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A new synthesis was developed to prepare engineered biochar derived from phosphorous-rich water hyacinth. The statistical analysis indicated a significant correlation between P content and the removal rates of Pb (II), Cu (II), and Ag (I), revealing the pivotal role of enrich P in the biochar for heavy metals (HM) removal. SEM-EDX, XRD and FTIR analyses validated the presence of P functional groups on the surface of P-biochar. Batch experiments showed that the strong acidic initial solution negatively affected the adsorption of HM ions, and a similar negative impact was observed during Cu (II) adsorption under the high ionic strength conditions. Competitive adsorption experiment confirmed P-biochar's resilience against competing metal ions during the adsorption of HM ions. Pb (II) and Ag (I) adsorption were primarily governed by precipitation/reduction, along with complexation reactions involving P functional groups. Cu (II) adsorption was dominated by complexation between Cu (II) and P functional groups. [ABSTRACT FROM AUTHOR]

Abstract\nNOVELTY STATEMENTThe toxic Cr(VI) contaminating water released from the metallurgical, dyeing, and electroplating industries is getting worse day by day and is extremely hazardous to human health. Thus, the development of a cost-effective, quick, and efficient adsorbent is highly essential for the Cr(VI) decontamination from wastewater. Herein, a microwave-assisted carbon-based composite called Mg-Fe LDH@OPAC was prepared by assembling Mg-Fe LDH onto orange peel-activated carbon (OAPC). Prior to investigating deeply into the adsorption behavior of the composite, the Mg-Fe LDH@OPAC formation was confirmed by using instrumental techniques like FESEM, EDS, Zeta potential, XRD, FTIR, Raman, XPS, and BET analyzer. The material had a high surface area of 143.9 m2/g and showed a good monolayer Langmuir uptake capacity of 118.36 mg/g. Under ideal circumstances, the maximum amount of Cr(VI) was removed within just 120 min and showed high efficiency in the presence of other coexisting anions respectively. The adsorption was accounted by pseudo-second-order kinetics and spontaneous in nature. Ultimately, a possible adsorption mechanism was suggested, confirmed by XPS studies; which showed that oxidation-reduction, electrostatic interaction, and surface complexation reaction were responsible for Cr(VI) adsorption on Mg-Fe LDH@OPAC surface.Environmental contaminants like Cr(VI) in drinking water are highly toxic, and their long-term persistence in the water environment causes mutagenic effects on human beings. We present a novel material for the first time (yet not been reported) by intercalating activated carbon (from a low-cost wedge of orange peel) into Mg-Fe layered double hydroxide (abbreviated as Mg-Fe LDH@OPAC), which has superior hazardous hexavalent chromium metal uptake capability. With the order of SO42->F->CO32->I->PO43->NO3- the as-prepared Mg-Fe LDH@OPAC exhibits strong selectivity toward Cr(VI) in the presence of varied competing ions with a modest drop in removal effectiveness. The combined properties of AC and LDH make Mg-Fe LDH@OPAC potentially efficient adsorbent to remove Cr(VI) from the different water sources and potentially applied in wastewater treatment. [ABSTRACT FROM AUTHOR]

AbstractA portable device for digital image colorimetry (DIC) is reported for the determination of Ca in crude oil emulsions. ASTM D4807 was used for sample preparation for the isolation of saline species containing Ca. DIC was evaluated based on the complexation reactions with Ca using calcein, murexide, and calcon. Partial least squares (PLS) provided the best determination coefficients (higher than 0.990) for all complexing reagents. Significant interference of Mg was observed for the determination of Ca using calcein. PLS models with the lowest root mean square error of cross validation (RMSECV) values were obtained for murexide and calcon for a concentration of 0.250 mmol L−1 at pH of 13. The best conditions for camera focal length were 11 and 2 mm for murexide and calcon. For light intensity, the optimized conditions for murexide and calcon was 180 lux. Stabilities of color complexes over the time were 30 and 15 min for murexide and calcon, respectively. DIC/murexide provided the lowest root mean square error of prediction (RMSEP) and a linear response was observed from 0.5 to 10 mg L−1 Ca and the relative standard deviation (RSD) was lower than 10%. Significant differences were not observed between the results obtained by DIC/murexide and those obtained by microwave-assisted wet digestion (MAWD) with determination by inductively coupled plasma-optical emission spectrometry (ICP-OES). A limit of quantification of 0.50 mg kg−1 Ca were obtained using DIC/murexide. This approach is an alternative and useful method for the determination of Ca in crude oil samples, with advantages of miniaturization, low cost, and ease of operation. [ABSTRACT FROM AUTHOR]

2-Chlorobenzaldehyde thiocarbohydrazone (2-CBTCH) is proved as a novel analytical chelating reagent to developa simple, fast and selective liquid–liquid extractive spectrophotometric method for trace level determination of copper(II). The method was based upon the complexation reaction of copper(II) with 2-CBTCH in ethanol. It instantly forms orange coloured [Cu(II)-2 CBTCH] complex at room temperature, which was quantitatively extracted in 1-butanol and shows maximum absorption at 470 nm. The values of molar absorptivity and Sandell's sensitivity of [Cu(II)-2CBTCH] complex are found to be 0.3429 × 104 Lmol−1 cm−1 and 0.01851 µgcm−2, respectively. The system follows Beer's law up to 17.5 µgmL−1. The stoichiometry of the [Cu(II)-2CBTCH] complex in 1-butanol is determined by Job's method, mole ratio method is 1:2 and was confirmed by log-log plot method. To intuit the peak extraction conditions several experimental factors such as pH, reagent concentration, selection of solvent, shaking time, interference of cations and anions has been studiedwell. The usage of masking agent lifts the selectivity of the present method. The method has been effectively used for the determination of copper(II) in alloy samples, pharmaceutical samples, fertiliser samples and environmental samples such as leafy vegetables and water samples. [ABSTRACT FROM AUTHOR]

Triazine derivatives have attracted increasing attention due to their diverse applications in medicinal chemistry. They have been reported to be remarkably effective compounds regarding their bioactivities. Therefore, the synthesis and identification of new triazine-derived compounds are of interest for their therapeutic effects. Various approaches have been developed to synthesize triazine derivatives. In this review, a considerable number of studies on the synthesis of 1,2,4-triazine derivatives are investigated with 4-amino-3-thioxo-6-substituted-1,2,4-triazin-ones and 4-amino-3-hydrazino-6-substituted-1,2,4-triazin-5-ones as starting materials. Different types of chemical reactions have been applied to the efficient synthesis of 3-thioxo/hydrazino-6-substituted-1,2,4-triazin-5-ones, such as alkylation, acylation, aroylation, elimination, substitution, acidic/basic hydrolysis, oxidation, cyclocondensation, cycloaddition, phosphorylation, and complexation reactions. Interestingly, a set of compounds is identified to possess various biological activities, such as anticancer antibacterial, antifungal, acaricidal, and molluscicidal properties. Also, some 4-amino-3-thioxo-6-substituted-1,2,4-triazin-5-one derivatives are found to form metal complexes, be used as inhibitor probes for mild steel corrosion, prepare a selective sensor for the determination of gadolinium (III) ions in the soil and sediment samples, and demonstrate antibacterial activities. Finally, 4-amino-3-hydrazino-6-methyl-1,2,4-triazin-5-one was used as an ionophore to develop a chromium (III) ion-selective sensor beside the formation of silver complexes. [ABSTRACT FROM AUTHOR]

