Addition Of Alkali Metal Ions Research Articles

Triazole‐bearing oligo(ethylene glycol)‐strapped zinc porphyrins as dual mode ion‐binding receptors

AbstractA series of triazole‐bearing oligo(ethylene glycol)‐strapped zinc porphyrins (PZn4EG and PZn5EG) have been prepared as artificial ion‐binding receptors. Both PZn4EG and PZn5EG exhibit UV/Vis absorption changes in a solvent‐dependent manner upon titration with halides and alkali metal ions. In tetrahydrofuran, both PZn4EG and PZn5EG exhibit spectral shifts upon the addition of halide ions through axial coordination, whereas the absorption does not change upon the addition of alkali metal ions. On the other hand, in 10% MeCN/CHCl3, the UV/Vis absorption spectra of both PZn4EG and PZn5EG do not change upon the addition of an excess amount of halide ions; however, PZn4EG and PZn5EG show selective alkali metal ion‐binding properties in this solvent. PZn4EG and PZn5EG display dramatic color changes and spectral shifts upon the addition of Li+ and K+, respectively. Because of the dramatic color changes that occurred upon binding, the determination of alkali metal ions would be possible.

Reducibility Studies of Ceria, Ce0.85Zr0.15O2 (CZ) and Au/CZ Catalysts after Alkali Ion Doping: Impact on Activity in Oxidation of NO and CO

The aim of these studies was to perform thorough research on the influence of alkali metal ions (Li, Na, K and Cs) on the properties of nanogold catalysts supported on ceria–zirconia. The addition of alkali metal ions onto CeO2 further affected the reducibility, which was not noted for the Zr-doped support (Ce0.85Zr0.15O2). Despite the substantial impact of alkali metal ions on the reducibility of ceria, the activity in CO oxidation did not change much. In contrast, they do not have a large effect on the reducibility of Au/CZ but suppressed the activity of this system in CO oxidation. The results show that for CO oxidation, the negative effect of potassium ions is greater than that of sodium, which corresponds to the shift in the Tmax of the reduction peak towards higher temperatures. The negative effect of Li+ and Cs+ spans 50% CO conversion. The negative effect was visible for CO oxidation in both the model stream and the complex stream, which also contained hydrocarbons and NO. In the case of NO oxidation to NO2, two temperature regimes were observed for Au + 0.3 at% K/CZ, namely in the temperature range below 350 °C; the effect of potassium ions was beneficial for NO oxidation, whereas at higher temperatures, the undoped gold catalyst produced more NO2.

Self-assembly, conductivity and chemosensor behavior of biphenylsulfone based Janus polycatenar

A novel Janus polycatenar JP-I bearing a bisphenylsulfone central core, with a hydrophobic 3,4,5-tridodecyloxybenzylether unit at one side and a hydrophilic trioligoethylene oxide benzyl triazoly unit at another side has been synthesized via copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction. JP-I can display SmA2 phase triggered by the addition of alkali metal ions. The LC property of the doped system was well demonstrated by polarized optical microscopy (POM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD) experiments. The conductivity of the doped system (JP-I:LiOTf) is 4.0 × 10−8 S cm−1. JP-I could gel both in ethanol and aqueous ethanol. Such gel which formed in ethanol showed a helical nanostructure. The XRD displayed that the JP-I could self-assemble into a monolayer structure which had a small tilt angle in the layers. Furthermore, the gel system could be established to remove iodine from water. Additionally, JP-I could recognize Fe3+ with lower detection limit in aqueous ethanol. Finally, JP-I could self-assemble into micelles in aqueous solution and the critical micelle concentration CMC was determined to be 0.002 mg/ mL with the diameter of the spherical micelles about 15–20 nm.

8-Aza-2'-deoxyisoguanosine Forms Fluorescent Hydrogels whereas 8-Aza-2'-deoxyguanosine Assembles into Nucleoside Nanotubes.

