European Journal of Chemistry

The present investigation describes the synthesis and structural study of a metal-zinc ligand [ZnL.H₂O], which was used to generate three dimensional supramolecular complex formulated as [Y{Zn(L)(SCN)}(SCN)₂].[Y{Zn(L)(SCN)}₂(DMF)₂].(NO₃). The title compound crystallizes in the triclinic space group P-1 with the following unit cell parameters: a = 14.8987(7) Å, b = 15.6725(8) Å, c = 19.2339(10) Å, a = 94.610(4)°, β = 103.857(4)°, γ = 101.473(4)°, V = 4234.4(4) ų, Z = 2, R₁ = 0.063 and wR₂ = 0.96. For this compound, the structure reveals that one heterodinuclear unit [Y{Zn(L)(SCN)}(SCN)₂] is co-crystallized with a heterotrinuclear unit [Y{Zn(L)(SCN)}₂(DMF)₂].(NO₃). In the dinuclear moiety, the organic molecule acts as a hexadentate ligand and in the trinuclear unit, it acts as a pentadentate ligand with one of the oxygen methoxy group remaining uncoordinated. In both units the coordination environment of the zinc metal can be described as distorted square pyramidal. In the dinuclear unit the Y(III) is hexacoordinated while it is octacoordinated in the trinuclear unit. The environment of the Y(III) can be described as a distorted octahedral geometry in the dinuclear and as a distorted square antiprism in the trinuclear units respectively.

We have synthesized and characterized a series of carbothioamide derivatived molecules, obtained by reaction of aromatic aldehyde (Anisaldehyde, 9-anthraldehyde, cinnamaldehyde, indole-3-carboxaldehyde, 1-naphthaldehyde and o-vanillin) with an equimolar amount of 4-phenylthiosemicarbazide with microwave irradiation. The synthesized compounds have been characterized by FT-IR, ¹H NMR and ¹³C NMR spectroscopy. Quantum calculations of the physical properties, based on density functional theory method at B3LYP/6-31+G(d,p) level of theory, were performed, by means of the Gaussian 09W set of programs. The theoretical ¹H NMR chemical shift results of the studied compounds have been calculated at B3LYP method and standard 6-31+G(d,p) basis set using the standard Gauge-Independent Atomic Orbital approach. The calculated values are also compared with the experimental data available for these molecules. A good linear relationship between the experimental and calculated data has been obtained.

Using free radical solution polymerization technique and Mannich reaction, five different polyacrylamides with similar molecular weight but variable charge densities were synthesized. High molecular weight polyacrylamides were synthesized using potassium persulfate and N,N,N',N'-tetramethylethylenediamine system as initiators. This was achieved by increasing the concentration of acrylamide monomer. They were then characterized by infrared spectroscopy, viscosity measurements and glass transition temperature measurement. These compounds with various cationic charge densities from 48.2, 161.7, 355, 425 and 485 C/g were prepared through Mannich reaction. The results indicate, by increasing the acidity of the polyacrylamide solution using sulfuric acid, the pH of the polyacrylamide solution decreases correspondingly. As a result, the positive charges increased resulting in the enrichment of charge densities.

New heterocyclic azo compounds were prepared by coupling the diazonium salts with N-(4-methylphenyl)maleimide with various different sulfa compounds. The structure of heterocyclic azo compounds was determined by MS, FT-IR and ¹H NMR techniques. The density function theory calculation at the B3LYP method with 6-311G(d,p) basis set is used to investigate the electronic structures of the prepared heterocyclic azo compounds. Mulliken charge distributions and HOMO-LUMO energies of the mentioned compounds have been also computed by same method and basis set.

Recently, there has been a surge in use of polymer-supported reagents and catalysts become common tools for organic synthesis in what is known as polymer-assisted synthesis since they can simplify product isolation and purification. In this context, coumarin derivative 3 was prepared in good yield and high purity, starting from 3-methoxy salicylaldehyde, using reagents supported on a macroporous ion exchange resin. For this purpose, iminocoumarin and unsaturated nitrile were used as starting materials. The synthesized compounds were characterized by IR, NMR and mass spectrometry.

