Br Anions Research Articles

Additive Selection Strategy for High Performance Perovskite Photovoltaics

Although much of the initial progress in perovskite solar cells has been made by the archetypal CH3NH3PbI3, incorporation of an additional cation such as formamidinium, cesium, and mixed halides have shown promising results in both stability and device performance. However, the role of the additional cations as well as the mixed halides is yet to be fully understood. In this work, we investigate the role of different additives including group I alkali metal cations (K, Rb, Cs and NH4) and halide anions (Br and I) on double-cation perovskites, i.e., [(MAPbBr3)0.15(FAPbI3)0.85]. A notably longer charge carrier lifetime is achieved for perovskite films with additives and may be attributed to defect passivation. Selection rules are put forward based on the effect of the ionic size of an additive on phase stabilization and defect passivation. Addition of complementary size cation with respect to cation size of the parent perovskite, mainly helps stabilizing the perovskite phase by tuning tolerance factor, whil...

Molecular Dynamic Simulations for the Extraction of Quinoline from Heptane in the Presence of a Low-Cost Phosphonium-Based Deep Eutectic Solvent.

The present study aims at the extraction of a polyaromatic hydrocarbon from fuel oils using a novel low-cost deep eutectic solvent (DES). The DES is prepared by mixing the hydrogen bond acceptor (HBA; methyltriphenylphosphonium bromide, MTPB) and hydrogen bond donor (HBD; ethylene glycol) at a molar ratio of 1:4. The liquid-liquid equilibrium is then measured at ambient condition. The classical molecular dynamic (MD) simulation technique is then employed to investigate and compare the experimental phase behavior of a DES-quinoline-heptane ternary system. For performing the MD simulations, two experimental feed points are considered which gave high selectivity and distribution coefficient values. The interaction energies of different species and the structural properties such as radial distribution functions, average number of hydrogen bonds, and spatial distribution functions (SDFs) are then computed. It is found that the cation within the HBA, namely, MTP, possesses favorable interactions with quinoline when compared to HBD or anion (Br). MTP here acts as a HBA and contributes to the hydrogen bonding with quinoline, which results in higher experimental selectivity values. The calculations of SDFs further reveal the fact that the DES molecules are evenly distributed around the active sites of the quinoline molecule, whereas heptane molecules are found to be distributed around the nonactive sites of the aromatic ring.

Pb2BO3Br: a novel nonlinear optical lead borate bromine with a KBBF-type structure exhibiting strong nonlinear optical response

Introducing a halogen bromine atom into a PbO–B2O3system generates a novel nonlinear optical material Pb2BO3Br.

Polymeric ionic liquid-assembled graphene-immobilized silica composite for selective isolation of human serum albumin from human whole blood.

Polymeric ionic liquids (PILs) with 1-vinyl-3-ethylimidazolium cations and two different anions of Br- and PF6- were assembled onto the surface of graphene (G) nanosheets. The derived two composites, i.e., PIL(Br)-G and PIL(PF6)-G, were further efficiently immobilized onto the surface of silica nanoparticles via self-assembly technique. The obtained two PIL-G/SiO2 nanocomposites exhibited diverse adsorption performances toward proteins through adjusting the anions of PILs. Electrostatic attractions between proteins and the nanocomposites dominated protein adsorption, while the presence of PF6- anions weakened electrostatic interactions and deteriorated the selective adsorption of target protein, i.e., bovine serum albumin (BSA) in this case. Specifically, PIL(Br)-G/SiO2 nanocomposite displayed high selectivity toward BSA and a high adsorption efficiency of ca. 98% was achieved for 100mgL-1 BSA in a Britton-Robinson (B-R) buffer at pH 5. HPLC analysis demonstrated the selectivity of PIL(Br)-G/SiO2 nanocomposite toward BSA in the presence of abundant hemoglobin and cytochrome c. The practical applicability was verified by performing selective isolation of human serum albumin (HSA) from human whole blood. Graphical abstract Selective isolation of human serum albumin from blood by polymeric ionic liquid assembled graphene immobilized silica nanocomposite with tunable anions.

