Replacement Of Anion Research Articles

Replacement of interlayer anion via memory effect of layered double hydroxide: A promising strategy for fabricating nanostructures with better flame-retardant performance

According to the memory effect of layered double hydroxide (LDH), the LDH nanostructure containing polyoxometalates anion (LDH-MoP) was prepared by an anion exchange process. Compared with the original LDH contained carbonate ion (LDH-C), the LDH-MoP exhibited a hydrotalcite laminated structure with larger interlayer spacing than that of LDH-C, implying that the carbonate ions between LDH-C layers were replaced by polyoxometalates anions. The LDH-MoP obtained via replacement of anions by polyoxometalates anion could lead to a more homogeneous dispersion and better synergistic effect of flame-retardant components than those in the physically mixed sample of LDH-C and Na3[PMo12O40] ·xH2O. After adding 3 wt% LDH-MoP in epoxy resin (EP), EP/LDH-MoP shows the most significant decrease in peak heat release rate (PHRR), total heat release (THR), peak smoke rate (PSPR), and total smoke release (TSR). The Limited Oxygen Index (LOI) value of EP/LDH-MoP has been significantly improved, and a UL-94 V-0 rating (LOI = 32.1%) can be achieved. In addition, compared with that of the physical mixture, the EP/LDH-MoP generates a denser and more compact char residue after the cone calorimeter test, suggesting that the oxygen exchange, smoke diffusion, and heat transfer could be more effectively hindered during the combustion process of the latter. This study could provide a novel strategy for designing high-performance flame retardants and some valuable clues for the enhancement of homogeneous dispersion and the synergistic effect of inorganic flame retardants.

The simulation of a green room-temperature ternary solution of water, methanol and 1-ethyl-3-methyl imidazolium chloride by all-atom Monte Carlo and DFT computational approaches

A highly dense ternary solution of water, methanol and 1-ethyl-3-methyl imidazolium chloride [emim][Cl] was investigated by a Monte Carlo (MC) program written in C language, Density Functional Theory (DFT) and Atoms-In-Molecules (AIM) theory. The all-atom approach in MC calculations of a ternary solution, the use of nonzero LJ parameters for all hydrogen atoms in simulation box and the creation of a new strategy for filling simulation box with many molecules were adopted in this research to yield a comprehensive, accurate and different work. The radial distribution function, the molar heat capacities in constant volume and pressure, the thermal expansivity, and the isothermal compressibility of the ternary system were calculated. The chemical potentials were calculated at different temperatures through Widom insertion method and the behaviors of both ideal and excess parts of chemical potentials were analyzed versus temperature. The value of electric permittivity of solution, the change of number of methanol and water molecules and the replacement of chloride anion with iodide in ionic liquid were also explored through separate simulations. The solvation structure and coordination number were investigated for various systems. The optimized sites for water and methanol around [emim]+ recognized by DFT and the HOMO and LUMO isosurfaces were discussed. Also, the hydrogen bonds between components of ternary solution were determined by AIM theory. It was shown that the results of quantum mechanics calculations confirm those of MC simulations.

Tunable phase transition, band gap and SHG properties by halogen replacement of hybrid perovskites [(thiomorpholinium)PbX3, X = Cl, Br, I

By the replacement of halogen anion, three new multifunctional organic-inorganic hybrid perovskites (thiomorpholinium)PbX3 (X = Cl, Br, I) were successfully synthesized and underwent reversible structural transformation above room temperature, accompanied by the anomalous change of dielectric constant. With the adjustment of the halogen anion from Cl to I in the inorganic skeleton, the space group is transformed from centrosymmetric space group P21/c ((thiomorpholinium)PbCl3) to chiral one P212121 ((thiomorpholinium)PbBr3, (thiomorpholinium)PbI3) at room temperature. The ordered-disordered transition of organic cations and the change of hydrogen bonds with the increase of temperature lead to above-room-temperature phase transitions. Ultraviolet absorption and second-harmonic generation (SHG) measurements confirmed that both the band gap and SHG activity of (thiomorpholinium)PbX3 (X = Cl, Br, I) crystals were tunable. The band gaps reveal a broadening trend with 3.532 eV, 3.410 eV and 3.175 eV along the Cl → Br → I series. This work provides an effective molecular design for multifunctional organic-inorganic perovskites.