Some encapsulation process and formulation parameters influence on several physicochemical properties of the encapsulated products. In this study, the influence of the OEO:β-CD ratio and stirring speed on the total oil, surface oil, oil retention, entrapment efficiency, yield, size distribution (d10, d32, and d43), span value, bounding rectangle aspect ratio (BRAR), Feret's aspect ratio (FAR), circularity, smoothness, and opacity of microparticles were examined. The superior entrapment efficiency (95.18%), highest oil retention (79.13%), and lowest surface oil content (10.02 mg oil/g powder microparticles) were achieved at an OEO:β-CD ratio of 0.15 (w/w) and stirring speed of 700 rpm. Likewise, all microparticles showed irregular and elongated shapes, in which the opacity distribution was more influenced. Finally, the obtained FTIR spectra contained OEO bands hidden inside β-CD peaks, indicating the occurrence of a complexation reaction after encapsulation. [ABSTRACT FROM AUTHOR]

The extraction of Nd(III), Eu(III), Am(III), and Cm(III), trivalent lanthanides and actinides in high level nuclear waste, by the extractant N,N-di(2-ethylhexyl)-thio-diglycolamic acid (HDEHSDGA, HA) is investigated via thermochemical and spectroscopic methods. In this study, HDEHSDGA behaves as a conventional mono-basic cation-exchanging ligand extracting Ln(III) and An(III) from nitrate solutions of pH region. The information obtained from the extraction experiments and the spectroscopic analyses indicate that the primary extracted complex species may be MA3 · 2H2O for these four cations and likely for the other trivalent f-elements. In the extracted complexes, the anionic monomer extractant A− coordinates to the metal ions presumably forming bidentate coordination via the carbonyl oxygen atom and one of the oxygen atoms of the carboxylate; it appears that the thio-ether does not directly participate in the complexation reaction. The results ultimately demonstrate that HDEHSDGA does not exhibit significant selectivity for An(III) over Ln(III), in contrast to results reported in a previous study conducted with unpurified extractant. [ABSTRACT FROM AUTHOR]

The supramolecular interaction between Uridine (UR) and β-cyclodextrin (β-CD) has been investigated in liquid, solid, and virtual state. Noncovalent interaction between UR and β-CD in aqueous medium was confirmed by using absorption, fluorescence emission, and time-resolved fluorescence spectroscopy. The solid inclusion complex was prepared using physical mixing, kneading method, and coprecipitation method and it was characterized using FT-IR, SEM, powder X-ray diffraction patterns TG/DSC, and 1H NMR techniques. The stoichiometric ratio of the inclusion complex was found to be 1:1 and the binding constant of the inclusion complex at 303 K were determined using Benesi–Hildebrand plot. The changed in the Gibbs free energy for the complexation reaction was determined and it was found that the complexation process was spontaneous. As the changes in the chemical shift, values of the UR have been observed after the formation of an inclusion complex. The inclusion process is virtually evident by molecular docking studies using the patch-dock server. As the biological application of this complexation, the cytotoxic activity has also been successfully tested against breast cancer cell line which exposed at different concentration for 74 h. [ABSTRACT FROM AUTHOR]

In the present study, the performance of biochar-based filtration bed was assessed to enhance the removal efficiency of Cr(VI), from the pre-treated synthetic tannery wastewater. The pre-treatment of wastewater was carried out with aluminium formate (AF) as a coagulant and 80% Cr(VI) removal was observed which might be due to the formation of carboxylic complexation reaction. The purity of coagulant and the sludge components were validated with XRD analysis and the results revealed the formation of pure aluminium formate compound as well as a clear change in the crystalline structure in the treated sludge. FT-IR spectra demonstrated the carboxylic compound participated in the removal of Cr(VI) during the coagulation process. The pre-treated wastewater having 20 mg/L (residual) Cr(VI) was passed through a three-layered filtration bed containing biochar, which showed complete removal of Cr(VI) ∼ 99.99% by precipitating into bind form under the influence of CaCO3 and formate ions. The possible mechanistic approach might be due to the presence of formate ions in the pre-treated wastewater, the precipitation of Cr(VI) occurred in the form of Cr(OH)2 by the release of bicarbonate (HCO3−), carbonate ion (CO32−) and hydroxide (OH−) ions in the filtration bed. The properties of the biochar were investigated by XRD and FTIR analysis and the results revealed the existence of hydroxyl, carboxyl and carbonyl groups, which participated during the removal of Cr(VI). The results suggest that biochar-based filtration bed could be a promising method for the treatment of pre-treated tannery wastewater. [ABSTRACT FROM AUTHOR]

This paper investigates interaction processes of the Fe3+, Cu2+, Ni2+, and Co2+ cations with humic acids isolated from brown coals of Ekibastuz basin. It was demonstrated that the sorption of heavy metal ions by humic acids (HA) depends on the concentration and nature of cations and decreases in the order of Fe3+ > Cu2+ > Ni2+ > Co2+; while increase in the concentration of humic acids (HA) results in the higher yield of ions and metals. The occurrence of ion exchange and complexation reactions in metal-humic acid systems is confirmed by the appearance of new bands and the shift of the absorption bands corresponding to stretching and deformation vibrations of carboxylate ions, C = O and OH groups. The occurrence of these processes is also evidenced by spectrophotometric data, as well as a decrease in the pH of the solution due to deprotonation of humic acids during these reactions. Thus, based on the data on the degree of sorption of metal cations by humic acids, the results of infra-red spectroscopy and spectrophotometry, it can be concluded that the Fe3+, Ni2+, Co2+, Cu2+ cations interact with HA by the ionic mechanism and by the complexation mechanism with electron-donating functional groups. Electrochemical studies of the Cu2+ – humic acid system carried out by the method of cyclic voltammetry also indicate the occurrence of the interaction of humic acid with copper cations. Modification of humic acid with copper ions shows the electrochemical activity of copper immobilized on the surface of dispersed humic acid, which is important for the implementation of electrocatalytic reactions on modified glassy carbon-humic electrodes. [ABSTRACT FROM AUTHOR]