Fluorescent hydrogels have attracted attention for applications in tissue engineering, drug delivery or as molecular machines. This study describes a nucleoside hydrogel formed by 8-aza-2'-deoxyisoguanosine (z8 isoGd ). The new hydrogel is the first guanosine gel that has intrinsic fluorescence. It has long-term stability and a higher thermal stability (Tgel =77 °C) than gels of 2'-deoxyisoguanosine (Tgel =67 °C) and 2'-deoxyguanosine (Tgel =50 °C). Furthermore, the minimum gel concentration is lower at 0.3 mg per 100 μL for z8 isoGd compared to 0.7 mg for 2'-deoxyisoguanosine. Scanning electron microscopy images show that the z8 isoGd gel forms dense bundles of fibers. The related nucleoside 8-aza-2'-deoxyguanosine does not form a hydrogel but forms nanotube-like structures in the solid state. The fluorescence of the z8 isoGd hydrogel responds to external stimuli such as the addition of alkali metal ions, pH change, heat, and UV irradiation. In binary mixtures with nucleoside shape mimics such as 7-deaza-2'-deoxyisoguanosine, the z8 isoGd hydrogel disintegrates.

Influence of doping alkali metal ions on the structure and luminescent properties of microwave synthesized CaMoO4:Dy3+ phosphors

A series of Ca0.98−xMoO4:Dy3+0.02,M+x (M = Li, Na, K, 0 ≤ x ≤ 0.16) phosphors were synthesized rapidly using microwave radiation method in 30 min. The effects of doping alkali metal ions on the phase structure and luminescent properties of the phosphors were analyzed using X-ray powder diffraction, scanning electron microscopy, fourier transform infra-red spectroscopy, and fluorescence spectrophotometry. The results confirmed that all the samples were pure tetragonal CaMoO4 structure. The samples consisted of many cubic particles and some irregular polyhedron particles, assembled by fine spherical-like grains. The main emission peak was located at 574 nm, which was attributed to the 4F9/2 → 6H13/2 transition of Dy3+. The addition of alkali metal ions could effectively improve the intensity of the main emission peak. K+ had better improvement on emission intensity than Na+ and Li+. For the series of Ca0.98−xMoO4:Dy3+0.02,K+x phosphors, the optimum doping content of K+ was 0.10 with 2.6 times of the emission intensity at 574 nm of the undoped-K+ sample. The color coordinates gradually shifted from yellow-green region to the yellow region with the increasing of K+ content (0 ≤ x ≤ 0.10). When x = 0.10, the sample shows the strongest yellow-emitting.

Influence of doping group I elements on structural, optical and magnetic properties of nanocrystalline ZnO

Pure ZnO and group-I elements doped ZnO nanocrystals were synthesized by solution combustion method. The XRD analysis reveals that all the ZnO doped nanocrystals have hexagonal wurtzite crystal structure. Scanning electron microscopy reveals the growth of rod like structure for Na doped sample. The UV–Vis absorption results show that the band gap of ZnO doped nanocrystals is red shifted with decrease in crystallite size. A sharp peak at 434 cm−1 was observed in Raman spectra which correspond to the high frequency E2 mode of ZnO. Photoluminescence properties of pure and group-I elements doped ZnO nanocrystallites have strong blue emission at 421 nm. The peak positions were found to be almost same even after the addition of alkali metal ions owing to the variation in the nanostructure and difference in ionic radii. Vibrating sample magnetometer studies show that the doping of group-I elements show ferromagnetic behavior compared to pure ZnO samples which are paramagnetic. Our investigations make, hence, useful contributions to nano-photonics, luminescence and optoelectronic devices.

