European Journal of Chemistry

All-solid state potentiometric ion selective electrodes have the merits of being portable, small and suitable for small volume samples. Herein, disposable home-made screen printed polymeric ion selective electrode (SPE) is developed for determination of oxymetazoline (OXM) in pharmaceutical nasal drops and drug substance. Ion selective electrodes with optimal potentiometric response were achieved by careful selection of the ion exchanger and plasticizer. A screen printed electrode utilizing oxymetazoline-tetraphenyl borate (OXM-TPB) as an ion exchanger and dibutyl phthalate (DBP) as a plasticizer exhibited a Nernstian slope of 59.5±0.5 mV/decade (n=3) over the concentration range from 1×10^-5 to 1×10^-2 M OXM (r = 0.9999) with a detection limit of 5.0×10^-6 M. The electrode is useful over a wide pH range from 4.0 to 8.0. The electrode showed a high selectivity for OXM against several common interfering ions. The potential interference from benzalkonium chloride was easily eliminated by treatment the sample with KI. Comparable potentiometric characteristics including linearity, detection limit, pH range and selectivity pattern were obtained with a carbon paste electrode (CPE) comprising same ion exchanger and plasticizer. The electrodes were successfully used for the assay of OXM in the drug substance and in the dosage form in presence of benzalkonium chloride with high accuracy (±2%) and precision (%RSD ˂2.5). The proposed method is simple, accurate and precise.

The present study describes, the X-ray single crystal analysis of 4-((2-chloro-6-methoxyquinolin-3-yl)methyl)-2-phenyl-2H-1,2,4-triazol-3(4H)-one (TMQ). The crystal data for C₁₉H₁₅ClN₄O₂: monoclinic, space group P2₁/n (no. 14), a = 7.3314(15) Å, b = 12.459(3) Å, c = 18.948(4) Å, β = 98.322(9)°, V = 1712.5(6) Å³, Z = 4, T = 296.15 K, μ(MoKα) = 0.245 mm^-1, Dcalc = 1.423 g/cm³, 5082 reflections measured (3.926° ≤ 2Θ ≤ 38.556°), 1428 unique (R_int = 0.0545, R_sigma = 0.0574) which were used in all calculations. The final R₁ was 0.0423 (I >2σ(I)) and wR₂ was 0.1145 (all data). The Density functional theory optimized molecular geometries in TMQ agree closely with those obtained from crystallographic studies. The Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) energy levels and energy gap were calculated by experimental (UV absorption & Cyclic voltammetry) and theoretical studies in two different solvents. The natural bond orbital analysis was performed to understand the molecular interaction on the basis of stability of molecule arising from hyper-conjugative interaction and charge delocalization. Hirshfeld surface and their related fingerprint plots enabled the identification of significant intermolecular interaction. The molecular electrostatic potential analysis provides the visual image of the chemically active sites and comparable reaction of atoms.

A lingo-cellulosic material Jute Stick Powder was used as a biosorbent to remove Pb(II) ions from aqueous solution and the biosorption behavior was investigated as a function of pH, metal ion concentration, adsorbent dosages and agitation time. Sorption binding sites present in JSP was assessed by Infrared spectroscopy (IR) and Scanning Electron Micrograph (SEM). The determined experimental data were fitted to some common kinetic and equilibrium models. Langmuir isotherm and pseudo-second-order kinetic model gave better fit to experimental data. The study revealed that spontaneous ion-exchange and complexation process involved in the adsorption mechanism. When the repeated adsorption-desorption cycles were performed, JSP kept its adsorptive efficiency even after three cycles of reuse.