Pharmacologically active organic ligands (N-[-(4-chlorophenyl) methylene] nicotinohydrazide) synthesized through the condensation of equimolar mixture of anti-mycobacterial agent (nicotinohydrazide) with aromatic aldehyde. The reaction progress and purity of organic ligands were verified by thin layer chromatography. Formation of organic ligands was confirmed with the help of MP, IR, 1H NMR, 13C NMR and elemental analysis. Further formation of complexes of transition elements such as Mn(II), CO(II), Ni(II), Cu(II) and Zn(II) with organic ligand (Schiff base) N-[-(4-chlorophenyl)methylene] nicotinohydrazide were studied by the pH-metric technique at 25 °C, 35 °C and 45 °C in 70% (v/v)ethanol – water medium at 1 M (NaClO4) ionic strength. The stability constants of these binary complexes were evaluated and order of stability constant found as Co (II) < Mn (II) < Ni (II) < Cu (II) < Zn (II). The thermodynamic parameters associated with the complexation reactions also were calculated. It is found that the change in enthalpy (ΔH) and change in Gibb's free energy (ΔG) were negative for all of the systems which suggested that all of the reactions were exothermic. The change in entropy (ΔS) found positive for most of the complexes which indicate in metal-ligand binding process is entropy favorable. [ABSTRACT FROM AUTHOR]

In this work, a zirconium/magnesium-modified bentonite (ZrMgBT) was prepared and characterized by SEM, EDS, XRD and pHPZC. The performance and mechanism of phosphate adsorption onto ZrMgBT was evaluated in detail using batch experiments and 31P NMR. Results showed the adsorption isotherm data were well described by the Langmuir, Freundlich and Dubinin-Radushkevich models, and the kinetic data fitted better to the pseudo-second-order kinetic model than the pseudo-first-order kinetic model. The phosphate adsorption capacity of ZrMgBT was slightly affected by the presence of Na+, K+, Cl−, SO 4 2 − and NO 3 − , but it was enhanced by coexisting Mg2+ and HCO 3 − . The mechanism for phosphate adsorption onto ZrMgBT at pH 7 was mainly the complexation reaction between phosphate and zirconium. In addition, ZrMgBT exhibited more excellent adherence to phosphate than zirconium-modified bentonite (ZrBT). Especially, the maximum monolayer phosphate adsorption capacity for ZrMgBT at pH 7 and 0.5 g/L of adsorbent dosage calculated based on the Langmuir isotherm model (13.0 mg P/g) was 67.5% higher than that for ZrBT. The higher phosphate adsorption capacity for ZrMgBT than ZrBT could be attributed to the higher specific surface area as well as higher Mg2+ releasing ability of the former. The enhancement of phosphate adsorption by the release of Mg2+ from ZrMgBT could be mainly due to the formation of MgHPO 4 0 in the solution firstly and then the adsorption of MgHPO 4 0 on ZrMgBT forming ≡Zr(OPO3H)Mg on the ZrMgBT surface. In general, we conclude that ZrMgBT is a more promising adsorbent for phosphate removal from aqueous solution than ZrBT. [ABSTRACT FROM AUTHOR]

In this research work, a new approach is developed for the extractive determination of chromium. The principle of this approach is based on the complexation reaction between 4-(4ʹ-chlorobenzylideneimino)-3-methyl-5-mercapto-1,2,4-triazole (CBIMMT) in dichloromethane as a complexing reagent and chromium(III) in presence of potassium iodide to form a yellow coloured complex at room temperature. The 1:2:2 [Cr(III)-CBIMMT-iodide] ternary complex was quantitatively extracted in dichloromethane from 2.5 mol L−1 of hydrochloric acid medium which showed maximum absorption intensity at λmax 411 nm and was stable for more than 72 h. The values of molar absorption coefficient and Sandell's sensitivity of the complex were found to be 0.7019 × 104 L mol−1 cm−1 and 0.00748 µg cm−2, respectively. The system adheres to Beer's law from 1.5 to 6.0 µg mL−1; however, Ringbom's plot suggests optimal concentration range was 1.8–5.8 µg mL−1. The limit of detection and limit of quantification of the approach is 0.26 and 0.79 µg mL−1. This approach was successfully used for the determination of chromium from wastewater effluents from the tannery industries (Kolhapur, MS, India), alloy samples and for separation of it from synthetic mixtures. The present experimental approach is apparently much simpler than the conventional method comprising multistep processes. [ABSTRACT FROM AUTHOR]

Density functional theory calculations, using the B3LYP parameterisation, were performed to determine structures, vibrational frequencies, and binding energies for complexation of Ni+ and Ni2+ cations with benzene and naphthalene molecules and clusters. The calculations employed the Stuttgart basis set with ECP pseudo potentials for the Ni cations and basis sets of at least triple ζ plus polarisation, and diffuse quality for C and H. The effect of electron correlation on non-bonded interactions was accounted for by the Grimme GD3 dispersion correction. Counterpoise computations were made for BSSE. Comparison between experiment and theory provide fascinating new insight into the bonding for these prototypical organometallic (OM) complexes. These structures have a sandwich topology, indicating major structural reorganisations occuring when benzene or naphthalene interact with Ni cations. Adiabatic electron affinities and ionisation potentials agree well with experiment when available. Binding energies were also determined, providing insight into the stability of the complexes. The results presented here provide important information for future studies to address additional investigations of both problems of the electronic structure properties of these complexes, as well as the role of the polycyclic aromatic hydrocarbons (PAHs) in the interstellar medium (ISM) and soot formation in combustion. The Ni+/Ni2+ + aromatic organometallic bonding is of the same order of stability as an aromatic C–H bond. Such bonding modifies the IR spectrum of the complexed aromatic molecules by enhancing the 3.3 μm feature and decreasing the C–H bands in the 11–12 μm range (γ C–H). Organometallic complexation reactions may contribute significantly to metal depletion in the ISM. [ABSTRACT FROM AUTHOR]

In this study, we measured the effect of EPS on Cd and proton adsorption behaviors by measuring the extent of adsorption onto biomass with and without the EPS removed via a cation exchange resin. We conducted both Cd adsorption experiments and potentiometric titrations of biomass using three common bacterial species: one Gram-positive (Bacillus subtilis) and two Gram-negative (Shewanella oneidensis, Pseudomonas putida) species. The Cd adsorption experiments were conducted as a function of metal loading in order to probe whether environmentally-low metal loadings lead to different adsorption mechanisms and roles for EPS than the higher metal loadings of most previous adsorption studies. We suspended each biomass sample in a solution of dissolved Cd in 0.01 M NaClO4 at metal loadings of 1, 2, 5, and 74 μmol/g. Surface complexation modeling (SCM) was used to determine stability constants for the important Cd-bacteria complexes, and the effect of metal loading on the resulting calculated stability constant values was determined. In general, the measured bulk Cd adsorption behavior is unaffected by EPS removal. However, our potentiometric titration results suggest that EPS removal does alter the distribution of site types, but not the mass-normalized total site concentration within the biomass. SCM suggests that high affinity sulfhydryl sites control Cd binding under low metal loading conditions for B. subtilis and P. putida, and that sulfhydryl sites are present both on the cells and within the EPS for these species. Conversely, the SCM results suggest that Cd-sulfhydryl binding is un-important on the EPS of S. oneidensis. [ABSTRACT FROM AUTHOR]

