Compound K0 Research Articles

Novel acetylcholinesterase inhibitors: Synthesis and structure–activity relationships of phthalimide alkyloxyphenyl N,N-dimethylcarbamate derivatives

Based on the multiple binding sites of acetylcholinesterase (AChE), a series of AChE inhibitors: phthalimide alkyloxyphenyl N,N-dimethylcarbamate were designed and synthesized. AChE inhibitory activity and structure–activity relationship of the compounds were researched also. The influence of structural variations on the inhibitory potency was carefully investigated by modifying different alkyloxy chain length and position between phthalimide and phenyl N,N-dimethylcarbamate (PDM). The biological properties of the series were investigated by considering the activity on isolated enzyme. Some of the newly synthesized derivatives, when tested on isolated AChE from head of housefly ( Musca domestica), were more active than PDM. The compounds J1, J2 and K1– K8 demonstrated higher inhibitory activity (5- to 404-fold) for AChE than that of PDM. In particular, compound K1 displayed the best AChE inhibition (404-fold higher than PDM), which suggested that phthalimide group of K1 strongly bound at the residues lining the gorge while phenyl N,N-dimethylcarbamate bound at the catalytic site.

Multiglass order and magnetoelectricity in Mn2+ doped incipient ferroelectrics

“Multiglass” materials with simultaneous occurrence of two different glassy states extend the frame of conventional multiferroicity, which is devoted to crystalline materials with coexisting uniform long-range electric and magnetic ordering. The concept applies to Sr0.98Mn0.02TiO3 ceramics, where A-site substituted Mn2+ ions are at the origin of both a polar and a spin cluster glass. Spin freezing is initiated below the dipolar glass temperature, Tg e ≈ 38 K, which is seemingly indicated by a divergence of the nonlinear susceptibility, χ3. Below Tg m ≈ 34 K both glass phases are independently verified by memory and rejuvenation effects. Biquadratic interaction of the Mn2+ spins with ferroelectric correlations of their off-center pseudospins in the incipient ferroelectric host crystal SrTiO3 explains the high spin glass temperature and comparably strong third-order magnetoelectric coupling between the polar and the magnetic degrees of freedom. Preliminary results on the related compound K0.97Mn0.03TaO3 favorably comply with the magnetoelectric multiglass concept.

Features of electron states of compounds with strong electron correlations probed by radiation-induced disorder

The radiation-disordering method is used for investigating features of electron states of two classes of systems with strong electron correlations: high-temperature superconductors (HTSCs) and heavy-fermion (HF) systems. At low temperatures, the electron states of these systems are formed in a strong interaction between conduction electrons and localized magnetic moments. To clarify the factors leading to a change in the properties of these compounds, the radiation-disordering effects are analyzed first in simpler systems: (I) superconducting (SC) intermetallic compounds MgB2 and MgCNi3; (II) compounds In x Bi2−x Te3 and HgSe with a relatively low charge-carrier concentration, pyrolytic graphite, and (i)-AlPdRe quasicrystal; and (III) oxide compounds K0.3WO3 and Sr2RuO4. It is shown that a number of essential properties of the electron states of the initial (ordered) compounds could be established when analyzing the experimental data within the framework of simple models. In systems with a carrier concentration n = (1017−1019) cm−3, the formation of radiation defects carrying an effective charge results in the Fermi-level shift that is the key factor for the observed changes in transport properties, while the scattering effects on additional defects are less significant. In the HTSC and HF systems, the observed disordering effects are qualitatively different. In this case, the presence of initial unique electron states formed through the interaction of electrons with localized magnetic moments and responsible for the “unusual” superconductivity is a more essential factor than the defect doping. The crystal order is very important for the existence of these low-temperature states and its damage results in their suppression. The nature of degradation of the HF states upon disordering depends on the effective mass m*: from the complete suppression for m*/m e > 100 to relatively weak changes in properties for m*/m e < 10. The decay of a coherent-electron system into two weakly interacting subsystems caused by disordering is a radiation defect common for the HTSC and HF systems, leading to a fast suppression of SC states. The crystal-order damage in these systems changes the type of interaction from collective to local, which can be considered as a continuous phase transition; this circumstance is often ignored when constructing the theoretical models for description of these fine quantum states.