Cathodic voltammetric behaviors of drospirenone and ethinylestradiol were used for the simultaneous determination of both drugs in bulk and in pharmaceutical formulation (Yasmin® tablets) without the interference of excipients. The determinations were made on hanging mercury dropping electrode using square-wave technique in a voltammetric cell containing 10 mL of 0.04 mole/L Britton-Robinson. After every aliquot addition, the solution was stirred for 10 s at 1000 rpm, rested for 10 s then square wave voltammetry mode was ramped from +100 to -1700 mV with scan rate of 100 mV/s, pulse amplitude of 50 mV and measurement time of 5 ms. Several factors such as pH, type of supporting electrolyte, pulse amplitude and scan rate were studied to optimize the condition for voltammetric determination of these drugs. With optimized experimental parameters, a good linearity was obtained for both drugs over a range of 1.36×10^-6 to 1.91×10^-7 mole/L and 6.75×10^-8 to 6.07×10^-7 mol/L of drospirenone and ethinylestradiol, respectively. Characterization of the proposed method was done according to International Conference on Harmonization, Q2B: Validation of Analytical procedures. The proposed method was statistically compared with the reference method and the results revealed no significant difference regarding accuracy and precision.

The catalytic decomposition of H₂O₂ on differently pre-treated Au/CeO₂ catalyst was studied by kinetic measurements at 20-50 °C. The prepared catalyst was subjected to pre-treatment by heating either in oxidative (10% O₂/N₂) or inert (pure N₂)atmosphere at 400 °C. The different oxidation states of gold were determined by X-ray photoelectron spectroscopy measurements. The Au/CeO₂ catalyst exhibited an excellent catalytic activity towards H₂O₂ decomposition. The catalytic activity of oxygen pre-treated sample was about twice higher than that measured for nitrogen pre-treated sample. This finding ran parallel to the amount of Auⁿ⁺ as determined by XPS, indicating the role played by Auⁿ⁺ species as the most active catalyst’s constituent. However, one cannot overlook the role of metallic gold in catalyzing the H₂O_2, decomposition showing small activity compared to that of cationic gold. The average crystallites size of metallic gold particles was found to be 7±0.5 nm independent of the pre-treatment conditions. The apparent activation energy of the catalyzed reaction was found to be 46.5 and 47.8 kJ/mol for oxygen and nitrogen pre-treatment, respectively.

The vibrational frequencies, atomic charges and the related properties of the 2,2,2-trichloro-N,N-bis(2-(2,2,2-trichloroacetamido)phenyl)acetamide (H₂L^NNN) were investi-gated by Ab-initio Hartree-Fock (HF) and Density Functional Theory (DFT) methods such as BLYP, B3LYP, B3PW91 and mPW1PW91 functionals with 6-31G(d,p) and 6-311G(d,p) basis sets. The experimentally determined parameters were compared with those calculated theoretically and they were found to complement each other with a very good correlation. The theoretical vibrational spectrum of H₂L^NNN molecule was interpreted by means of potential energy distributions using the SQM 2.0 program. The Hirshfeld surface analysis was carried out to discuss the role of the hydrogen bonds and other intermolecular contacts in crystal lattice. Hirshfeld surface analysis revealed the occurrence of Cl⋯H, Cl⋯Cl, Cl⋯C, H···H, O⋯H, C···H and Cl···π interactions that display an important role on the crystal packing stabilization of the compound.

A highly sensitive and stable solid-state electrochemiluminescence (ECL) sensor was developed based on tris(2,2’-bipyridyl)ruthenium(II) (Ru(bpy)₃²⁺) integrating with 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) functionalized graphene. Ru(bpy)₃²⁺ is incorporated with the ABTS functionalized graphene based on not only the π-π stacking but also electrostatic interactions. Coupled with capillary electrophoresis (CE), this ECL sensor was used to detect tyramine and 5-hydroxytryptamine (5-HT) based on their quenching effects for the Ru(bpy)₃²⁺/tripropylamine (TPA) system. The quenching mechanism was illustrated and the conditions for CE separation and ECL detection were optimized. Based on an S/N = 3, the limit of detection (LOD) for tyramine and 5-HT were 0.1 μM and 0.02 μM, respectively. The applicability of the proposed method was further illustrated in the determination of tyramine and 5-HT in human plasma samples from small intestine carcinoid patients.