Although computer-aided drug design has greatly improved over time, its application in the pharmaceutical industry is still limited by the accuracy of association constant (Ka) predictions. Towards improving this situation, the Statistical Assessment of the Modeling of Proteins and Ligands (SAMPL) is a series of community-wide blind challenges aimed to advance computational techniques as standard predictive tools in rational drug design (https://en.wikipedia.org/wiki/SAMPL%5fChallenge). As an empirical contribution to SAMPL6, we report here the Ka and thermodynamic parameters (∆G, ∆H, - T∆S) of eight guests binding to two hosts (OA and TEMOA) using ITC. Both hosts contain a unique, well-defined binding pocket capable of storing guests with up to ten non-hydrogen atoms, whilst the selection of amphiphilic guests contain a range of saturated and unsaturated substituents. The thermodynamic data from this study will allow the challenge participants of SAMPL6 to test the accuracy of their computational protocols for calculating host-guest affinities. [ABSTRACT FROM AUTHOR]

The host-guest complexations of fifteen protonated azaspirocyclic, oxa,azaspirocyclic, and diazaspirocyclic guests, three-dimensional analogues of morpholinium, piperidinium, and piperazinium cations, respectively, with cucurbit[7]uril (CB[7]) were investigated using 1H NMR spectroscopy in an acidic aqueous solution. The host-guest stability constants (KCB[7]) for the protonated spirocyclic guests were determined to range from 104-1011 M−1. The relative stability constants have been analyzed in terms of ring sizes and molecular volume (packing coefficient), and the presence and positions of additional oxygen and quaternary nitrogen heteroatoms. The larger the size of both the rings of the guest molecules the higher the observed binding constants for these guests with CB[7]. The largest values for KCB[7] were found for 1- and 2-azaspiro[3.5]nonane, 2- and 8-azaspiro[4.5]decane, and 2-azaspiro[5.5]undecane, when the guest contained 9-11 heavy atoms. Adding oxygen heteroatoms decreased the binding constants by 2-3 orders of magnitude for the azaspirocyclic guests. [ABSTRACT FROM AUTHOR]

Two coordination complexes, [Mn2(pydco)2(phen)2(H2O)2]·2H2O (1) and [Mn(3-pyco)2(H2O)4] (2), based on Mn(II), pyridine-2,5-dicarboxylic acid N-oxide (H2pydco), and 1,10-phenanthroline (phen) as organic ligands have been synthesized and characterized by elemental analyses, infrared spectroscopy, and single crystal X-ray diffraction. We have synthesized the first Mn(II) complex of H2pydco. Interestingly, in situ hydrothermal decarboxylation occurred in 2 and (pydco)2- was totally transformed into pyridine-3-carboxylate N-oxide (3-pyco)- under hydrothermal conditions. The complexation reactions of these molecules with Mn2+ ions were investigated by means of solution studies. The stoichiometry of the most abundant species in the solution (prior to the pH at which precipitation occurs) was very close to that of the corresponding crystalline solid-state complexes. [ABSTRACT FROM AUTHOR]

Current scenario in asthmatic prevalence worldwide calls for a facile, cost-effective, and energy efficient methodology to formulate the potent bronchodilator, theophylline (THP), into an effective dosage forms. Since the uses of THP are severely impeded by its poor aqueous solubility and low bioavailability, solid inclusion complexes (ICs) of THP in β-cyclodextrin (β-CD) were prepared to overcome the limitations. The ICs were developed by conventional methods and also by microwave irradiation method, which is environmentally more benign and requires lesser reaction time. The complexation phenomenon was effectual by the co-precipitation, freeze-drying, and microwave methods as affirmed from various spectroscopic analyses. 1H NMR and molecular docking studies illustrated the total inclusion of THP into β-CD cavity. Better efficacy of the microwaved product was witnessed in terms of drug content, dissolution, and anti-biofilm activities. Thus microwave irradiation can be utilised as a naive and economical methodology to design β-CD-THP dosage formulations. [ABSTRACT FROM AUTHOR]

Mono-, tetra-, and octa-bromo substituted Mn(II)- and Mn(III)-tetraarylporphyrins were synthesized by reactions of manganese(II) chloride with corresponding porphyrin ligands or their Cd(II)-complexes in DMF. With the use of the metal exchange reaction, the time of the Mn-porphyrins formation is significantly reduced with increase in yield of final products in comparison with the complexation reaction. Mn(III)-tetraarylporphyrins reduce to the Mn(II)-porphyrins in DMF in the presence of NaOH and in pure DMF. The obtained compounds were identified using UV-vis and 1H NMR spectroscopy, mass-spectrometry, and elemental analysis. [ABSTRACT FROM AUTHOR]

The problem of legacy alkaline high-level waste (HLW) both in the US and Russia, as a result of weapons production, has prompted studies of ligands for extraction of actinides, that could be possibly used in the future together with Cs extractants for combined HLW extraction processes. The tripodal trisulphonamide ligand 1,3,5-tris-(4-(iso-propyl)-phenylsulfamoylmethyl)benzene (4-iPr-tsa), which has pre-organised functional groups for An(III) binding was synthesised and studied for potential Sm(III) and Am(III) binding and extraction by theoretical (DFT) and experimental (extraction) methods (for Sm(III) only). Both theory and experiments suggest that even though this family of ligands shows promise for Ln(III) and An(III) binding with minima for complex formation, complexation is competing with hydrolysis, and extraction is only feasible in alkaline solutions, in the presence of high concentrations of nitrate ions. Nevertheless, up to 51.8% of Sm(III) was removed under optimal conditions (NaOH = 2 × 10−4 M, NaNO3 = 0.1 M, [Sm]init = 5 × 10−5 M). Quantum chemical calculations demonstrate that the extraction of Sm(III) and Am(III) from the aqueous phase in the form of [M·(H2O)4·(OH)2·(NO3)] to the organic phase in the form of [M·4-iPr-tsa·(H2O)3] is thermodynamically favourable. Theory also shows that Sm(III) is a reasonably good surrogate for Am(III), as the optimised structures of the Sm and Am complexes show remarkable similarities. Even though the ligand was designed with the goal of introducing favourable cation-arene interactions, along with the expected N-binding mode of the ligand in its deprotonated form, it was found that these cation-arene interactions are rather weak in this case, and coordination with O atoms of the sulphonamide, and external water molecules, is favoured instead. [ABSTRACT FROM AUTHOR]

Herein we utilized a new methylene carbenoid as an extremely simple and highly practical reagent for the preparation of vinyl ether with good to excellent yield. This method efficiently effects methoxymethylenation or vinyl ether formation of enolizable, nonenolizable, and sterically hindered ketones. The complexation of Ti-Mg-CHOMe was facilitated, presumably, by THF dramatically increasing the feasibility; and scope of this protocol is to produce vinyl ethers which can be used as convenient building blocks for the preparation of biologically useful molecules. [ABSTRACT FROM AUTHOR]