Light-emitting diodes based on two-dimensional PA<sub>2</sub>(CsPbBr<sub>3</sub>)<sub><italic>n</italic></sub><sub>−</sub><sub>1</sub>PbBr<sub>4</sub> layered perovskites

Solution-processed organometal halide perovskites (formulated as ABX3, where A is the methylammonium (CH3NH3+) (MA) or metal cesium cation (Cs+), B is the lead cation (Pb2+) and X is the halide anion (Br−, I−, Cl−)) are promising candidates for next generation light-emitting materials owing to their unique optoelectronic properties. These properties mainly include extremely high photoluminescence quantum yield (PLQY), easily tunable band gap and narrow emission characteristics. During the past two years, impressive progresses have been made in perovskite light-emitting diodes (PeLED) with hybrid organic–inorganic perovskite materials (i.e., CH3NH3PbBr3). So far, the best external quantum efficiency (EQE) of CH3NH3PbBr3-based PeLED was reaching up to ~8.53% which was close to the results of organic light-emitting diodes (OLED). Despite the remarkable performance of the devices demonstrated, the stability of organic–inorganic hybrid perovskites remains a major concern. To circumvent this problem, all-inorganic halide perovskites exhibiting higher thermal and chemical stability, such as cesium lead bromide (CsPbBr3), have been used as alternative emitters in PeLED. Despite the advantages described above, both the brightness and the EQE of CsPbBr3-based PeLED remain limited. One important reason for low efficiency of CsPbBr3-based PeLED is the facile dissociation of excitons in 3D perovskites due to their small exciton binding energy. One promising way to enhance the exciton binding energy is reducing the grain size of perovskites. Herein, we report a solution process to form highly uniform and ultra-flat perovskite films with nanometre-sized grains that allow us to demonstrate efficient PeLED. By mixing long-chain ammonium halides of CH3CH2CH2NH3Br (PABr) with the 3D CsPbBr3 perovskite precursor solution, the growth of 3D perovskite grains are dramatically impeded and the PA2(CsPbBr3) n −1PbBr4 quantum dots with grain size of ~100 nm were achieved. This is because the long-chain ammonium ions cannot fill the corner of PbBr4 octahedral layers and therefore impedes the 3D perovskite formation. Moreover, the nanometre-sized grains feature reduced dimensionality, starting a transition from 3D to 2D layered (so-called Ruddlesden-Popper phase) perovskite structures. The SEM image show the morphology of PA2(CsPbBr3) n −1PbBr4 layer was dense and uniform, which is very important to suppress the leaking current in the PeLED. We found that PA2(CsPbBr3) n −1PbBr4 film mainly consists of two different 2D structures, namely PA2PbBr4 ( n =1) and PA2(CsPbBr3)PbBr4 ( n =2), according to the analysis of XRD pattern. Compared to the single UVs absorption peak of CsPbBr3 at ~520 nm, PA2(CsPbBr3) n −1PbBr4 film show multiple absorption peaks, indicating several extonic states are formed upon light excitation. Although several extonic states exist, photoluminescence (PL) with only one peak of 506 nm was observed in PA2(CsPbBr3) n −1PbBr4 film. We suspect that the energy transfer occurs from the excitons with larger bandgap to those with smaller bandgap, making recombination occurs only in the excitons with the smallest bandgap. For the PeLED with structure of ITO/PEDOT:PSS/PA2- (CsPbBr3) n −1PbBr4/TPBi/Cs2CO3/Al, the turn-on voltage is ~4.2 V, the maximum luminance is ~2370 cd/m2, the maximum current efficiency is ~1.06 cd/A, and maximum EQE is ~0.57%. Compared to the traditional method achieving blue PeLED by substituting halide anions, obvious improvements can be seem not only in the material processing and the perovskites film quality, but also in the PeLED′s performance. Our studies may provide an alternative way to explore low-cost and high- efficiency blue PeLED.

An Investigation of the Symmetric and Asymmetric Cleavage Products in the System Aluminum Trihalide/1-Butylimidazole.

