K+掺杂双钙钛矿Cs2AgInCl6的发光性质

采用固相球磨法制备了K⁺掺杂双钙钛矿Cs₂AgInCl₆纳米材料,该方法无需配体辅助,绿色环保。通过X射线衍射谱和拉曼光谱对晶体结构进行研究,通过激发光谱、发射光谱和时间分辨光谱对其发光性能进行研究。结果表明,Cs₂AgInCl₆为立方晶体,属于Fm3m空间群,由于宇称禁戒跃迁,其荧光量子产率(PLQY)低,小于0.1%。低于60%的K⁺掺杂主要取代Ag⁺的位置,引起Cs₂AgInCl₆的晶格膨胀,消除了晶格结构的反演对称性,打破了宇称禁戒跃迁,掺杂后Cs₂AgInCl₆的光致发光强度显著增强。K⁺的最佳掺杂比例为40%,Cs₂Ag_0.6K_0.4InCl₆发出中心波长为640 nm,半高宽为180 nm,平均荧光寿命达到29.2 ns,PLQY达到10.5%。当K⁺掺杂比例超过60%,K⁺开始取代Cs⁺的位置,产物发生相变,出现立方相的Cs_2-xK_1+x-yAg_yInCl₆和单斜相的Cs_2-xK_1+xInCl₆产物,这些产物由于强电子-声子耦合,非辐射复合占据主导地位。     

Possible explanation of unstable superconducting phase in KxC60 with Tc=21 K

EPR and MMMA methods revealed two K₃C₆₀ phases, the unstable one with T_c=21.0 K containing C¹⁻₆₀ centers and a stable one with T_c=18.0 K constituting of C₆₀ molecules in the form of C³⁻₆₀ ions. The metastable phase appears only in the first stage of potassium intercalation of fullerene at the C₆₀/K₃C₆₀ phase boundary. This phase is being transformed to a stable one on further doping to K₃C₆₀. The appearance of a metastable phase is related to the instability of the fullerene C₆₀ fcc structure during the process of octahedral sites being filled by potassium ions. The critical temperature T_c shift upwards from 18.5 to 21.0 K is ascribed to the possible process of potassium transient back charge transfer valency, i.e. K₃¹⁺C₆₀³⁻↔K₂¹⁺K¹⁻C₆₀¹⁻ [3K¹⁺+C³⁻₆₀⇔2K¹⁺+K¹⁻+C₆₀¹⁻], which could enlarge the unit cell necessary to shift a superconducting critical temerature according to T_c on volume dependence.     

Tricaesium tris(oxalato‐κ2O1,O2)chromate(III) dihydrate

The title compound, Cs₃[Cr(C₂O₄)₃]·2H₂O, has been synthesized for the first time and the spatial arrangement of the cations and anions is compared with those of the other members of the alkali metal series. The structure is built up of alternating layers of either the d or l enantiomers of [Cr(oxalate)₃]³⁻. Of note is that the distribution of the [Cr(oxalate)₃]³⁻ enantiomers in the Li⁺, K⁺ and Rb⁺ tris(oxalato)chromates differs from those of the Na⁺ and Cs⁺ tris(oxalato)chromates, and also differs within the corresponding BEDT‐TTF [bis(ethylenedithio)tetrathiafulvalene] conducting salts. The use of tris(oxalato)chromate anions in the crystal engineering of BEDT‐TTF salts is discussed, wherein the salts can be paramagnetic superconductors, semiconductors or metallic proton conductors, depending on whether the counter‐cation is NH₄⁺, H₃O⁺, Li⁺, Na⁺, K⁺, Rb⁺ or Cs⁺. These materials can also be superconducting or semiconducting, depending on the spatial distribution of the d and l enantiomers of [Cr(oxalate)₃]³⁻.     

