One Pot Synthesis of Some New Spiro[3H-Indol-3,5′(4′H)-[1,2,4] Oxadiazol]-2-Ones and Bis[Spiro[3H-Indol-3,5′(4′H)-[1,2,4] Oxadiazol]-2-Ones]

A facile preparation of the title compound by 1,3-dipolar cycloaddition reaction of benzonitrile oxides with isatin imines or isatin diimines, in excellent yield, are reported.     

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.     

Indigo Carmine as New Label in PNA Biosensor for Detection of Short Sequence of p53 Tumor Suppressor Gene

A new electrochemical PNA hybridization biosensor for detection of a 15‐mer sequence unique to p53 using indigo carmine (IC) as an electrochemical detector is described in this work. This genosensor is based on the hybridization of target oligonucleotide with its complementary probe immobilized on the gold electrode by self‐assembled monolayer formation. Because this label is electroactive in acidic medium, the interaction between IC and short sequence of p53 is studied by differential pulse voltammety (DPV) in 0.1 M H₂SO₄. The results of electrochemical impedance spectroscopy and cyclic voltammetry in the solution of [Fe(CN)₆]^3?/4? shows no breakage in PNA‐DNA duplex. A decrease in the voltammetric peak currents of IC is observed upon hybridization of the probe with the target DNA. The influence of probe concentration on effective discrimination against non‐complementary oligonucleotides is investigated and a concentration of 10^?7 M is selected. The diagnostic performance of the PNA sensor is described and the detection limit is found to be 4.31×10^?12 M.     

A New Solvated Phosphoric Triamide, [(C6H4(3-CH3)NH)3P(O)] · (C2H5OH): A Database Analysis of N Atom Geometry in Compounds with an [N]3P(O) Fragment

Abstract

In the crystal structure of the title compound C₂₁H₂₄N₃OP · C₂H₅OH, there are three crystallographically independent phosphoric triamide molecules and three ethanol molecules. The environments of the nitrogen atoms are practically planar. The phosphorus atoms display a distorted tetrahedral environment; the maximum and minimum values of angles are observed for one O?P?N and one N?P?N angles, respectively. In this structure, the phosphoramide and ethanol molecules are linked by some different intermolecular O?H···O and N?H···O hydrogen bonds to form chains. The title solvated compound has been further characterized by IR and ³¹P{¹H}, ¹H and ¹³C NMR spectroscopy. The geometry of the nitrogen atoms in this compound is analyzed and compared with those of analogous structures deposited in the Cambridge Structural Database (CSD; Allen, Acta Cryst. 2002, B58, 380-388).     

Conformational flexibility in amidophosphoesters: a CSD analysis completed with two new crystal structures of (C6H5O)2P(O)X [X = NHC7H13 and N(CH2C6H5)2]

The crystal structures of diphenyl (cycloheptylamido)phosphate, C₁₉H₂₄NO₃P or (C₆H₅O)₂P(O)(NHC₇H₁₃), ( I ), and diphenyl (dibenzylamido)phosphate, C₂₆H₂₄NO₃P or (C₆H₅O)₂P(O)[N(CH₂C₆H₅)₂], ( II ), are reported. The NHC₇H₁₃ group in ( I ) provides two significant hydrogen‐donor sites in N—H…O and C—H…O hydrogen bonds, needed for a one‐dimensional hydrogen‐bond pattern along [100] in the crystal, while ( II ), with a (C₆H₅CH₂)₂N moiety, lacks these hydrogen bonds, but its three‐dimensional supramolecular structure is mediated by C—H…π interactions. The conformational behaviour of the phenyl rings in ( I ), ( II ) and analogous structures from the Cambridge Structural Database (CSD) were studied in terms of flexibility, volume of the other group attached to phosphorus and packing forces. From this study, synclinal (±sc), anticlinal (±ac) and antiperiplanar (±ap) conformations were found to occur. In the structure of ( II ), there is an intramolecular C_ortho—H…O interaction that imposes a +sc conformation for the phenyl ring involved. For the structures from the CSD, the +sc and ±ap conformations appear to be mainly imposed by similar C_ortho—H…O intramolecular interactions. The large contribution of the C…H/H…C contacts (32.3%) in the two‐dimensional fingerprint plots of ( II ) is a result of the C—H…π interactions. The differential scanning calorimetry (DSC) analyses exhibit peak temperatures (T_m) at 109 and 81 °C for ( I ) and ( II ), respectively, which agree with the strengths of the intermolecular contacts and the melting points.     

Solubility and thermodynamic properties of acetaminophen in 1-hexyl-4-methylpyridinium bromide and water mixtures

The solubility data of acetaminophen in binary mixtures of 1-hexyl-4-methylpyridinium bromide and water were obtained over the temperature range from 293.15 to 313.15 K by using the gravimetric method under atmospheric pressure. Using the experimentally measured solubility values, the thermodynamic properties of dissolution, mixing and transfer processes were evaluated. The measured solubilities were correlated by the modified Wilson and the electrolyte non-random two liquid (E-NRTL) models.     