A simple isocratic reversed-phase HPLC method for quantification of clobetasone in bulk and cream dosage forms has been developed. Chromatographic analysis was accomplished on an C18 column utilizing a mixture of methanol and water (84:16 v:v, pH = 6.0) as mobile phase. An effluent flow rate of 1 mL/min was adjusted and the detection was made at 240 nm wavelength. The method was evaluated according to ICH guidelines Q2 R1 for linearity, specificity, sensitivity, precision and accuracy. The method exhibited good linearity with correlation coefficient (r²) of 0.9993 over the concentration range from 5 to 50 μg/mL. The recoveries of the test drug from the cream sample was found to be 98.56 to 99.51% and the limit of detection and quantification were calculated as 0.85 and 2.83 μg/mL, respectively, suggesting the accuracy and sensitivity of the developed method. The precision was demonstrated by a low percentage of relative standard deviation (<1%) from six independent assay analysis performed for the cream formulation. Stability indicating property of the proposed method was demonstrated by performing the analysis of forced degradation samples. The developed method can be used for estimation of the clobetasone butyrate in bulk and pharmaceutical formulations for routine analysis in the quality control laboratories.

By addition of semicarbazide or phenylhydrazine hydrochloride to thienoylisothiocyanate (1) resulted in building of thiosemicarbazide derivative (2), triazole derivative (4) and thiophene-2-carboxamide (5), respectively. Basic cyclization of compound 2 led to formation of oxadiazine (3). Synthesis of thiadiazine derivative (6) was achieved via reaction of compound 5 and maleic anhydride in triethyl amine. Heating of compound 5 with ethyl chloroacetate or sodium ethoxide produced thiadiazine derivative (7) and triazolethione (8), respectively. Thiosemicarbazide derivative 11 was synthesized by addition of nicotinic hydrazide to compound 1. Refluxing of compound 11 with lead acetate afforded triazole (13). Moreover, acid and base mediated cyclizations of compound 11 gave thiadiazole (12) and 1,2,4-triazolethione (14) throughout thiophene intermediate, respectively. Addition of ethyl 2-aminothiophene-3-carboxylate to compound 1 formed thiourea (15) which was refluxed with ethoxide giving thiophene-3-carboxylic acid (16). Lastly, nucleophilic addition of amino phenol or ethylene diamine to compound 1 yielded oxazine structure (18) and imidazole derivative (19), respectively. The yields of the synthesized compounds were 61-95%. The detailed synthesis and spectroscopic data of the new compounds are reported.

The present manuscript describes the adsorptive batch and column treatment of synthetic Congo Red dye onto naturally prepared adsorbents viz. gulmohar leaf powder and activated gulmohar leaf powder using sulfuric acid. The surface characterizations of naturally prepared adsorbents were performed by various sophisticated analytical techniques. Effect of various process parameters like adsorbent dosage, temperature, initial concentration, and pH for batch study; and flow rate and bed height for column study are explored. All batch adsorption data are analyzed using Freundlich and Langmuir adsorption isotherm model. The Thomas, Yoon-Nelson, Adams and Bohart, and Bed Depth Service Time model are applied to predict the breakthrough curves and to determine the characteristic parameters of the column useful for process design. Activated gulmohar leaf powder is more feasible adsorbent compared to normal gulmohar leaf powder. Maximum adsorption capacity related to Adams and Bohart model; and Langmuir isotherm was found to be 919.4 mg/L; and 434.7 mg/g, respectively, for activated gulmohar leaf powder.

The main purpose of the present study was to develop and validate a high performance thin layer chromatographic (HPTLC) method for quantitative determination of an antiviral agent, zanamivir in pure drug and diskhaler powder formulation. Chromatography was performed on aluminum TLC plates pre-coated with silica gel 60F₂₅₄, employing a mixture of chloroform:methanol:ammonia (9.5:3.2:0.2,v:v:v) as mobile phase. The TLC scanner was operated in the absorbance mode at a wavelength of 230 nm for evaluation of chromatograms. The system has given well resolved peak of zanamivir (R_f = 0.56). The linearity of the method was established in the range of 20-300 ng/spot; correlation coefficient (r) was 0.9995. The low values of limit of detection and limit of quantification (12.4 and 37.5 ng/spot, respectively) have demonstrated the sensitivity of the developed method. The reported method was precise in both intra-day as well as inter-day analysis; % RSD of peak area was found to be less than 2%, and has an accuracy within 100 ± 2%. The developed method has a potential to quantify zanamivir from its diskhaler formulation without any interference from other components. The applicability of the method was demonstrated by excellent recovery of analyte (99.8%) from diskhaler formulation. The current analytical method can be applied for routine analysis of zanamivir in pure form and pharmaceutical formulation in quality control laboratories.