Structures and Bonding in K0.91U1.79S6 and KU2Se6

The compounds K0.91U1.79S6 and KU2Se6, members of the AAn2Q6 actinide family (A = alkali metal or Tl; An = Th or U; Q = S, Se, or Te), have been synthesized from US2, K2S, and S at 1273 K and U, K2Se, and Se at 1173 K, respectively. KU2Se6 shows Curie-Weiss behavior above 30 K and no magnetic ordering down to 5 K. The value of mu(eff) is 2.95(1) mu(B)/U. Its electronic spectrum shows the peaks characteristic of 5f-5f transitions. It is a semiconductor with an activation energy of 0.27 eV for electrical conduction. Both K0.91U1.79S6 and KU2Se6 crystallize in space group Immm of the orthorhombic system and are of the KTh2Se6 structure type. Both contain infinite one-dimensional linear Q-Q chains characteristic of the AAn2Q6 family. Typical of the known AAn2Q6 compounds, in KU2Se6, there are two alternating Se-Se distances of 2.703(2) and 2.855(2) A, both much longer than an Se-Se single bond. In contrast, in K0.91U1.79S6, the first sulfide of this family to be characterized structurally, there are alternating normal S2(2-) pairs 2.097(5) A in length. In K0.91U1.79S6, the formal oxidation state of U is 4+.

Infrared properties of W-doped charge-density-wave material K0.3MoO3

The optical conductivity spectra of quasi-one dimensional compounds K0.3Mo1−xWxO3 (x=0, 0.03 and 0.15) have been studied over broad frequencies. While the DC resistivity measurements indicate no sign of CDW transition in heavily W-doped blue bronze, the optical conductivity spectra still show a single particle gap at around 0.2eV for E parallel to the chain direction. Such impurity effect challenges our understanding about the occurrence of the optical gap with the CDW transition.

Electronic structure of the Peierls compound K0.9Mo6O17

The purple potassium bronze of molybdenum is a quasi two-dimensional compound showing a Peierls transition at 120 K. This transition is driven by the properties of the conduction electrons. In order to confirm the nature of the transition, we have investigated at room temperature the electronic structure of this oxide and established its band structure in the ΓK direction. A weak conduction band is detected, well separated from the valence band by a depleted region. The valence band shows several structures attributed to oxygen-type states and to the K3p shallow core level. The structures of the conduction band reveal the presence of at least two bands crossing the Fermi level, in relatively good agreement with the calculated band structure.

Comment on¶Low temperature specific heat of blue bronze K 0.30MoO 3, by J. Odin, J.C. Lasjaunias, K. Biljaković, K. Hasselbach, and P. Monceau

Eur. Phys. J. B 24, 315 (2001) Here we comment on a recently published paper on the presence of a phason contribution in the low temperature heat capacity data of the charge-density-wave compounds K0.3MoO3 and (TaSe4)2I. We have shown that the anomaly in the CP/T3 data reported by Odin et al. is straightforwardly interpreted in terms of low energy phonon modes resulting from the peculiar topology of these compounds.

Electron Diffraction Study of Intercalation Compounds Derived from 1T-MoS2

The structure of the intercalation compound K0.7MoS2as well as of its hydrated (K0.3(H2O)yMoS2) and oxidation (1T-MoS2) derivatives were studied by means of selected area electron diffraction (SAED). All the derivatives are shown to have superstructures related to the structure of 2H-MoS2. The intercalation compound K0.7MoS2has a 2a×2a-type superstructure (a=lattice parameter of 2H-MoS2), whereas the superstructure of the hydrated derivative (K0.3(H2O)yMoS2) corresponds roughly to ana×a3-type. Three domains are present in different orientations, each of which can be related to each other by angles of 60° or 120°. 1T-MoS2has an hexagonala3×a3-type superstructure.

Syntheses and Crystal Structures of Three Copper Tellurides: BaDyCuTe3, K1.5Dy2Cu2.5Te5, and Acentric K0.5Ba0.5DyCu1.5Te3

Three compounds, BaDyCuTe3, K1.5Dy2Cu2.5Te5, and K0.5Ba0.5DyCu1.5Te3, were synthesized from the reaction at 850 °C of the pure elements with fluxes such as BaCl2 or a eutectic mixture of LiCl/KCl. The crystal structures of the three compounds were determined by the single-crystal X-ray method. The final R-values for the three crystals were, respectively, 4.34%, 3.95%, and 3.46%. All three structures can be viewed as tetrahedral structures based on CuTe4 units. BaDyCuTe3 crystallizes in the orthorhombic space group Cmcm (no. 63) with cell dimensions of a = 4.4286(3) Å, b = 14.7895(10) Å, c = 11.3454(8) Å, and Z = 4. BaDyCuTe3 is isotypic with the known structure of KZrCuS3. The other compounds, K0.5Ba0.5DyCu1.5Te3 and K1.5Dy2Cu2.5Te5, belong to new structure types. The structure of the former compound is a filled version of the BaDyCuTe3 compound noted above. However, unlike BaDyCuTe3, K0.5Ba0.5DyCu1.5Te3 crystallizes in the noncentrosymmetric orthorhombic space group Cmc21 (no. 36) with cell dimensions of a = 4.3877(3) Å, b = 14.9001(12) Å, c = 11.4847(9) Å, and Z = 4. While BaDyCuTe3 contains infinite one-dimensional chains of tetrahedra with stoichiometry [CuTe35-]∞, the new phase K0.5Ba0.5DyCu1.5Te3 forms a three-dimesional framework of tetrahedra. The compound K1.5Dy2Cu2.5Te5 crystallizes in another orthorhombic space group, Pmnn (No. 58) with cell axes of a = 4.3307(1) Å, b = 16.6766(2) Å, c = 17.6945(2) Å, and Z = 4. This final structure can also be related to that of K0.5Ba0.5DyCu1.5Te3.