Quantum chemistry calculations indicate that BN nanocage is a good candidate for selective complex formation with Li+in the presence of different alkali metal ions. Density functional theory (DFT) calculations were applied at the M05-2X/6-311++G(d,p) level of the theory to investigate the interaction of the B12N12nanocage (BN) and alkali metal ions (Li+, Na+, K+, Rb+and Cs+) in the gas phase and in water. On the basis of the results, BN nanocage is able to form a selective complex with Li+. Water, as a solvent, reduces the stability of the metal ion-BN complexes in comparison with the gas phase. Natural bond orbital (NBO) and quantum theory of atoms in molecules (QTAIM) analyses, reveal that the electrostatic interaction between the BN and metal ions can be considered as the driving force for complex formation in which the role of water is of significance. Density of states (DOSs) analysis of the BN nanocage structure in the presence of different metal ions showed a noticeable change in the frontier orbitals, especially in the gas phase, and Fermi level shifting toward the lower values. [ABSTRACT FROM AUTHOR]

This study aims to demonstrate the selective removal of iron from acidic leach solutions using an effective purification method and to convert nickel into a usable form. The method of removing iron by using CaCO3, which is a better precipitation reagent, was optimized using Response Surface Methodology. A further evaluation was carried out on the complexation of Ni(II) ions with dimethylglyoxime to obtain a high-yield nickel-dimethylglyoxime complex from nickel remaining in the solution after iron precipitation. Taking into account nickel losses to remove iron, pH should be within the range of 3–4, and low temperatures around 25°C should be used. [ABSTRACT FROM AUTHOR]

A simple colorimetric chemosensor 1 was developed for the sequential detection of Cu2+ and S2−. Sensor 1 could rapidly detect Cu2+ by an obvious color change from colorless to yellow. The binding mode of 1 to Cu2+ was determined to be a 1:1 complexation stoichiometry through Job plot and ESI-mass spectrometry analyses. The sensing mechanism of Cu2+ by 1 was proposed by theoretical calculations. Importantly, the detection limit for Cu2+ was found to be 0.12 μM, which was much lower than the recommended value (31.5 μM) of the World Health Organization (WHO). Additionally, 1 could detect and quantify Cu2+ in real water samples. Moreover, the resulting 1-Cu2+ complex could be used as a highly selective colorimetric sensor for S2− in the presence of various anions without any interference. The detection limit for S2− was determined to be 1.66 μM, which was much lower than the guideline (14.8 μM) recommended by WHO in fresh water. [ABSTRACT FROM AUTHOR]

Opipramol (OPI), a tricyclic antidepressant and anxiolytic compound, is administered orally in the form of a dihydrochloride. Salt form of the drug has a higher solubility in water and hence bioavailability and stability. A similar effect can be achieved by closing the hydrophobic part of the drug molecule in the cyclodextrin cavity. The paper presents opipramol inclusion complexes with beta-cyclodextrin (β-CD) in 1:1 molar ratio. Studies on the formation of inclusion complexes were carried out both in solution and in the solid state. The formation and physicochemical characterisation of the complexes were determined by UV spectroscopic measurement (UV–vis), Fourier Transform Infrared (FTIR) Spectroscopy,1H Nuclear Magnetic Resonance (1H NMR, 2D NOESY NMR), thermoanalytical methods (TGA – Termogravimetric analysis, DSC – differential scanning calorimetry), X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The phase solubility profile with β-CD was classified as the AN- type, indicating the formation of the inclusion complex with a drug. [ABSTRACT FROM PUBLISHER]

This study presents an efficient removal of Cu(II) in water using the polymer enhanced ultrafiltration (PEUF) method. Polymer of different molecular weight (MW) (polyethyleneimine (PEI), sodium lignosulfonates (SLS) and dextrans) were investigated to evaluate efficiency in removal of Cu(II) in water by the PEUF method. The decomposition of Cu(II)-polymer complex was also evaluated in order to reuse polymers. Cu(II) complexation depends on the MW of chelating polymer and the pH of feed solution. It was found that the Cu(II) rejection increased with the polymer dosage with high removal of Cu(II) when using PEI and SLS at a 10:20 (mg/mg) ratio ([Cu(II)]:[polymer]). It was found that the maximum chelating capacity was 15 mg of Cu(II) per 20 mg of PEI. The Cu(II)–PEI complex could be decomposed by acid addition and the polymer could be efficiently reused with multiple complexation–decomplexation cycles. A conceptual flow chart of the integrated process of efficient removal of Cu(II) by PEUF method is suggested. [ABSTRACT FROM AUTHOR]

The influence of the metallic cation of the base (Li+, Na+or K+) was determined on the acid–base constants ofp-t-butylthiacalix[4]arene (TC4),p-t-butylcalix[4]arene (CA4) andp-t-butylcalix[6]arene (CA6) in ethanol/water in an large interval of pH values by potentiometry and spectrophotometry. The pKavalues determined by both methods correlate very well and these are characteristic for each macrocycle with influence of the cation of the base without a straight evidence of an effect by the size of the metallic cation. In the case ofTC4, pKa1and pKa2were lower to Li+and Na+than with K+. ForCA4, an effect of K+on the pKa2with respect to Li+was observed. A very different behaviour was observed forCA6with Li+and K+showing a lower pKa2and a higher pKa3than with Na+. These effects were interpreted on the basis of the interaction/complexation of each cation with each macrocycle. [ABSTRACT FROM PUBLISHER]

Glutaraldehyde-crosslinked O-carboxymethyl chitosan (O-CMC)–gum Arabic (GA) coacervates were characterized against coacervation acidity. As the coacervation pH increased from 3.0 to 6.0, the crosslinking degree of the coacervates and its sensitivity to glutaraldehyde concentration variation declined gradually, but the elasticity increased markedly. Crosslinking improved the structure compactness and thermal stability of the coacervates and high coacervation pH favored the increase of the two parameters, but a reverse trend was observed regarding swelling ratio in the simulated gastric fluid. It was concluded that glutaraldehyde-crosslinked O-CMC–GA coacervates with required properties could be tailored by selecting an appropriate complexation acidity. [ABSTRACT FROM AUTHOR]

In the present work a new ligand, 2-(2-(phenyl(pyridin-2-yl)methyleneamino)ethylamino)ethanol (L), and its Zn(II) and Cd(II) complexes, [Zn(L)Br2] (1), [Cd(L)Br2] (2) and [Cd(L)I2] (3), have been synthesized and characterized by elemental analysis, FT-IR, Raman and 1H NMR spectroscopies as well as X-ray crystallography. All complexes are isostructural and their metal ions have distorted square pyramidal geometry with an MN3X2 (X: Br, I) environment. During the complexation process, the amine group of the ligand becomes a chiral center. In the solid-state, an R-configuration was observed in all three complexes. Furthermore, the molecules form intermolecular C–H⋯O, C–H⋯X and O–H⋯X (X: Br, I) hydrogen bonds in the solid-state. [ABSTRACT FROM AUTHOR]