Hydrogenation of carbon dioxide to light olefins over non-supported iron catalyst

The hydrogenation of CO 2 to light olefins was investigated over non-supported Fe catalysts. It was found that the addition of alkali metal ions to the Fe catalyst led to significant increases in both the CO 2 conversion and the selectivity for olefins. Over K- or Rb-modified catalysts, about 40% CO 2 conversion and more than 50% olefin selectivity were obtained. The yield of C 2 –;C 4 olefins exceeded 10% over these modified catalysts. Catalyst characterization suggested that the formation of iron carbide species was accelerated by the modification of the Fe catalyst with alkali metal ions, and this enhancement may be one of the key reasons for the enhanced catalytic performance. For the K-modified Fe catalysts, K content has a major influence on the catalyst behavior. An increase in the K content from 1 to 5 wt% increased both CO 2 conversion and olefin selectivity. However, too high a K content led to a decrease in the activity, probably because of decreases in the surface area and CO 2 chemisorption capacity of the catalyst. The presence of an appropriate amount of B in the K-modified Fe catalyst was found to be beneficial to the olefin selectivity, without significantly decreasing the conversion of CO 2 . 研究了非负载型铁催化剂上CO 2 加氢制低碳烯烃反应. 结果显示, 添加碱金属可显著提高铁催化剂上的CO 2 转化率和烯烃选择性. 在经K和Rb修饰的Fe催化剂上, CO 2 转化率可达约40%, 烯烃选择性达到50%以上, 其中C 2 ∼C 4 烯烃收率超过10%. 催化剂表征结果表明, 碱金属促进了催化剂中碳化铁的生成, 这可能是催化剂性能提高的一个关键原因. 随着K含量由1 wt%增加至5 wt%, CO 2 转化率及烯烃选择性均升高. 但K含量过高时, 催化剂活性降低. 这可能是由于催化剂比表面积和CO 2 化学吸附量降低所致. 当K含量为5%∼10%时, K-Fe催化剂上烯烃收率较高; 进一步添加适量的硼可进一步提高烯烃选择性, 且CO 2 转化率下降不大. The modification of a non-supported Fe catalyst by alkali metal ions, particularly K + , in combination with a small amount of B, significantly enhanced the hydrogenation of CO 2 to light olefins.

Alkali‐Metal‐Promoted Pt/TiO2 Opens a More Efficient Pathway to Formaldehyde Oxidation at Ambient Temperatures

Addition of alkali metal ions significantly promotes the activity of the Pt/TiO2 catalyst for the HCHO oxidation reaction by stabilizing an atomically dispersed Pt-O(OH)x alkali metal species and opening a new low-temperature reaction pathway. The atomically dispersed Na-Pt-O(OH)x species can effectively activate H2O and catalyze the facile reaction between surface OH and formate species to total oxidation products.

Computational investigations into new fluorescence quenching process induced by complexation of alkali metal ion

A novel fluorescent switchable chemosensor 1, which is composed of an anthracene-modified calix[4]crown in the 1,3-alternate conformation, was calculated by density functional theory and time-dependent density functional theory method. Geometries, molecular orbitals and binding thermal energies were evaluated at the restricted hybrid Becke's three-parameter exchange functional using 6-31 G(d) basis set and relativistic effective core potentials. The metal–ligand and cation–π interactions were investigated acting as two main types of driving force. Our calculations clearly show that solvent effects strongly influence cation selectivity, and K+ selectivity is recovered when even a few waters of hydration are considered. The calculations indicate that because of the photoinduced electron transfer effect, the addition of alkali metal ions have hardly any effect on the fluorescence of ligand 1 under neutral or basic conditions. Also, the high selectivity of ligand 1 for K+ and Rb+, under acidic conditions, the complexed metal ion can result in ammonium ion deprotonation, which leads to quenching of fluorescence of 1•H+. Copyright © 2012 John Wiley & Sons, Ltd.