Two organic salts between diethanolamine (DEA) and ortho- and para-isomers (OABA and PABA) of aminobenzoic acid (ABA) have been obtained and their X-ray single crystal structures determined. In both salts, cationic and anionic components are incorporated into dimers by the two H-bonds formed between ABA carboxylate oxygen atoms and nitrogen and one of oxygen atoms of DEA which close a cycle with the graph-set notation of R₂²(9). Further dimers are associated by intricate systems of the H-bonds into 1D- and 3D-network structures in crystals of DEA·OABA and DEA·PABA, respectively. H-bonding which generates these dimers may be considered as a synthon specific for yielding of salts between DEA and mono-substituted aromatic benzoic acids.

Thermo-responsive vegetable oil-based polyurethanes were successfully prepared by poly-condensation reaction in the mixture of polyol and hexamethylene diisocynate. The functionality and high molecular weight of the polyurethanes were characterized by Fourier Transform Infrared Spectroscopy (FTIR), Proton Nuclear Magnetic Resonance Spectroscopy (¹H NMR), Carbon Nuclear Resonance Spectroscopy (¹³C NMR), and Gel Permeation Chromatography. The viscosity of the polyols was characterized by Rheometry and flow rate of the polyols were derived from power law model. The kinetic and thermodynamic parameters of synthesized polyurethanes HSCP and HPCP were calculated from by TG curve. Five different mass loss temperature was obtained in the TGA curve of HSCP and HPCP, which corresponded to the decomposition of the physically observed NH and C=O formed between polyol and diisocyanate, respectively. The average value of the activation energy calculated by Murray and White, Coats and Redfern, Doyle’s, and Freeman-Carroll’s method. The success of the investigated different vegetable oil-based polyurethanes, in comparison with the activation energy of the Freeman-Carroll’s method to determine the thermal stability and the lifetime prediction of the peanut and sesame oil-based polyurethanes is 1.87×10⁵ and 1.27×10⁴ s^-1.

Attempt has been made to develop a new, accurate, precise and economic spectrophotometric method for the simultaneous determination of ketorolactromethamine (KTR) and tiemoniummethylsulphate (TMS) in pharmaceutical formulation and bio-samples. It is noted that KTR shows two absorption peaks at 320 and 245 nm whereas TMS shows maximum absorption at 235 nm. In a mixture solution, peaks at 245 nm for KTR and at 235 nm for TMS are merged into a single peak at 240 nm. Hence KTR might be determined using its calibration equation constructed at 320 nm but the determination of TMS alone in their mixture measuring its absorption at 240 nm is difficult. Therefore, for the determination of TMS, a mathematical expression x_T = k₁.y_K+T - k₂.y_K + k₃ (y = Absorbance, x = Concentration) has been derived. This expression will give its concentration in mixture without having its absorption at 240 nm. Method has been applied to pharmaceutical and bio-samples successfully. Results have been compared to that estimated by new UPLC method developed as to validate this spectrophotometric method. The LOD and LOQ were found to be 0.25, 0.80 μg/mL for KTR and 0.31, 0.95 μg/mL for TMS, respectively.

The compound, C₁₆H₁₄O₃, (except H atoms) is almost planar [r.m.s. deviations for all non-H atoms = 0.001 Å] and the dihedral angle between the aromatic rings is 9.35 (7)°. In the crystal, molecules are linked by intermolecular O—H···O and C—H···O hydrogen bonds, forming a three-dimensional network structure. Furthermore, a weak π-π stacking interactions [centroid-to-centroid distance = 3.7055 (9) Å] contributes to the stabilization of the molecular packing. Crystal Data for C₁₆H₁₄O₃ (M = 254.27 g/mol): Orthorhombic, space group Pbca (no. 61), a = 13.4563(16) Å, b = 11.4986(14) Å, c = 16.720(2) Å, V = 2587.1(5) Å³, Z = 8, T = 296(2) K, μ(MoKα) = 0.090 mm^-1, D_calc = 1.306 g/cm³, 61402 reflections measured (4.88° ≤ 2Θ ≤ 56.76°), 3240 unique (R_int = 0.0334, R_sigma = 0.0120) which were used in all calculations. The final R₁ was 0.0438 (I≥2σ(I)) and wR₂ was 0.1228 (all data).