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Samples of humic materials—humic acids and fulvic acids—derived from Tisul lignite (Kansk-Achinsk Basin) are investigated by ESR (electron spin resonance) spectroscopy. The concentration of free radicals declines in the following sequence: lignite, humic acids, fulvic acids. The proportion of aliphatic radicals increases in the same sequence. By simulation of the ESR spectra of the fulvic acids and comparison with the experimental spectra, natural complexes of fulvic acids with Fe3+ and Mn2+ ions are detected. By determining the splitting parameters in zero field (D and E), it is established that the complexes with Fe3+ have axial symmetry, with a complex multilevel structure. The internal coordination sphere of the complex consists of water molecules, whereas the external coordination sphere consists of oxygen-bearing fulvic acid groups. The calculated hyperfine structure constant of the experimental ESR spectra for the complexes with Mn2+ (79.7 G) is lower than the typical value for the octahedral Mn2+ complex [Mn(H2O)6]2+. That indicates partial replacement of the water molecules by oxygen-bearing functional groups of fulvic acids. [ABSTRACT FROM AUTHOR]

The thermal conductivity of liquid alloys of the cesium–bismuth system with 20–66 at % Bi in the temperature range from the liquidus line to 1173 K has been studied experimentally with an error of 4–6%. It was found that the thermal conductivity of liquid cesium bismuthides for the indicated compositions and temperatures takes low values from 0.7 to 4.5 W/(m K) typical for liquid salts. The thermal diffusivity and Lorenz number were calculated from the results of thermal conductivity measurements. An analysis of the temperature and concentration dependences of the studied properties indirectly confirms current views on the presence of ordered structures called ionic complexes in alkali metal bismuthide melts, which significantly affect the thermophysical properties of melts and are destroyed at elevated temperatures. [ABSTRACT FROM AUTHOR]

π‐π stacking and ion‐pairing interactions induced the generation of α‐amino radicals under the irradiation of visible light without the requirement of an expensive photocatalyst. This strategy enabled the construction of functionalized amines via three‐component coupling reactions with broad scope (we report >50 examples with an up to 90 % yield). This synthetic pathway also delivered complex functionalized amines with a very high yield. Quantum chemistry Density Functional Theory (DFT) calculations identified π‐π stacked ionic complexes; time‐dependent DFT was employed to simulate the absorption spectra, and nudged elastic band (NEB) methodology provided a possible interaction/reaction picture of the selected species. [ABSTRACT FROM AUTHOR]

Four dioxidovanadium(V) complexes with Schiff-base ligands based on 2-hydroxybenzhydrazide with four different substituted salicylaldehydes (5-chlorosalicylaldehyde, 3,5-dichlorosalicylaldehyde, 5-nitrosalicylaldehyde, 3-bromo-5-chlorosalicylaldehyde) were synthesized and described, by using V2O5 and triethylamine. The single crystal X-ray structure measurements as well as elemental analyses and IR spectra confirmed the formulas of the ionic complexes with a protonated triethylamine acting as counterion, HTEA[VO2(L)] (HL = Schiff-base ligand). The kinetic stability of the complexes at pH = 2 and 7 was discussed with respect to the neutral vanadium(V) complexes previously studied as potential insulin-mimetic agents. A correlation between the substituents in an aromatic ring of the Schiff-base ligands with crystal packing, and also with the stability of the compounds, was presented. [ABSTRACT FROM AUTHOR]

Below, the possibilities of computer modeling are used to explain the experimental data obtained by us (pulsating rays in a mixture of propane air). With the use of the computer mathematical program MATHCAD, the role of the heat released during the decomposition of ozone molecules, induced by ionic molecules and surface ion-frozen active centers (H2⋅Cl–), into ozone molecules, the self-decay of which highly heats the medium, and resulted in the birth of both concentration traveling waves and weak shock waves in reactors. [ABSTRACT FROM AUTHOR]