Synthesis and Study of Unsymmetrical Schiff Base Mn(III) Complexes with Pendant Aza-crown or Morpholino Groups as Catalyst in Aerobic Oxidation for p-Xylene to p-Toluic Acid

A series of novel unsymmetrical Schiff base Mn(III) complexes with pendant aza-crown or morpholino groups have been synthesized and studied as catalysts in aerobic oxidation of `p-xylene to p-toluic acid (PTA). The oxidation of p-xylene to p-toluic acid with air at 120°C under normal atmospheric pressure occurred efficiently in the presence of aza-crown ether substituted unsymmetrical Schiff base Mn(III) complexes. Significant selectivity (up to ∼90%) and conversion levels (up to ∼40%) were obtained. The effect of the aza-crown ring appended in Mn(III) Schiff base complexes on the oxidation of p-xylene were also investigated by comparison with the morpholino group pendant analogues. The addition of alkali metal ions accelerates the rate of conversion of p-xylene to p-toluic acid.

An efficient aerobic oxidation for p-xylene to p-toluic acid catalyzed by cobalt (II) hydroxamates with benzo-15-crown-5

Cobalt (II) hydroxamates with the benzo-15-crown-5 (B15C5) pendant have been synthesized and characterized. These complexes were successfully employed to the oxidation of p-xylene to p-toluic acid with air at 110°C under normal atmospheric pressure. The effects of the B15C5 pendant, the length of chain bonding of B15C5 in these complexes and the addition of alkali metal ions on the oxidation for p-xylene are also investigated by the comparison with the crown-free analogue.

Absorption‐ and fluorescence‐spectral sensing of alkali metal ions in anionic micelle solutions containing crowned spirobenzopyrans

AbstractSpirobenzopyran derivatives bearing a monoazacrown ether moiety (monoaza‐12‐crown‐4, ‐15‐crown‐5, and ‐18‐crown‐6) and an octadecyl group as a lipophilic moiety, called crowned spirobenzopyrans were synthesized, which can be dissolved in anionic micelle solutions. We examined absorption‐and fluorescence‐spectral changes of micelle solutions containing a crowned spirobenzopyran on addition of alkali metal ions. The crowned spirobenzopyrans are in their merocyanine form in an anionic micelle solution even under dark conditions, showing a significant absorption in the visible region which is attributable to the merocyanine moiety. Crowned spirobenzopyran bearing a monoaza‐12‐crown‐4 moiety exhibited a drastic hypsochromic shift in the absorption and also an enhanced fluorescence on addition of Li+ to the micelle solutions under alkaline conditions. These spectral changes can be attributed to a strong interaction between Li+ bound by the crown ether moiety and a phenolate ion of the merocyanine moiety. Similar absorption and fluorescence‐spectral changes were induced in the anionic micelle solutions containing the other crowned spirobenzopyrans on addition of alkali metal ions. The intensity of the absorption‐spectral changes in the systems of the three crowned spirobenzopyrans, however, differed from each other, depending on the strength of interaction between a metal ion bound to the crown ether moiety and the phenolate ion of the merocyanine moiety. On the other hand, the extent of enhanced relative fluorescence intensity is dependent on the strength of interaction between metal ion and a nitrogen atom of azacrown ether moiety, because the fluorescence spectrum is quenched by photoinduced electron transfer (PET) from the nitrogen atom to the merocyanine moiety. Copyright © 2007 John Wiley & Sons, Ltd.

Rapid Communication Effect of Alkali Metal Ions on Photochromic Behavior of Bisviologen-incorporated Oligo-oxyethylene Units ¶

Abstract Two bisviologen derivatives, 1,11-bis(N-propyl-4,4′-bipyridinium)-3,6,9-trioxaundecane tetrakis-(hexafluorophosphate) (1) and 1,8-bis(N-propyl-4,4′-bipyridinium)-3,6-dioxaoctane tetrakis-(hexafluorophosphate) (2), each incorporating trioxaundecane and dioxaoctane groups between two viologen units, respectively, were prepared so that their photochromic behavior in the absence and the presence of alkali metal ions in a thin polymer film could be investigated. Photoirradiation of the films containing 1 and 2 caused color changes from pale yellow to blue, associated with the photoinduced reduction of the viologen units from the dication to the radical cation. The addition of alkali metal ions, especially, K+ and Na+, caused change in the spectra of the photoreduced viologen radical cation for 1 and 2, respectively, because of the increase in the fractional amplitude for the dimer component of the radical cation rather than the monomer one. This may be related to the guest-induced conformational chang...

