Self-assembly snapshots of a 2 × 2 copper(I) grid

Self-assembled 2 × 2 grids have been characterised as high-fidelity species produced when the correct stoichiometric ratios are met, but rarely are the individual steps leading to and from their formation characterised. Here, we present such a study using equilibrium-restricted factor analysis to model a set of UV–vis spectra starting from a bis-bidentate ligand to the assembly of a 2 × 2 grid complex upon titration with 1 equiv. of [Cu(MeCN)₄](PF₆) and to disassembly upon further titration. Intermediate species [CuL₂]⁺, [Cu₂L₃]²⁺, [Cu₃L₂]³⁺ and [Cu₂L]²⁺ are evidenced along the assembly and disassembly pathways. Complementary ¹H NMR titrations are consistent with the rich set of complexes and equilibria involved. Given the nature of the assembly process, the assembly is entropy driven and likely enthalpy driven as well. The disassembly process is both enthalpy and entropy driven according to the standard free energy values derived from the modelling of the spectrophotometric titration data.     

Cu(ClO4)2 · 6H2O as an Efficient Catalyst for the Synthesis of 3,4-Dihydropyrimidin-2(1H)-ones Under Solvent-Free Conditions

Cu(ClO₄) · 6H₂O efficiently catalyzes the three-component Biginelli reaction of aldehyde, β-dicarbonyl compounds, and urea or thiourea under solvent-free conditions to afford the corresponding 3,4-dihydropyrimidin-2(1H)-ones in excellent yields.      

Densities and Viscosities for Binary and Ternary Mixtures of 2-Methylbutan-2-ol (1) + Trichloroethylene (2) + Acetonitrile (3) at 298.15 K and at Ambient Pressure (81.5 kPa)

Densities (ρ) and viscosities (η) of ternary mixtures of 2-methylbutan-2-ol (1) + trichloroethylene (2) + acetonitrile (3) and the related binary mixtures of {2-methylbutan-2-ol (1) + trichloroethylene (2)}, {2-methylbutan-2-ol (1) + acetonitrile (3)}, and {trichloroethylene (2) + acetonitrile (3)} have been measured over the whole composition range at 298.15 K and at ambient pressure (81.5 kPa). Excess molar volumes $ V_{\text{m}}^{\text{E}} $ , viscosity deviations Δη, and excess Gibbs energies of activation ΔG ^*E were derived from the experimental data. The binary and ternary data of $ V_{\text{m}}^{\text{E}} $ , Δη, and ΔG ^*E for the binary and ternary mixtures were correlated as functions of the mole fraction by using the Redlich–Kister and the Cibulka equations. Kinematic viscosities of the binary mixtures were correlated by means of several semi-empirical equations to determine the fitting parameters and the SDs. The experimental results are analyzed to discuss the nature and strength of intermolecular interactions in these mixtures.     

Thermodynamic Model for ThO<Subscript>2</Subscript>(am) Solubility in Alkaline Silica Solutions

No thermodynamic data for Th complexes with aqueous Si are available. To obtain such data, extensive studies on ThO₂(am) solubility were carried out as functions of: (1) a wide range of aqueous silica concentrations (0.0004 to 0.14 mol⋅L⁻¹) at fixed pH values of about 10, 11, 12, and 13; and (2) and variable pH (ranging from 10 to 13.3) at fixed aqueous Si concentrations of about 0.006 mol⋅L⁻¹ or 0.018 mol⋅L⁻¹. The samples were equilibrated over long periods (ranging up to 487 days), and the data showed that steady-state concentrations were reached in < 29 days. X-ray diffraction, FTIR, and Raman analyses of the equilibrated solid phases showed that the Th solids were amorphous ThO₂(am) containing some adsorbed Si. The solubility of ThO₂(am) at pH values ranging from 10 to 13.3 at fixed 0.018 mol⋅L⁻¹ aqueous Si concentrations decreases rapidly with an increase in pH, and increases dramatically with an increase in Si concentrations beyond about 0.003 mol⋅L⁻¹ at fixed pH values > 10. The data were interpreted using both the Pitzer and SIT models, and required only the inclusion of one mixed-hydroxy-silica complex of Th [Th(OH)₃(H₃SiO₄)₃²⁻]. Both models provided similar complexation constant values for the formation of this species. Density functional theory calculations predict complexes of this stoichiometry, having six-fold coordination of the Th cation, to be structurally stable. Predictions based on the fitted value of log ₁₀ K ⁰=−18.5±0.7 for the ThO₂(am) solubility reaction involving Th(OH)₃(H₃SiO₄)₃²⁻[ThO₂(am)+3H₄SiO₄+H₂O↔Th(OH)₃(H₃SiO₄)₃²⁻+2H⁺], along with the thermodynamic data for aqueous Si species reported in the literature, agreed closely with the extensive experimental data and showed that under alkaline conditions aqueous Si makes very strong complexes with Th.     