Characteristic Fragmentation of Polysiloxane Monolayer Films by Bombardment with Monatomic and Polyatomic Primary Ions in TOF-SIMS

This study reports the characteristic fragmentation patterns from two polysiloxane polymers that form ordered overlayer on silver substrates. Results are compared for the bombardment of various monatomic and polyatomic projectiles of Cs⁺, C₆₀⁺ (10 keV), Bi₁⁺, and Bi₃⁺ (25 keV) in the high mass range time-of-flight secondary ion mass spectrometry (TOF-SIMS) spectra. Results are reported from sub-monolayer (solution cast) coverages of poly(dimethylsiloxane)s with the number average molecular weights (M_n) of 2200 and 6140 Da, respectively, and Langmuir-Blodgett monolayers of poly(methylphenylsiloxane) with molecular weights (MW) from 600 and 1000 Da. For each film, Bi projectiles resulted in the emission of positive silver cluster ions from the substrate under the polymer overlayer and peaks corresponding to silver cluster ions with larger mass were observed by impact of polyatomic 25 keV Bi₃⁺ projectiles. In addition, depending on the change of energy of Bi₃⁺, a different pattern of fragments was observed. With Cs⁺ and C₆₀⁺ impact, however, the emission of silver cluster ions was not detected. In the case of C₆₀⁺ impact for PDMS-6140, peaks corresponding to silver-cationized intact oligomers were not observed. In this paper, these results are explained by the possible bombardment mechanism for each projectile, based on its mass, energy, and split trajectories of the component atoms under the polyatomic impact.     

ESR,XPS, UV-VIS and FT-IR investigations on the interaction of no and O2 with highly dispersed C60 supported on silica,titania and alkali cation-exchanged Y-zeolites

The characteristics of the radical sources in highly dispersed C₆₀ samples supported on silica, titania ad alkali cation-exchanged Y-zeolite were investigated in the presence and absence of NO and O₂by means of ESR, FT-IR and UV-diffuse reflectance spectroscopies, the results of which were compared with those of the bulk C₆₀ sample. In the presence of O₂, C₆₀ dispersed onto supports was found to easily generate ESR signals in ambient conditions or under UV-irradiation. The intensity of the ESR signal of the C₆₀ samples were found to strongly depend on the dispersibility of C₆₀, the kind of support and the degassing temperature. Based on these results, the nature of these ESR active species in C₆₀ was discussed in detail for the first time. The addition of NO led to a dramatic decrease in the intensity of the ESR signal, its extent also strongly depending on the kind of support, i.e., silica or Y-zeolite and the exchanged-alkali cations on zeolite, i.e., H⁺, Na⁺, Cs⁺, while such a decrease was not observed for the bulk C₆₀.     

Cover Feature: Are the Accompanying Cations of Doping Anions Influential in Conducting Organic Polymers? The Case of the Popular PEDOT (Chem. Eur. J. 63/2019)

Conducting organic polymers (COPs) are made of a conjugated polymer backbone supporting a certain degree of oxidation. These positive charges are compensated by the doping anions that are introduced into the polymer synthesis along with their accompanying cations. In this work, the influence of these cations on the stoichiometry and physicochemical properties of the resulting COPs have been investigated, something that has previously been overlooked, but, as here proven, is highly relevant. As the doping anion, metallacarborane [Co(C₂B₉H₁₁)₂]⁻ was chosen, which acts as a thistle. This anion binds to the accompanying cation with a distinct strength. If the binding strength is weak, the doping anion is more prone to compensate the positive charge of the polymer, and the opposite is also true. Thus, the ability of the doping anion to compensate the positive charges of the polymer can be tuned, and this determines the stoichiometry of the polymer. As the polymer, PEDOT was studied, whereas Cs⁺, Na⁺, K⁺, Li⁺, and H⁺ as cations. Notably, with the [Co(C₂B₉H₁₁)₂]⁻ anions, these cations are grouped into two sets, Cs⁺ and H⁺ in one and Na⁺, K⁺, and Li⁺ in the second, according to the stoichiometry of the COPs: 2:1 EDOT/[Co(C₂B₉H₁₁)₂]⁻ for Cs⁺ and H⁺, and 3:1 EDOT/[Co(C₂B₉H₁₁)₂]⁻ for Na⁺, K⁺, and Li⁺. The distinct stoichiometries are manifested in the physicochemical properties of the COPs, namely in the electrochemical response, electronic conductivity, ionic conductivity, and capacitance.     