Synthesis, thermal properties, vibrational spectra and computational studies of Trioctylmethylammonium bis(trifluoromethylsulfonyl)imide ionic liquid

In this work, Aliquat 336 ([Aliquat+]) based ionic liquids containing the fluorinated anion bis(trifluoromethylsulfonyl)imide [NTf2−] was successfully prepared by the anionic exchange replacement of the chloride anion. The reaction of lithium bis(trifluoromethylsulfonyl)imide with N-Methyl-N,N,N-trioctylammonium chloride ([N1,8,8,8][Cl] in water lead to the corresponding IL, namely ([Aliquat+][NTf2−]). The obtained ionic liquid was characterized by using infrared and Raman spectra and its structure was confirmed by 1H NMR, 13C NMR, and 19F-NMR. The thermal properties were investigated by two complementary thermal analysis techniques: TGA and DTA. A hexadentate coordination mode between cation-anion was predicted by atoms in molecules (AIM) studies for the [Aliquat+][NTf2−] IL by using B3LYP/6–31G* calculations where three O atoms of the anion in Cis conformation are linked to six H atoms of cation by S-O•••H interactions. Changes in the bond orders of S and O atoms of the cation supported such observations. The predicted cation-anion distances were in the range 2.30–2.60 Å. The harmonic force fields of cation and anion were calculated and the complete assignments were performed for both species while the most important bands observed in the infrared and Raman spectra of the IL were assigned. In addition, the scaled force constants of cation and anion of the IL were also reported.

Does the salt really matter? Impact of the counterion upon ECL signal

The incorporation of counterions into a variety of substances to control a number of their physiochemical properties is vital within a range of fields. Electrochemiluminescence (ECL) based sensors have grown in popularity in recent years with their employment observed across analytical and bioanalytical applications. ECL is typically concerned with the core electroactive functionality of the species of interest, with structural similarities commonly employed to determine the likelihood of a species ECL capability. However, to date no consideration has been given to the impact of different counterions toward an analytes ECL mechanism. Here we report for the first time how a simple alternation to a co-reactants counterion can significantly impact upon its recorded ECL response. Utilizing the tropane alkaloid scopolamine and its hydrobromide and hydrochloride salt forms, we have seen through interrogation with the traditional ruthenium luminophore, that replacement of the bromide anion for the chloride anion can reduce the electroactivity of the species. Direct comparison between the hydrobromide and hydrochloride salt forms relived differences in respect of their emission potentials and intensities. The impact of the salt form upon the ECL response has here been investigated, in respect to predicted concentrations. Results demonstrated how vastly different concentrations were obtained dependent upon the salt form present within the sample and that which was used to produce the calibration curve. The impact of this discovery will be of interest to the electrochemiluminescent and electroanalytical communities, and in particular forensic practitioners where electrochemical and ECL based sensors are of increasing interest. Ultimately the application of an ECL sensor within an analytical environment relies upon its accuracy and hence a thorough understanding of the phenomenon observed will only stand to widen the acceptance of ECL within the wider analytical community and increase its potential future applications.

Enhancement of Lignin Extraction of Poplar by Treatment of Deep Eutectic Solvent with Low Halogen Content.

A novel choline-based deep eutectic solvent (DES) with low halogen content—namely choline lactate-lactic acid (CLL)—was synthesized by replacing the chloride anion with lactate anion in choline chloride-lactic acid (CCL). CLL and CCL treatments were conducted at 140 °C for 12 h with hydrogen bond acceptor/hydrogen bond donor =1/10, thereafter composition analysis and characterizations of the lignin extracted by DES treatment (DES lignin) and the solid residue were carried out. The proposed low halogen content DES presented an improved lignin extraction efficiency. The CLL treatment extracted 90.13% of initial lignin from poplar, while CCL extracted 86.02%. In addition, the CLL treatment also provided DES lignin with an improved purity (91.17%), lower molecular weight (Mw/Mn=1805/971 g/mol) and more concentrated distribution (polydispersity index=1.86). The efficient lignin extraction was mainly ascribed to the cleavage of β-O-4 bonds in lignin macromolecule, especially in the guaiacyl units, thereby breaking them into smaller molecules, facilitating the lignin extraction. The replacement of chloride anion allowed CLL acting as a more efficient DES to interact with lignin macromolecules, thus providing lignin with higher uniformity and suitable molecular weight. The low halogen content DES system proposed in present work could benefit the fractionation of biomass, improve the valorization of lignin compounds and facilitate industrial process in the downstream.

Improved performance of pure red perovskite light-emitting devices based on CsPb(Br1-xIx)3 with variable content of iodine and bromine.