Mixtures of AlX3 (X=Cl, Br) with 1-butylimidazole (BuIm) in various ratios were investigated. The mixtures were characterized by multinuclear (1 H, 27 Al, 13 C, and 15 N) NMR, IR, and Raman spectroscopy and in part by single-crystal X-ray diffraction. Depending on the molar fraction x(AlBr3 ) of the AlBr3 -based mixtures, the cationic aluminum complexes [Al(BuIm)6 ]3+ and [AlBr2 (BuIm)4 ]+ , the neutral adduct [AlBr3 (BuIm)], as well as the anions Br- , [AlBr4 ]- , and [Al2 Br7 ]- could be identified as the products of the symmetric and asymmetric cleavage of dimeric Al2 Br6 . Furthermore, there are hints at the formation of [AlBr2 (BuIm)2 ]+ or related cations. Comparison of the AlBr3 /BuIm system with AlCl3 -based mixtures revealed the influence of the halide: In contrast to AlBr3 , the trication [Al(BuIm)6 ]3+ could not be detected as main product in a 1:6 mixture of AlCl3 and BuIm. Additionally, [AlCl3 (BuIm)] crystallizes from a mixture with x(AlCl3 )=0.60 at room temperature, whereas the corresponding AlBr3 -based mixture remains liquid even at +6 °C. Three AlBr3 -based mixtures are liquid at room temperature, whereas all other mixtures are solids with melting points between 46 and 184 °C. The three liquid mixtures exhibit medium to high viscosities (117 to >1440 mPa s), low conductivities (0.03-0.20 mS cm-1 ), but high densities (1.80-2.21 g cm-3 ). Aluminum could be successfully deposited from one of the neat Lewis acidic mixtures of the AlBr3 -based system.

Surprising behaviors in the temperature dependent kinetics of diatomic interhalogens with anions and cations.

Rate constants and product branching fractions of reactions between diatomic interhalogens (ICl, ClF) and a series of anions (Br-, I-) and cations (Ar+, N2+) are measured using a selected ion flow tube apparatus and reported over the temperature range 200-500 K. The efficiency of both anion reactions with ICl is 2%-3% at 300 K to yield Cl-, increasing with temperature in a manner consistent with the small endothermicities of the reactions. The anion reactions with ClF are 10%-20% efficient at 300 K to yield Cl- and also show a positive temperature dependence despite being highly exothermic. The stationary points along the anion + ClF reaction coordinates were calculated using density functional theory, showing no endothermic barriers inhibiting reaction. The observed temperature dependence can be rationalized by a decreasing dipole attraction with increasing rotational energy, but confirmation requires trajectory calculations of the systems. All four cation reactions are fairly efficient at 300 K with small positive temperature dependences, despite large exothermicities to charge transfer. Three of the four reactions proceed exclusively by dissociative charge transfer to yield Cl+. The N2+ + ClF reaction proceeds by both non-dissociative and dissociative charge transfer, with the non-dissociative channel surprisingly increasing with increasing temperature. The origins of these behaviors are not clear and are discussed within the framework of charge-transfer reactions.

Preparation and orthogonal postmodification of dual‐clickable polymer precursors bearing both aldehyde and alkyne groups

ABSTRACTA new styrenic monomer 2‐propargyloxy‐5‐vinylbenzaldehyde (PVB) containing both aldehyde and alkyne reactive groups was designed for the synthesis and subsequent orthogonal postfunctionalization of dual‐clickable polymer precursor. Reversible addition‐fragmentation chain transfer polymerization of PVB afforded a structurally well‐defined polymer poly(2‐propargyloxy‐5‐vinylbenzaldehyde) (PPVB) bearing alkyne and aldehyde functionalities that are reactive towards azide‐ and aminooxy‐containing molecules, respectively. Therefore, the resulting PPVB can be served as a dual‐clickable polymer scaffold for construction of multiple functional polymers via orthogonal alkyne–azide and aldehyde–aminooxy click reactions. Postpolymerization modification of PPVB sequentially with aminooxy‐terminated poly(ethylene oxide)s (H2NO‐PEO) and azide‐functionalized imidazolium‐type ionic liquid (N3‐IL·TFSI, having bis(trifluoromethane)sulfonamide, TFSI, counter‐anion) yielded an interesting multicomponent graft polymer PPVB‐g‐(PEO‐and‐IL·TFSI). After anion exchange of hydrophobic TFSI counter‐anion by bromide (Br) anion, the resulting graft copolymer PPVB‐g‐(PEO‐and‐IL·Br) becomes soluble in water, and its imidazolium units can capture negatively charged tetraphenylethylene disulfonate derivative (TPE‐2 ) guest molecule via electrostatic complexation to form in situ self‐assembled fluorescent nanoaggregates with colloidal stability imparted by hydrophilic PEO chains. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 2650–2656

Field-Assisted Slow Magnetic Relaxation in a Six-Coordinate Co(II)-Co(III) Complex with Large Negative Anisotropy.

