Crystal Structures and Solution Studies of Two Novel Zinc(II) Complexes of a Proton Transfer Compound Obtained from 2, 6‐Pyridinedicarboxylic Acid and 1, 10‐Phenanthroline: Observation of Strong Intermolecular Hydrogen Bonds

The proton transfer compound LH₂ , (phenH⁺)₂(pydc^2—), has been prepared from 1, 10‐phenanthroline, phen, and 2, 6‐pyridinedicarboxylic acid, (dipicolinic acid), pydcH₂. Characterization was performed using solution and solid phase CP/MAS ¹³C NMR and IR spectroscopy. The reactions of this adduct with ZnSO₄·7H₂O and Zn(NO₃)₂·4H₂O give the complexes, [Zn(pydc)₂][Zn(phen)₂(H₂O)₂]·7H₂O (1) and [Zn(phen)₃]₄(H(Hpydc)₂)(NO₃)₇·26H₂O (2) , respectively. These complexes were characterized by ¹H and ¹³C NMR spectroscopy and single crystal X‐ray analysis. The complexes crystallize in the triclinic space group P1 with Z = 2. The unit cell dimensions for complex 1 and 2 are: a = 9.9838(9) Å, b = 14.7483(13) Å, c = 14.8365(13) Å and a = 12.640(4) Å, b = 15.855(5) Å, c = 21.830(7) Å, respectively. In complex 1 (pydc^2—) and phen, are tri‐ and bidentate ligands, respectively, and an anionic [Zn(pydc)₂]^2— and cationic [Zn(phen)₂(H₂O)₂]²⁺ complex are formed simultaneously. In complex 2 , three phen participate in complexation leaving hydrogen‐bis(pyridine‐2‐carboxylate), (H(Hpydc)₂)^— as a supramolecular anion. The fragments (H(Hpydc)₂)^—, 7 NO₃^—, and 26 H₂O in complex 2 are joined together by extensive and strong H‐bonding; therefore, the structure is composed of [Zn(phen)₃]₄⁸⁺, and an anionic hydrogen bond supramolecular assembly with the formula, {(H(Hpydc)₂(NO₃)₇)^8— · 26H₂O}_n. The anionic species (H(Hpydc)₂)^— has a special position at the inversion center, as well as one of the NO₃^— anions, which is disordered over the inversion center. Most of the hydrogen bonds in complex 2 represent strong H‐bonding. The protonation constants of the building blocks of the pydc‐phen adduct, the equilibrium constants for the reaction of (pydc^2—) with phenanthroline and the stoichiometry and stability of the Zn^II complex with LH₂ on aqueous solution were determined by potentiometric pH titration. The solution study results support self‐association between (pydc^2—) and (phenH⁺) with a stoichiometry for the Zn(II) complex similar to that observed for the isolated crystalline complex.     

A Novel Proton Transfer Compound Containing 2, 6‐Pyridinedicarboxylic Acid and Creatinine and its Zinc(II) Complex — Synthesis,Characterization, Crystal Structure,and Solution Studies

The 1:1 proton transfer compound LH₂, (creatH)⁺ (pydcH)^?, has been prepared from the reaction of creatinine, creat, and dipicolinic acid, pydcH₂, (2, 6‐ pyridinedicarboxylic acid) and characterized using IR, ¹H and ¹³C NMR spectroscopy. The first coordination complex (creatH)[Zn(pydc)(pydcH)]·4H₂O, was prepared using LH₂ and zinc(II) nitrate, and characterized using IR, ¹H and ¹³C NMR spectroscopy and single crystal X‐ray crystallography. The crystal system is triclinic with space group with two molecules per unit cell. The unit cell dimensions are a = 8.085(2) Å, b = 10.802(4) Å, c = 13.632(4) Å, α = 104.98(2)°, β = 90.31(2)° and γ = 92.55(3)°. The structure has been refined to a final value for the crystallographic R factor of 0.0381 based on 3003 reflections. The zinc atom is six‐coordinated with a distorted octahedral geometry. The (pydc)^2? and (pydcH)^? units are almost perpendicular to each other. Extensive hydrogen bondings between carboxylate groups, (creatH)⁺ and water molecules throughout the zinc(II) complex as well as π–π stacking and ion pairing play important roles in stabilizing the corresponding lattices. The protonation constants of the building blocks of the pydcH₂‐creat adduct, the equilibrium constants for the reaction of (pydc)^2? with creat and the stoichiometry and stability of the Zn^II complex with LH₂ in aqueous solution were accomplished by potentiometric pH titration. The solution studies support a self‐associated (creatH)⁺(pydcH)^? as the most abundant species at pH = 3.4. The stoichiometry of the crystalline complex (i.e. (creatH) [Zn(pydc)(pydcH)])and that of the most abundant species detected in solution were found the same.     