PROTON AND ALKALI METAL IONS ATTACHED TO ALKYLPEROXYL RADICALS: STRUCTURE AND STABILITY OF M+-CnH2n+1O2 (M = H, Li, Na, K; n = 1 ~ 3) COMPLEXES

The structure and stability of the still experimentally unknown M +- C n H 2n+1 O 2 ( M = H , Li , Na , K ; n = 1 ~ 3) complexes were theoretically investigated via density function theory at the B3LYP/6-311+G(3df,2p)//B3LYP/6-311G(d,p) level. The addition of alkali metal ions ( Li , Na , and K ) to C n H 2n+1 O 2 are found to form only one stable structure, while proton transfer reactions with C n H 2n+1 O 2 produce two isomers except for CH 3 CH 2 CH 2 O 2. The optimized geometries and Mulliken population analysis indicate that the M + ( M = Li , Na , K )- C n H 2n+1 O 2 complexes exist as ion-dipole molecules. Our prediction for the affinity energies of M + to C n H 2n+1 O 2 are 165.4, 178.0, 181.9 and 176.8 kcal/mol ( H +); 34.3, 36.4, 37.5, and 38.4 kcal/mol ( Li +); 24.4, 26.1, 26.9, and 27.5 kcal/mol ( Na +); and 17.5, 19.2, 19.6, and 20.0 kcal/mol ( K +), respectively. Thus, these values suggest that C n H 2n+1 O 2- M + ( M = H , Li , Na , K ) complexes could be detected as stable species in gas phase at room temperature by ion attachment mass spectrometry.

Synthesis and Study of Mono-Schiff Base MnIII Complexes with Aza-crown or Morpholino Pendant as Catalyst in Aerobic Oxidation of p-xylene to p-toluic Acid

Novel mono-Schiff base MnIII complexes with pendant aza-crown or morpholino groups have been synthesized and studied as catalysts in aerobic oxidation of p-xylene to p-toluic acid. The oxidation of p-xylene to p-toluic acid with air at 120 °C under normal atmospheric pressure occured efficiently in the presence of aza-crown ether substituted mono-Schiff base MnIII complexes. Significant selectivity (up to ~90%) and conversion levels (up to ~38%) were obtained. The effect of the aza-crown ether pendant in MnIII Schiff base complexes on the oxidation of p-xylene was also investigated by comparison with the morpholino pendant analogues. The addition of alkali metal ions accelerated the rate of conversion of p-xylene to p-toluic acid.

Additive effect of alkali metal ions on preferential CO oxidation over Pt/Al 2O 3

In the preferential CO oxidation under H 2-rich gas, CO conversion and selectivity of CO oxidation were enhanced by the addition of alkali metal ions (M = Li, Na, K, Rb, Cs) to Pt/Al 2O 3 in the range of the molar ratio (M/Pt) lower than 3, and TOFs monotonously increased along with the basicity strength of added alkali metal ions. In contrast, in the range of M/Pt ⩾ 5, the order of additive effect was K > Na > Rb > Cs. This can be related to a moderate strength of basicity of potassium. In addition, the promoting effect of the presence of H 2 on CO oxidation was also clearly observed on K–Pt/Al 2O 3.