The reaction of Co(CH3COO)2·4H2O with the Schiff base ligand LH4 derived from o-vanillin and tris(hydroxymethyl)aminomethane produces the dinuclear mixed-valence complex [CoIICoIII(LH2)2(CH3COO)(H2O)](H2O)3 (1), which has been investigated using IR spectroscopy, X-ray crystallography, temperature-dependent magnetic susceptibility, magnetization, HFEPR spectroscopy, and ac susceptibility measurements at various frequencies, temperatures, and external magnetic fields. The structure of 1 consists of neutral molecules in which two cobalt ions with distorted octahedral geometries, CoIIO6 and CoIIIN2O4, are bridged by two deprotonated -CH2O- groups of the two LH22- ligands. 1 completes a series with Cl, Br, NO3, and NCS anions published before by different authors. Low-temperature HFEPR measurements reveal that the ground electronic state of the Co(II) center in 1 is a highly anisotropic Kramers doublet; the effective g values of 7.18, 2.97, and 1.96 are frequency-independent over the frequency ranges 200-630, 200-406, and 200-300 GHz for the highest, intermediate, and lowest geff values, respectively. The two lower values were not seen at higher frequencies because the magnetic field was not high enough. Temperature-dependent magnetic susceptibility and field-dependent magnetization data confirm high magnetic anisotropy of the easy axis type. Complex 1 behaves as a single-ion magnet under a small applied external field and demonstrates two relaxation modes that strongly depend on the applied static dc field. The observation of multiple relaxation pathways clearly distinguishes 1 from the Cl and Br analogues.

Theoretical insights into the interaction between RunPt13-n (n = 4, 7 and 9) clusters and [BMIM]+ based ionic liquids: Effect of anion

Density functional theory has been performed to systematically study the interactions between RunPt13-n (n=4, 7 and 9) clusters and [BMIM]+ based ionic liquids. Ionic liquids [BMIM][Br], [BMIM][BF4], [BMIM][PF6], [BMIM][CF3SO3], and [BMIM][NTf2] have different effects on the stability of Ru7Pt6. Ionic liquids with median size anions of PF6− and CF3SO3− can better improve the stability of Ru7Pt6 than those with the small anions of Br− and BF4− and large anion of NTf2−. Based on negative relaxation energies, the stabilities of Ru4Pt9, Ru7Pt6, and Ru9Pt4 are all enhanced after interacting with [BMIM][CF3SO3]. The stability enhanced degree is in agreement with the interaction strength. For Ru7Pt6–n{[BMIM][CF3SO3]} (n=1, 2, 3, 4), the interaction between ionic liquid and cluster plays the primary role in stabilizing the cluster in Ru7Pt6–[BMIM][CF3SO3]. With the increase of the number of [BMIM][CF3SO3], the role of the interaction in stabilizing the cluster is getting weaker, while the role of steric protection is getting more important.

ESI activity of Br⁻, BF₄⁻ , ClO₄⁻ and BPh₄⁻ anions in the presence of Li⁺ and NBu⁴⁺ counter-ions.

To improve our understanding of the electrospray ionization (ESI) process, we have subjected equimolar mixtures of salts A+ X- (A+ =Li+ , NBu4+ ; X- =Br- , ClO4- , BF4- , BPh4- ) in different solvents (CH3 CN, tetrahydrofuran, CH3 OH, H2 O) to negative-ion mode ESI and analyzed the relative ESI activity of the different anionic model analytes. The ESI activity of the large and hydrophobic BPh4- ion greatly exceeds that of the smaller and more hydrophilic anions Br- , ClO4- and BF4- , which we ascribe to its higher surface activity. Moreover, the ESI activity of the anions is modulated by the action of the counter-ions and their different tendency toward ion pairing. The tendency toward ion pairing can be reduced by the addition of the chelating ligands 12-crown-4 and 2.2.1 cryptand and is, although to a smaller degree, further influenced by the variation of the solvent. Complementary electrical conductivity measurements afford additional information on the interactions of the ionic constituents of the sample solutions. Copyright © 2017 John Wiley & Sons, Ltd.

