MOFs with Open Metal(III) Sites for the Environmental Capture of Polar Volatile Organic Compounds

Metal–Organic Frameworks (MOFs) with open metal sites (OMS) interact strongly with a range of polar gases/vapors. However, under ambient conditions, their selective adsorption is generally impaired due to a high OMS affinity to water. This led previously to the privilege selection of hydrophobic MOFs for the selective capture/detection of volatile organic compounds (VOCs). Herein, we show that this paradigm is challenged by metal(III) polycarboxylates MOFs, bearing a high concentration of OMS, as MIL-100(Fe), enabling the selective capture of polar VOCs even in the presence of water. With experimental and computational tools, including single-component gravimetric and dynamic mixture adsorption measurements, in situ infrared (IR) spectroscopy and Density Functional Theory calculations we reveal that this adsorption mechanism involves a direct coordination of the VOC on the OMS, associated with an interaction energy that exceeds that of water. Hence, MOFs with OMS are demonstrated to be of interest for air purification purposes.     

Symmetrical and Asymmetrical Bisphosphonate Esters. Synthesis, Selective Hydrolysis, and Isomerization

Summary. Two simple and efficient one-pot procedures for the synthesis of a series of α-branched N-heterocycle-substituted methane-1,1-bisphosphonates are outlined. In the first method, the parent halosubstrates were reacted with cyanomethylphosphonate followed by reaction with dialkyl phosphonates to give asymmetrical or symmetrical bisphosphonates (BPs). In the second approach, the same halocompounds were reacted with tetraethyl methyl-1,1-bisphosphonate to give the requisite BPs. Partial and complete hydrolysis of the prepared BPs were also investigated. The products contain functional groups advantageous for further synthetic modification as structural units for coupling with the drug.     

Synthesis and Antimicrobial Evaluation of Newly Synthesized N,S‐Bisphosphonate Derivatives

An easy strategy for the synthesis of tetraethyl‐2‐(3‐mercapto‐4H‐1,2,4‐triazol‐4‐ylamino)‐2‐(aryl)ethane‐1,1‐diyldiphosphonate and tetraethyl‐(6‐(aryl)‐5,6‐dihydro[1,2,4]triazolo[3,4‐b]‐[1,3,4]thiadiazol‐6‐yl)methylenediphosphonate derivatives with reasonable 67–85% overall yields has been developed. The approach was achieved via applying Wadsworth–Horner–Emmons reagent, tetraethylmethylenebisphosphonate, to 4‐(arylideneamino)‐4H‐1,2,4‐triazole‐3‐thiols under phase‐transfer catalysis conditions. Screening results of antimicrobial potency for 12 out of 17 methylene‐1,1‐bisphosphonate products were reported. Two of the tested thiadiazolomethylenebisphosphonates displayed better spectrum of antimicrobial activity against the pathogens, compared with that of the positive controls.     

Transition metal complexes of 6‐mercaptopurine: Characterization,Theoretical calculation,DNA‐Binding,molecular docking,and anticancer activity

6‐mercaptopurine (6‐MP) is used for treating various cancers and autoimmune disorders. A few examples of transition metal complexes of 6‐MP have been shown to enhance its anticancer activity, but many remain untested. We isolated five highly stable and colored metal complexes of 6‐MP and confirmed their structures by elemental analysis, spectral, and thermal techniques. Infrared (IR) spectra revealed that 6‐MP is a bidentate ligand that interacts through sulfur and pyrimidine nitrogen in a 1:2 (M:L) molar ratio. The magnetic susceptibility and electron paramagnetic resonance (EPR) spectra for the Cu(II) complex revealed an octahedral arrangement around the metal ion with strong covalent bonding. The fully optimized geometries of the metal structures obtained using density function theory (DFT)/B3LYP calculations were used to verify the structural and biological features. DNA titration revealed that the octahedral Cu(II) complex has a critical binding constant value of K_b = 8 × 105. Docking studies using three different cancer protein receptors were used to predict the biological applications of the synthesized drug‐metal complexes. Finally, cytotoxicity assays against a myeloma cancer cell line (MM) and a colon cancer cell line (Caco‐2) revealed favorable anticancer activity for the copper complex, exceeding that of the gold‐standard chemotherapeutic cisplatin.     