Fluorescence Ratiometry of Monomer/Excimer Emissions in a Space-Through PET System

[Reaction: see text]. Fluorogenic calix[4]arenes (1 and 2) bearing a pendent ethyleneamine on their triazacrown rings, respectively, were synthesized in the cone conformation. Compared with 4, free 1 and 2 display a relatively weak emission, reflecting that a PET process from the pendent amine group (-CH2CH2NH2) to the fluorogenic pyrenes is mainly operated. Addition of various metal ions or anions to the solution of 1 or 2 reduces the PET because the pendent alkylamine takes part in the complexation, causing their fluorescence spectra to be changed. When Pb2+, a quenching metal ion, is added to 1 or 2, their pyrene monomer emission is enhanced with their excimer emission quenched, which is due to conformational changes of the facing carbonyl groups as well as to the participation of the ethyleneamine into the three-dimensional Pb2+ ion encapsulation. In contrast, upon addition of alkali metal ions to the 1 and 2, both monomer and excimer emissions are observed to increase, which is attributable to the CHEF effect and the retained conformations. For anion sensing, both 1 and 2 show a high selectivity for F- ions over other anions tested. When the F- ion is bound to 1 or 2 by hydrogen bonding between the amide NH of the triazacrown ring and F-, both their monomer and excimer emissions are weakened due to PET from the bound F- to the pyrene units.

An Efficient Aerobic Oxidation for p-Xylene to p-Toluic Acid using Azacrown Ether-tethered Mn(III) Schiff Base Complexes as Catalysts

The oxidation of p-xylene to p-toluic acid with air at 110°C under normal atmospheric pressure occurs efficiently in the presence of crown Mn(III) Schiff base complexes [Formula: See Text] (n=1-4). Significant conversion levels (up to 75%) and selectivity (up to 92-96%) are obtained; the effect of the azacrown ether pendants in Mn(III) Schiff base complexes on the oxidation of p-xylene are also investigated by comparison with the crown-free analogues [Formula: See Text] Moreover, addition of alkali metal ions accelerates the rate of conversion of p-xylene to p-toluic acid.

Effect of alkali metal ions on photochromic behavior of bisviologen-incorporated oligo-oxyethylene units.

Two bisviologen derivatives, 1,11-bis(N-propyl-4,4'-bipyridinium)-3,6,9-trioxaundecane tetrakis-(hexafluorophosphate) (1) and 1,8-bis(N-propyl-4,4'-bipyridinium)-3,6-dioxaoctane tetrakis-(hexafluorophosphate) (2), each incorporating trioxaundecane and dioxaoctane groups between two viologen units, respectively, were prepared so that their photochromic behavior in the absence and the presence of alkali metal ions in a thin polymer film could be investigated. Photoirradiation of the films containing 1 and 2 caused color changes from pale yellow to blue, associated with the photoinduced reduction of the viologen units from the dication to the radical cation. The addition of alkali metal ions, especially, K+ and Na+, caused change in the spectra of the photoreduced viologen radical cation for 1 and 2, respectively, because of the increase in the fractional amplitude for the dimer component of the radical cation rather than the monomer one. This may be related to the guest-induced conformational change of 1 and 2, in which the alkali metal ion is surrounded by the oligo-oxyethylene unit of 1 and 2. The regulation in photochromic properties of viologen derivatives can be achieved by addition of alkali metal ions.

Complexation behavior and crystal structure of a dithia[16.3.3](1,2,6)cyclophane: a novel one-dimensional coordination polymer with perchlorate anions as linkers

The synthesis of 20,28-dimethyl-24,33-dithia-1,4,7,10,13,16-hexaoxa[16.3.3](1,2,6)cyclophane 3 was achieved by cesium carbonate-assisted high dilution cyclization. Cyclophane 3 exhibited strong complexation towards all alkali metal ions. The change in chemical shift for the bridge methylene protons upon addition of alkali metal ions correlated to log K a. The crystal structure of cyclophane 3 as well as its sodium and potassium complexes was studied. Cyclophane 3 formed a novel one-dimensional coordination polymer with potassium perchlorate using anions as the linkers, while the complex of 3 with sodium perchlorate had a dimeric structure.