A core–shell additive with anionic Keggin‐type polyoxometalate (POM) cluster as core and N‐containing cation of ionic liquid (IL) as shell is proposed to stabilize Li‐metal batteries (LMBs). The suspended POM derived complex in ether‐based electrolyte is absorbed around the protuberances of anode and triggers a lithiophobic repulsion mechanism for the homogenization of Li+ redistribution. The gradually released POM cores with negative charge then enrich Li+ and co‐assemble with Li. The Li+ repulsion‐enrichment synergism can compact Li deposition and reinforce solid electrolyte interphase. This sustained‐release additive enables Li∥Li symmetric cells with a long lifetime over 500 h and 300 h at high current densities of 3 and 5 mA cm−2 respectively. The complex additive is also compatible with high‐voltage Li∥LiNi0.8Co0.15Al0.05O2 (NCA) cells. Even with a NCA loading as high as ca. 20 mg cm−2, the additive contained Li∥NCA cell can still cycle for over 100 cycles at 2.6 mA cm−2. [ABSTRACT FROM AUTHOR]

The thermal conductivity and thermal diffusivity of liquid alloys of rubidium–bismuth systems with Bi contents of 27.0, 50.0, and 66.7 at % are studied in the range of temperatures from the liquidus line to 1173 K using laser flash method. Equations are obtained for approximating the studied properties. Analysis of the temperature and concentration dependences of thermal conductivity and thermal diffusivity indicates the presence of ionic complexes in Rb–Bi melts that decompose as the temperature rises. [ABSTRACT FROM AUTHOR]

• A catalytic system based on cationic gallium phthalocyanines has been developed. • SbF 6 – and Sb 2 F 11 –/Sb 3 F 16 – were used as weakly coordinating counter-anions. • This catalytic system was used for donor-acceptor cyclopropanes chemistry. • [3 + 2]-Cycloaddition/annulation reactions with aldehydes have been studied. Cationic gallium phthalocyanine (RPcGa+) catalysts with SbF 6 – and Sb 2 F 11 –/Sb 3 F 16 – weakly coordinating anions were developed and used in the catalytic chemistry of donor-acceptor (D–A) cyclopropanes and related substrates. For the first time, these processes were implemented on the examples of [3 + 2]-cycloaddition/annulation reactions of D–A cyclopropanes and styrylmalonates with various aldehydes, as well as some other transformations with different substrates. [Display omitted] [ABSTRACT FROM AUTHOR]

The complexes [PhPR][OsBr], R = cyclo-CH ( I), n-CH ( II), cyclo-CH ( III), CHC(O)Ph ( IV), [PhPPr][OsBr] ∙ DMSO ( V), and [PhP(CH)PPh][OsBr] ∙ DMSO ( VI) (CIF files CCDC nos. 1000171, 1000148, 1000172, 1000173, 1000147, and 1000149 for structures I-VI, respectively) were prepared by reactions of sodium hexabromoosmate with phosphonium bromides in dimethyl sulfoxide. According to X-ray diffraction data, phosphorus atoms in the cations have slightly distorted tetrahedral coordination (CPC angles, 105.2(3)°-115.5(3)°; P-C, 1.773(6)-1.814(6) Å). In the octahedral [OsBr] anions, the Os-Br bond lengths are 2.4734(8)-2.5203(5) Å and the cis-BrOsBr and trans-BrOsBr angles are 88.38(2)°-91.53(3)° and 177.276(18)°-180°, respectively. The structural organization in the crystals is formed by H∙∙∙Br (2.74-3.04 Å) and H∙∙∙O (2.28-2.63 Å) ion-ion hydrogen bonds. [ABSTRACT FROM AUTHOR]

Ionic platinum(II) complexes [PtCl(PPh 3 )(L∧L)][BF 4 ] {L∧L = 2,2′-bipyridyl ( 1 ) 1,10-phenanthroline ( 2 )} and [PtCl(PPh 3 )(L) 2 ][BF 4 ] {L = pyridine ( 3 ), dimethyl sulfoxide ( 4 )} were synthesized by dehalogenation of cis- [PtCl 2 (PPh 3 )(NCMe)], followed by reaction with the suitable ligand. Chelating nitrogen ligands L∧L afforded single products, which were structurally characterized. In the other cases mixtures of geometric (L = pyridine) and/or coordination (L = dimethyl sulfoxide) isomers were observed in solution. In these cases the structures of the less soluble isomers were obtained via single crystal X-ray diffraction. All the complexes were tested in vitro for their antiproliferative activity on three human tumor cell lines: MSTO-211H, HeLa and HepG2. [ABSTRACT FROM AUTHOR]

