Medhat A. Shaker

Synthesis, computational, spectroscopic, thermal and antimicrobial activity studies on some metal-urate complexes

New sixteen uric acid metal complexes of different stoichiometry, stereo-chemistries and modes of interactions were synthesized using different metals Cr, Mn, Fe, Co, Ni, Cu, Cd, UO(2), Na and K. The synthesized complexes were characterized by elemental analysis, spectral (IR, UV-Vis and ESR) methods, thermal analysis (TG, DTA and DSC) and magnetic susceptibility studies. Molecular modeling calculations were used to characterize the ligation sites of the free ligand. Furthermore, quantum chemical parameters of uric acid such as the energies of highest occupied molecular orbital (E(HOMO)), energies of lowest unoccupied molecular orbital (E(LUMO)), the separation energy (ΔE=E(LUMO)-E(HOMO)), the absolute electronegativity, χ, the chemical potential, P(i), the absolute hardness, η and the softness (σ) were obtained for uric acid. Eight different microbial categories were used to study the antimicrobial activity of the free ligand and ten of its complexes. The results indicate that the ligand and its metal complexes possess antimicrobial properties. The stoichiometry of iron-uric acid complex was studied by using different spectrophotometric methods.

Dynamics and thermodynamics of toxic metals adsorption onto soil-extracted humic acid.

Humic acids, HA represent a large portion of natural organic matter in soils, sediments and waters. They are environmentally important materials due to their extensive ubiquity and strong complexation ability, which can influence heavy metal removal and transportation in waters. The thermodynamics and kinetics of the adsorption of Cd(II) and Cr(VI) onto solid soil-derived HA have been investigated at optimum conditions of pH (5.5±0.1), metal concentration (10-100mmolL(-1)) and different temperatures (293-323K). The suitability of adsorption models such as Freundlich and Langmuir to equilibrium data was investigated. The adsorption was well described by Langmuir isotherm model in multi-detectable steps. Adsorption sites, i (i=A, B, C) with different capacities, νi are characterized. The stoichiometric site capacity is independent of temperature and equilibrium constant, Ki. Adsorption sites A and B are selectively occupied by Cr(VI) cations while sites A and C are selectively occupied by Cd(II) cations. The thermodynamic parameters of adsorption systems are correlated for each adsorption step. The adsorption is endothermic, spontaneous and favorable. Different kinetic models are applied and the adsorption of these heavy metals onto HA follows pseudo-second-order kinetics and equilibrium is achieved within 24h. The adsorption reaction is controlled by diffusion processes and the type of the adsorption is physical.

Optimization, isotherm, kinetic and thermodynamic studies of Pb(II) ions adsorption onto N-maleated chitosan-immobilized TiO₂ nanoparticles from aqueous media.

Chitosan, CS was chemically engineered by maleic anhydride via simple protocol to produce N-maleated chitosan, MCS which immobilized on anatase TiO2 to synthesize novel eco-friendly nanosorbent (51±3.8 nm), MCS@TiO2 for cost-effective and efficient removal of Pb(II) ions from aqueous media. The chemical structure, surface properties and morphology of MCS@TiO2 were recognized by FTIR, (1)H NMR, XRD, TEM, DLS and zeta-potential techniques. The relations between %removal of Pb(II) and different analytical parameters such as solution acidity (pH), MCS@TiO2 dosage, time of contact and initial Pb(II) concentration were optimized using response surface methodology (RSM) and Box-Behnken design (BBD) statistical procedures. The fitting of the experimental data to four different isotherm models at optimized conditions was carried out by various statistical treatments including the correlation coefficient (r), coefficient of determination (r(2)) and non-linear Chi-square (χ(2)) test analyses which all confirm the suitability of Langmuir model to explain the adsorption isotherm data. Also, statistics predicted that the pseudo-second-order model is the optimum kinetic model among four applied kinetic models to closely describe the rate equation of the adsorption process. Thermodynamics viewed the adsorption as endothermic and feasible physical process. EDTA could release the sorbed Pb(II) ions from MCS@TiO2 with a recovery above 92% after three sorption-desorption cycles. The novel synthesized nanosorbent is evidenced to be an excellent solid phase extractor for Pb(II) ions from wastewaters.