Toxicity evaluation of selected ammonium-based ionic liquid forms with MCPP and dicamba moieties on Pseudomonas putida

Combination of the hydrophilic herbicidal anion with hydrophobic, antimicrobial ammonium cation allows to obtain compounds in ionic liquid form with better properties then conventional herbicides. Both cation and anion can be modified by selection of herbicide and the length of alkyl chains in cation structure. However the knowledge of their potential toxic effects are still limited. Furthermore, the relation between hydrophobicity associated with the length of alkyl chains and toxicity for ionic liquids has not been thoroughly studied. Therefore we investigated toxic effects of herbicidal ionic liquid forms on growth inhibition, given as EC50, of the common soil bacterium Pseudomonas putida. We thereby concentrated on quaternary ammonium salts. Analyzed compounds were composed of dicamba or MCPP moieties and cation with various alkyl chain lengths (n = 6,8,10) We compared them with commercial herbicides, and ammonium-based ionic liquids with neutral anion (Br−). In addition, cis-trans isomerisation of unsaturated membrane fatty acids in Pseudomonas putida was applied as the proxy for toxicity and membrane activity. We showed that toxicity increased with the length of alkyl chains. However, this correlation is only valid for six and eight carbon atom in alkyl chains, where for n = 10 the EC50 values rise by one order of magnitude. In our studies, the herbicidal ionic liquids [C10,C10,C1,C1N][MCPP] and [C10,C10,C1,C1N][dicamba] showed the lowest toxicity among analyzed quaternary ammonium salts and comparable toxicity with corresponding herbicides. No clear increase in toxicity could be followed by changing the anion moieties for ammonium-based ionic liquid forms.

Efficient exciton generation in atomic passivated CdSe/ZnS quantum dots light-emitting devices

We demonstrate the first-ever surface modification of green CdSe/ZnS quantum dots (QDs) using bromide anions (Br-) in cetyl trimethylammonium bromide (CTAB). The Br- ions reduced the interparticle spacing between the QDs and induced an effective charge balance in QD light-emitting devices (QLEDs). The fabricated QLEDs exhibited efficient charge injection because of the reduced emission quenching effect and their enhanced thin film morphology. As a result, they exhibited a maximum luminance of 71,000 cd/m2 and an external current efficiency of 6.4 cd/A, both significantly better than those of their counterparts with oleic acid surface ligands. In addition, the lifetime of the Br- treated QD based QLEDs is significantly improved due to ionic passivation at the QDs surface.

Hofmeister Anion Effects on Protein Adsorption at an Air-Water Interface.

Hofmeister anion effects on adsorption kinetics of the positively charged lysozyme (pH < pI) at an air-water interface were studied by surface tension measurements and time-resolved X-ray reflectometry. In the salt-free solution, the protein adsorption rate increases with decreasing the net positive charge of lysozyme. When salt ions are dissolved in water, the protein adsorption rate drastically increases, and the rate is following an inverse Hoffmeister series (Br(-) > Cl(-) > F(-)). This is the result of the strongly polarized halide anion Br(-) being attracted to the adsorbed protein layer due to strong interaction with local electric field, while weakly polarized anion F(-) having no ability to penetrate the protein layer. In X-ray reflection studies, we observed that the lysozyme molecules initially adsorbed on the air-water interface have a flat unfolded structure as previously reported in the salt-free solution. In contrast, in the concentrated salt solutions, the lysozyme molecules begin to refold during adsorption. This protein refolding as a result of protein-protein rearrangements may be a precursor phenomenon of crystallization. The refolding is most significant for Cl(-), which is a good crystallization agent, whereas it is less observed for the strongly hydrated F(-). It is widely known in the bulk state that kosmotropic anions tend to precipitate proteins but at the same time stabilize proteins against denaturing. On the other hand, at the air-water interface where adsorbed proteins usually unfold, we observed chaotropic anions strongly bound to proteins that reduce electrostatic repulsion between protein molecules, and subsequently they induce protein refolding whereas the kosmotropic anions do not.

