Highly selective and sensitive spectrophotometric determination of trace amounts of silver ion in surfactant media using 2-mercaptobenzoxazole

A simple and accurate spectrophotometric method for determination of trace amounts of silver ion in tap and wastewater solution and photographic solutions has been described. The spectrophotometric determination of silver ion using 2-mercaptobenzoxazole (MBO) in the presence of Triton X-100 as nonionic surfactant has been carried out. The Beer's law is obeyed over the concentration range of 0.1-9.0 microg mL(-1) of Ag+ ion with the detection limits of 1.6 ng mL(-1). The influence of type and amount of surfactant, pH, complexation time and amount of ligand on sensitivity of method were optimized. Finally the repeatability, accuracy and the effect of interfering ions on the determination of silver ion were evaluated. There is a good agreement between results of proposed method and atomic absorption spectrometry.     

Free of speckle ultrasound images of small tissue structures

By using the Born approximation deconvolved inverse scattering method instead of the traditional pulse-echo method for analyzing ultrasound pulse reflections from plastic phantoms and soft tissue specimens, improvement in image resolution is shown to be possible provided these targets are fair approximations to layered media. These images are free of speckle and are more vivid than the usual pulse-echo images.     

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.     

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.     

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.     

Synthesis and application of a novel nanomagnetic catalyst with Cl[DABCO-NO2]C(NO2)3 tags in the preparation of pyrazolo[3,4-b]pyridines via anomeric based oxidation

Research on Chemical Intermediates - A novel nanomagnetic catalyst with Cl[DABCO-NO2]C(NO2)3 tags was designed, synthesized and fully characterized by several techniques such as Fourier transform...     

Szeged index, edge Szeged index, and semi-star trees

A semi-star tree is a star tree whose some edges may be replaced by paths of length more than one. In this paper we present some increasing and decreasing transformations for Szeged index of the semi-star trees. Then we introduce palm semi-star tree and uniform semi-star tree and show that they are extremal with respect to the Szeged index and edge Szeged index. In addition, we investigate the relation between the Szeged index and edge Szeged index for all trees.     

Synthesis, characterization, solution study and crystal structure of complexes of Cr(III), Co(II), Ni(II) and Cu(II) with chelidamic acid and 2,9-dimethyl-1,10-phenanthroline

The title compounds, (dmpH)[Cr(chelH)₂]·3H₂O, 1, (dmpH)[Co(chelH₂)(chelH)]·3H₂O, 2, (dmpH)[Ni(chelH₂)(chelH)]·2H₂O, 3 and [Cu(chelH)(dmp)]·3H₂O, 4 (dmp is 2,9-dimethyl-1,10-phenanthroline and chelH₃ is chelidamic acid or 4-hydroxypyridine-2,6-dicarboxylic acid) were obtained by one-pot reaction of 2,9-dimethyl-1,10-phenanthroline and 4-hydroxypyridine-2,6-dicarboxylic acid with corresponding salts in aqueous solution. The compounds were identified by IR, MS, elemental analysis and single crystal X-ray crystallography; also they were studied in the solution phase. The compounds 1, 2 and 3 are similar in coordination sphere around the metal ions, with some differences between protonation sites of chelidamate ion and the charge of complex, but compound 4 is essentially different. The compounds 1, 2 and 3 are six coordinated, but 4 is five coordinated. There are various O–H···O, O–H···N and N–H···O hydrogen bonds found in the structures. In a solution study, the protonation constants of dmp and chel, the equilibrium constants of the chel–dmp proton-transfer system and the stoichiometry and stability of complexation of this system with Cr(III), Co(II), Ni(II) and Cu(II) ions in an aqueous solution were investigated by potentiometric pH titration method. The stoichiometry of the most complexes species in solution was found to be very similar to the crystalline cited metal ion complexes.     

Development of efficient method for preconcentration and determination of copper, nickel, zinc and iron ions in environmental samples by combination of cloud point extraction and flame atomic absorption spectrometry

A cloud point extraction procedure for the preconcentration of copper, nickel, iron and zinc ions in various samples has been described. Analyte ions in aqueous phase are complexed with 3-((indolin-3-yl)(phenyl)methyl)indoline (IYPMI) and following centrifugation quantitatively extracted to the aqueous phase rich in Triton X-114. The surfactant-rich phase was dissolved in 2.0 mol L⁻¹ HNO₃ in methanol prior to metal content determination by flame atomic absorption spectrometry (FAAS). The effects of some parameters including, the concentrations of IYPMI, Triton X-114 and HNO₃, bath temperature, centrifuge rate and time were investigated on the recoveries of analyte ions. At optimum conditions, the detection limits of (3 SDb m⁻¹) of 1.6, 2.8, 2.1 and 1.1 ng mL⁻¹ for Cu²⁺, Fe³⁺, Ni²⁺ and Zn²⁺ along with preconcentration factors of 30 and enrichment factor of 48, 39, 34 and 52 for Cu²⁺, Ni²⁺, Fe³⁺ and Zn²⁺ respectively, were obtained. The proposed cloud point extraction has been successfully applied for the determination of metal ions in real samples with complicated matrix such as biological, soil and blood samples with high efficiency.