Solvatochromaticity and pH dependence of the electronic absorption spectra of some purines and pyrimidines and their metal complexes

The solvatochromic responses of uric acid (Ua), 6-amino-2-thiouracil (ATU) and a series of their complexes dissolved in ten solvents of different polarity have been measured. The solvent-dependent UV/Vis spectroscopic absorption maxima, λ(max), are assigned to the corresponding electronic transitions and analyzed using SPSS program, regression analysis and Kamlet and Taft methods. The observed solvatochromism is discussed using various solute-solvent interaction mechanisms. The electronic absorption spectra of ATU were investigated in aqueous buffer solutions of varying pH and utilized for the determination of dissociation constants. The ranges of pH, where individual ionic species are predominant have been determined.

MP2 and DFT theoretical studies of the geometry, vibrational and electronic absorption spectra of 2-aminopyrimidine

The conformational stability, relative IR intensities and harmonic vibrational wave numbers of 2-aminopyrimidine in the electronically ground state have been investigated by a comparison of the experimental and calculated spectroscopy. Two ab initio theories, Möller–Plesset second-order perturbation theory and density functional theory DFT-B3LYP methods, were used at different extended basis sets. The vibrational wave numbers calculated with DFT method were scaled using two different methods. The solvent effects on the structural parameters were also extensively studied. A comparison between the computed structural parameters of the investigated compound and the experimental data was shown. A good agreement between the theoretical results and the experimental data was found.

Lauryl sulfate@magnetic graphene oxide nanosorbent for fast methylene blue recovery from aqueous solutions

Abstract Lauryl sulfate is utilized to functionalize magnetic graphene oxide (MGOLS) for fast removal of methylene blue (MB) using batch sorption experiments. The effects of different analytical parameters including medium pH, equilibration time, MGOLS dosage, initial MB concentration and temperature on the % MB removal are investigated. Among different isotherm and kinetic models, the experimental data were best fitted to the Langmuir and pseudo-second-order rate equations. The maximum Langmuir loading capacity reaches 624.42 mg g−1 for MGOLS under optimal conditions. Sorption kinetic of MGOLS is very fast: Approximately 96% of dye extraction was recorded within the first 2 minutes of this sorption process. The sorption mechanism is proposed and the feasibility, thermic and entropic characteristics were evaluated. Sorption and desorption performances of MGOLS are maintained almost constant over five cycles of sorption/desorption. The results concluded MGOLS as an efficient extractor for fast and feasible recovery of MB from aqueous matrices. Graphical Abstract

Kinetic and thermodynamic profile of solifenacin succinate sorption from wastewater by humic acid-coated TiO2 nanoparticles: An approach towards Green Chemistry