Interaction between Glyoxal-bis-(2-hydroxyanil) and Bovine Serum Albumin in Solution

The interaction between glyoxal-bis-(2-hydroxyanil) (GBH) and bovine serum albumin (BSA) was studied by spectroscopic methods including fluorescence spectroscopy, circular dichroism (CD) and UV–visible absorption spectra. The mechanism for quenching the fluorescence of BSA by GBH is discussed. The number of binding sites n and observed binding constant K _b were measured by the fluorescence quenching method. The thermodynamic parameters ΔH ^θ , ΔG ^θ , and ΔS ^θ were calculated at different temperatures and the results indicate that hydrogen bonding and van der Waals forces played major roles in the reaction. The distance r between the donor (BSA) and acceptor (GBH) molecules was obtained according to Förster’s theory of non-radiation energy transfer. Synchronous fluorescence and three-dimensional fluorescence spectra were used to investigate the structural change of BSA molecules that occur upon addition of GBH, and these results indicate that the secondary structure of BSA molecules is changed by the presence of GBH.     

KAl(SO4)2 · 12H2O as a Recyclable Lewis Acid Catalyst for Synthesis of Spirooxindoles in Aqueous Media

A simple and efficient procedure for the synthesis of spirooxindole has been described that employs a three-component condensation reaction in one pot using isatin, active methylene reagent, and 1,3-dicarbonyl compounds in an aqueous medium.     

KAl(SO4)2 · 12H2O as a Recyclable Lewis Acid Catalyst for Synthesis of Some Amidoalkyl Naphthols Under Solvent-Free Conditions

A general and practical one-pot synthesis of amidoalkyl naphthols derivatives using KAl(SO₄)₂ · 12H₂O as catalyst is described. This method provides several advantages such as short reaction times, good yields, and simple workup procedure.     

Cellulose-Supported Ni(NO3)2 · 6H2O/2,4,6-Trichloro-1,3,5-triazine (TCT) as a Mild,Selective, and Biodegradable System for Nitration of Phenols

Nitration of certain phenols and naphthols in the presence of biodegradable cellulose-supported Ni(NO₃)₂ · 6H₂O/2,4,6-trichloro-1,3,5-triazine was carried out in acetonitrile at room temperature. Ortho nitrated phenols were obtained regioselectively within a short reaction time with good yields. The reaction condition was mild, and the employed cellulose could be recovered several times for further use.      

MgCl(2)·4((CH(3))(2)CHCH(2)OH): A new molecular adduct for the preparation of TiCl(x)/MgCl(2) catalyst for olefin polymerization

A new molecular adduct of MgCl(2) with isobutanol, namely MgCl(2)·4((CH(3))(2)CHCH(2)OH) (MgiBOH), has been prepared as a precursor to the supporting material for an olefin polymerization catalyst. The MgiBOH adduct and final titanated Ziegler-Natta catalysts have been thoroughly characterized by powder XRD, thermal analysis, Raman spectroscopy and solid-state NMR for structural and spectroscopy aspects. A peak observed at 712 cm(-1) in the Raman spectra of MgiBOH indicates the characteristic Mg-O(6) breathing mode and the formation of the adduct. The diffraction feature at 2θ = 7.8° (d = 11.223 ?) in the XRD confirms the adduct formation and the layered structure. The aim of the present article is to study how the insertion of a bulky isobutanol moiety affects the structural and electronic properties of the MgCl(2)·isobutanol molecular adduct. Indeed, the focus of the present study is to explore how the presence of isobutanol, in the initial molecular adduct, influences the final Z-N catalyst properties and its activity.     