Group solution for an unsteady non-Newtonian Hiemenz flow with variable fluid properties and suction/injection

The theoretic transformation group approach is applied to address the problem of unsteady boundary layer flow of a non-Newtonian fluid near a stagnation point with variable viscosity and thermal conductivity. The application of a twoparameter group method reduces the number of independent variables by two, and consequently the governing partial differential equations with the boundary conditions transformed into a system of ordinary differential equations with the appropriate corresponding conditions. Two systems of ordinary differential equations have been solved numerically using a fourth-order Runge–Kutta algorithm with a shooting technique. The effects of various parameters governing the problem are investigated.     

Adsorption study of dimethylaminostyryl benzazoles onto Na-montmorillonite

The adsorption of 2-(4′-dimethylaminostyryl)benzoxazole (DMASBO) and its benzothiazole analogue (DMASBT) onto Na-montmorillonite (Na⁺-MMT) was studied. The adsorption data have been fitted with Freundlich and Dubinin-Radushkevich (D-R) equation to find the characteristic parameters of each model. From D-R isotherm, it was concluded that the adsorption is of chemical nature. The equilibrium adsorption constant, K_c, was determined and has been used to calculate the enthalpy and entropy of the adsorption process. The mechanism of the adsorption has been investigated by fluorescence, IR, X-ray and ESR spectroscopic measurements. These measurements indicate oxidation of the styryl dyes by the Lewis acidic sites of the clay and formation of radical cations at Na⁺-MMT surface without intercalation into the interior.     

Spectral,Thermal and DC Electrical Conductivity of Charge Transfer Complex Formed Between 5,7-Dimethyl-1-oxo-2-phenyl-1H-pyrazolo [1,2-α]pyrazol-4-ium-3-olate and Iodine

Reaction of phenylmalonic acid dihydrazide with 2,4-pentanedione proceeded through a novel rearrangement to give 5,7-dimethyl-1-oxo-2-phenyl-1H-pyrazolo[1,2-α]pyrazol-4-ium-3-olate (DPO). This peculiar structure had a positive charge (cation) localized on the pyrazolium ring and a negative charge localized on the other ring. The intermolecular charge-transfer complexes (CTC) formed between DPO as donor and iodine as an acceptor have been studied spectrophotometrically. Doping was done in two ways: by mixing and chemically using different ratios of I₂. The suggested structures of the solid iodine charge-transfer complexes were investigated by several techniques using electronic spectra, FTIR spectroscopy and thermal analysis (TGA and DTA). DC electrical conductivity variation with temperature in the range 300–500 K after annealing for 24 h at 100°C and after doping with different ratios of I₂ through the two ways of doping is determined for comparison. The activation energies were calculated and the results were interpreted using the band energy model. DC electrical conductivity of the iodine CTC increased with increasing temperature. The iodine CTC are only one or two orders of magnitude higher in DC electrical conductivity than the undoped material, however the energy gap is very small in addition to its thermal stability which suggests the use of these materials in applications like photovoltaic cells.     

Effect of molecular structure on the phase behaviour of some liquid crystalline compounds and their mixtures VIII. Quaternary mixtures of enantiotropes

Transition temperatures of quaternary mixtures prepared from the cyano and nitro derivatives of the two series, 4-hexadecyloxyphenyl 4-substituted benzoates (Ia,b) and 4-substituted phenyl 4-hexadecyloxy benzoates (IIa,b) have been determined by DSC and the transitions identified with polarized light microscopy. The cyano and nitro derivatives, in both series, were used because their molecules are enantiotropic. The method described before for the ternary system was extended to elucidate the eutectic composition of the quaternary system from the knowledge of either the eutectic compositions of the four possible ternary mixtures or of those of the six individual binary systems. A general equation was deduced to calculate the eutectic composition of any multi-component system from values determined for their individual binary systems. T_c values of binary, ternary, or quaternary mixtures were related to the polarizability anisotropy, Deltaalpha_X, of the individual C_Ar-X bonds. The mixture law was successfully applied.     

Modified nodal cubic spline collocation for biharmonic equations

We formulate a modified nodal cubic spline collocation scheme for the solution of the biharmonic Dirichlet problem on the unit square. We prove existence and uniqueness of a solution of the scheme and show how the scheme can be solved on an N × N uniform partition of the square at a cost O(N ² log₂ N + mN ²) using fast Fourier transforms and m iterations of the preconditioned conjugate gradient method. We demonstrate numerically that m proportional to log₂ N guarantees the desired convergence rates. Numerical results indicate the fourth order accuracy of the approximations in the global maximum norm and the fourth order accuracy of the approximations to the first order partial derivatives at the partition nodes.