All-inorganic cubic α-CsPbI3 perovskite for red perovskite light-emitting device (PeLED) applications is suffering from a phase transition. Unstable black α phase tends to transit to yellow δ phase under ambient conditions, which results in poor performance of the CsPbI3-based PeLEDs. Partial replacement of iodine anion with a comparatively smaller bromine anion in the perovskite film can effectively adjust the Goldschmidt tolerance factor and stabilize the α-phase. A phase-stable CsPb(Br1-xIx)3 perovskite has been obtained at low annealing temperature of 50°C by tuning the iodine-to-bromine ratios. A PeLED with pure red emission based on the CsPb(Br0.43I0.57)3 perovskite has been demonstrated. The maximum luminance and efficiency were 2200cd/m2 and 0.38 cd/A, respectively. Moreover, the PTAA layer was introduced between the PEDOT:PSS and perovskite film to improve the surface morphologies of perovskite. As a result, red PeLEDs with a maximum luminance of 2765cd/m2 have been achieved.

The effect of imidazolium salts with amino acids as counterions on the reactivity of 4-nitrophenyl acetate: A kinetic study

As a first approach to improve the “green character” of the surfactants based on imidazolium cations, three surfactants using 1-tetradecyl-3-methylimidazolium [C14mim]+ as cation and different amino acids (AA) as counterion, were synthetized [C14mim][AA], where AA: L-alanine (L-Ala); L-phenylalanine (L-Phe) or L-proline (L-Pro). The aggregation behavior of these surfactants in water was characterized by surface tension, conductivity measurements and ITC, in order to determine the critical micelle concentration (CMC) and to provide aggregation parameters. In other to evaluate the replacement of a simple inorganic anion [Br]− by AAs in the structure of these surfactants, the characterization of [C14mim][Br] was including as well.We present the application of the micellar solutions (formed with this surfactants), as reaction media for the reaction of 4-nitrophenyl acetate (NPA) and found that reaction rates (kobs) increase significantly compared to the reaction in water. Additionally, a novel reactivity modulation of NPA in these micellar systems was found.

Promising Directions for the Stabilization of Ferroalloy Production Slags

In this paper the analysis of the processes for spontaneous decay of slags from the production of refined ferroalloy grades is performed. It is shown that the main reason for the decay is the formation of a dicalcium silicate in highly basic melts with CaO / SiO2 ratio of 1.5-3.1. Based on the performed studies, three main promising directions for the stabilization of slags of ferroalloy production have been formed. First direction is the replacement of the calcium cation (or transformation) in a dicalcium silicate, for example, with the magnesium cation or the production of non-decaying compounds of the gehlenite type (2CaO·Al2O3·SiO2), mainly due to the application of phase composition peculiarities of the waste rock for ferroalloy raw materials. Second direction is the reduction of the dicalcium silicate content with a decrease in the ratio of CaO / SiO2 in the slag less than 1.4, due to the separation of the silicothermic reduction process into two stages, obtaining in the first stage a low-basic (CaO / SiO2 = 1.3-1.4) non-decaying tailing slag, and on the second one - highly basic return slag (1.8-1.9), which is used in the first stage of this technological chain. The third direction is the replacement of the SiO anion of dicalcium silicate with other anions, for example, ВО by means of small additions of calcium borate, colemanite, etc. A possibility for stabilization of ferroalloy production slags with obtaining of construction crushed stone corresponding to the requirements of TU 0798-69-00186499-2014 "Crushed stone and sand from ferroalloy slags. Technical conditions», is shown experimentally.

Stable, color-tunable 2D SCN-based perovskites: revealing the critical influence of an asymmetric pseudo-halide on constituent ions.