Synthesis and adsorption investigations of zeolites MCM-22 and MCM-49 modified by alkali metal cations

Ion exchange was made on MCM-22 and MCM-49 zeolites with different Si/Al molar ratios, with Li⁺, Na⁺, K⁺, and Cs⁺ ions and the study of the influence of alkali metal cations on CO₂ adsorption properties was performed. The degree of ion-exchange decreased for larger cations (Cs⁺) apparently due to steric hindrances. The exchange with different cations led to a decrease in the surface area and the micropore volume. Our study shows that the adsorption capacity of the tested zeolites depends significantly on the nature and the concentration of the charge-compensating cations. The highest CO₂ adsorption capacity was obtained on the MWW zeolites with the lowest Si/Al molar ratio and the Li⁺ or K⁺ cations.     

Optical response of cesium coated C60

Photoabsorption spectra are reported for Cs _n ⁺ and C₆₀Cs_n ⁺ + clusters for n=40, 60, 120 and 310. The spectra were obtained by heating the mass selected clusters in a beam by means of photoabsorption until they evaporated metal atoms. The resulting mass loss was observed in a time-of-flight mass spectometer. The plasmon-like resonance in pure Cs clusters shifts to lower energies with decreasing cluster size. The collective electronic excitations in clusters containing C₆₀ are split in energy as would be expected for fullerene molecules coated with layers of metal.     

Preparation of Thallium Hexacyanoferrate Film and Mixed‐Film Modified Electrodes with Cobalt(II) Hexacyanoferrate

Thallium hexacyanoferrate films have been prepared from various aqueous electrolyte solutions using consecutive cyclic voltammetry. The cyclic voltammograms recorded the direct deposition of thallium hexacyanoferrate films from the mixing of Tl³⁺ and [Fe(CN)₆]^3? ions from solutions of seven cations: Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, H⁺, and Tl⁺. An electrochemical quartz crystal microbalance (EQCM) and cyclic voltammetry were used to study the in situ growth of the thallium hexacyanoferrate films. The thallium hexacyanoferrate film shows a single redox couple with a formal potential between +0.6 V and +1.2 V, and shows a cation effect (H⁺, Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, and Tl⁺). A mixed film and a two‐layered modified electrodes composed of a thallium hexacyanoferrate film with cobalt(II) hexacyanoferrate film were prepared.     

Synthesis of macrocyclic tetraamides derived from α-amino acids and their investigations using ESI-MS technique

Chiral α,ω-diesters react under high-pressure conditions (10 kbar) with α,ω-diamines to give chiral cyclic tetraamides of C₂-symmetry. The complexation properties of tetraamides towards alkali metal cations (Li⁺, Na⁺, K⁺, Rb⁺ and Cs⁺) were estimated on the basis of ESI-MS spectra.     

Reaction of C60 with KMnF4 : Isolation and characterization of a new isomer of C60F8 and re-evaluation of the structures of C60F7(CF3) and the known isomer of C60F8

The volatile fluorofullerene products of high-temperature reactions of C₆₀ with the ternary manganese(III, IV) fluorides KMnF₄, KMnF₅, A₂MnF₆ (A⁺ = Li⁺, K⁺, Cs⁺), and K₃MnF₆ were monitored as a function of reaction temperature, reaction time, and stoichiometric ratio by in situ Knudsen-cell mass spectrometry. When combined with fluorofullerene product ratios from larger-scale (bulk) screening reactions with the same reagents, an optimized set of conditions was found that yielded the greatest amount of C₆₀F₈ (KMnF₄/C₆₀ mol ratio 28-30, 470 °C, 4-5 h). Two isomers of C₆₀F₈ were purified by HPLC, one of which has not been previously reported. Quantum chemical calculations at the DFT level combined with 1D and 2D ¹⁹F NMR, FTIR, and FT-Raman spectroscopy indicate that the C₆₀F₈ isomer previously reported to be 1,2,3,8,9,12,15,16-C₆₀F₈ is actually 1,2,3,6,9,12,15,18-C₆₀F₈, making it the first high-temperature fluorofullerene with non-contiguous fluorine atoms. The new isomer, which was found to be 1,2,7,8,9,12,13,14-C₆₀F₈, is predicted to be 5.5 kJ mol⁻¹ more stable than 1,2,3,6,9,12,15,18-C₆₀F₈ at the DFT level. In addition, new DFT calculations and spectroscopic data indicate that the compound previously isolated from the high-temperature reaction of C₆₀ and K₂PtF₆ and reported to be 16-CF₃-1,2,3,8,9,12,15-C₆₀F₇ is actually 18-CF₃-1,2,3,6,8,12,15-C₆₀F₇.     