The impact of the association of lithium cation with NCS ion in acetonitrile on the vibrational spectrum was studied by the density-functional method in the B3LYP/6-31+G(d,p) approximation. The best agreement between experimental and calculated ionic association data was achieved taking into account the nonspecific solvation, oversolvation, and solubility of ionic complexes within the discrete-continuum model. The microstructures of the thiocyanate ion in a contact ion pair with lithium cation and ion-pair dimer and trimer in acetonitrile were established. [ABSTRACT FROM AUTHOR]

Various specially designed poly(N-isopropylacrylamide-co-acrylic acid) (NIPA-co-AAc) nanogels (NGs) with different NIPA/AAc molar composition were synthesized by precipitation/dispersion polymerization and evaluated as carriers for drug delivery systems (DDSs) of doxorubicin hydrochloride (DOXO·HCl) for cancer therapies. The NGs presented excellent dispersability in physiological environments (pH 7.4 and 5 at 37 °C), as shown by dynamic light scattering (DLS). Moreover, the NGs exhibited high drug loading capacity and efficiency due to the ionic interaction of the cationic drug with the anionic NGs. NG-DOXO·HCl formulation presented excellent dispersability in water and minimal leakage of the cargo at plasma simulated medium (pH 7.4 and 0.14 M NaCl) at 37 °C and a triggered release at lysosomal simulated medium (pH 5 and 0.14 M NaCl). This release behavior together with their size and the low cytotoxicity determined by the MTT assay converts these NGs in great candidates for their application as carriers in cancer therapies based on the enhanced permeability and retention effect (EPR) with drug pH-triggered release after endocytosis in tumor cells. [ABSTRACT FROM AUTHOR]

The geochemical behaviour of Rare Earth Elements, Zr and Hf was investigated in the thermal waters of Nevado del Ruiz volcano system. A wide range of pH, between 1.0 and 8.8, characterizes these fluids. The acidic waters are sulphate dominated with different Cl/SO 4 ratios. The important role of the pH and the ionic complexes for the distribution of REE, Zr and Hf in the aqueous phase was evidenced. The pH rules the precipitation of authigenic Fe and Al oxyhydroxides producing changes in REE, Zr, Hf amounts and strong anomalies of Cerium. The precipitation of alunite and jarosite removes LREE from the solution, changing the REE distribution in acidic waters. Y–Ho and Zr–Hf (twin pairs) have a different behaviour in strong acidic waters with respect to the water with pH near-neutral. Yttrium and Ho behave as Zr and Hf in waters with pH near neutral-to-neutral, showing super-chondritic ratios. The twin pairs showed to be sensitive to the co-precipitation and/or adsorption onto the surface of authigenic particulate (Fe-, Al-oxyhydroxides), suggesting an enhanced scavenging of Ho and Hf with respect to Y and Zr, leading to superchondritic values. In acidic waters, a different behaviour of twin pairs occurs with chondritic Y/Ho ratios and sub-chondritic Zr/Hf ratios. For the first time, Zr and Hf were investigated in natural acidic fluids to understand the behaviour of these elements in extreme acidic conditions and different major anion chemistry. Zr/Hf molar ratio changes from 4.75 to 49.29 in water with pH < 3.6. In strong acidic waters the fractionation of Zr and Hf was recognized as function of major anion contents (Cl and SO 4 ), suggesting the formation of complexes leading to sub-chondritic Zr/Hf molar ratios. [ABSTRACT FROM AUTHOR]