Two-dimensional (2D) layered perovskites (An+1BnX3n+1, n = 1, 2, …) have recently attracted significant research interest because of their enhanced ambient stability compared to their conventional 3D counterparts. In addition to the common A-site cation engineering, using an asymmetric pseudo-halide anion, SCN-, in the anion X-site has been recently proven to be another effective approach to constitute 2D perovskites. Among these, 2D (MA)2Pb(SCN)2I2 was the most widely investigated and was considered to be a promising material owing to its good optoelectronic properties; however, its poor stability has aroused concerns in recent researches. In this study, systematical composition engineering of A2Pb(SCN)2X2 (A = FA+, MA+, Cs+ and X = Br-, I-) was conducted. Our results revealed that the linear SCN- anion dictates critical restrictions on the constituent ions of its derived 2D framework (PbX4(SCN)2), which has not yet been extensively discussed. We demonstrated that using a smaller Cs+ cation can afford a more favorable 2D structure compared with the MA+ cation. Cs2Pb(SCN)2I2 was revealed to possess improved stability and photo-response compared to (MA)2Pb(SCN)2I2. Interestingly, Cs2Pb(SCN)2I2 and (MA)2Pb(SCN)2I2 appear to possess distinct electronic band structures. This is indicated by their discrepant photoluminescence spectra, in which the former exhibits a rather intense singlet emission at room temperature in contrast with the latter, which shows a dominant emission associated with triplet or defective states. Furthermore, using a smaller Cs+ cation enables facile replacement of a smaller halide anion. A series of mixed-halide 2D Cs2Pb(SCN)2(I1-xBrx)2 (x = 0, 1/3, 1/2, 2/3, 1) with varying vivid colors was explored by both calculation and experimental efforts to corroborate the enhanced stability when the x value increases. The results revealed in this study might represent a novel discovery of an inherent trait of the 2D SCN-based perovskites and also suggest that the all-inorganic 2D Cs2Pb(SCN)2X2 perovskite system is a promising class of materials with good stability and color-tunability that deserves further exploration.

Mg1-xZnxFe2O4 nanoparticles: Interplay between cation distribution and magnetic properties

Correlation between cationic distribution, magnetic properties of Mg1-xZnxFe2O4 (0.0 ≤ x ≤ 1.0) ferrite is demonstrated, hardly shown in literature. X-ray diffraction (XRD) confirms the formation of cubic spinel nano ferrites with grain diameter between 40.8 to 55.4 nm. Energy dispersive spectroscopy (EDS) confirms close agreement of Mg/Fe, Zn/Fe molar ratio, presence of all elements (Mg, Zn, Fe, O), formation of estimated ferrite composition. Zn addition (for Mg) shows: i) linear increase of lattice parameter aexp, accounted for replacement of an ion with higher ionic radius (Zn > Mg); ii) presence of higher population of Fe3+ ions on B site, and unusual occurrence of Zn, Mg on A and B site leads to non-equilibrium cation distribution where we observe inverse to mixed structure, and is in contrast to reported literature where inverse to normal transition is reported; iii) effect on A-A, A-B, B-B exchange interactions, affecting coercivity Hc, Ms. A new empirical relation is also obtained showing linear relation between saturation magnetization Ms – inversion parameter δ, oxygen parameter u4¯3m. Non-zero Y-K angle (αYK) values implies Y-K type magnetic ordering in the studied samples.

Effect of aromatic/aliphatic based ionic liquids on the phase behavior of methane hydrates: Experiments and modeling

Abstract In this study, eight ionic liquids (ILs) from the two varieties of ILs, namely, aromatic and aliphatic ILs, have been considered to carry out experimental studies for their effect on the phase behavior of methane hydrate. We have employed five aromatic based ILs with several cations, such as 1-butyl-3-methyl imidazolium, 1-hexyl-3-methyl imidazolium, 1-octyl-3-methyl imidazolium and various anions, such as [Cl]−, [Br]−, [HSO4]−, and three aliphatic based ILs with various cations, such as di-ethyl-ammonium, tri-propyl-ammonium, tri-butyl-ammonium and [HSO4]− anion. All the experiments were performed in the hydrate equilibrium pressure and temperature ranges of 3.86–7.66 MPa and 276.68–283.18 K, respectively. It has been observed that all the investigated ILs have shown inhibition effect on methane hydrate system. Aromatic ionic liquids have shown their dominance over aliphatic ionic liquids in terms of methane hydrate inhibition. ILs with similar class of cation with varying carbon chain length have not shown significant improvement in hydrate inhibition. However, the replacement of anion by [HSO4]− in imidazolium-based ILs improves methane hydrate inhibition. 1-butyl-3-methyl imidazolium sulphate ([BMIM]+[HSO4]−) found to be the best methane hydrate inhibitor among all investigated ILs. In addition, a phase behavior model incorporating a single tuning parameter has been proposed to predict the phase behavior of methane hydrate in the presence of various ionic liquids and salt solutions. The absolute average deviation in pressure (AARD-P, %) for proposed model with an experimental data generated in this work and for various data sets from the literature has been found to be within ±2.90% of the experimental values. Both cation and anion of the ionic liquids have shown to exhibit inhibition effect on the methane hydrate phase stability. The study indicates that the selection of ionic liquids with tunable cation and anion may provide an opportunity to design the best inhibitor for methane hydrate.

Anion-Controlled Positional Switching of a Phenyl Group about the Dinuclear Core of a AuSb Complex.