Enhancement of Oxygen Evolution Activity of Nickel Oxyhydroxide by Electrolyte Alkali Cations

Herein, the effect of the alkali cation (Li⁺, Na⁺, K⁺, and Cs⁺) in alkaline electrolytes with and without Fe impurities is investigated for enhancing the activity of nickel oxyhydroxide (NiOOH) for the oxygen evolution reaction (OER). Cyclic voltammograms show that Fe impurities have a significant catalytic effect on OER activity; however, both under purified and unpurified conditions, the trend in OER activity is Cs⁺ > Na⁺ > K⁺ > Li⁺, suggesting an intrinsic cation effect of the OER activity on Fe‐free Ni oxyhydroxide. In situ surface enhanced Raman spectroscopy (SERS), shows this cation dependence is related to the formation of superoxo OER intermediate (NiOO^?). The electrochemically active surface area, evaluated by electrochemical impedance spectroscopy (EIS), is not influenced significantly by the cation. We postulate that the cations interact with the Ni?OO^? species leading to the formation of NiOO^??M⁺ species that is stabilized better by bigger cations (Cs⁺). This species would then act as the precursor to O₂ evolution, explaining the higher activity.     

Electrochemically induced transformations of ruthenium(III) trichloride microcrystals in salt solutions

Ruthenium (III) trichlorid solid crystals have been mechanically attached to gold surfaces and studied by cyclic electrochemical quartz crystal microbalance measurements in the presence of aqueous solutions of different concentrations containing M⁺Cl⁻, where M⁺=H⁺, Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺. The RuCl₃ and the complexes formed during the electrochemical transformations show two or more reduction and reoxidation pairs of waves, depending on the experimental conditions (concentration, scan rate, and potential range). The voltammetric peaks are shifted into the direction of higher potentials with increasing electrolyte concentrations except at very high concentrations when the peaks belong to the first reduction/reoxidation processes move oppositely. The mass change was reversible, during reduction mass increase, while during oxidation mass decrease occurred at medium electrolyte concentrations in two, more or less distinct steps. At high or low concentrations the mass excursions are more complex involving different mass increase/decrease regions as a function of potential which vary with the potential range of the measurements. The peak potentials and the electrochemical activity strongly depend on the nature of the cations and pH. It is related to the formation of complexes in different compositions. The mass change decreases with increasing electrolyte concentrations attesting the important role of the water activity and the transport of solvent molecules. It was concluded that in dilute solutions during the first reduction step M⁺ ions enter the surface layer. The strongly hydrated Li⁺ ions transfer water molecules into the microcrystals, while simultaneously with the incorporation of K⁺, Rb⁺, and Cs⁺ ions H₂O molecules leave the surface layer. The opposite transport of ions and solvent molecules occur during oxidation. In the course of further reduction the incorporation of all ions studied except that of Cs⁺ ions is accompanied with water sorption. The number of sorbed water molecules is proportional to the hydration number of these ions. A reaction scheme is proposed in which M⁺ _m-3[Ru^IIICl _m (H₂O) _n ]^3-m · xH₂O (m≥3) and [Ru^IIICl _m (H₂O) _n ]^3-m (Cl⁻)_3-m · xH₂O (m≤3) type complexes are reduced to the respective – or depending on the electrolyte concentration higher or lower – Ru(II)chloro complexes resulting in mixed valence compounds (phases). Taking into account the layered structure of RuCl₃ the electrochemical reduction can be explained as an intercalation reaction in that mixed valence intercalation phases with a general formula M _x ⁺(H₂O) _y [RuCl₃] ^x− are formed from RuCl₃·x H₂O. The reduction/reoxidation waves are related to the redox transformations of Ru(III) to Ru(II) sites, while the composition of the polynuclear complexes and the structure of microcrystals change. Presented at the 4th Baltic Conference on Electrochemistry, Greifswald, March 13.−16., 2005.     