C Nanocrystals (NCs) are solution-grown, nanometer-sized, inorganic particles that are stabilized by a Self-Assembled Monolayer (SAM) of surfactants attached to their surface. NCs possess useful properties that are controlled by their composition, size and shape, and the SAM coating ensures that these structures are easy to fabricate and process further into more complex structures. This combination of features makes colloidal NCs attractive and promising building blocks for advanced materials, green chemistry, and specifically in catalysis. Colloidal NCs are potentially able to blend the many advantages of heterogeneous catalysis with the versatility of homogeneous catalysts. This presentation will focus on: (i) Advantages of continuous-flow processing in in-situ preparation of Fe3O4 NCs from a Fe (e.g., FeCl2·4H2O, FeCl3·6H2O, and Fe(OAc)2) precursor using hydrazine hydrate as the reducing agent to catalyze the organic reactions (e.g., reduction of nitroarenes) and (ii) Shape-selective synthesis of TiO2 colloidal NCs and their application in a continuous-flow photocatalytic transformation.P have evolved bioactive metabolites of great complexity and potency, however the compounds found in the wild-type plant representonly a fraction of the genomic capability of the species, If we could only “tell” plants what bioactivity we required from them, this would open a new chapter in plant drug discovery. Naprogenix’ novel technology achieves this by “evolving” plant biosynthesis, via mutation and selection, toward metabolites targeted on specific proteins. This can increase yields of known compounds, or generate active metabolites which are not detectable in the wild-type plant. Proof of concept has used several plant species and several targets, but this example describes the production of inhibitors of the human dopamine transporter (DATa molecular target in Parkinson’s disease) in cell cultures of a native Lobelia species. This plant contains small amounts of lobinaline, a previously uninvestigated inhibitor of the DAT, which would be a conventional lead compound except that it is a complex binitrogenous alkaloid with 5 chiral centers and no known chemical synthesis. However, this complexity makes it an excellent example of the value of target-directed biosynthesis. First, we expressed the human DAT target protein in cells of this species, making them susceptible to a cytotoxin which is accumulated intra cellularly by the DAT. Mutants which are overproducing inhibitors of the DAT now have a survival advantage when exposed to the toxin. About 1/300 gain-of-function mutants survived selection, providing 120 toxin-resistant individual clones. Extracts from 41 of these showed greatly increased levels of DAT inhibition, and 16 of these were overproducing lobinaline. However, the other 25 clones were overproducing other metabolites, 8 of which were not detectable in the wild-type plant. Several of these showed chemical similarity to lobinaline and putatively represent a biosynthetic active compound library. In this way it is possible to tell a plant species to synthesize metabolites with a specific bioactivity and, by selection, the plant cell also does the initial pharmacological screening. Mankind can become the orchestrator of plant biosynthetic evolution rather than its passive beneficiary.T chemical fixation and activation of CO2 by metal complexes may lead to certain devices that can eliminate the CO2 present in the air and hence controlling its concentration and reducing the environmental problems due to the greenhouse effect and global warming. This can be achieved by designing “inexpensive inorganic compounds” that rapidly and effectively catalyze the atmospheric CO2 fixation. In slightly basic solutions, the atmospheric fixation of CO2 by metal complexes, through hydroxo-species, afford the carbonato metal complexes. A number of simple N-donor ligands and multi-dentate Schiff bases containing two or three N-atoms, phenolic and alkoxy groups are to used synthesize a series of 3d(M(II) = Ni, Cu, Zn) and 4f(Ln(III) = lanthanides) complexes. The incorporation of lanthanide (III) ion into the skeleton of3d complexes to produce 3d-4f heteronuclear metal complexes should increase the affinity of the compounds for CO2 fixation into the Ln (III) pocket (Ln3+ ion is a hard Lewis acid which strongly bound to hard Lewis bases; O-donor species such as CO32ion). The carbonato complexes are not only interesting from the structural and geometrical points of view, but alsomay result in the discovery of interesting Single Molecular Magnets (SMM’s) which can be used to increase the memory of the computers. The resulting carbonato-bridged compounds can also be used to prepare some useful organic compounds. Recent developments concerning synthesis and structure characterization of different coordination carbonato-bridged compounds, magnetic properties and their potential applications will be addressed.T global drive towards the reduction of energy consumption, emissions and minimisation of waste are increasingly important and becoming major technological, political and societal issues. A promising approach to address the current challenges is to adopt green chemistry and sustainability during process design, innovation, integration and optimisation. The use of green chemistry and process intensificationin the processing of polymeric, inorganic and composite materials will be described. The emerging of eco-friendly and sustainable non vacuum chemical processing technologies will be presented for the production of nanostructured materials and high value added superthin/thin films and thick coatings. These processes that are not only low cost, less polluting, conserve energy, reduce waste but also increase efficiency and enhance product performance. Case studies leading to sustainable products and increasing profits for a variety of applications, including fine chemicals, clean energy, engineering, and biomedical sectors will be presented.S succinate, a pharmaceutical used in industry is an organic contaminant that has the potential to create environmental toxicity and pollution problems and cause health risks for humans as well as biota. Natural organic matters, such as humic acid, HA in aquatic environments can increase the stability of nanoparticles. In this work, solifenacin succinate in wastewater was removed by a biosorption method using HA-coated TiO2 nanoparticles. The FTIR, EDX and FESEM studies were used to characterize the fabricated nanosorbents. Mathematical adsorption and kinetics models representing the biosorption processes were formulated, supporting the Langmuir isotherm and pseudo-second order rate equation for the adsorption of aqueous solifenacin succinate using batch mode experiments. All