The capacity of silencing genes makes small interfering RNA (siRNA) becomes potential candidates for curing many fatal diseases. Due to the low stability and delivery efficiency of siRNA, the design of amphiphilic carrier for siRNA delivery is vital for the practical gene therapy. In the present work, we explored how the complexation and dissociation of siRNA with poly (maleic anhydride-alt-1-decene) substituted with 3-(dimethylamino) propylamine (PMAL), which is a recent synthesised amphiphilic polymer and can be used in delivery of siRNAs and proteins, using traditional molecular dynamics simulations, together with steered molecular dynamics simulations. It was shown that the complexation of siRNA with PMALs can spontaneously occur, no matter what unit number of PMAL is. PMALs of different unit numbers form micelle-like structures and interact with siRNA surface. With the increase of unit number, PMAL becomes more flexible and interacts with siRNA from attachment to entanglement. The dissociation of PMAL from siRNA is an energy-consuming process. The free energy difference increases with the unit number of PMAL. The free energy for dissociation involves both the stretch of PMAL and the separation of PMAL from siRNA. Therefore, an optimal unit number of PMAL is critical for the delivery efficiency of siRNA when PMAL is used as carrier. In present work, when the radius of gyration of PMAL approaches to that of siRNA, PMAL gives a favoured both complexation and dissociation between siRNA and PMAL. Finally, we propose the mechanism of complexation and dissociation of PMAL with siRNA. The above simulation established a molecular insight of the interaction between siRNA and PMAL and was helpful for the design and applications of new PMAL-based polymers as siRNA delivery carriers. [ABSTRACT FROM AUTHOR]

Mono-altro-cyclodextrin (altro-CD) may undergo a conformational change of its altropyranose unit when encapsulating guest molecules of different sizes. This conformational transition is found to be coupled to the inclusion processes. In the present contribution, the possible conformational transition pathways in the four (self-)inclusion processes of altro-α and -β-CDs with moieties of variant shapes are explored from the insights of free-energy calculations. The two-dimensional free-energy landscapes characterising the coupled (self-)inclusion and isomerisation processes are determined, and the lowest free-energy pathways (LFEP) connecting the minima of the landscapes are located. The conformational statistics of the altropyranose units along the LFEPs reveal different transition pathways in the four (self-) inclusion processes. It can be concluded that when accommodating a free bulky guest molecule, the altropyranose unit will adjust its conformation to match the guest. However, such induced fit effect in the self-complexation of altro-CD derivatives will be weakened. The conformation of the altropyranose unit changes accompanying the self-complexation, but always adopts the 4C1 one in the self-inclusion complex, irrespective of the shape of the guest moieties. The present results help determine the transition states of the (self-)inclusion processes of CDs and further improve the understanding of the mechanical properties of CD-based molecular shuttles. [ABSTRACT FROM AUTHOR]

Inclusion complexation between crown ethers (CEs) (viz., 15-crown-5, 18-crown-6) and an ionic liquid (IL) (viz., 1-ethyl-3-methylimidazolium tosylate) in aqueous medium have been demonstrated by conductivity, surface tension and1Proton Nuclear Magnetic Resonance (H NMR) study. The results show the formation of 1:1 complexes between CEs and the IL through electron-deficient imidazolium cation and electron pairs of oxygen atoms of the CEs. Hydrogen bonding is the key factor responsible for complexation, while, the ion–dipole interactions also contribute towards the complex formation. The formation constants have been derived from conductivity study and the complexes have been analysed by1H NMR study. [ABSTRACT FROM AUTHOR]

We performed a systematic comparative theoretical study of noncovalent interactions of free-base H2Pc and a series of 3d transition metal(II) phthalocyanines (where the transition metals included manganese, iron, cobalt, nickel, copper and zinc) with fullerene C60, by employing a DFT technique accounting for vdW interactions (PBE GGA functional with a dispersion correction by Grimme). We observed four different types of Pc interaction with fullerene cage, depending on central metal atom. Upon complexation with C60, the macrocyclic plane undergoes distortion in all cases, to a different degree. Some correlation was observed between the calculated formation energies for Pc'fullerene complexes and intermolecular separations in them, where stronger binding is generally associated with shorter M. . .CC60 and N. . . CC60 distances. Despite of considerable differences in the structure of Pc-fullerene complexes, the latter do not exhibit notable variations in the distribution of electrostatic potential, contrary to spin density plots for open-shell species. Similarly, HOMO and LUMO distribution can vary within some limits. [ABSTRACT FROM AUTHOR]

Complexation of biologically active water-soluble flexible chain microassembledN-vinylpyrrolidone–N-vinylamine copolymers withions was studied by complex chromatographic techniques (high-performance liquid chromatography and thin-layer chromatography). Constants of complex formation were evaluated (Kb = 4.6 × 105). Hydrodynamic behavior and molecular radii of the prepared metal-polymeric compounds were evaluated by molecular optics and hydrodynamic methods [viscosimetry, sedimentation diffusion analysis, dynamic light scattering, and flow birefringence (Maxwell effect)]. No significant changes in hydrodynamic properties of metal-polymeric complexes as compared with those of the pure copolymers were observed. Thus, the suggested approach seems to be promising for producing noninvasive metal-polymeric complexes for biological purposes. [ABSTRACT FROM AUTHOR]

The present study describes non-covalent interaction and complexation behaviour of sodium ascorbate (SA) with cucurbit[6]uril (CB[6]) at neutral pH in aqueous Na2SO4solution. The interaction behaviour is investigated using various analytical techniques like NMR, UV–Vis, fluorescence, TGA and DRS. The substantial increase in the intensity of emission and absorption spectra of sodium ascorbate is observed. The Benesi–Hildebrand evaluation method is used to determine the stoichiometry and equilibrium constant of the cucurbit[6]uril–sodium ascorbate complex, which suggested the 1:1 complex. Time-dependent1H NMR,13C CP MAS and CD studies also echoed non-covalent interaction between SA with CB[6]. [ABSTRACT FROM AUTHOR]

