European Journal of Chemistry

Benzodiazepines are drugs used for treatment of several central nervous system disorders, such as anxiety and sleep. In spite of their wide and popular usage in clinics, the mechanism explaining why a certain pharmacological activity is superimposed onto another for a given benzodiazepine remains unclear. The knowledge of the conformation of benzodiazepines and their electronic charge distribution at molecular surfaces may give new insights into the pharmaco-benzodiazepine receptor interactions, contributing to the improvement of the existing models. In the present study, the solid state geometric and conformational parameters of the available X-ray benzodiazepine structures were analyzed and reviewed. The electronic features of two groups of benzodiazepines with different substituents at C₇ and C₂’ positions were studied by DFT quantum chemical calculations. The conformations of the molecules with optimized geometry were also analyzed. The relative charge distribution around the benzodiazepinic rings and electrostatic potential mapped on electronic density surfaces were obtained. The ring geometric parameters for the diazepine moiety in 1,4-benzodiazepines, do not vary significantly except for a few compounds in which steric and/or intermolecular interactions play a part. The benzodiazepine ring assumes a pseudo-symmetrical boat conformation and the torsion angle around the C₅-Ph bond varies depending on the nature of the substituent on C₂’. Also, the presence of the nitro or chloride substituent on the C₇ position and the presence of a fluorine atom on the C₂’ position significantly alter the relative charge distributions at the attached carbon atoms and the topology of the surface electrostatic potential.

SnO₂ cluster-system structures were synthesized via a two-step temperature-rising thermal evaporation method with short oxidation time. Field emission scanning electron microscopy, X-ray diffraction and transmission electron microscopy were used to characterize the morphological and structural feature of the product as nanowire cluster and nanoparticle cluster. The photoluminescence spectra exhibit that, as annealing time in air increases, the intensity of the newly found strong ultra-violet emission decreases while the green emission is increased. Raman spectrum and X-ray photoelectron spectroscopy investigations reveal that the relatively decreasing intensity was dominated by the increasing oxygen vacancy. Further calculation based on the SnO₂ crystal lattices with H₂O molecules at different steps in evaporation process was performed. The result of this calculation confirms that, rather than the influence of H₂O molecules from air, the decreasing intensity is the result of the combined action of the formation of oxygen vacancy and the energetic oxygen compensation in annealing treatment.

In this study, we report that interaction of the network functional polymers based on cis-tetraphenylcalix[4]resorcinarene with aqueous solutions of electrolytes is controlled by diffusion of ions in a polymeric phase. The nanoreactor effect consisting in sufficiently high rate increase of a cation diffusion flux in bifunctional polymers containing sulfonic acid and phenol ionogenic groups has been found. For steady and non-steady states the solutions of the fundamental differential equation of cation diffusion in bifunctional polymers by means of the spherical layer model are obtained for a variety of initial and boundary conditions with constant diffusion coefficient. The proposed mathematical model explains the nanoreactor effect in bifunctional polymers.

Novel 3,4,5-substituted-oxazolidin-2-ones containing piperazine, 1-(4-chlorophenyl) piperazine, benzhydrylpiperazine, morpholine and piperidine rings were synthesized via Mannich reaction. The stereochemistry of syn and anti-isomers was assigned using the observed differences in the chemical shifts of the oxazolidinone ring protons and the values of vicinal coupling constants (³J) between the two protons of the oxazolidin-2-one ring. For all compounds NOE (Nuclear Overhauser Effect) NMR spectra were measured in order to prove additionally the position of the substituents in the oxazolidin-2-one ring. Some physic chemical, steric and electronic properties of the compounds were determined in order to establish the similarity between the synthesized and reference compounds. The performed computations showed that the anti-isomers possessed lower electronic energies in comparison to these of syn-compounds. The nucleus-nucleus repulse energies (NRE) and the highest occupied molecular orbital energies (HOMO) of the anti-isomers are higher than the HOMO and NRE energies of syn-compounds. The Connolly Solvent Accessible Surface Area (SAS) and Connolly Molecular Surface Area (MS) values of anti-isomers are lower than these of syn-isomers. The same relations were observed for the reference compounds. Probably the differences in the electronic and steric properties are responsible not only for the higher LD₅₀ value of the reference anti-compound, but also may contribute to the higher toxicity of the prepared anti-Mannich bases in comparison to that of the syn-diastereoisomers.