parameters influencing the removal efficiency such as: Adsorbent dose, medium pH, initial adsorbate concentration and temperature were considered for optimizing the experimental conditions. Thermodynamic study was carried out to describe the feasibility, thermic and entropic behaviors of the investigated biosorption process. The results showed that the method developed here is very effective for the removal of solifenacin succinate from an aqueous environment.C is one of the most powerful tools of green chemistry, enabling reactions with lower energy consumption and providing new pathways for bond formation. Catalytic C-H functionalizations, in particular, are powerful methodologies for installing functional groups in previously non-functionalized positions of a molecule and the use of catalyst directing groups has enabled a wide variety of exciting bond formations with remarkable selectivities and broad applicability. One of the greatest current challenges in this research area is how to catalyze analogous C-H functionalization reactivity without the presence of catalyst directing groups. Such transformations often suffer from the lack of a strong catalyst pre-coordination, which can lead to lower reactivities. The research described in this presentation will showcase basic principles of catalyst and methodology design to achieve non-directed C-H functionalizations and provide insights into reactivity and selectivity-determining factors for the C-H aminations of arenes and the alpha-C H oxidation of tertiary amines.P synthesis has received significant recent research interest in the context of ideal synthesis and green sustainable chemistry. In general, organolithium species react with electrophilic functional groups very rapidly, and therefore such functional groups should be protected before an organolithium reaction, if they are not involved in the desired transformation. If organolithium chemistry could be free from such a limitation, its power would be greatly enhanced. A flow microreactor enables such protecting-group-free organolithium reactions by choosing the appropriate residence time and the reaction temperature. Organolithium species bearing alkoxycarbonyl, nitro, and ketone carbonyl groups can be generated and reacted with various electrophiles using a flow-microreactor system. In addition, asymmetric carbolithiation of conjugate enzymes can be also achieved without the epimerization of a configurationally unstable chiral organolithium intermediate based on precise control of the residence time using a flow microreactor. In this presentation, we report that a flow microreactor system enables the generation of various unstable organolithium compounds.D green catalysts is the key for the development of next-generation technologies to convert biomass molecules into liquid fuels or other value-added chemicals. Recently, a few hydrogenation catalysts have been developed to effectively drive biomass conversions. However, designing hydrogenation catalysts that can work under mild conditions such as low pressure, low temperature, and green solvent remains a challenge. To provide the insights for designing greener hydrogenation catalysts, we explored the thermodynamics conditions (e.g., temperature, pressure, and solvents) for various hydrogenation or hydrogenolysis reaction based on biomass model compounds, by combining the Ab initio quantum chemistry calculations and experimental explorations. Our results show that thermodynamically it is indeed possible to design greener catalysts (e.g., robust and economic catalysts that work under mild conditions) for converting biomass molecules into value-added chemicals. In addition, we showed that optimal hydrogenation catalysts could be sought under the guidance of inverse design methods.We report densities, ijk ρ and speeds of sound, ijk u of 1-ethyl-3-methylimidazolium tetrafluoroborate (i) + water (j) + formamide or N,N- dimethylformamide (k) ternary mixtures over entire composition range at 293.15, 298.15, 303.15, 308.15 K. The heat capacities, Cpof 1-ethyl-3-methylimidazolium tetrafluoroborate, water, formamideand N,N- dimethylformamide have also been measured at 293.15, 298.15, 303.15, 308.15 K using micro differential scanning calorimeter (Model -µDSC 7 Evo). The measured ijk ρ and ijk u data have been utilized to determine their excess molar volumes, E ijk V andThe presence of bark in wood can constitute a serious limitation for the bioconversion of forest residues into bioethanol, especially due to the presence of high content of extractives, which may inhibit ethanol fermentation. However, a perfectly debarked wood chip may not represent an economical source of carbohydrates for industrial applications. An option is to utilise bark as a source of renewable energy and chemicals, within a biorefinery platform. In this study, enzymatic hydrolysis and bioethanol fermentation of Douglas-fir bark were studied before and after organosolv and diluted acid pre-treatments performed at 150°C and 180°C. The recovery of valuable platforms molecules was also determined after pre-treatment. Results showed that an organosolv-free acid pre-treatment performed at 150°C gave the best results in terms of platforms molecules recovery (40% w/w) and bioethanol yield (2 g.100g-1 total solids). However, the low glucose and ethanol yields obtained (6% and 16% of the theoretical values, respectively) confirmed that enzymatic hydrolysis remains the limiting step of bioethanol fermentation from bark. Interestingly, ethanol was produced without inhibition of fermentation from the untreated and pretreated substrates.W have studied in the last 15 years the efficiency of oxime-derived palladacycles as pre-catalysts in carbon-carbon forming reactions such as, Heck, Suzuki, Stille, Hiyama, Ullmann, Sonogashira and Glaser reactions by in situ generation of palladium nanoparticles. Interestingly, they exhibit increasing catalytic activity when water is used as solvent due to the formation of threeand four-palladium atom clusters as has been recently found out by Corma and col. In this talk recent challenge applications of these palladacycles working in aqueous media will be presented. Matsuda-Heck reactions have been performed efficiently in water at rt. In the case of the Suzuki-Miyaura reaction, deactivated aryl chlorides and imidazolylsulfonates can be cross-coupled with boronic acids or potassium trifluoroborates using water as solvent. The copper-free Sonogashira reaction has been also performed with deactivated aryl chlorides and with aryl imidazolylsulfonates under copper-free conditions using water as solvent. The head to head dimerization of terminal alkynes in water allows the steroselective preparation of (E)-1, 4-enynes in the presence of an imidazolinium salt.