First-Principles Molecular Dynamics of Non-Arrhenius Li+ Diffusion in Solid Electrolytes for Batteries

Our simulations address a long-standing problem in the design of solid-state batteries – the low ionic conductivity across solid-solid interfaces and through the solid electrolyte. Significant insights in developing new battery materials can be achieved through understanding of Li+ ion diffusion, using first-principles molecular dynamics simulations. Previous research from our group has determined the mechanism for the lithium ion diffusion pathway through the Li3InBr6 crystal1. Our results expanded on these findings by simulating diffusion in Li3InCl6 and Li3InBr6-xClx. In particular, we focus on determining the effects of high temperature and electronic structure, in order to explain variation in the Li+ conductivity in these lithium halides. We explore the hypothesis that covalent-like bonds between Li+ and the halide anions help drive conductivity through correlated motion of the Li+ ions. Our novel approach dynamically tracks covalent bonds, especially correlated bond breaking and forming. Thus, the electronic structure must be simulated and to do this we use ab-initio DFT simulations, within the Quantum Espresso implementation. In our previous research, we noted that the conductivity of Li3InBr6 is non-Arrhenius at high temperatures. The diffusion mechanism does not change with temperature, so the effect was hypothesized to be from changes in the electronic structure, such as the weakening of bonds. The first step of our investigation was to determine the simulated melting temperature of Li3InBr6, as our simulations at 900K may be near the simulated melting temperature, which could explain the weakening of bonds. The melting temperature is simulated starting with an amorphous, 3 x 3 x 3 supercell containing 520 atoms. Then using the two-phase approach (TPA) with 1040 atoms, we determined the melting temperature. Second, we simulated Li+ diffusion along with the breaking and forming of covalent-like bonds using first principle dynamics and Wannier analysis. Exchange of Br anions with Cl anions changes the nature of covalent type bonds, but does not affect ionic bonds. To further explore nature of the interaction between the Li+ and the anion sub-lattice, the Br concentration in Li3InBr6-xClx was varied and bond breaking and forming is tracked. We established that lithium ion diffusion, near the melting temperature, is impeded compared to lower temperatures owing to a degradation of covalent-like bonds. The Li+ diffusion mechanism, from octahedral to tetrahedral back to octahedral sites, is propelled by the fluctuations of neighboring covalent-like bonds. Decreasing the Br concentration in Li3InBr6-xClx shows a non-monotonic change in conductivity, which is unexplainable in a purely ionic view of Li+ diffusion. The disorder caused by different bonds strength between Li+ and Cl- versus Br- leads to a relatively high conductivity when the ratio of Cl to Br is 1:1 but a marked decrease with other ratios2. Our novel first-principles study of the dynamic electronic structure is the only way to understand these unusual trends in conductivity and potentially predict conductivity in many solid state electrolytes. 1) Adelstein, N. and Wood, B. Li+ conductivity in a superionic solid electrolyte driven by dynamically frustrated bond disorder. Journal of Materials Chemistry (2016) submitted. 2. Tomita, Y. Substitution effect of ionic conductivity in lithium ion conductor, Li3InBr6-xClx. Solid State Ionics. (2008) 179, 867-870.

Facile fabrication of large-grain CH3NH3PbI3-xBrx films for high-efficiency solar cells via CH3NH3Br-selective Ostwald ripening.

Organometallic halide perovskite solar cells (PSCs) have shown great promise as a low-cost, high-efficiency photovoltaic technology. Structural and electro-optical properties of the perovskite absorber layer are most critical to device operation characteristics. Here we present a facile fabrication of high-efficiency PSCs based on compact, large-grain, pinhole-free CH3NH3PbI3−xBrx (MAPbI3−xBrx) thin films with high reproducibility. A simple methylammonium bromide (MABr) treatment via spin-coating with a proper MABr concentration converts MAPbI3 thin films with different initial film qualities (for example, grain size and pinholes) to high-quality MAPbI3−xBrx thin films following an Ostwald ripening process, which is strongly affected by MABr concentration and is ineffective when replacing MABr with methylammonium iodide. A higher MABr concentration enhances I–Br anion exchange reaction, yielding poorer device performance. This MABr-selective Ostwald ripening process improves cell efficiency but also enhances device stability and thus represents a simple, promising strategy for further improving PSC performance with higher reproducibility and reliability.