Single crystal X-ray diffraction has established the absolute configuration of the indole alkaloids from Vinca erecta such as akuammiline-o-acyl derivative of akuammine with a 3D stable polycyclic framework. Crystal data for C₂₄H₂₈N₂O₅: orthorhombic, space group P2₁2₁2₁ (no. 19), a = 7.349(3) Å, b = 16.099(5) Å, c = 17.323(5) Å, V = 2049.5(12) Å³, Z = 4, T = 293(2) K, μ(CuKα) = 0.789 mm^-1, Dcalc = 1.376 g/cm³, 1742 reflections measured (7.496° ≤ 2Θ ≤ 119.792°), 1742 unique (R_sigma = 0.0374) which were used in all calculations. The final R₁ was 0.0608 (I > 2σ(I)) and wR₂ was 0.1680 (all data). The polycyclic framework of the well-known picrinine and akuammine is compared. The ether bridges located in different positions of the framework and forming five-membered cycles do not change the conformation of the polycyclic akuammiline framework. In V. erecta alkaloids, the exomethylene fragment (C18-C19=C20-C21) of the polycyclic backbone always takes on the E-condition.

Daclatasvir (DAC), sofosbuvir (SOF) and ribavirin (RIB) have been recently co-formulated in tablet dosage form for the treatment of Hepatitis C virus infections. In this work, the resolution and quantitation of overlapped spectral signals was achieved by both univariate and multivariate algorithms. Pure component contribution algorithm (PCCA) as a novel approach was applied along with factor based partial least squares (PLS) algorithms using both full range and synergistic intervals (siPLS). Each drug could be determined at its λ_max using PCCA, while PLS and siPLS were used for multivariate determination of the three components. Good linear relationships were obtained in the ranges of 5.45-16.35, 4.40-44.00 and 5.50-35.00 µg/mL for DAC, SOF and RIB, respectively, by PCCA. The PLS and siPLS models were built for the three compounds each in the concentration range of 2.00-10.00, 10.00-20.00 and 10.00-26.00 µg/mLfor DAC, SOF and RIB, respectively. Validation of the proposed methods was ascertained according to ICH guidelines for PCCA and through the use of internal and external validation sets for PLS and SiPLS models. The three methods were successfully applied for determination of DAC, SOF and RIB in pure form and in tablets.

Structural modification of lead compounds is a great challenge in organic synthesis. Introduction of different functional groups not only modify the structure of starting material but also improve their biological activeness. Small synthetic molecules are favored in spite of the reality that majority of drug molecules derived from natural sources, are in vogue. In the present work, acetamide derivatives were synthesized using chloroacetyl chloride. After synthesizing targeted series of acetamide derivatives these compounds were further modified using different amines including 2-aminobenzene thiol, benzyl amine, benzene 1,4-diamine, 4-amino-1,5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-one, 4-aminophenol, hydrazine and 4-amino-N-(5-methylisoxazol-3-yl)benzenesulfonamide. All of these synthesized compounds were characterized by FT-IR, ¹H NMR, ¹³C NMR and X-ray crystallography. The compounds were assessed for their anti-bacterial activity using disc diffusion method against Staphylococcus aureus and Escherichia coli. The compounds were found to exhibit comparable activity to the standard drug used. This was further supported by molecular docking studies using bacterial DNA gyrase and Topoisomerase II targets causing bacterial death as they are major bacterial proteins known to be involved in transcription and replication process. Results proved that the compound 2b was the most efficacious antimicrobial compound among the synthesized set of compounds. To tackle the growing drug resistance acetamide based functionalities can be regarded as the active lead compounds to target different drug resistance microorganism.