Novel Methods of Synthesis of Dibenzo[3n]crown-n and Their Cation Binding Studied by Fluorescence Spectroscopy. Part V

The dibenzo[3n]crown-n were synthesised starting from bis[2-(o-hydroxyphenoxy)ethyl]ether obtained from bis[2-(o-formylphenoxy)ethyl]ether via Baeyer-Villiger oxidation in H₂O₂/CH₃COOH in a good yield. The cyclic condensation ofbis[2-(o-hydroxyphenoxy)ethyl]etherwith tri- and tetraethylene glycol bisdichlorides andthe bisditosylate of pentaethylene glycol in DMF/Me₂CO₃ afforded the large cyclic ethers of dibenzo[21]crown-7, dibenzo[24]crown-8 and dibenzo[27]crown-9. The structures were analysed with IR, ¹H NMR, ¹³C NMR and low-resolution mass spectroscopy methods. The Na⁺, K⁺, Rb⁺ and Cs⁺ cations' recognition of the molecules were conducted withsteady-state fluorescence spectroscopy. The 1:1 association constants, K_a, in acetonitrile were estimated. Dibenzo[21]crown-7 was the best both for K⁺ and Rb⁺ binding but showed too small an effect on Cs⁺. Dibenzo[24]crown-8 exhibited the binding power in the order of Rb⁺ > K⁺ > Na⁺ > Cs⁺. However, dibenzo[27]crown-9 displayed marked binding with only K⁺ but not with Rb⁺ or with Cs⁺ cations probably due to the heavy atom effect of fluorescence quenching.     

K+掺杂双钙钛矿Cs2AgInCl6的发光性质

采用固相球磨法制备了K⁺掺杂双钙钛矿Cs₂AgInCl₆纳米材料,该方法无需配体辅助,绿色环保。通过X射线衍射和拉曼光谱对晶体结构进行研究,通过激发光谱、发射光谱和时间分辨光谱对其发光性能进行研究。结果表明,Cs₂AgInCl₆为立方晶体,属于Fm3m空间群,由于宇称禁戒跃迁,其荧光量子产率(PLQY)低,小于0.1%。低于60%的K⁺掺杂主要取代Ag⁺的位置,引起Cs₂AgInCl₆的晶格膨胀,消除了晶格结构的反演对称性,打破了宇称禁戒跃迁,掺杂后Cs₂AgInCl₆的光致发光强度显著增强。K⁺的最佳掺杂比例为40%,Cs₂Ag_0.6K_0.4InCl₆材料发射中心波长为640 nm,半高宽为180 nm,平均荧光寿命达到29.2 ns,PLQY达到10.5%。当K⁺掺杂比例超过60%,K⁺开始取代Cs⁺的位置,产物发生相变,出现立方相的Cs_2-xK_1+x-yAg_yInCl₆和单斜相的Cs_2-xK_1+xInCl₆产物,这些产物由于强电子-声子耦合,非辐射复合占据主导地位。     

Relationship between the Physicochemical Properties of Electrolytes and the Electronic Structure of Solvated Alkali Metal Cations

Group theoretical analysis and linear combinations of molecular orbitals of the cation and solvent are used to establish the nature and stability of bonds and hence the electric mobility of the cation and the viscosity of the electrolyte depending on the type of cation (Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺) and molecules (H₂O, NH₃, H₂CO, (CH₃)₂CO, CH₃CN). Solvation effects on the UV photoelectron and intramolecular vibrational IR and NMR spectra are revealed.     