As part of our continuing interest in redox-active, anion-responsive main-group transition-metal platforms, we have investigated the effect of chloride by fluoride anion substitution on the core structure of a dinuclear AuSb platform. Starting from [(o-(iPr2P)C6H4)2Cl2SbPh]AuCl (2) in which the antimony-bound phenyl group is positioned trans to the gold atom, we found that the introduction of fluoride anions, as in [(o-(iPr2P)C6H4)2F2SbPh]AuCl (3) and [(o-(iPr2P)C6H4)2ClFSbPh]AuCl (4), produces structures in which the phenyl group switches to a perpendicular direction with respect to the gold atom. Replacement of the gold-bound chloride anion in 3 by a fluoride anion can be achieved by successive treatment with TlPF6 and [nBu4N][Ph3SiF2]. These reactions, which proceed via the intermediate zwitterionc gold antimonate complex [o-(iPr2P)C6H4)2F3SbPh]Au (6), trigger migration of the phenyl group to gold and afford [(o-(iPr2P)C6H4)2F3Sb]AuPh (7). Because the phenyl group in 7 is orthogonal to that in 3 and opposite to that in 2, the title AuSb platform can be regarded as a molecular analogue of a mechanical three-way switch in which the switching element is a phenyl group. Finally, while all complexes involved retain a Au → Sb interaction, this interaction is no longer present in the zwitterionic derivative 6 because of the neutralization of the Lewis acidity of the antimony center.

Ion-Exchange in Glass-Ceramics

In the past few years ion-exchange in glasses has found a renewed interest with a lot of new development and research in industrial and academic labs and the commercialization of materials with outstanding mechanical properties. These glasses are now widely used in many electronic devices including hand-held displays and tablets. The exchange is generally conducted in a bath of molten salt below the transition temperature of the glass. The exchange at the surface of an alkali ion by a bigger one brings compressive stress at the surface. The mechanical properties are dependent on the stress level at the surface and the depth of penetration of the bigger ion. As compared to glasses, glass-ceramics have the interest to display a wide range of aspects (transparent to opaque) and different mechanical properties (especially higher modulus and toughness). There has been little research on ion-exchange in glass-ceramics. In these materials the mechanisms are much more complex than in glasses because of their polyphasic nature: ion-exchange generally takes place mostly in one phase (crystalline phase or residual glass). The mechanism can be similar to what is observed in glasses with the replacement of an ion by another in the structure. But in some cases this ion-exchange leads to microstructural modifications (for example amorphisation or phase change). This article reviews these ion-exchange mechanisms using several transparent and opaque alumino-silicate glass-ceramics as examples. The effect of the ion exchange in the various glass-ceramics will be described, with particular emphasis on flexural strength.

Electrochemical doping of polyaniline with the tetracyanoquinodimethane anion

A new complex of aniline (An) with tetracyanoquinodimethane (TCQM) An(TCQM)4 has been obtained and studied. The redox cycling of polyaniline (PAni-sulfo) in a neutral electrolyte containing Cl– and ClO4− anions led to a replacement of the sulfate anion by the Cl– and ClO4− anions. The TCQM anion can also replace the sulfate anions in polyaniline (PAni) during the cycling of the latter in a neutral electrolyte containing TCQM anions. The introduction of TCQM in PAni creates conditions for generating nanocrystalline regions inside the polymer.

The effect of the precipitation conditions on the morphology and the sorption properties of CuS particles

The effect of the nature of the copper salt precursor anion and the pH of a solution on the morphology and the phase composition of CuS particles has been studied upon precipitation from thiourea solutions. It has been established that, irrespective of the precipitation conditions, generation of the CuS phase and the chalcanthite impurity phase CuSO4 • 5H2O is recorded according to the X-ray diffraction analysis data. At pH 8 and a c((NH2)2CS): c(Cu2+) ratio of 1: 1, from nitrate solutions a fine powder is formed that consists of spherical particles smaller than 100 nm in size. An increase in the c((NH2)2CS): c(Cu2+) ratio and in the precipitation pH results in coarser particles of up to 1.5 μm in size. The replacement of the salt precursor anion by SO 4 2- facilitates the decrease in the spherical particle size to 1 μm and that by Cl– to 0.7 μm. The synthesis conditions of the CuS sorbent that control the latter’s morphological properties have an effect on the sorption of cadmium from aqueous solutions.