The aim of this work was to study in-depth the acid dissociation constants of Ritodrine, phenylepherine and Midodrine using the potentiometric technique in an aqueous solution and three different mixtures of water and dioxane. Also, the dissociation constants of Ritodrine, phenylepherine and Midodrine have been calculated in an aqueous medium with an ionic strength of 0.15–0.30 mol L−1NaNO3. The dissociation constants (pKa) values for the ionisation in a water (1) + dioxane (2) mixture have been determined at different temperatures ranging from 298.15 to 328.15 K. Then, the thermodynamic parameters (have been examined and discussed. The ligation action of ligands was studied in order to get an idea about their potentiality towards some transition metalsin vitrosystems. The formation of binary complexes of [Cu+2, Co+2, Cd+2, Ni+2, Mn+2and Zn+2] with Ritodrine, phenylepherine and Midodrine has been studied by pH-metric titrations at 37.0 ± 0.1°C and with an ionic strength ofI = 0.15 mol L−1(NaNO3) in an aqueous solution. Along with their overall stability, constants were taken by the HYPERQUAD 2008 program from the potentiometric data. The thermodynamic parameters were determined and discussed for Cu+2–L (L: Ritodrine, phenylepherine and Midodrine). The formation in the binary and ternary complexes of the Cu+2, Co+2and Ni+2metal ion with aromatic acid (anthranilic acid and 5-sulfosalicylic acid and phenylepherine) was estimated by means of potentiometry and conductometry at 37°C and inI = 0.15 mol. Results showed that L−1NaNO3was with stoichiometric coefficients 1:1:1. The ternary system formation has been displayed in a stepwise mechanism. The stability constants of these ternary systems have been calculated and discussed. The concentration distributions of the various complex species in solution have been evaluated and discussed. [ABSTRACT FROM PUBLISHER]

Supramolecular complexation of C60withL1-L5were studied in toluene, chloroform and 1,2-dichlorobenzene solvents using UV–vis, fluorescence,1H,13C NMR spectroscopy as well as density functional theory (DFT) calculations. The Job’s plot of continuous variation method established 1:1 stoichiometry forL1-L5/C60. Binding constants (K) calculated forL1-L5/C60were also determined employing UV–vis and fluorescence spectroscopy. Both steady-state and time-resolved fluorescence spectroscopic surveys showed remarkable fluorescence quenching phenomenon forL1-L5in the presence of C60which was primarily attributed to involvement of a static process. The observed fluorescence quenching inL1–L5was described in terms of both π–π and n–π interactions of the naphthalene moieties and the nitrogen donor groups on the aza-crown macrocyclic ligands with C60, respectively. Moreover, DFT calculations using B3LYP/6-31G* basis set confirmed on the aforesaid π–π interaction of naphthalene groups on the aza-crowns with C60. The DFT calculations also established significant distributions of charge between C60andL1-L5in according to the electronic structure and geometry ofL1-L5/C60, very similar to phthalocycnine/C60systems. [ABSTRACT FROM PUBLISHER]

In order to carry out MD simulations for the racemic system consisting of two different enantiomers of a chiral ruthenium complex and nematic liquid crystal molecules accurately, we here proposed modified force field parameters for the chiral dopant. The validity of the modified parameter was confirmed by performing MD simulations for pure ruthenium complex system at crystalline state. MD simulations for the racemic system of Δ- and Λ-isomers of the chiral dopant molecule and nematic solvent molecules led to the accurate and precise determination of the helical twisting power of the chiral dopant. [ABSTRACT FROM AUTHOR]

The geometries of triafulvene (TF) and its exocyclic Si, Ge, and Sn analogues complexes with F, Cl, Br, and I halogen atoms (TF(X)···Y, X═C, Si, Ge, and Sn; Y═F, Cl, Br, and I) were studied. The complexes were optimized at DFT(B3LYP)/6–311+G(d,p) level of theory. To assess the aromaticity of the considered complexes the geometry-based (HOMA), magnetism-based (NICS), and recently introduced electronic-based (electric field gradient (EFG(0); Shannon aromaticity (SA)) aromaticity indices were employed. The increasing tendency of aromaticity in each complex species was noted as the series of TF(X)···F > TF(X)···Cl > TF(X)···Br > TF((X)···I. Then, the binding energies corrected by basis set super position error (BSSE) were calculated by single point energy calculations at M06-2X/6-311+G(d,p) level. Natural bond orbital (NBO) analysis confirmed that the charge transfer takes place from TF(X) to the halogen atoms. Some topological parameters, within the framework of the quantum theory of atoms in molecules (QTAIM), were also calculated to estimate the aromaticity of the complexes. It was seen that there are some important correlations between the topological parameters and aromaticity indices. In addition the most striking finding was that all the TF(X) molecules are connected with the halogen atoms through Y···C1═C2 (π) noncovalent interaction. This interaction was also investigated through noncovalent interaction (NCI) analysis. [ABSTRACT FROM AUTHOR]

In the present study, a lyophilized milk-based solid dispersion (SD) of ritonavir (RTV) was developed with the goal of improving its aqueous solubility. The SD was prepared by lyophilization, and characterized for its physicochemical and functional properties. Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), photomicroscopy and powder X-ray diffraction (PXRD) were used to confirm the formation and robustness of the SD formulation. The prepared SD formulations were functionally evaluated by saturation solubility,in vitrodrug release andex vivopermeation studies. The optimized SD formulation exhibited a significantly higher (30-fold) aqueous solubility (11.36 ± 0.06 μg/mL), compared to the pure RTV (0.37 ± 0.03 μg/mL). Thein vitrodissolution studies revealed a significantly higher (∼10-fold) efficiency of the optimized SD formulation in releasing the RTV, compared to the pure RTV. Theex vivopermeation studies with theeverted intestinemethod showed that prepared SD formulation significantly improved the permeation of RTV (75.6 ± 3.09, % w/w), compared to pure RTV (20.45 ± 1.68, % w/w). Thus, SD formulation utilizing lyophilized milk as a carrier appears to be a promising alternative strategy to improve the aqueous solubility of poorly water soluble drugs. [ABSTRACT FROM PUBLISHER]

As a tribute to Pieter R. Cullis, this manuscript identifies a liposomal formulation that bears his initials: the PRCosomes. “Pretty” Reactive Complexes within liposomes were observed, while the senior author of this manuscript completed his Ph.D. thesis under Pieter’s supervision. The dye (safranine) was used as a tool to measure the magnitude of the transmembrane gradient generated with liposomes. The dye’s redistribution is easily detected by eye and correlates with >98% encapsulation of the dye. This observation became the basis from which remote drug loading methods developed. Remote loading methodology involves the addition of drugs to pre-formed liposomes with a transmembrane gradient, which results in drug redistribution to the liposome interior. Doxorubicin, as an example drug candidate, complexes manganese trapped within the liposome. A color change accompanied drug encapsulation as the solution went from an orange to purple. This manuscript reviews and adds a novel perspective on the use of metal complexation reactions to prepare PRCosomes. The technology described provides a versatile method to form metal–drug complexed within liposomes. The purpose of this work is to differentiation between drug candidate loading that is caused by metal–drug complexation and loading driven by formation of a pH gradient. [ABSTRACT FROM AUTHOR]