Dodecahydro-<Emphasis Type="Italic">closo</Emphasis>-dodecaborate anion intercalation into graphite oxide

It is demonstrated by X-ray diffraction that, in the case of dodecahydro-closo-dodecaborates with small cations (H⁺, Li⁺, Na⁺, K⁺, NH ₄ ⁺ ), the intercalation of the B₁₂H ₁₂ ^2? anion into the interlayer space of graphite oxide is more favorable than the crystallization of a free salt. In the case of large cations commensurable with B₁₂H ₁₂ ^2? (e.g., Cs⁺), no intercalation takes place because these cations and the dodecaborate-closo-dodecaborate anion form stable cubic crystals as a separate phase outside the graphite oxide structure.     

Facilitated Transfer of Alkali Metal Ions by a Tetraester Derivative of Thiacalix[4]arene at the Liquid–Liquid Interface

The facilitated transfer of alkali metal ions (Na⁺, K⁺, Rb⁺, and Cs⁺) by 25,26,27,28‐tetraethoxycarbonylmethoxy‐thiacalix[4]arene across the water/1,2‐dichloroethane interface was investigated by cyclic voltammetry. The dependence of the half‐wave transfer potential on the metal and ligand concentrations was used to formulate the stoichiometric ratio and to evaluate the association constants of the complexes formed between ionophore and metal ions. While the facilitated transfer of Li⁺ ion was not observed across the water/1,2‐dichloroethane interface, the facilitated transfers were observed by formation of 1 : 1 (metal:ionophore) complex for Na⁺, K⁺, and Rb⁺ ions except for Cs⁺ ion. In the case of Cs⁺ a 1 : 2 (metal:ionophore) complex was obtained from its special electrochemical response to the variation of ligand concentrations in the organic phase. The logarithms of the complex association constants, for facilitated transfer of Na⁺, K⁺, Rb⁺, and Cs⁺, were estimated as 6.52, 7.75, 7.91 (log β₁°), and 8.36 (log β₂°), respectively.     

The reactivity enhancement in Diels–Alder cycloaddition of 1,3-diene by cation encapsulation to C60: a computational insight

The origin of the experimentally known preference for [6,6] bonds in cycloaddition reactions involving C₆₀ has been computationally explored. To this end, we examined the reactions of 1,3-dienes with fullerene (C₆₀) in the context of an approach to open a large orifice on the fullerene framework by using the activation model of reactivity in combination with the energy analysis method. In this study, the effect of the alkali metal of Li⁺, Na⁺, and K⁺ as an encapsulated element was investigated on the kinetic and thermodynamic behaviors of the Diels–Alder (DA) process. Our calculations indicated that encapsulated Na⁺ and K⁺ cations are located close to the center of the C₆₀ molecule; however, encapsulated Li⁺ is displaced from the center, which leads to a higher reactivity for Li⁺@C₆₀ in DA cycloaddition reaction in the gas phase. Also, benzene as a non-polar solvent affects the DA reactions greater than water as a polar solvent. Different analyses show that solvent changes the catalysis reaction performance, in which a greater efficiency was obtained for K⁺ in the solvent in comparison with other alkali ions because of a facilitated mechanism of electron transfer.

     

A raman,infra-red and n.m.r. spectroscopic study of the pentafluorotellurate(IV) ion

The Raman, and infra-red spectra of Na⁺, K⁺, Rb⁺, Cs⁺, NH₄⁺, C₅H₅NH⁺ and $\text{n}$-Bu₄N⁺ salts of the TeF₅^- ion are reported. They are assigned C_s symmetry. ¹⁹F n.m.r. spectra of the $\text{n}$-Bu₄N⁺ salt show J(F_ax-F_eq)50.4Hz, J(¹⁹F_eq-¹²⁵Te)1375.7Hz, J(¹⁹F_ax-¹²⁵Te)2883.3Hz and J(¹⁹F_eq-¹²³Te)1143.8Hz. No n.m.r. evidence was found for TeF₆^2-.