Improving the antidepressant action and the bioavailability of sertraline by co-crystallization with coumarin 3-carboxylate. Structural determination

To improve the antidepressant action of sertraline a new salt with coumarin-3-carboxylate anion (SerH-CCA) has been synthesized by two different methods and characterized by FTIR spectroscopy and structural determinations by X-ray diffraction methods. The new salt is stabilized by strong intermolecular H-bonds involving the protonated amine group of SerH and the deprotonated carboxylate group of CCA. These findings can be correlated with the interpretation of the infrared spectrum. The salt, sertraline (SerHCl) and the sodium salt of coumarin-3-carboxylate (NaCCA) were orally administered male Wistar rats (10 mg/kg, based on sertraline). Rats were evaluated in separate groups by means of the forced swimming (FST). SerH-CCA produced antidepressant effects in a magnitude that exceeded SerHCl individual effects. None of these treatments affected activity levels by the open field OFT tests. We have also determined that the ion pair also improve the binding to bovine serum albumin (BSA) of the drug but retain its antimicrobial activity. It is reasonable to conclude that the replacement of chloride anion by a large organic anion in sertraline strengthens the pharmacological action of the native drug, binding to BSA with higher activity and retaining the antimicrobial activity of the antidepressant compound.

Peculiarities of bright blue liquid-phase chemiluminescence of the Eu2+* ion generated at interactions in the systems EuX3·6H2O–THF–R3−nAlHn–O2 (X=Cl, NO3; R=Bui, Et and Me; n=0, 1)

The influence of experimental conditions on the chemiluminescence (CL) and photoluminescence (PL) in the systems EuX3·6H2O–THF–EOC–O2 (X=Cl, NO3; EOC=organoelement compounds) was studied, including the concentration of europium, additives of luminescent compounds TbCl3·6H2O and Ru(bpy)2Cl2·6H2O, the nature and concentrations of EOC (Bui2AlH, Me3Al, Et3Al, Bui3Al, 9-borabicyclo(3.3.1.)nonane (9-BBN), diborane B2H6, sodium borohydride NaBH4), replacement of chloride anion in the EuCl3·6H2O salt to an NO3, CO3, SO4, concentration and conditions of the introduction of oxygen into the reaction solution. The quantum yields of CL occurring in the systems EuCl3·6H2O–THF–Bui2AlH–O2 (5.85·10−4Einsteinmol−1) and Eu(NO3)3·6H2O–THF–Bui2AlH–O2 (9·10−9Einsteinmol−1) were measured. The PL quantum yields of the Eu2+* ion of the isolated complex EuCl2·(THF)2 in THF (φPL=0.07), in the reaction solutions obtained after the interactions in the systems EuCl3·6H2O–THF–Bui2AlH–O2 (φPL=0.51) and Eu(NO3)3·6H2O–THF–Bui2AlH–O2 (φPL=0.05) were measured.

On the structural and magnetic study of Mg1−xZnxFe2O4

Mg1−xZnxFe2O4 (with x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) spinel ferrite was synthesized via sol-gel auto combustion method. XRD confirms the formation of spinel phase with a secondary phase of Fe2O3 (in case of x = 1.0). Structural parameters changes as the Zn concentration increases which can be ascribed to the replacement of an ion with lower ionic radius (Mg2+) with that of an ion with higher ionic radius (Zn2+). Variation in the magnetic properties with Zn content are interpreted in terms of migration of Fe3+ between tetrahedral and octahedral sites.

Engineering of Acentric Stilbazolium Salts with Large Second-Order Optical Nonlinearity and Enhanced Environmental Stability

A series of organic nonlinear optical (NLO) materials based on the stilbazolium derivatives of 4-N,N-dimethylamino-4′-N′-methyl-stilbazolium tosylate (DAST) were synthesized, and the single crystals were grown from the solutions. Single-crystal structure determinations and Kurtz powder tests reveal that replacement of the p-toluenesulfonate anion in the DAST crystal, forming 4-N,N-dimethylamino-4′-N′-methyl-stilbazolium 4-aminotoluene-3-sulfonate (1) and 4-N,N-dimethylamino-4′-N′-methyl-stilbazolium p-chlorobenzenesulfonate (2), constructs new acentric crystals with quite a large powder second-harmonic generation (SHG) of more than 3 orders of magnitude larger than that of urea around 2.0 μm, whereas the other two complexes show their centrosymmetric structures without any SHG effects. A possible estimation of the molecular first hyperpolarizabilities βijk performed on 2 further confirms its origin of its enhanced NLO merits. Furthermore, both 1 and 2 exhibit even higher environmental stabilities, includi...