via alkylation of 2-oxonicotinonitriles 3a–c with propargyl bromide in base medium. [2?+?3] cycloaddition of acetylenes 4a–c with ethyl 2-azidoacetate, p-acetylphenylazide, and p-tolylsulfonylazide in the presence of Cu(I) afforded 1,2,3-triazoles 5a–c, 7a–c, and 9, respectively (via click reaction). The triazoles 5a–c were subjected to saponification process to give the acids 6a–c. The fluorescence and antimicrobial properties of triazoles 5a–c, 7a–c, and 9 were investigated and significant results were obtained.     

A Mononuclear CoII Coordination Complex Locked in a Confined Space and Acting as an Electrochemical Water‐Oxidation Catalyst: A “Ship‐in‐a‐Bottle” Approach

Preparing efficient and robust water oxidation catalyst (WOC) with inexpensive materials remains a crucial challenge in artificial photosynthesis and for renewable energy. Existing heterogeneous WOCs are mostly metal oxides/hydroxides immobilized on solid supports. Herein we report a newly synthesized and structurally characterized metal–organic hybrid compound [{Co₃(μ₃‐OH)(BTB)₂(dpe)₂} {Co(H₂O)₄(DMF)₂}_0.5]_n?n H₂O ( Co‐WOC‐1 ) as an effective and stable water‐oxidation electrocatalyst in an alkaline medium. In the crystal structure of Co‐WOC‐1 , a mononuclear Co^II complex {Co(H₂O)₄(DMF)₂}²⁺ is encapsulated in the void space of a 3D framework structure and this translationally rigid complex cation is responsible for a remarkable electrocatalytic WO activity, with a catalytic turnover frequency (TOF) of 0.05 s^?1 at an overpotential of 390 mV (vs. NHE) in 0.1 m KOH along with prolonged stability. This host–guest system can be described as a “ship‐in‐a‐bottle”, and is a new class of heterogeneous WOC.