The solubility and solution behavior of F and Cl in peralkaline aluminosilicate compositions in the systems Na2O-Al2O3-SiO2 and K2O-Al2O3-SiO2 have been determined for glasses quenched from melts equilibrated at 1400 and 1600 °C in the 1.0-2.5 GPa pressure range. With Al/(Al+Si) increasing from 0 to 0.33 in sodium aluminosilicate melts, F solubility (saturation concentration) increases from 3.3 to 7.4 mol%, whereas Cl solubility decreases from 5.7 to 2.5 mol%. There is no difference in F solubility in sodium or potassium aluminosilicate melts. However, the Cl solubility in potassic aluminosilicate melts is 40-60% lower than in sodic melts with the same Al/(Al+Si) and Na or K mole fraction. Fluorine depolymerizes the silicate melt structure and forms Si-F, Al-F, and Na-F complexes, the proportion of which depends on the melt Al/(Al+Si) ratio. Dissolution of Cl results in a small degree of depolymerization of Al-free silicate melt, whereas Cl has a polymerizing effect in aluminosilicate melts. In both cases, formation of Na-Cl complexes appears to be the driving solution mechanism. The differences in F and Cl solution mechanisms result in contrasting depolymerizing effects that become more pronounced with increasing degree of magmatic differentiation. Through such modifications of melt structure, F and Cl have significant effects on magma properties such as viscosity, compressibility, and element partitioning. [ABSTRACT FROM AUTHOR]

Abstract: Poly(β,L-malic acid) (PMLA) was made to interact with the cationic anticancer drug Doxorubicin (DOX) in aqueous solution to form ionic complexes with different compositions and an efficiency near to 100%. The PMLA/DOX complexes were characterized by spectroscopy, thermal analysis, and scanning electron microscopy. According to their composition, the PMLA/DOX complexes spontaneously self-assembled into spherical micro or nanoparticles with negative surface charge. Hydrolytic degradation of PMLA/DOX complexes took place by cleavage of the main chain ester bond and simultaneous release of the drug. In vitro drug release studies revealed that DOX delivery from the complexes was favored by acidic pH and high ionic strength. [Copyright &y& Elsevier]

Abstract: The low bioavailability of enalapril maleate associated to its instability in solid state motivated the development of a polyelectrolyte-drug complex between enalapril maleate and the cationic polymethacrylate Eudragit E100. The solid complexes were characterized by DSC–TG, FT-IR and X-ray diffraction. Their aqueous dispersions were evaluated for drug delivery in bicompartimental Franz cells and electrokinetic potentials. Stability in solid state was also evaluated using an HPLC–UV stability indicating method. Absorption of enalapril maleate was assessed thorough the rat everted gut sac model. In addition, urinary recovery after oral administration in rats was used as an indicator of systemic exposition. The solid materials are stable amorphous solids in which both moieties of enalapril maleate are ionically bonded to the polymer. Their aqueous dispersions exhibited controlled release over more than 7h in physiologic saline solution, being ionic exchange the fundamental mechanism that modified the extent and rate of drug release. Intestinal permeation of enalapril maleate was 1.7 times higher in the presence of the cationic polymer. This increase can be related with the capacity to adhere the mucosa due to the positive zeta potential of the complexes. As a consequence bioavailability was significantly improved (1.39 times) after oral administration of the complexes. In addition, no signs of chemical decomposition were observed after a 14months period. The results indicated that the products are new chemical entities that improve unfavorable properties of a useful drug. [Copyright &y& Elsevier]

Structural and thermodynamic characteristics of molecular and ionic complexes of aluminum trichloride with pyrazine (pyz) and 4,4′-bipyridyl (bipy) are calculated at the RI-BP86/def2-SVP level. It is found that for molecular 2AlCl·3L and 4AlCl·3L complexes an energy difference between isomers does not exceed 4 kJ/mol, and the rotation barrier of the AlCl moiety relative to the N-Al-N bond does not exceed 24 kJ/mol. A comparison of the stability of molecular and ionic complexes of aluminum in the gas phase shows that the maximum energy difference is ∼60 kJ/mol. For L = pyz the molecular complex is more stable whereas for L = bipy it is the ionic one. [ABSTRACT FROM AUTHOR]