Gold-coated fused-silica sheathless electrospray emitters based on vapor-deposited titanium adhesion layers

Gold-coated fused-silica electrospray (ES) emitters based on vapor-deposited adhesion layers of titanium have been manufactured to investigate the possibilities of producing durable ES emitters applicable in chip-based analytical devices. The stabilities of the emitters were studied by both electrospray and electrochemical experiments and a marked increase in the emitter lifetime, compared to that for Cr/Au coated emitters, was found for the Ti/Au emitters in the ES durability tests. This indicates that Ti (rather than Cr) adhesion layers should be used in association with large-scale fabrication of ES emitters by vapor-deposition techniques. The lifetime of about 500-700 hours also allowed the Ti/Au-coated emitter to be used as an integrated part of a capillary liquid chromatography column coupled to a mass spectrometer in a series of LC/MS experiments. The Ti/Au coating was further studied by electrochemical techniques and scanning electron microscopy in conjunction with X-ray spectroscopy. It is shown that the eventual failure of the Ti/Au emitters in ES experiments was due to an almost complete detachment of the gold layer. Experimental evidence suggests that the detachment of the gold coating was due to a reduced adhesion to the titanium layer during oxidation in positive electrospray. Most likely, this was caused by the formation of an oxide layer on the titanium film. It is thus shown that unlimited emitter stabilities are not automatically obtained even if the metallic adhesion layer is stabilized by an oxide formation under positive electrospray conditions.     

Prediction of CO2 and H2 solubility,diffusion, and permeability in MFI zeolite by molecular dynamics simulation

Structural Chemistry - Molecular dynamics simulation has been employed to calculate the amounts of solubility, diffusion coefficient, and permeability for the pure and volumetric binary mixture of...     

Highly selective and sensitized spectrophotometric determination of iron (III) following potentiometric study

A simple, selective and sensitized spectrophotometric method for determination of trace amounts of Fe3+ ion in tap and waste water solutions has been described. The spectrophotometric determination of Fe3+ ion using Ferron in the presence of N,N-Dodecytrimethylammonium bromide (DTAB) has been carried out. The Beer's law is obeyed over the concentration range of 0.05-2.6 microg mL(-1) of Fe3+ ion with the relative standard deviation (RSD %) <0.2% and the molar absorptivity of complexes in pH 3.5 is 3.8 x 10(3) L mol(-1) cm(-1). Potentiometric pH titration has been used for prediction of protonation constants of ferron, and evaluating its stoichiometry and respective stability constant with Fe3+ ion. As it is obvious the most likely species of ferron alone and its complexes are LH (log = 7.64), LH2 (logK = 10.52), LH3 (logK = 11.74) and ML2 (logbeta = 23.68), ML3 (logbeta = 23.68), ML3H (logbeta = 23.68), ML3H2 (logbta = 23.68) and ML(OH)2 (logbeta = 23.68) respectively.     

Microspectrophotometric determination of erythrosine in beverage and water samples after ultrasonic assisted supramolecular-based dispersion solidification liquid–liquid microextraction

An ultrasonic assisted supramolecular solvent based dispersion solidification liquid–liquid microexraction method was used for the separation and preconcenteration of erythrosine prior to its determination by microspectrophotometry. Under the optimal conditions, the enrichment and preconcentration factors obtained 142 and 33.33 respectively. The calibration curve was linear in the range of 1.0–100 ng/mL of erythrosine with R ² = 0.9949. Detection limit was 0.6 ng/mL and the RSD for 7 replicate determination of 40.0 ng/mL erythrosine was ±1.4%. The applicability of the methods was examined by determining erythrosine in water and beverage samples.     