The 1,3-dipolar cycloaddition reaction of bis-hydrazonyl chlorides with methyl propiolate afforded dimethyl 1,1¢-aryl-3,3`-bipyrazole-4,4`-dicarboxylates (5a,b). Heating the later compound 5a with a mixture of HCl/AcOH gave 3,3`-bipyrazole-5,5`-dicarboxylic acid derivative 6. Treatment of the hydrazonoyl chloride (1a) and 3,3`-bipyrazole-5,5`-dicarboxylic acid (6) with palladium(II) chloride gave the corresponding Pd-complexes 7 and 8, respectively. The catalytic activity of the prepared Pd-complexes was examined in the Suzuki cross-coupling reaction of phenylboronic acid with activated and deactivated aryl(hetaryl) bromides. The catalyst system provides very good to excellent yields, 85-94%. The structures of the obtained products were established from their elemental analysis, spectral data, XPS, EDX, and single crystal X-ray crystallography. Crystal data for C₁₀H₇N₂O₂ (6): triclinic, space group P-1 (no. 2), a = 3.9956(10) Å, b = 9.8917(18) Å, c = 10.810(3) Å, α = 94.167(15)°, β = 94.979(19)°, γ = 98.953(15)°, V = 418.83(16) Å³, Z = 2, T = 296.(2) K, μ(Cu Kα) = 0.887 mm^-1, D_calc = 1.484 g/cm³, 5469 reflections measured (11.72° ≤ 2Θ ≤ 133.24°), 1420 unique (R_int = 0.0633, R_sigma = 7.24%) which were used in all calculations. The final R₁ was 0.1055 (>2sigma(I)) and wR₂ was 0.3620 (all data).

Structures of alkaloid convolvine (1) isolated from Convolvulus subhirsutus and its derivatives-convolamine(N-methylconvolvine) (2) and hydrochloride of N-benzylconvolvine (3) have been determined by single crystal X-ray diffraction technique. Compounds were crystallized in monoclinic space groups having four molecules in unit cell. All compounds contain a bicyclic ring system of tropane, where piperidine rings in all case adopt chair conformation. Hydrogen atom and methyl- and benzyl-substituents located in nitrogen atom of studied compounds occupy equatorial positions. The substituent of tropane core- the veratroyloxy group containing in all compound molecules is an α-axial oriented relative to the tropane core. In crystal structures of compound 1 and 2, the molecules are located in the distance of van der Waals interactions. The H-bond between the anion Cl and the proton of the N atom is observed in the crystal of N-benzylconvolvine hydrochloride (Cl···N 3.337 Å, Cl···H 2.42 Å and Cl-H-N 175°).

A new enaminone was synthesized by reacting 3,5-bis-(trifluoromethyl)acetophenones and N,N-dimethylformamide dimethyl acetal and its detailed structural and crystalline properties were studied. The crystal data were found to be as C₁₃H₁₁F₆NO, monoclinic, space group P2₁/c (no. 14), a = 8.1556(8) Å, b = 24.877(3) Å, c = 7.6067(7) Å, β = 116.745(6)°, V = 1378.2(3) Å³, Z = 4, T = 293(2) K, μ(MoKα) = 0.150 mm^-1, Dcalc = 1.500 g/cm³, 40777 reflections measured (5.594° ≤ 2Θ ≤ 56.786°), 3413 unique (R_int = 0.1040, R_sigma = 0.0584) which were used in all calculations. The final R₁ was 0.0771 (I > 2σ(I)) and wR₂ was 0.2541 (all data).

The title molecule, N,N'-(azanediylbis(2,1-phenylene))bis(2-chloropropanamide) (L^NNN) was synthesized and characterized by means of Hirshfeld surface analysis and vibrational (FT-IR and RAMAN) studies. Ab-initio Hartree-Fock (HF) and density functional theory (DFT; BLYP, B3LYP, B3PW91 and mPW1PW91) calculations were accomplished using 6-31G(d,p) and 6-311G(d,p) basis sets. The comparison of calculated bond lengths and angles with X-ray crystal structure shows sufficient agreement. The solid phase FT-IR and FT-RAMAN spectra of L^NNN have been recorded in the regions 4000-525 cm^-1 and 4000-50 cm^-1, respectively. A comparative analysis between the calculated and experimental vibrational frequencies was carried out and significant bands were assigned. The results indicated a good correlation between experimental and theoretical IR and RAMAN frequencies. A detailed analysis of the intermolecular interactions via Hirshfeld surface analysis and fingerprint plots revealed that supramolecular structure of the L^NNN is stabilized mainly by the formation of H···H, C···H, Cl···H ve O···H  intermolecular interactions.