As a result of the experiment ionic complexes between high molecular polyethylene oxide and salts of monovalent and divalent metals were obtained and examined. Concentration ranges were established. This study focused on the concentration dependence of the bulk conductivity of the studied binary systems of polyethylene oxide and lithium chlorate. The results show that the conductivity is being increased nonlinearly with an increase in its content. [ABSTRACT FROM AUTHOR]

Abstract: The ionic Pd(II)-complexes of 2 (ammonium-[1-(2-hydroxyethyl)-3-methylimidazolium] bis[3-(diphenylphosphino)benzenesulfonate]-dichloropalladium(II) ([(NH4)(Hemim)][PdCl2(TPPMS)2])) and 3 (bis[1-n-butyl-3-methylimidazolium] bis[3-(diphenylphosphino)benzenesulfonate]-dichloropalladium(II) ([Bmim]2[PdCl2(TPPMS)2])) were synthesized and fully characterized. The single crystal X-ray diffraction analyses show that 2 and 3 are composed of the imidazolium-based cations and [PdCl2(TPPMS)2]2− anions. The properties of such imidazolium-based Pd-complexes of 2 and 3, in terms of the aqueous solubilities and the catalytic behaviors in water, could be dramatically varied. When 2 and 3 were applied as the precatalysts for the Sonogashira coupling of iodobenzene with phenylacetylene under aerobic and CuI-free conditions, the much higher yields of 1,2-diphenylethyne were obtained due to their amphiphilicity. The wide generality of 2 was available for aqueous–organic biphasic Sonogashira reactions. [Copyright &y& Elsevier]

Density functional PBE/TZ2p quantum chemical calculations of activated complexes and pathways of model catalytic transformations of propane under the action of aluminum chloride-cobalt chloride ionic bimetallic complexes were carried out. The formation of an intermediate with a broken C-C bond can occur on the cationic cluster CoAlCl characterized by the strongest coordination of propane molecule. The activation barrier to the reaction is Δ G = 25.0 kcal mol. Activation of alkane C-H bonds follows the alkyl pathway involving the formation of bimetallic alkyl complexes. The interaction of activated hydrocarbon fragments bound to transition metal atoms in cobalt-chloroaluminate clusters can result in alkane metathesis products (in this case, ethane and a polymetallic cluster containing an extendedchain alkyl radical). [ABSTRACT FROM AUTHOR]

Various quaternary ammonium salts as cationic binding sites were introduced to pseudo-bilayer membranes based on partially hydrolyzed poly(ethylene-co-vinyl acetate) (EVA). Three types of quaternary ammonium salts such as bolaform electrolytes, gemini surfactants, and conventional surfactants were used in this study. Gemini surfactants were uptaken more in the membranes than bolaform electrolytes because of the amphiphilicity. The surfactants were dispersed and acted as a binding site for anionic dye in the hydrolyzed membrane under the optimal conditions. [ABSTRACT FROM AUTHOR]

High-level ab initio calculations are employed to generate potential energy curves for rare gas cations, RG+, interacting with neutral atoms of other rare gases, RG', that are lighter (RG' = Ne-Rn). The calculations employ the RCCSD(T) method, with doubly-augmented basis sets of quintuple-ζ quality. The interaction potential curves, with the full counterpoise correction applied, are calculated point-by-point. Spin-orbit coupling is applied analytically in an atom-based model. The potentials are used to calculate spectroscopic parameters, which are then compared to recent experimental work, and the very limited previous theoretical work. In addition, the potentials are used to calculate ion transport properties and the ion mobilities are compared to the few experimental data available. [ABSTRACT FROM AUTHOR]

Density functional calculations of binary and ternary propane complexes with aluminum and cobalt(II) chlorides were carried out. Interaction of metal chloride complexes with the methylene and methyl groups of propane is coupled with strong polarization of C-H bonds. The direction of polarization is opposite to that observed under interaction with the typical Lewis acids including aluminum halides. In the interaction of bimetallic (transition metal/aluminum) complexes with saturated C-H bonds, the key role is played by the transition metal ion rather than the stronger Lewis center (Al). The negative atomic charge on carbon increases, which may facilitate the formation of metal-alkyl compounds with a carbanion-type organic radical. [ABSTRACT FROM AUTHOR]