Ion Exchange of Cesium on Potassium Nickel Hexacyanoferrate (II)s

The ion exchange of Cs+ on a nonstoichiometric compound K0.87Ni0.57[NiFe(CN)6]·nH2O (KNiFC) was examined by batch methods. The distribution coefficient of Cs+, Kd,Cs, was independent of Na+ concentration up to 5M (=mol/dm3), while it decreased with increasing concentrations of both K+ and NH4 +. The separation factor for Cs/Rb, αcs/Rb, was 4.7×102 in the presence of 5M Na+. The decreasing order of Kd,Cs in the coexisting cations was found to be NH4 +K+, H+Na+, Ca2+. The uptake of Cs+ on KNiFC followed a Langmuir-type isotherm and the maximum amount of Cs+ taken up was estimated to be 2.57±0.074mmol/g. The free energy of K+←Cs+ ion exchange was calculated to be −15.4±1.4kJ/mol by Kielland plot.

Ion Exchange of Cesium on Potassium Nickel Hexacyanoferrate (II) s.

The ion exchange of Cs+ on a nonstoichiometric compound K0.87Ni0.57[NiFe(CN)6]·nH2O (KNiFC) was examined by batch methods. The distribution coefficient of Cs+, Kd,Cs, was independent of Na+ concentration up to 5M (=mol/dm3), while it decreased with increasing concentrations of both K+ and NH4 +. The separation factor for Cs/Rb, αcs/Rb, was 4.7×102 in the presence of 5M Na+. The decreasing order of Kd,Cs in the coexisting cations was found to be NH4 +K+, H+Na+, Ca2+. The uptake of Cs+ on KNiFC followed a Langmuir-type isotherm and the maximum amount of Cs+ taken up was estimated to be 2.57±0.074mmol/g. The free energy of K+←Cs+ ion exchange was calculated to be −15.4±1.4kJ/mol by Kielland plot.

Evidence of charge-density-wave fluctuations in the low frequency optical conductivity of K0.3MoO3and (TaSe4)2I

Abstract The low temperature charge-density-wave (CDW) ground state has been extensively studied in the model quasi one-dimensional compounds K0.3MoO3 (blue bronze) and (TaSe4)2I. Below the Peierls transition temperature T 3D (183 K and 263 K in blue bronze and (TaSe4)2I, respectively) the conduction electrons exhibit long-range, three-dimensional order, and the interesting low temperature properties, including the pinned mode resonance and bound phonon states, have been clearly established. In contrast, the high temperature metallic state in these compounds has not been characterized nearly as extensively. In this paper we present the results of optical conductivity measurements performed above T 3D in the millimeter and submillimeter frequency range which, when combined with higher frequency infrared to ultraviolet reflectivity measurements, show clear deviations from simple metallic behavior. Futhermore, the pronounced excitations which appear in the spectra below 50 cm−1 for the electric field E polar...

Attempts to modify an electrode with a conducting platinum cluster compound

AbstractA conducting platinum cluster compound K1.64Pt(C2O4)2 was electrochemically synthesized on a glassy carbon electrode through the electrooxidation of K2Pt(C,2O4)2 in an aqueous medium using single potential step and cyclic voltammetry methods. The precursor K2Pt(C2O4)2 was prepared by a ligand exchange reaction between C2O42− and PtCl42−. During single potential step experiments, the electrolytic current corresponding to the oxidation of K2Pt(C2O4)2 increased dramatically after a sharp decrease at the beginning (due to the formation of conducting K1.64Pt(C2O4)2 on the surface of the working electrode). Two kinds of mechanism account for the current transients at the different applied potentials. Cyclic voltammetry was conducted with K1.64Pt(C2O4)2 on the surface of the working electrode and a steady‐state diffusion current was observed. Since the material grew in a fibrous manner, each conducting fiber which was in contact with the electrode could serve as an ultramicroelectrods. The behavior of the working electrode was thus changed from a plain to an ultramicroelectrode array.