Vilsmeier-Haack reaction conditions were applied on some methyl ketone aryl phosphonicdihydrazones to yield some interesting bis-pyrazole derivatives containing a hydro-phosphoryl unit. Bis-{4-formyl-3-aryl-1H-pyrazol-1-yl}phosphine oxides (4a,b) were condensed with some nucleophiles such as aniline, phenacyltriphenylphosphonium bromide and 4-phenylthiosemicarbazide followed by treatment with thioglycolic acid, diethyl phosphite and/or acetic anhydride to yield a novel class of bis-pyrazoles containing sulfur and phosphorus derivatives. Most of the newly synthesized compounds were evaluated for their in vitro antimicrobial activities.

In the present study we have determined the fundamental physico-chemical properties such as, ionization constant (pKa) and lipophilicity (log P) of some b-blockers and anti-diabetic drugs. The apparent ionization constant (psKa) of selected drugs were determined using potentiometric titration in various co solvent-water mixtures (methanol, ethanol, acetonitrile and dioxane) at different temperatures (25 to 45 °C) and ionic strengths (0.15 to 0.5 M). Effect of temperature, ionic strength and dielectric constant on dissociation constant has been compared. The aqueous pKa values were then obtained by Yasuda-Shedlovsky extrapolation. In the case of water-soluble drugs (Amiloride hydrochloride, metoprolol tartrate and propranolol hydrochloride), the extrapolated results were in good agreement with that of pKa values measured in aqueous solutions under the same experimental conditions, while for the water insoluble drugs (atenolol, amlodipine besylate, gliclazide, glipizide, glibenclamide and pioglitazone), the extrapolated results were in good agreement with the literature values. For few of the selected drugs, the psKa was determined spectrophotometrically and the results were compared with that of potentiometry in various co solvent mixtures. The measured log P values of selected drugs showed acceptable range to that of literature values.

Synthesis and antimicrobial evaluation of some typical macrocyclic crown ethers including amide, sulfonamide, and disulfide moieties are reported. Novel macrocyclic bis-sulfonamide, amide, and disulfides are prepared by reacting the bis-chlorides and diamines by fast addition method. The antimicrobial activities of the synthesized compounds are measured. Bis-sulfonamide and disulfide crown ethers showed antibacterial activities against most strains tested.

Benzofuroxan derivative (1a) reacts with the cyanoacetanilides (2a-d) to give the benzimidazole derivatives (3a-d). Benzofuroxan (1b) reacts with rhodanine derivatives (4a,b) in presence of sodium ethoxide to give the arylaminobenzoimidazole derivatives (6a,b); while the last reaction afforded the thiazolidinone derivatives (8a,b) and the o-benzoquinone dioxime derivatives (9a,b) when it was repeated in the presence of sodium acetate. Moreover, a series of quinoxalinyl 1,4-di-N-oxide derivatives were prepared starting from quinoxalin-1,4-di-N-oxide derivatives (10a-c). Plausible mechanisms to account for the formation of the products are discussed.

An efficient synthesis of the title compound, 2-(4-(methylthio)phenyl)-1H-benzo[d]imidazole, was carried out by the condensation reaction of o-phenylenediamine and p-thiomethyl benzaldehyde in benzene. The structure was confirmed by spectroscopic data and elemental analyses. The molecular structure was determined from single crystal X‐ray diffraction data. The compound crystallizes in the orthorhombic space group Pbca with a = 8.544(2) Å, b = 9.700(3) Å, c = 29.684(8) Å, V = 2460.0(11) ų, Z = 8. The crystal structure is stabilized by intermolecular C-H…N, N-H…N and π-π interactions.

Sorption capacity of single-walled carbon nanotubes, detonated nanodiamonds and graphene to humic substances was studied by radiotracer method. Tritium labeled brown coal humic acids and fulvic acids separated from Suwannee River were used as sorbates. Adsorption isotherms were described by Langmuir equation. It was found that, for all tested carbon-based nanomaterials, adsorption of coal humic acids is higher than of river fulvic acids. Adsorption capacity of nanomaterials in attitude to humic substances was changed in the order, nanodiamonds < single-walled nanotubes < graphene. Composites of humic substances with carbon-based nanomaterials were subjected to dynamic light scattering analysis.