The complexation between methyl acetoacetate and certain lanthanides was studied in the mixed ethanol–water solvent (90% ethanol) using electronic absorption spectroscopy. The formation of the cationic 1:2 type complexes was shown at alkalescent medium. Based on the energy of the f–f transitions, the interelectronic repulsion parameters (Slater integrals) were determined by a least-square fit using effective Hamiltonian comprised of electrostatic and spin–orbit components and the nephelauxetic ratio was calculated as a ratio of the second-order Slater integrals. The nephelauxetic ratio was found to be proportional to the relative shortening of the lanthanide–oxygen bond length when the geometry of the complexes was optimized by semiempirical Sparkle/Parametric Method 7. [ABSTRACT FROM PUBLISHER]

This study investigated the bonding of calcium and magnesium to specific sites in humic acid as a function of pH, temperature, and trace metal concentrations. Other metals were investigated but not in detail. Using a surface complexation model with well-defined phenolic and carboxylic sites in humic acid, the fractions of calcium/magnesium and trace metals that bond with the various sites were quantified. These sites were also classified as monodentate or bidentate. The goal of the study was to understand the conditions that favor calcium/magnesium bonding to bidentate humic acid. Therefore, adsorption measurements were performed followed by surface complexation simulations. The total metal and labile metal ion formed in the ultrafiltrate were determined by inductively coupled plasma mass spectrometry and square-wave anodic stripping voltammetry, respectively. The results showed that the adsorption capacity of each metal to humic acid was influenced by pH and metal loading. For example, zinc(II) and copper(II) were statistically different in their adsorption capacities. The Morel and Dzombak surface complexation models showed stronger lead and copper interactions with monodentate sites compared to bidentate sites. The phenolic sites were weakly involved in bonding, and the bonding capacities of calcium and magnesium ions to phenolic or carboxylic were pH dependent. For example, lead(II) used only 5% of bidentate carboxylic–phenolic sites at 45°C showing 95% favorable calcium/magnesium bonding to these sites in humic acid. These results may allow substantial scale reduction. [ABSTRACT FROM AUTHOR]

Cucurbit[8]uril (CB[8]) is robust in encapsulating a stacking dimer of two identical or different aromatic units in water. In recent years, this ternary host–guest complexation motif has found wide applications in constructing supramolecular systems by noncovalently connecting molecular, supramolecular and polymeric precursors. This review summarises the important advance, in particular, in the generation of linear supramolecular polymers and extended supramolecular networks including periodic supramolecular organic frameworks. [ABSTRACT FROM AUTHOR]

A macrocyclic ring comprising multiple hydrogen-bonding sites as well as metal-chelating sites is shown to play the role of ligand in active templated, copper-catalysed [2]rotaxane formation via Huisgen and Glaser reactions. The crystallographic structure and copper ion binding studies are provided for the free macrocycle, along with molecular modelling, barbital, N,N′-trimethyleneurea and copper (I) binding information for the new rotaxanes. [ABSTRACT FROM AUTHOR]

Schiff base pyridin-2-ylimino methyl naphthanol (HL) was synthesized and characterized by spectroscopic (FTIR, ESIMS, and NMR) techniques. The ligand was reacted with perchlorate salts of Mn+2, Co+2, and Ni+2. ESIMS mass spectra indicate the formation of mononuclear complex ML2for all three complexes. CoL2crystallizes inP21/nspace group, adopting a distorted tetrahedral geometry where Co is in a N2O2donor environment. Structure of the Co complex was optimized by DFT calculation. Solution-phase complexation between the ligand and the three metals ions: Mn+2, Co+2, and Ni+2(pH 7.2 in tris buffer), in CH3CN–H2O was performed spectrophotometrically by UV–vis spectral study. Job’s plot from each titration suggests a 1 : 2 metal to ligand combination. The association constants for the formation of ML2are as follows: Mn (19.80 × 103 M−1), Co (14.54 × 103 M−1) and Ni (19.04 × 103 M−1). [ABSTRACT FROM AUTHOR]

Erlotinib (ERL), the anticancer drug of poor bioavailability, was quantified in terms of bio-relevant physicochemical parameters, such as acid–base properties, lipophilicity and solubility, and a comprehensive study on its inclusion complexation was carried out. The protonation constant of ERL (logK = 5.32) indicates that it exists mainly in deprotonated form at the pH of blood plasma. The high lipophilicity (logp = 2.75) explains its good permeability, while the very low solubility (S0 = 12.46 μM) causes its low bioavailability and renders injection formulation a difficult job. This problem could be alleviated by enhancing ERL solubility through cyclodextrin (CD) inclusion complexation. Therefore, ERL–CD interactions were studied by a number of analytical techniques. The apparent stability constants of ERL with seven different CDs were determined using affinity capillary electrophoresis. Results indicated that the seven-memberedβ-CD and its derivatives were the most suitable hosts. Using UV Job plot titration 1:1 stoichiometry was determined, confirmed by electrospray ionisation-mass spectrometry experiments. The geometry of the inclusion complex was investigated by 2D ROESY NMR techniques, revealing that the ethynylphenyl ring enters theβ-CD cavity. Phase-solubility analysis shows greatly enhanced solution concentration by CD complexation. The determined equilibrium and structural information offer molecular basis to elaborate improved drug formulation with enhanced bioavailability. [ABSTRACT FROM AUTHOR]

The interactions between two synthetic polymers used in biomedical applications, maleic acid-styrene copolymer (MAc-St) and poly(vinylcaprolactam) (PVCL), were investigated in dilute aqueous solution considering the influence of the pH, the added salt and the ratio between the components in the mixture. Hydrogen-bonding interactions between the COOH groups of MAc-St and the C═O groups of PVCL, together with hydrophobic interactions are involved in the formation of the interpolymer complex. The complex is insoluble below pH = 2.85 in aqueous solution, but the addition of NaCl enlarged the pH domain where the precipitation of the complex occurred. When the ratio between the polymers was varied, two maxima of the optical density were obtained: at a 1:1 ratio between the COOH and caprolactam groups, and also at a lower ratio (1:3). Other investigations, like the measurements of the turbidity in situ during mixing, and fluorescence, viscometric and potentiometric measurements were performed in order to understand these interactions. The phase separation of the thermosensitive poly(vinylcaprolactam) in the presence of MAc-St was also studied. The cloud point and the phase transition profile were found to be influenced by the amount of polyacid, as well as by the pH. [ABSTRACT FROM PUBLISHER]

Results of potentiometric and spectral studies have shown that ind-glucuronic acid (GluA) with Cu2+or Mg2+systems, the complexes ML and ML(OH)xare formed. Overall stability constants (logβ) and equilibrium constants (logKe) were calculated for all complex forms. The mode of coordination for each form was concluded on the basis of spectral values, Vis, EPR, and chemical shifts in the13C NMR. According to spectral analysis, Cu(GluA) exists in two possible forms, which confirm the occurrence of the coordination dichotomy in the system. The main center of interactions in the hydroxyl complexes Cu(GluA)(OH)xand MgGluA are oxygens from the carboxyl group. Differences in the coordination mode in the copper(II) and magnesium systems at low pH were observed. [ABSTRACT FROM AUTHOR]