Amine functionalised metal organic frameworks (MOFs) as adsorbents for carbon dioxide

Three different porous metal organic framework (MOF) materials have been prepared with and without uncoordinated amine functionalities inside the pores. The materials have been characterized and tested as adsorbents for carbon dioxide. At 298 K the materials adsorb significant amount of carbon dioxide, the amine functionalised adsorbents having the highest CO₂ adsorption capacities, the best adsorbing around 14 wt% CO₂ at 1.0 atm CO₂ pressure. At 25 atm CO₂ pressure, up to 60 wt% CO₂ can be adsorbed. At high pressures the CO₂ uptake is mostly dependent on the available surface area and pore volume of the material in question. For one of the iso-structural MOF pairs the introduction of amine functionality increases the differential adsorption enthalpy (from isosteric method) from 30 to around 50 kJ/mole at low CO₂ pressures, while the adsorption enthalpies reach the same level at increase pressures. The high pressure experimental results indicate that MOF based solid adsorbents can have a potential for use in pressure swing adsorption of carbon dioxide at elevated pressures.     

Simple Protocol for the Synthesis of 3,4‐Dihydropyrimidin‐2(1H)‐ones Using SnCl2 · 2H2O–LiCl as an Inexpensive Catalyst System

Abstract

A one‐pot synthesis of the 3,4‐dihydropyrimidin‐2(1H)‐ones catalyzed by tin chloride–lithium chloride combination catalyst system involving three component heteroannular cyclization is reported.     

ZrOCl2 · 8H2O as an Efficient Reagent for the Solvent‐Free Synthesis of 3,4‐Dihydropyrimidin‐2‐(1H)‐ones

ZrOCl₂ · 8H₂O, a commercially available reagent, can be used for the promotion of the synthesis of 3,4‐dihydropyrimidin‐2(1H)‐ones under solvent‐free reaction conditions. All reactions were performed at 90°C in good to high yields.     

Hetero-heptanuclear (Fe–Na) complexes of salicylaldehydes: crystal and molecular structure of [Fe2(3-OCH3-salo)8 · Νa5] · 3OH · 8H2Ο

The reaction of Fe(III) with the substituted salicylaldehydes [X-saloH, where X = 3-OCH₃ (L ¹ ), 5-CH₃ (L ² ), 5-Cl (L ³ ), 5-NO₂ (L ⁴ )] led to the formation of four new iron(III) hetero-heptanuclear complexes (Fe–Na) under the general formula [Fe₂(X-salo)₈Νa₅] · 3OH · zH₂Ο. The two different coordination modes of the ligand, as well as the geometry around the metal ions were deduced by X-ray structure analysis of compound 1, [Fe₂(3-OCH₃-salo)₈Νa₅] · 3OH · 8H₂Ο. The complexes have also been characterized by physicochemical and spectroscopic (IR, UV–Vis, Mössbauer) methods.     

A capillary column packed with a zirconium(IV)-based organic framework for enrichment of endogenous phosphopeptides

A zirconium(IV)-based metal organic framework (Zr-MOF) was deposited on polydopamine-coated silica microspheres to form microspheres of type SiO₂@PDA@Zr-MOF. These were packed into capillary columns for enrichment of phosphopeptides. The column was off-line coupled to both matrix-assisted laser desorption/ionization time of flight mass spectrometry and LC-ESI-MS/MS. The method has a detection limit as low as 4 fmol of β-casein digest and a selectivity as high as 1:1000 (molar ratio of β-casein and BSA digest). It was applied to the analysis of human saliva. In total, 240 endogenous phosphopeptides were identified in only 25 μL human saliva.