Some new pyrido[2,3-d]pyrimidine derivatives (3a-c) were synthesized from 2-amino-5-cyano-6-methoxy-4-(4-methoxyphenyl)pyridine-3-carboxamide. 7-methoxy-5-(4-methoxy phenyl)-4-oxo-2-phenyl-3,4-dihydropyrido[2,3-d]pyrimidine-6-carbonitrile (3b) and 7-met-hoxy-5-(4-methoxyphenyl)-4-oxo-3,4-dihydropyrido[2,3-d]pyrimidine-6-carbonitrile (3c) are used in synthesizing 7a,b, then 8a,b. 7-methoxy-5-(4-methoxyphenyl)-2-methyl-4-oxo-3,4-dihydropyrido[2,3-d]pyrimidine-6-carbonitrile (3a) and 4-hydrazinyl-7-methoxy-5-(4-methoxyphenyl)pyrido[2,3-d]pyrimidine-6-carbonitrile (8b) were condensed with different carbonyl compounds to produce compounds 4, 5, 6 and 9, 10, 11, 12. 3-Methoxy-1-(4-methoxyphenyl)-6-phenyl-7-hydropyridino[2,3-d]1,2,3,4-tetrazolo[1,5-e]pyrimidine-2-carbo-nitrile (13) was synthesized from 8a or 7a. Condensation of 8b with acetophenone to yield 14, which on further reaction gave 15 then 16. 4-Hydrazinyl-7-methoxy-5-(4-methoxyphenyl)-2-phenylpyrido[2,3-d]pyrimidine-6-carbonitrile (8a) also condensed with 4-amino antipyrine giving 17 then 18. Structures of these compounds have been deduced upon the basis of elemental analysis and spectral data. Significant antifungal activities were observed for some of the synthesized compounds.

N-(3-methylphenyl)-2,2-dichloroacetamide of the configuration X_yC₆H_5-y-NHCO-CHCl₂ (where, X = CH₃ and y =1) was synthesized and an extensive spectroscopic investigations have been carried out by recording the Fourier transform infrared (FT-IR) and FT-Raman spectra in an effort to provide the complete analysis of the fundamental modes of the compound. The ab initio and DFT studies were carried out with 6-311++G(d,p) and 6-31G(d,p) basis set to determine the structural, thermodynamical and vibrational characteristics of the compound. The steric influence of methyl group on the characteristic frequencies of amide (-CONH-) group has been analysed.

New thermally stable epoxy polymers containing copper and nickel ions have been prepared by curing diglycidyl ether of bisphenol A (DGEBA) with amino-thiourea metal complexes. Characterization of the metal complexes was carried out using infrared spectroscopy, elemental analysis and mass spectrometry. Determination of the optimum value of the epoxy/thiourea metal complex ratio was studied by means of differential scanning calorimetry. This method is based on the search for the maximum enthalpy change. The properties of the resulting metal-containing epoxy polymers were investigated with respect to glass transition temperature, thermal stability, tensile strength, and viscoelastic properties. Introduction of metal ions, especially the copper ion, into the polymer matrices produced polymers with good thermal stability and mechanical properties. The polymer showed good thermal stability compared to the DGEBA-DDM (DDM: 4,4’-diaminodiphenylmethane) system. The copper-containing epoxy polymer obtained at a mole ratio of copper complex:DGEBA (24:100) showed a 2.6% weight loss after heating at 400 °C and had a storage modulus of 6080 MPa at 125 °C, which is comparable to the epoxy-DDM system.

The simultaneous removal of cationic radionuclides, ¹³⁷Cs(I), ⁶⁰Co(II) and ^152+154Eu(III), and a chemically toxic anionic pollutant, the analytical reagent chromotrope 2B (C2B), from simulated mixed radioactive process wastewater (MRPWW) has been investigated using bentonite modified with cetyltrimethylammonium bromide. Modification was confirmed by elemental analysis, X-ray diffraction and infrared spectroscopy. Bentonite partially modified to 78% of the cation exchange capacity (PMB) was found capable to adsorb adequately both C2B and the radionuclides from aqueous solutions. Detailed batch kinetics and isotherm studies for removal of C2B singly and the radionuclides simultaneously were performed. The C2B and radionuclides kinetics conform to pseudo-first-order rate equation and the adsorption isotherms are treated with Freundlich and Langmuir models. Thermodynamic parameters were evaluated. Results suggest physisorption and ion-exchange as the principal uptake mechanism for C2B and the radionuclides, respectively. High simultaneous removal was obtained for C2B (≈ 100%) and each of the test radionuclides (>99%) from the simulated MRPWW.

Imidazo[2,1-b][1,3,4]thiadiazoles (4a-g) were synthesized from 3,4,5-trimethoxy benzoic acid and thiosemicarbazide. Reaction of 4 with Vilsmeier-Haack reagent yielded imidazo [2,1-b][1,3,4] thiadiazole–5-carbaldehyde derivatives (5a-g). Obtained imidazo[2,1-b][1,3,4] thiadia zoles-5-carbaldehydes were subjected to Knoevenagel condensation with 2-(2,4-dioxothia zolidin-3-yl)acetic acid (1) and 2-(4-oxo-2-thioxothiazolidin-3-yl)acetic (2) in the presence of catalytic amount of piperidine and acetic acid to afford imidazo[2,1-b][1,3,4]thiadiazoles (6a-g) and (7a-g), respectively. The structures of the newly synthesized compounds were confirmed by IR, NMR and elemental analyses. All compounds were screened for their antibacterial and antifungal activities. Some of the compounds displayed good antibacterial and antifungal activity.

The one-pot three-component coupling reaction of phenylacetylene, aldehyde and amine derivatives in the presence of ferric hydrogensulfate, [(Fe(HSO₄)₃], as an efficient heterogeneous catalyst is reported. The catalyst displayed high activity and afforded the corresponding propargylamines in good to excellent yields. This method provides the wide range of substrate applicability. Heterogeneous nature of the catalyst made it reusable for further chemical reactions.

It is more economic to apply photodegradation of organic pollutants in presence of the visible light irradiation (sunlight) than applying more costfull ultraviolet lamps. Hence, platinum 1,10-phenanthroline complex has been prepared and tested as a photosensitizer for photodegrading 4-chlorophenol in water, which has been found almost completely achieved (98.5 %) after three hours of visible irradiation. Nevertheless, irradiation at 364 and 254 nm exhibits lower efficiencies. At visible irradiation, the platinum complex gives the highest activation of singlet state oxygen formation (¹O₂) compared to 364 and 254 nm irradiation as supported by electron para-magnetic resonance data. On the other hand, the behavior of formation and disappearance of photodegradation intermediates: hydroquinone, benzoquinone, hydroxybenzoquinone, using the platinum complex applying the three current irradiations are found to supports these findings. However, organic acids have accumulated as a function of irradiation time and hence considered to be rate-controlling.

Cyclic voltammetric behaviour of three flavonoids: quercetin, morin and rutin was investigated for their interaction with DNA at pH = 4.7 and pH = 7.4 at body temperature (310 K), using glassy carbon electrode. The diffusion coefficients of the free and DNA bound forms of the flavonoids were evaluated using Randles–Sevcik equation. The binding parameters like binding constant, binding site size and binding free energy were also determined from voltammetric data. Moreover, the binding modes of flavonoids with DNA were evaluated from viscommetric analysis. A comparatively high value of binding constant, binding site size and diffusion coefficients for quercetin reveals its stronger binding with DNA under physiological conditions. The negative values of ∆G indicate the spontaneity of binding of flavonoids with DNA.

A simple, selective, precise and stability indicating high performance thin layer chromatographic method has been established and validated for analysis of manidipine hydrochloride in bulk. The compound was analyzed on aluminium backed silica gel 60 F₂₅₄ plates with methanol:water, 8.5:1.5 (v:v) as mobile phase. The system was found to give compact spots for manidipine dihydrochloride (R_F=0.75). Densitometric analysis was performed at 230 nm. Regression analysis data for the calibration plot indicated good linear relationships between response and concentration over the range of 500-3000 ng/spot. The correlation coefficient, r² was 0.998. The values of slope and intercept of the calibration plot were 2785.5 and 62.314, respectively. The method was validated for precision, recovery and robustness. The limits of detection and quantification were 20 and 50 ng, respectively. Manidipine dihydrochloride was subjected to acid, base, peroxide and sunlight induced degradation. In stability test the drug was susceptible to acid and base hydrolysis, oxidation and photodegradation. Statistical analysis proved that the method is repeatable, selective and accurate for manidipine. Because the method could effectively separate the drug from their degradation products, it can be used as a stability indicating method.

The synthesis of 8-hydroxy-6-methoxy-3-pentyl-1H-isochromen-1-one (1) isolated from the stem and root bark extracts of Tessmannia densiflora has been described. The reaction of 3,5-dimethoxyhomophthalic anhydride (2) with hexanoyl chloride in the presence of 1,1,3,3-tetramethylguanidine and triethylamine afforded 6,8-dimethoxy-3-pentylisocoumarin (3). Regioselective demethylation of the latter using anhydrous aluminum chloride furnished the title isocoumarin (1).

Thin layer cycle voltammetry is one of the most efficient methods to investigate liquid/liquid interface. The advantages of this approach lie on its simplicity and effectiveness. The paper represents the progress that has been made in experiments and theories, analyzing the factors that affect rate constants and discussing how to get steady-state currents.