Kinetics study of selective removal of lead(II) in an aqueous solution containing lead(II), copper(II) and cadmium(II) across bulk liquid membrane

Transport of Pb(II) ion from equimolar aqueous solutions of Pb(II), Cu(II) and Cd(II) as well as from aqueous solutions containing only Pb(II) source phase (C_metal = 1.0 × 10^?4 mol L^?1) through bulk liquid membranes containing crown ether and oleic acid as carrier has been investigated. The initial fluxes of transported metal ions depend on the hydrophile–lipophile balance (HLB) and molar volumes (Vx) of crown ethers. The initial fluxes of Pb(II), Cu(II), and Cd(II) decrease with increase of HLB value for azacrown ether, i.e., tetraaza-14-crown-4 (A₄14C4), L1 > benzo-15-crown-5 (B15C5), L2 > 4′-Aminobenzo-15C5, L3 > nitrobenzo-15-crown-5 (NB15C5), L4. The selectivity of the metal ions showed the following separation factors (SF): SF_Pb–Cu = 2.15, SF_Cu–Cd = 2.10, SF_Pb–Cd = 4.52. The highest transport recovery for Pb(II) was observed for L1 (99.3 %).     

A novel amido–pyrophosphate MnII chelate complex with the synthetic ligand O{P(O)[NHC(CH3)3]2}2 (L): [Mn(L)2{OC(H)N(CH3)2}2]Cl2·2H2O

The title complex, trans‐bis(dimethylformamide‐κO)bis{N,N′‐N′′,N′′′‐tetra‐tert‐butyl[oxybis(phosphonic diamide‐κO)]}manganese(II) dichloride dihydrate, [Mn(C₁₆H₄₀N₄O₃P₂)₂(C₃H₇NO)₂]Cl₂·2H₂O, is the first example of a bis‐chelate amido–pyrophosphate (pyrophosphoramide) complex containing an O[P(O)(NH)₂]₂ fragment. Its asymmetric unit contains half of the complex dication, one chloride anion and one water molecule. The Mn^II atom, located on an inversion centre, is octahedrally coordinated, with a slight elongation towards the monodentate dimethylformamide ligand. Structural features of the title complex, such as the P=O bond lengths and the planarity of the chelate ring, are compared with those of previously reported complexes with six‐membered chelates involving the fragments C(O)NHP(O), (X)NP(O) [X = C(O), C(S), S(O)₂ and P(O)] and O[P(O)(N)₂]₂. This analysis shows that the six‐membered chelate rings are less puckered in pyrophosphoramide complexes containing a P(O)OP(O) skeleton, such as the title compound. The extended structure of the title complex involves a linear aggregate mediated by N—H...O and N—H...Cl hydrogen bonds, in which the chloride anion is an acceptor in two additional O—H...Cl hydrogen bonds.     

Thermodynamic Study of Poly(vinyl pyrrolidone) in Water/Dimethyl Sulfoxide Solutions by Viscometry

In this work, the intrinsic viscosities of poly(vinyl pyrrolidone) with a molar mass of 58?kg?mol^?1 were measured in water?Cdimethyl sulfoxide solutions at temperatures from (298.15 to 318.15)?K. The expansion factors of the polymer chains were calculated from the intrinsic viscosity data. The thermodynamic parameters (entropy of dilution parameter, the heat of dilution parameter, theta temperature, polymer?Csolvent interaction parameter and second osmotic virial coefficient) were derived by the temperature dependence of the polymer chain expansion factor. The thermodynamic parameters indicate that mixtures of water/dimethyl sulfoxide become poorer solvents for poly(vinyl pyrrolidone) as the temperature is increased. Also, the thermodynamic parameters indicate that water/dimethyl sulfoxide mixtures become better solvents for poly(vinyl pyrrolidone) by increasing the volume fractions of dimethyl sulfoxide.     

Dynamic analysis of a novel wide-tunable microbeam resonator with a sliding free-of-charge electrode

In this paper, a MEMS-based resonator with a novel effective stiffness tunability is presented. The performance of the proposed resonator is based on the transversal vibration of the two porous cantilever microbeams with a rectangular microplate at the end of the structure. The microplate as a free-of-charge slider electrode is in contact with two other fixed substrate electrodes via the thin layer of dielectric material. Applying a constant DC voltage to the two fixed electrodes leads to the movement of free electrons in the slider and eventually to the formation of two series capacitors. As a result, the slider meets a nonlinear electrostatic force proportional to the square of the applied DC voltage. It will act as a nonlinear spring with a tunable stiffness during the oscillation of the resonator. The coupled nonlinear equations governing the longitudinal and transversal vibration of the resonator are extracted in the presence of the nonlinear voltage-sliding spring. Its steady-state solution is obtained based on a physically based learning method that makes it possible to obtain frequency response for the first harmony as well as for the higher harmonies and to predict primary and secondary resonances in different harmonies of the response. The effect of the applied tuning DC voltage, the geometrical parameters of the resonator, and the cantilever's porosity on the dynamic response of the resonator are investigated. It is shown that the tuning stiffness of this voltage-sliding spring provides a highly effective solution to realize an extreme tunable range. In the end, a modified tunable structure is introduced in which the folded beams are replaced with common ones. The modified resonator by making the nonlinear behavior of the resonator least can improve its performance significantly.