New ionic complexes of fullerene C60: {CrI(C6H6)2•+} · (C60•-) · C6H4Cl2(1); {(MDABCO+) · CoIITMPP·}2 · (C60-)2 · (C6H4Cl2)2.5 · (C6H5CN)1.5 (2); and (DMETEP+)2 · (C60-)2 · {(MnIITPP)2 · DMP} · (C6H4Cl2)5(3) were obtained and studied by temperature EPR, SQUID and optical spectroscopy. Fullerene radical anions were shown to form (C60-)2 dimers in these complexes. The (C60-)2 dimer in 1 reversibly forms in the 160-240 K range and is bonded by one single bond (σ-dimer). According to magnetic data this dimer is diamagnetic. Complex 2 contains a new type of (C60-)2 dimer bonded by two single bonds (π-dimer). Magnetic measurements show that this dimer has about two spins per dimer and, consequently, has biradical state at 300 K. The energy gap between triplet and singlet states for this dimer was estimated to be 70 ± 2 CM-1. Complex 3 contains dimers of both types. The σ-dimer has 86% occupancy and the occupancy for the π-dimer is only 14%. It was shown that σ-dimer in 3 has the highest stability among studied ionic complexes of fullerenes and dissociates only in the 320-360 K range. The reasons for the difference in the electronic states of σ- and π-dimers of (C60-)2 are discussed. [ABSTRACT FROM AUTHOR]

Abstract: We have applied the model-potential analysis of Breckenridge and co-workers to the Alk+/Rg systems, where Alk is an alkali atom and Rg is a rare-gas atom. Three spectroscopic constants, R e, D e and ω e, are employed to obtain the potential, with fitted parameters being the A and b repulsive Born–Mayer potential parameters, and the effective charge on the metal center, Z. From the analysis, it is concluded that all of these systems can be described in physical terms, with the calculated charge on the metal center being very close to 1.00. Interestingly the effective charge on the metal atom from such model-potential calculations is consistently very slightly greater than 1.00. We discuss and investigate several possible sources for this small anomaly, including a minor breakdown of the model at small internuclear separations, where the “lengths” of the induced multipoles become significant compared to the internuclear separation R. Despite this small breakdown, overall the model is remarkably successful in reproducing high-level ab initio curves for the titular complexes over wide ranges of internuclear distances. [Copyright &y& Elsevier]

The chemistry of binuclear palladium(II) and platinum(II) complexes has been reviewed. This review deals with complexes derived from various classes of ligands and covers various aspects, viz. synthesis, spectroscopic and structural features and chemical reactivity, of these complexes. Applications of these complexes are briefly described in the respected sections. [Copyright &y& Elsevier]

Hydrolytic degradation of an aliphatic polyacetamidine at different pH values was studied using 1H NMR spectroscopy. It could be shown that degradation occurred at neutral and basic conditions whereas under acidic conditions the polyamidine was stable. In the course of degradation, aliphatic acetamide, amine and acetic acid are formed. The ability of the polyamidine to release active compounds bonded ionically to the polymer backbone by hydrolytic decomposition was studied by UV spectroscopy. The measurements were performed on a mixture of the polyamidine and salicylic acid as an example. The release behavior of a 1:0.8 mixture at pH 7 was nearly linear within the first 10 h and went to completion after 30 h. This system is discussed with respect to the development of new drug delivery systems based on polyamidines. [Copyright &y& Elsevier]

Summary Electrosynthesis of κ -carrageenan–ovalbumin complexes, in alkaline solution and containing both components in ratios varying from 1 : 5 to 5 : 1, is described. Complexes had compositions varying from 1 : 10 to 1 : 1.8. Components were covalently bound, as deduced from the insolubility of the complexes in 7 m urea, the infrared spectra, and thermogravimetric studies. The thermal stability of these complexes was higher than that of κ -carrageenan and lower than that of ovalbumin. [ABSTRACT FROM AUTHOR]