The ab-initio DFT method (B3LYP) is applied to the study of the C-C and C-H bond cleavage reactions in acenaphthylene molecule. It is found that the C-C bond cleavage proceeds via a singlet aromatic transition state, compelled through a disrotatoric ring opening reaction. A sigmatropic H atom shift follows the transition state in some of these reactions, where the formation of a methylene -CH₂,acetylenyl-, allenyl- or butadienyl moiety in the final product is possible. The calculated activation and reaction energies for the C-C ring opening are 164-236 and 52-193 kcal/mol, respectively. The calculated cleavage reaction energies for the C-H bonds are 117-122 kcal/mol and the activation energies are 147-164 kcal/mol.

The single crystal X-ray diffraction method established the absolute configuration of the Vinca erecta indole alkaloids of the akuammidine sarpagine type (3S, 5S, 15R, 16R) and its o-acyl derivative, as well as the type of ajmaline, quebrachidine (2S, 3S, 5S, 7R, 15S, 16R, 17S) and majoridine (2R, 3S, 5S, 7R, 15R, 16S, 17R). Crystal data for C₂₁H₂₄N₂O₃ (1): orthorhombic, space group P2₁2₁2₁ (no. 19), a = 6.3949(5) Å, b = 13.5009(10) Å, c = 22.461(3) Å, Z = 4, 7694 reflections measured (7.64° ≤ 2Θ ≤ 152.294°), 3813 unique (R_int = 0.0798) which were used in all calculations. The final R₁ was 0.0680 (I > 2σ(I)) and wR₂ was 0.1650 (all data). Crystal data for C₂₃H₂₆N₂O₄ (2): orthorhombic, space group P2₁2₁2₁ (no. 19), a = 9.9730(13) Å, b = 10.2090(10) Å, c = 20.409(3) Å, Z = 4, 7959 reflections measured (8.666° ≤ 2Θ ≤ 151.998°), 4212 unique (R_int = 0.0386) which were used in all calculations. The final R₁ was 0.0477 (I > 2σ(I)) and wR₂ was 0.1171 (all data). Crystal data for C₄₂H₄₈N₄O₆ (3): monoclinic, space group P2₁ (no. 4), a = 8.9320(10) Å, b = 21.515(5) Å, c = 9.5420(10) Å, β = 97.103(10)°, Z = 2, 16677 reflections measured (9.34° ≤ 2Θ ≤ 151.836°), 7393 unique (R_int = 0.0278) which were used in all calculations. The final R₁ was 0.0366 (I > 2σ(I)) and wR₂ was 0.1037 (all data). Crystal data for C₂₃H₂₈N₂O₃ (4): orthorhombic, space group P2₁2₁2₁ (no. 19), a = 10.636(2) Å, b = 11.208(12) Å, c = 16.725(13) Å, Z = 4, 1650 reflections measured (9.498° ≤ 2Θ ≤ 119.97°), 1650 unique (R_int = 0.0436) which were used in all calculations. The final R₁ was 0.0608 (I > 2σ(I)) and wR₂ was 0.1720 (all data). In alkaloids such as sarpagine and ajmaline exo, the substituents of alkaloids do not lead to conformational changes of a stable polycyclic framework. In the series of sarpagine, alkaloids form mono-salts in the tetrahedral nitrogen N4, and in indolines of the ajmaline type, the tetrahedral hybridization of the N1 and N4 atoms favors the formation of disols. In V. erecta alkaloids, the exomethylene fragment (C18-C19=C20-C21) of the polycyclic backbone always takes on the E-state.