Porous polymers bearing functional quaternary ammonium salts as efficient solid catalysts for the fixation of CO2 into cyclic carbonates

A series of porous polymers bearing functional quaternary ammonium salts were solvothermally synthesized through the free radical copolymerization of divinylbenzene (DVB) and functionalized quaternary ammonium salts. The obtained polymers feature highly cross-linked matrices, large surface areas, and abundant halogen anions. These polymers were evaluated as heterogeneous catalysts for the synthesis of cyclic carbonates from epoxides and CO2 in the absence of co-catalysts and solvents. The results revealed that the synergistic effect between the functional hydroxyl groups and the halide anion Br− afforded excellent catalytic activity to cyclic carbonates. In addition, the catalyst can be easily recovered and reused for at least five cycles without significant loss in activity.

Mutual neutralization of He(+) with the anions Cl(-), Br(-), I(-), and SF6 (.).

Mutual neutralization (MN) rate coefficients kMN for He(+) with the anions Cl(-), Br(-), I(-), and SF6 (-) are reported from 300 to 500 K. The measured rate coefficients may contain a contribution from transfer ionization, i.e., double ionization of the anion. The large rate coefficient for He(+) + SF6 (-) (2.4 × 10(-7) cm(3) s(-1) at 300 K) is consistent with earlier polyatomic MN results found to have a reduced mass dependence of μ(-1/2). Neutralization of He(+) by the atomic halides follows the trend observed earlier for Ne(+), Ar(+), Kr(+), and Xe(+) neutralized by atomic halides, kMN (Cl(-)) < kMN (Br(-)) < kMN (I(-)). Only an upper limit could be measured for the neutralization of He(+) by Cl(-). Predictions of the rate coefficients from a previously proposed simple model of atomic-atomic MN results are consistent with the present He(+)-halide rate coefficients. The temperature dependences are modestly negative for Br(-) and I(-), while that for SF6 (-) is small or negligible.

Ionic Polymer Microspheres Bearing a Co(III) -Salen Moiety as a Bifunctional Heterogeneous Catalyst for the Efficient Cycloaddition of CO2 and Epoxides.

We report a unique strategy to obtain the bifunctional heterogeneous catalyst TBB-Bpy@Salen-Co (TBB=1,2,4,5-tetrakis(bromomethyl)benzene, Bpy=4,4'-bipyridine, Salen-Co=N,N'-bis({4-dimethylamino}salicylidene)ethylenediamino cobalt(III) acetate) by combining a cross-linked ionic polymer with a Co(III) -salen Schiff base. The catalyst showed extra high activity for CO2 fixation under mild, solvent-free reaction conditions with no requirement for a co-catalyst. The synthesized catalyst possessed distinctive spherical structural features, abundant halogen Br(-) anions with good leaving group ability, and accessible Lewis acidic Co metal centers. These unique features, together with the synergistic role of the Co and Br(-) functional sites, allowed TBB-Bpy@Salen-Co to exhibit enhanced catalytic conversion of CO2 into cyclic carbonates relative to the corresponding monofunctional analogues. This catalyst can be easily recovered and recycled five times without significant leaching of Co or loss of activity. Moreover, based on our experimental results and previous work, a synergistic cycloaddition reaction mechanism was proposed.

Anti-bacterial screening of water soluble carbonyl diimidazolium salts and its derivatives

We have examined the antibacterial screening against Gram positive and Gram negative pathogens with nearly eight different counter anions containing carbonyl diimidazolium salts. We have carried out antibactericidal studies under well diffusion and micro dilution as well as docking techniques for carbonyl diimidazolium salts. Counter anion Br− and CF3SO3− containing carbonyl diimidazolium salt with benzyl substituted compounds showed better inhibitory activities than the others. We have described the hydrogen bonding and binding energy between the proteins and our carbonyl diimidazolium salts under computer assisted docking analysis.