FT-IR spectroscopy was used to study the specific interactions in an aliphatic polyacetamidine and its mixtures with a dicarboxylic acid. In the pure polyacetamidine, hydrogen bonds between the amidine groups were observed. After heating, considerable changes in the position of the interacting group vibration bands were found. These changes were reversible on cooling. In mixtures with glutaric acid strong acid base interactions resulting in the formation of ionic polymer networks were observed. These networks have proven stable up to at least 150 °C. [Copyright &y& Elsevier]

The intermolecular interaction and microsolvation process of isomeric C3H3+ ions in molecular nitrogen are characterized by infrared (IR) photodissociation spectroscopy of C3H3+–(N2)n complexes (n=1–6) and quantum chemical calculations (n=0–4). The rovibrational analysis of the C3H3+–N2 spectrum unambiguously reveals the presence of (at least) two C3H3+ isomers in the ion source, namely the propargyl (H2CCCH+) and the cyclopropenyl (c-C3H3+) cations. Analysis of the cluster size-dependent vibrational frequency shifts and splittings, the photofragmentation branching ratios, and the results of density functional calculations provides a consistent picture of the microsolvation of c-C3H3+ and H2CCCH+ in inert nitrogen. In the most stable c-C3H3+–(N2)n complexes, the first three N2 ligands form (nearly) linear and equivalent proton bonds to the three protons of c-C3H3+, leading to highly symmetric planar structures with C2v (n=1, 2) and D3h symmetry (n=3). After completion of this first solvation subshell at n=3, further N2 ligands form weaker intermolecular bonds to the C atoms of the nearly planar c-C3H3+–(N2)3 ion core. The dissociation energies of the H-bonds and C-bonds in c-C3H3+–(N2)n are estimated as D0(H)=900±130 cm−1 and D0(C)=860±170 cm−1, respectively. In the most stable H2CCCH+–N2 complex, the N2 ligand forms a linear ionic H-bond to the acetylenic C&z.sbnd;H group of H2CCCH+, leading to a planar structure with C2v symmetry. The calculations suggest that the next two ligands bind to the protons of the CH2 group giving rise to planar structures with Cs (n=2) and C2v symmetry (n=3), and these structures are compatible with the observed IR spectra. [Copyright &y& Elsevier]

The lyophilizing ability of a series of water-soluble cationic copolymers based on N,N′ -diallyl- N,N′ -dimethylammonium chloride (DADMAC) was estimated by turbidimetric titration. The copolymer of DADMAC with N- vinylpyrrolidone (DADMAC-VP) that has the best lyophilizing ability was chosen for further modification with betulonic acid (BA) triterpenoid to give ionic complexes with various compositions. The DADMAC-VP/BA complexes were characterized by spectroscopy, thermal analysis, and laser light scattering. The DADMAC-VP/BA complexes self-assemble into nano- and microparticles in aqueous solutions. It has been shown that these particles can solubilize molecules of compounds that are poorly soluble in water. [Display omitted] • The lyophilizing ability of cationic copolymers was evaluated. • The ionic complexes self-assemble into nano- and microparticles in aqueous solutions. • The ionic complexes based on a DADMAC-VP modified by triterpenoid were prepared. • The particles of ionic complexes can solubilize water-insoluble substances. [ABSTRACT FROM AUTHOR]

Topical administration to the eye for the treatment of glaucoma is a convenient route because it increases the patient comfort. Timolol can efficiently diminish the intraocular pressure (IOP) of the eye; however the topical application as a solution of timolol maleate (TM) has poor therapeutic index and presents severe side effects. The encapsulation of timolol in nanomaterials has appeared as a technology to increase its residence time in the eye thus achieving a sustained release and consequently diminishing the doses of this drug and their number. The preparation of nanogels (NGs) based on N-isopropylacrylamide (NIPA) and acrylic acid (AAc), easily synthesized by precipitation/dispersion free radical polymerization, is reported in this paper. Such NGs presented excellent dispersability in eye simulated fluid and ideal size for topical application. NGs can load efficiently timolol through ionic interaction, and the in vitro release showed that NGs deliver timolol in a sustained manner. In vivo sustained efficacy of the NGs-timolol nanoformulations was demonstrated in rabbit's glaucoma model, in which the IOP could be diminished and maintained constant for 48 h with only one application. Overall, the synthesized NGs in combination with timolol have potential as drug delivery system for glaucoma therapy. Unlabelled Image • Poly(NIPA- co -AAc) nanogels were prepared through a simple methodology. • Nanogels were loaded with timolol through strong ionic interaction. • In vitro release showed a slow and sustainable release of timolol. • In vivo studies demonstrated an improve in therapeutic index of timolol for glaucoma. [ABSTRACT FROM AUTHOR]