The specific heat study of charge-density-wave phase transitions for the blue bronze Tl0.3MoO3

The specific heat of the blue bronze Tl0.3MoO3 is measured using an adiabatic continuous heating method from 100 to 220 K. A specific heat anomaly is observed at 172.3 K. The specific heat jump, and enthalpy and entropy changes associated with the CDW phase transition are estimated. The results suggest that the phase transition is of second order and that the lattice plays an important role in thermodynamics in this system, by analogy with the behaviour of its isostructural compound K0.3MoO3. The mean-field theory seems not to be adequate for describing the CDW phase transition in this compound.

Low temperature phonon thermal conductivity of the quasi-one-dimensional compounds (NbSe4)3I, (TaSe4)2I and K0.3MoO3

We report on measurements of the thermal conductivity of quasi-one-dimensional compounds K0.3MoO3, (NbSe4)3I, and (TaSe4)2I between 0.07K and 4 K. Despite the presence of a charge-density wave, the observed behaviour is similar to that expected in good insulating crystals, where the thermal conductivity well below 1 K is mainly governed by boundary scattering with some degree of specular reflection. However a pronounced anomaly is detected in (TaSe4)2I as a sharp maximum around 1 K, followed by a broad minimum around 3 K. We ascribe this anomaly to strong scattering by low-lying transverse acoustic phonons, with a very weak dispersion over a large part of the Brillouin zone, lying at an unusually low frequency.

Unusual voltammetric behaviour of an electrochemically synthesized conducting platinum cluster compound K1.64[Pt(C2O4)2

The compound K1.64[Pt(C2O4)2] was electrochemically synthesized on a glassy carbon electrode using both single-potential step and cyclic voltammetry techniques; voltammetric behaviour of the working electrode was changed dramatically with deposition of the conducting material on the surface of the electrode.

High-Resolution Electron Microscopy of condensed clusters in a potassium barium oxomolybdate

The recently synthesized compound K0.19Ba3.81Mo22O34 is a representative of the ternary and quaternary reduced molybdenum oxides in which clusters built from molybdenum octahedra are arranged in layers of composition AxByMo4n+2O6n+4. The number of trans-edgesharing molybdenum octahedra in the cluster is represented by n. The general concept of cluster condensation is formulated and discussed elsewhere. For K0.19Ba3.81Mo22O34, n is equal to 5. A ternary representative, likewise with n = 5, is In6Mo22O34.By x-ray structure analysis, K0.19Ba3.81Mo22O34 proved to crystallize in space group P21/a with parameters a = 0.9908(2) nm, b = 0.9353(2) nm, c = 1.5951(3) nm, and β = 98.78(2)°. The potassium atoms were found to reside on the same sites as the barium atoms with an almost statistical distribution.We studied K0.19Ba3.81Mo22O34 by high-resolution electron microscopy (HREM). Small fragments of a crystal were investigated using a Philips CM30/ST microscope operating at 300 kV (point resolution 0.19 nm). At appropriate orientations of the crystal fragments, HREM images reveal domains of two ordered polytypes: a monoclinic and an orthorhombic one (Figs. 1 and 2).

Dielectric hysteresis and relaxation in the charge-density-wave compound K0.3MoO3.

The electrical properties of the charge-density-wave compound blue bronze (${\mathrm{K}}_{0.3}$${\mathrm{MoO}}_{3}$) have been investigated at several temperatures around T=4.2 K. A nonlinear current-voltage relationship was observed with an increase of the conductance by six orders of magnitude above a well-defined threshold voltage ${V}_{T}$. A giant remanent dielectric polarization was recorded below ${V}_{T}$. The polarization exhibits slow relaxation with a logarithmic or stretched exponential time dependence over the time domain of 10 msec\char21{}1000 sec.

Ionic conductivity of hollandite type compound at 9.54 and 32.8 GHz

The microwave ionic conductivity σ of single-crystals of K-Mg priderite ( a hollandite type compound ) K1·6Mg0·8Ti7·2O16 has been measured using a standing wave method at 9.54 and 32.8 GHz from 83 to 616 K. The results of σT−1T characteristic are divided into two regions, one is the part of higher temperatures I and the other is the part of lower temperatures II. As the ionic conductivity at 32.8 GHz at the region I is interpreted by the configurational model proposed by Bayeler et al., the frequency-independent intrinsic ionic conductivity dominated by the configurational model is predicted to be observed at higher frequencies than 32.8 GHz.

A structure analysis of the compound K0.27WO(3+y)

A structure analysis of the compound K_0.27WO_(3+<i>y</i>)