Water Mediated Domino Knoevenagel‐Michael‐cyclocondensation Reaction of Malononitrile,Various Aldehydes and Barbituric Acid Derivatives Using Boric Acid Aqueous Solution System Compared with Nano‐titania Sulfuric Acid

Nano‐titania sulfuric acid (TSA) and boric acid [B(OH)₃] were efficiently utilized for domino Knoevenagel‐Michael‐cyclocondensation reaction of malononitrile, various aldehydes and barbituric acid derivatives to synthesis of pyrano[2,3‐d]pyrimidine diones. It is interesting that in boric acid aqueous solution system, H⁺ which abstracted from water by the interaction with B(OH)₃, efficiently catalyzed the reaction.     

Basic Propositional Calculus II. Interpolation

Let ℒ and ? be propositional languages over Basic Propositional Calculus, and ℳ = ℒ∩?. Weprove two different but interrelated interpolation theorems. First, suppose that Π is a sequent theory over ℒ, and Σ∪ {C⇒C′} is a set of sequents over ?, such that Π,Σ⊢C⇒C′. Then there is a sequent theory Φ over ℳ such that Π⊢Φ and Φ, Σ⊢C⇒C′. Second, let A be a formula over ℒ, and C ₁, C ₂ be formulas over ?, such that A∧C ₁⊢C ₂. Then there exists a formula B over ℳ such that A⊢B and B∧C ₁⊢C ₂. Received: 7 January 1998 / Published online: 18 May 2001     

Pressure-Gradient Turbulent Boundary Layers Developing Around a Wing Section

A direct numerical simulation database of the flow around a NACA4412 wing section at R e _c = 400,000 and 5^° angle of attack (Hosseini et al. Int. J. Heat Fluid Flow 61, 117–128, 2016), obtained with the spectral-element code Nek5000, is analyzed. The Clauser pressure-gradient parameter β ranges from ? 0 and 85 on the suction side, and from 0 to ? 0.25 on the pressure side of the wing. The maximum R e _?? and R e _τ values are around 2,800 and 373 on the suction side, respectively, whereas on the pressure side these values are 818 and 346. Comparisons between the suction side with zero-pressure-gradient turbulent boundary layer data show larger values of the shape factor and a lower skin friction, both connected with the fact that the adverse pressure gradient present on the suction side of the wing increases the wall-normal convection. The adverse-pressure-gradient boundary layer also exhibits a more prominent wake region, the development of an outer peak in the Reynolds-stress tensor components, and increased production and dissipation across the boundary layer. All these effects are connected with the fact that the large-scale motions of the flow become relatively more intense due to the adverse pressure gradient, as apparent from spanwise premultiplied power-spectral density maps. The emergence of an outer spectral peak is observed at β values of around 4 for λ _z ? 0.65δ ₉₉, closer to the wall than the spectral outer peak observed in zero-pressure-gradient turbulent boundary layers at higher R e _?? . The effect of the slight favorable pressure gradient present on the pressure side of the wing is opposite the one of the adverse pressure gradient, leading to less energetic outer-layer structures.     

Bifurcation and nonlinear dynamic analysis of a rigid rotor supported by two-lobe noncircular gas-lubricated journal bearing system

This paper presents the study of the dynamic analysis of a rigid rotor supported by a two-lobe non-circular gas-lubricated journal bearing. A finite element method has been employed to solve the Reynolds equation in static and dynamical states and the dynamical equations have been solved using Runge–Kutta method. To analyze the behavior of the rotor center in horizontal and vertical directions under the different operating conditions, the dynamic trajectory, the power spectra, the Poincare maps, and the bifurcation diagrams are used. Results of this study indicates that by considering bearing number and rotor mass as the parameters of the system, complex dynamic behavior comprising periodic, KT-periodic, and quasi-periodic responses of the rotor center has occurred.