Zoledronic acid (ZA), a third-generation nitrogen-heterocycle-containing bisphosphonate, has been frequently used as an anti-resorptive agent to treat cancer-involved hypercalcemia and painful bone metastases. In order to expand the clinical applications of ZA toward the extraskeletal tumor treatment, it is essential to develop the functionalized nanocarriers capable of carrying high ZA payload and achieving intracellular triggered ZA release. In this end, the ZA-encapsulated hybrid polymeric nanoparticles were fabricated in this work by co -association of the amphiphilic diblock copolymer poly(lactic- co -glycolic acid)-b-poly(ethylene glycol) (PLGA-b-PEG), tocopheryl polyethylene glycol succinate (TPGS) segments and ionic complexes composed of ZA molecules and branched poly(ethylenimine) (PEI) segments. Notably, the ionic pairings of PEI segments with ZA molecules not only assisted encapsulation of ZA into the PLGA-rich core of hybrid nanoparticles but also reduced adhesion of ZA on the surfaces of hydrophobic cores, thus largely increasing ZA loading capacity. The dynamic light scattering (DLS) and transmission electron microscopy (TEM) characterization revealed that the ZA/PEI-loaded nanoparticles had a well-dispersed spherical shape. Moreover, compared to short PEI 1.8k (1.8 kDa) segments, the longer PEI 10k (10 kDa) segments formed more robust complexes with ZA molecules, thus prominently promoting ZA loading content of hybrid nanoparticles and their colloidal stability. Interestingly, with the suspension pH being reduced from 7.4 to 5.0, the considerable disruption of ZA/PEI ionic complexes owing to the acid-activated protonation of ZA molecules and the developed proton sponge-like effect inside the nanoparticle matrix upon the protonated PEI segments facilitated the rapid release of ZA molecules from drug-loaded hybrid nanoparticles. The results of in vitro cellular uptake and cytotoxicity studies showed that the ZA/PEI-loaded hybrid nanoparticles were internalized by MCF-7 cells upon energy-dependent endocytosis and displayed a superior cytotoxic effect to free ZA. This work demonstrates that the unique ZA/PEI-loaded hybrid polymeric nanoparticles display great promise for anticancer applications. Unlabelled Image • The encapsulation of ZA/PEI 10k ionic complexes into PLGA-rich core of hybrid nanoparticles largely increased ZA loading. • The ZA/PEI 10k -loaded hybrid nanoparticles exhibited acid-triggered rapid ZA release. • The ZA/PEI 10k -loaded hybrid nanoparticles showed the superior colloidal stability in FBS-containing aqueous solution. • The ZA/PEI 10k -loaded hybrid nanoparticles endocytosed by MCF-7 cells displayed a superior cytotoxic effect to free ZA. [ABSTRACT FROM AUTHOR]

• A new reaction of donor–acceptor cyclopropanes with dienes is suggested. • This process is promoted by GaCl 3 and occurs via 1,2-zwitterions. • It involves formal [2 + 4]-cycloaddition to the diene system. • The process is similar to the Diels-Alder reaction in ionic version. • Resulting structures have a functional substituted cyclohexene skeleton. A selective process of formal [2 + 4]-cycloaddition of donor–acceptor cyclopropanes (2-arylcyclopropane-1,1-dicarboxylates) in the presence of GaCl 3 to conjugated dienes to give cyclohex-3-ene-1,1-dicarboxylates has been developed. This process occurs by generation of 1,2-zwitterionic gallium complexes and involves the addition of a carbocationic center to a terminal diene atom followed by 1,6-cyclization to the allyl position of the resulting intermediate. [ABSTRACT FROM AUTHOR]