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Graphical abstract A zirconium-based metal organic framework (Zr-MOF) was modified outside of polydopamine-coated silica microspheres to form microspheres named SiO₂@PDA@Zr-MOF. Then they were packed in capillary columns for selective enrichment of phosphopeptides via interaction between Zr-O clusters and phosphate groups. The pre-concentration resulted in a better detection of phosphopeptides by mass spectrometry. Tris: Tris(hydroxymethyl)aminomethane; DMF: Dimethyl Formamide; Zr-MOF: Zirconium(IV)-organic framework; MOAC: Metal oxide affinity chromatography.

     

Facile and Efficient Michael Addition of Indole to Nitroolefins Catalyzed by Zn(OAc)2 · 2H2O

The Zn(OAc)₂2H₂O-catalyed Michael addition reaction of indole to electron-deficient nitroolefins to afford the corresponding adducts in good to excellent yields with high selectivity is reported.     

Synthesis, Solution Equilibria and Antibacterial Activity of Co(II) with 2-(Aminomethyl)-Benzimidazole and Dicarboxylic Acids

Formation equilibria of cobalt(II) complexes of 2-(aminomethyl)-benzimidazole (AMBI) and the ternary complexes Co(AMBI)L (L = aliphatic or aromatic dicarboxylic acids) were investigated in aqueous solutions at 25?°C and 0.1 mol?dm^?3 ionic strength. Stoichiometry and stability constants are reported for the complexes formed. The speciation of the complexes was resolved. Values of $\log_{10}\ (K_{\mathrm{Co(AMBI)L}}^{\mathrm{Co(AMBI)}})$ and Δlog?₁₀ K are calculated and discussed. The effect of chelate ring size of the dicarboxylic acid complexes on their stability constants was examined. The effect of temperature on the dissociation constant of AMBI, CBDCA, and the formation constant of Co(AMBI) and Co(AMBI)-CBDCA complexes was studied and the thermodynamic parameters were calculated. Formation of the metal complexes has been found to be spontaneous, exothermic and entropically favorable. The solid complexes of [Co(AMBI)L] (L = oxalic acid, 1,1-cyclobutanedicarboxylic acid (CBDCAH₂) and malonic acid) have been synthesized and characterized by elemental analysis, infrared, spectra, magnetic and conductance measurements. Electronic spectra and μ _eff values suggest a tetrahedral geometry for Co(II)-complexes. The isolated metal chelates have been screened for their antibacterial activities and the complexes show a significant antibacterial activity against Pseudomonas fluorescence (Gram ?ve) and Bacillus subtilis (Gram +ve). The activity increases at higher concentration of the compounds.     

Potassium Dodecatungstocobaltate Trihydrate (K5CoW12O40 · 3H2O) as an Efficient Catalyst for Aminolysis of Epoxides

Abstract

Aminolysis of epoxides using various amines was catalyzed with potassium dodecatungstocobaltate trihydrate in a convenient and efficient method with good selectivities.     

Thermodynamic Model for ThO<Subscript>2</Subscript>(am) Solubility in Isosaccharinate Solutions

Extensive studies on ThO₂(am) solubility were carried out as functions of a wide range of isosaccharinate concentrations (0.0002 to 0.2 mol⋅kg⁻¹) at fixed pH values of about 6 and 12, and varying pH (ranging from 4.5 to 12) at fixed aqueous isosaccharinate concentrations of 0.008 mol⋅kg⁻¹ or 0.08 mol⋅kg⁻¹, to determine the aqueous complexes of isosaccharinate with Th(IV). The samples were equilibrated over periods ranging up to 69 days, and the data showed that, in most cases, steady-state concentrations were reached in <15 days. The data were interpreted using the SIT model, and required the inclusion of mixed hydroxy-ISA complexes of Th(IV) [Th(OH)ISA²⁺, Th(OH)₃(ISA)₂^-_{2}^{-}, and Th(OH)₄(ISA)₂^2-]_{2}^{2-}] with log ₁₀ K ⁰=12.5±0.5,4.4±0.5 and −3.2±0.5 for the reactions: