Abstract  Organic solvent-free mobile-phase systems in ion-pair reversed-phase partition high-performance liquid chromatography (IPRP-HPLC) are demonstrated; using urea at 3.0 - 7.0 molal (mol kg(-1)) as a modifier in a mobile phase on an octadecylsilanized silica column, four nitrophenolates and metal 4-(2-pyridilazo)resorcinol (PAR) chelates (in PAR chelates system an aqueous mobile phase with 15 wt% methanol was used) were separated rapidly within 6 min at no sacrifice to the separation efficiency. On the addition of urea in the mobile phase, reduced retention times of nitrophenolates and naphthalenesulfonates and also diminution of the height equivalent to a theoretical plate were observed. The addition of urea and guanidium chloride (GuCl) in the mobile phase gave rise to a decrease in the mobile phase volume; in turn, this meant an increased volume of the stationary phase. As the concentration of urea and GuCl in the mobile phase increased, the volume of the mobile phase in the column decreased within about 70% and 40% at 7.0 molal of urea and GuCl, respectively. A decrease in the mobile phase volume suggests an increase in the extent of solvation of the bonded hydrocarbon chain of the stationary phase. The possible explanations for the LC behavior with the urea and GuCl are turned into reduction of hydrophobic interaction in LC processes, solute partitioning and entangling of alkyl chain brushes, with the addition of urea. The water structure breakers, urea and GuCl, most likely affect the solvation states of both solute molecules and the hydrocarboneous stationary phase by changing the nature of the water solvent, which provides a new technique for fine tuning of the LC resolution of the analytes.

Abstract  A simple and reliable RP-HPLC method for the separation and quantitative determination of p-phenylenediamine, p-aminophenol, m-aminophenol, resorcinol, and 2,6-diaminopyridine in commercial oxidation hair dyes was developed. The separation was carried out on a mu -Bondapak C-18 column with methanol-aqueous solution containing 0.1% triethylamine and 0.02 mol 1(-1) NH4Ac (pH = 5.20) (10:90, vol./vol.) as the mobile phase. Without a complex extraction procedure, the method is sufficiently rapid and accurate for routine analyses. Two kinds of commercial hair dye samples were determined successfully.

Abstract  Resorcinol administered at high doses to rodents can disrupt thyroid hormone synthesis and can produce goitrogenic effects. These effects were not seen in a 2-year bioassay at doses of up to 520 mg/kg/day. There are species-specific differences in synthesis, binding, and transport of thyroid hormone that complicate interpretation of goitrogenesis in rodents. Clinical case reports from patients undergoing resorcinol therapy for dermatological indications reveal thyroid side effects when copious amounts of resorcinol-containing ointments are applied to integrity-compromised skin for months to years. Effect levels were greater than 34 mg/kg/day. Occupational epidemiology studies provide no evidence that exposure to resorcinol at levels greater than found in the general environment causes thyroid dysfunction. Studies investigating the relationship between endemic goiter and exposure to "phenolics," including resorcinol, in drinking water do not fulfill accepted scientific criteria for establishing resorcinol as a cause of thyroid disease. Those reports neither quantify exposure levels nor demonstrate dose-response relationships or rule out confounding by the multiple other chemicals present in water supplies, by bacterial contamination of water, or by nutritional factors. A risk assessment comparing potential worst-case exposures to resorcinol through its use in dermatological preparations supports the conclusion that under real-world conditions, human exposures to resorcinol are not expected to cause adverse effects on thyroid function.

Abstract  The adsorption capacity of ciprofloxacin (CPX) was determined on three types of carbon-based materials: activated carbon (commercial sample), carbon nanotubes (commercial multi-walled carbon nanotubes) and carbon xerogel (prepared by the resorcinol/formaldehyde approach at pH 6.0). These materials were used as received/prepared and functionalised through oxidation with nitric acid. The oxidised materials were then heat treated under inert atmosphere (N2) at different temperatures (between 350 and 900°C). The obtained samples were characterised by adsorption of N2 at -196 °C, determination of the point of zero charge and by temperature programmed desorption. High adsorption capacities ranging from approximately 60 to 300 mgCPxgC(-1) were obtained (for oxidised carbon xerogel, and oxidised thermally treated activated carbon Norit ROX 8.0, respectively). In general, it was found that the nitric acid treatment of samples has a detrimental effect in adsorption capacity, whereas thermal treatments, especially at 900 °C after oxidation, enhance adsorption performance. This is due to the positive effect of the surface basicity. The kinetic curves obtained were fitted using 1st or 2nd order models, and the Langmuir and Freundlich models were used to describe the equilibrium isotherms obtained. The 2nd order and the Langmuir models, respectively, were shown to present the best fittings.

Abstract  Adsorption of resorcinol and other phenolic derivatives on pristine multi-walled carbon nanotubes (MWCNTs) and HNO(3) treated MWCNTs has been investigated in attempt to explore the possibility to use MWCNTs as efficient adsorbents for pollutants. MWCNTs showed higher adsorption ability in a rather wide pH range of 4-8 for resorcinol, while decreased uptake capacity was found for acid-treated MWCNTs. Other phenolic derivatives such as phenol, catechol, hydroquinone and pyrogallol were employed to study the influence of the number and position of hydroxyl groups on the adsorption capacity. The amounts adsorbed by MWCNTs increased with the increasing number of hydroxyl. The substitution of phenol with a hydroxyl in meta-position leads to a much higher absorption ability than substitution in ortho- or para-position, which suggested that MWCNTs possess a great potential in removal of resorcinol from water, as well as the other phenolic derivatives. (c) 2007 Elsevier B.V. All rights reserved.

Abstract  The acidity constants of Alizarine Red S were determined spectrophotometrically at 25 degrees C and at constant ionic strength 0.1 M (KNO3) in pure water as well as in aqueous media containing variable mole percentages (5-70%) of organic solvents. The organic solvents used were methanol, ethanol, N,N-dimethyl formamide (DMF), dimethyl sulfoxide (DMSO), acetonitrile and dioxan. The acidity constants of all related equilibria are estimated using the whole spectral fitting of the collected data to an established factor analysis model. DATAN program was applied for determining of acidity constants and pure spectra of different form of Alizarine Red S. The obtained results indicated that acidity constants decrease as the content of an organic solvent in the medium increases. There are linear relationship between acidity constants and the mole fraction of various organic solvents in the solvent mixtures. Effect of various solvents on acidity constants and pure spectrum of each component are also discussed.

Abstract  Fluorescence resonance energy transfer (FRET) was employed to monitor the dynamics of hydrogen-bonded hexameric assemblies formed from resorcin[4]arenes and pyrogallol[4]arenes. Studies were designed to provide further insights into the degree of assembly and stability of these self-assembled capsules at the micro- to nanomolar concentration ranges that are not accessible by NMR studies. The results of this investigation reveal factors that influence the self-assembly of these macrocycles into hexameric capsules. Pyrogallolarenes are very sensitive to the concentration of mixing, with an increase in the equilibration half-life from 36 min at 250 nM to 156 min at 10 microM. The resorcinarenes showed little difference in exchange rates over the same concentration range. The temperature of mixing of the macrocycles was found to be important for both systems with a 12-fold increase in exchange rates over a 20 degree range for the pyrogallolarenes and a 2-fold rate increase for the resorcinarenes over the same temperature range. The stability of the capsules to polar additives such as methanol was probed, with the pyrogallolarenes requiring a higher percentage (1.6% v/v in dichloromethane) of methanol to disassemble the capsules than the resorcinarenes (1.0% v/v in dichloromethane). Pyrogallolarenes assemble in both anhydrous and wet solvents whereas water-saturated solvents are necessary to facilitate the formation of resorcinarene capsules. In addition to these studies, evidence of strict self-sorting in the formation of distinct pyrogallolarene and resorcinarene hexamers was obtained.

Abstract  A novel flow injection analysis (FIA) system suitable for measurement of S-nitrosothiols (RSNOs) in blood plasma is described. In the proposed (FIA) system, samples and standards containing RSNO species are injected into a buffer carrier stream that is mixed with the reagent stream containing 3,3'-dipropionicdiselenide (SeDPA) and glutathione (GSH). SeDPA has been shown previously to catalytically decompose RSNOs in the presence of a reducing agent, such as GSH, to produce nitric oxide (NO). The liberated NO is then detected downstream by an amperometric NO sensor. This sensor is prepared using an electropolymerized m-phenylenediamine (m-PD)/resorcinol and Nafion composite films at the surface of a platinum electrode. Using optimized flow rates and reagent concentrations, detection of various RSNOs at levels in the range of 0.25-20 μM is possible. For plasma samples, detection of background sensor interference levels within the samples must first be carried out using an identical FIA arrangement, but without the added SeDPA and GSH reagents. Subtraction of this background sensor current response allows good analytical recovery of RSNOs spiked into animal plasma samples, with recoveries in the range of 90.4-101.0%.

Abstract  A competitive spectrophotomeric nlc method has been used for the study of complexation between Cu2+, Zn2+ and Cd2+ (M) and 18-crown-6(18 CS, B) in methanol using 4-(2-thiazolylazo) resorcinol (TAR, NL) as the colorimetric complexant. Absorption spectra of the species in the M-TAR-18 Cb system at various concentrations of 18C6 showed no formation of ternary complex; MLB;, aand the stoichiometry of the resulting complexes was found to be 1:1 under the condition used The formation constants of bath types of complexes (ML and MB) were determined using the conditional formation constant of ML complexes at Constant acidity in the absence (K-ML') Land Presence (K-M'L') Of 18C6. The results showed that the K-MB values increased in the order of Cu2+

Abstract  The electronic absorption spectra of 4-(4,6-dimethylpyrimidin-2-ylazo)benzene-1,3-diol have been studied in organic solvents of different polarities as well as in buffer solutions of varying pH. The observed UV-vis absorption bands are assigned to the corresponding electronic transitions. The effect of methanol ratio on the pK-value is discussed. Also, semiemperical molecular orbital calculations at the AM1 level have been performed to investigate the molecular and electronic structures of the free ligand in the ground state. According to these calculations, an intramolecular hydrogen bond leads to increasing of the molecular stability. The important bands in the IR spectrum as well as the main signals in the (1)H NMR spectrum are also assigned. The interaction of Cu(II) ion with the titled azo-dye in solution is studied spectrophotometrically and conductometrically. Optimization of the various experimental conditions is also described. Beer's law is obeyed in the range 0-11.43 ppm while that obtained applying Ringbom is 1.26-6.61 ppm. The use of the titled azo-dye as an indicator for determination of Cu(II) is considered. The solid Cu(II) complexes are synthesized and characterized by spectral, magnetic, conductance and thermal studies (TGA and DTA). The results indicate the formation of 1:1 and 1:2 (M:L) complexes. The kinetic parameters (n, E, A, DeltaS, DeltaH and DeltaG) of the thermal decomposition stages were computed and discussed.

Abstract  Equilibrium swelling of natural rubber composites containing aluminium powder has been investigated in a series of aromatic hydrocarbon solvents, such as benzene, toluene, xylene, and mesitylene. These composites were vulcanized by four vulcanizing systems, viz. conventional, efficient, dicumyl peroxide, and a mixture, consisting of sulfur and dicumyl peroxide. In each system, the effect of aluminium powder with and without bonding agent was studied. The results showed that addition of bonding agent reduced the swelling considerably, and its effect is more pronounced in the conventional system due to increased adhesion. The dependence of the diffusion coefficient on the crosslinking system and the solvent–polymer interaction parameter were calculated from diffusion data. These results are also indicative of the improved adhesion with hexa-resorcinol–silica bonding system in these composites.

Abstract  The acidity constants of some newly synthesized Schiff base derivatives were determined by hard-model based multivariate data analysis of the spectrophotometric data in the course of pH-metric titration in 50% (v/v) methanol-water binary solvent. The employed data analysis method was also able to extract the pure spectra and pH-dependent concentration profiles of the acid-base species. The molecules that possess different substituents (both electron donating and withdrawing) on the ortho-, meta- and para-positions of one of the phenyl ring showed variable acidity constants ranging from 8.77 to 11.07 whereas the parent molecule had an acidity constant of 10.25. To investigate the quantitative effects of changing of substitution pattern on the acidity constant, a quantitative structure-property relation analysis was conducted using substituent constants and molecular descriptor. Some models with high statistical quality (measured by cross-validation Q(2)) were obtained. It was found that the acidity constant of the studied molecules in the methanol-water mixed solvent not only is affected by electronic features of the solutes but also by the lipophilic interaction between methanol part of solvent and the deprotonated solutes.

Abstract  The benzo[de]benzo[4,5]imidazo[2,1-a]isoquinolin-7-one (1) shows solvent dependent fluorescence emission. The compound shows quenching of fluorescence emission on interaction with polyhydroxy compounds such as 1,3-dihydroxybenzene, 1,4-dihydroxybenzene. The result on fluorescence quenching is attributed to the hydrogen bonding interactions. Similar observation of fluorescence quenching by protic solvent is observed with isoindolo[2,1-a] perimidin-12-one (2). In the case of 2-(2-amino-phenyl)-isoindole-1,3-dione (3) enhancement of fluorescence emission in methanol solution is observed over benzene solution. This is explained on the basis of intermolecular hydrogen bonding. The crystal structure of adduct of 1 with 1,3-dihydroxybenzene, 1,4-dihydroxybenzene respectively and 3 are reported.

Abstract  Fluorophoreappended resorcin[4]arenebased cavitands having pyrene 2 and anthracene 3 moieties attached to the rims were prepared by short synthetic routes. Both undergo reversible temperature and acid CF3COOD induced vasekiteswitching as evidenced by 1H NMR spectroscopy. The 1H NMR spectra also suggest that suitably sized solvents, such as [D8]toluene, efficiently solvate the cavity, reducing the conformational flexibility. In [D12]mesitylene, both cavitands undergo remarkably stable hostguest inclusion complexation with cycloalkanes. The larger cavity of 3preferentially hosts cyclohexane, whereas the smaller cavity of 2forms the most stable complex with cyclopentane. The propensity for the cavitands to facilitate stacking between the chromophores was confirmed by both 1H NMR and fluorescence spectroscopy. The interchromophoric interaction is strongly solventdependent: stacking between the pyrene moieties of 2is not as efficient in [D8]toluene, as it solvates the inner cavity and prevents the two chromophores from approaching each other. Fluorescence studies revealed an unexpectedly large conformational flexibility of the cavitand structures both in the vase and kite forms, which was further confirmed by molecular dynamics simulations. Excimer formation is most preferred in [D12]mesitylene when the cavities are empty, whereas efficient solvation or guest binding in the interior spaces reduces the propensity for excimer formation. The observed high conformational flexibility of the cavitands in solution explains previous differences from the behavior of related systems in the solid state. This study shows that the rigid, perfect vase and kite geometries found for bridged resorcin[4]arene cavitands in the solid state are largely a result of crystal packing effects and that the conformational flexibility of the structures in solution is rather high.

Abstract  The controllable switching of suitably bridged resorcin[4]arene cavitands between a "vase" conformation, with a cavity capable of guest inclusion, and a "kite" conformation, featuring an extended flattened surface, provides the basis for ongoing developments of dynamic molecular receptors, sensors, and molecular machines. This paper describes the synthesis, X-ray crystallographic characterization, and NMR analysis of the "vase-kite" switching behavior of a fully pyrazine-bridged cavitand and five other mixed-bridged quinoxaline-bridged cavitands with one methylene, phosphonate, or phosphate bridge. The pyrazine-bridged resorcin[4]arene cavitand displayed an unexpectedly high preference for the kite conformation in nonpolar solvents, relative to the quinoxaline-bridged analogue. This observation led to extensive solvent-dependent switching studies that provide a detailed picture of how solvent affects the thermal vase-kite equilibration. As for any thermodynamic process in the liquid phase, the conformational equilibrium is affected by how the solvent stabilizes the two individual states. Suitably sized solvents (benzene and derivatives) solvate the cavity of the vase form and reduce the propensity for the vase-to-kite transition. Correspondingly, the kite geometry becomes preferred in bulky solvents such as mesitylene, incapable of penetrating the vase cavity. As proposed earlier by Cram, the kite form is preferred at low temperatures due to the more favorable enthalpy of solvation of the enlarged surface. Furthermore, the kite conformation is more preferred in solvents with substantial hydrogen-bonding acidity: weak hydrogen-bonding interactions between the mildly basic quinoxaline and pyrazine nitrogen atoms and solvent molecules are more efficient in the open kite than in the closed vase form. Vase-to-kite conversion is entirely absent in dipolar aprotic solvents lacking any H-bonding acidity. Thermal vase-kite switching requires fully quinoxaline- or pyrazine-bridged cavitands, whereas pH-controlled switching is also applicable to systems incorporating only two or three such bridges.

Abstract  4-(5-H/methyl/chloro/nitro-1H-benzimidazol-2-yl)-benzene-1,3-diol (HL(X): X=1-4) ligands and HL(1) complexes with Fe(NO(3))(3), Cu(NO(3))(2), AgNO(3), Zn(NO(3))(2), K(2)PdCl(4) and HAuCl(4) have been synthesized and characterized. The structures of the compounds were confirmed on the basis of elemental analysis, molar conductivity, magnetic moment, FT-IR, ESI-MS, NMR and UV-visible spectroscopy. The antimicrobial activities of the ligands and the complexes were evaluated using the disk diffusion method in DMSO as well as the minimum inhibitory concentration (MIC) dilution method, against Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Salmonella typhi, Shigella flexneri, Proteus mirabilis and the results are compared with Cefuroxime and Ciprofloxazin. Antifungal activities were reported for Candida albicans, and the results were referenced against Clotrimazole antifungal agents. Pd(II), Ag(I) and Au(III) complexes showed considerable antibacterial and antifungal activity while the ligand itself has no activity.

Abstract  BACKGROUND: The heterocyclic hydrazones constitute an important class of biologically active drug molecules. The hydrazones have also been used as herbicides, insecticides, nematocides, redenticides, and plant growth regulators as well as plasticizers and stabilizers for polymers. The importance of the phenolic quinolyl hydrazones arises from incorporating the quinoline ring with the phenolic compound; 2,4-dihydroxy benzaldehyde. Quinoline ring has therapeutic and biological activities whereas, phenols have antiseptic and disinfectants activities and are used in the preparation of dyes, bakelite and drugs. The present study is planned to check the effect of the counter anions on the type and geometry of the isolated copper(II)- complexes as well as the ligational behavior of the phenolic hydrazone; 4-[(2-(4,8-dimethylquinolin-2-yl)hydrazono)methyl] benzene-1,3-diol; (H2L).

RESULTS: A phenolic quinolyl hydrazone (H2L) was allowed to react with various copper(II)- salts (Cl‾, Br‾, NO3‾, ClO4‾, AcO‾, SO42-). The reactions afforded dimeric complexes (ClO4‾, AcO‾ ), a binuclear complex (NO3‾ ) and mononuclear complexes (the others; Cl‾, Br‾, SO42-). The isolated copper(II)- complexes have octahedral, square pyramid and square planar geometries. Also, they reflect the strong coordinating ability of NO3‾, Cl‾, Br‾, AcO‾ and SO42- anions. Depending on the type of the anion, the ligand showed three different modes of bonding viz. (NN)0 for the mononuclear complexes (3, 4, 6), (NO)- with O- bridging for the dimeric complexes (1, 5) and a mixed mode [(NN)0 + (NO)- with O- bridging] for the binuclear nitrato- complex (2).

CONCLUSION: The ligational behavior of the phenolic hydrazone (H2L) is highly affected by the type of the anion. The isolated copper(II)- complexes reflect the strong coordinating power of the SO42-, AcO‾, Br‾, Cl‾ and NO3‾ anions. Also, they reflect the structural diversity (octahedral, square pyramid and square planar) depending on the type of the counter anion.