Monte Carlo-based QSAR modeling of dimeric pyridinium compounds and drug design of new potent acetylcholine esterase inhibitors for potential therapy of <Emphasis Type="Italic">myasthenia gravis</Emphasis>

The Monte Carlo method was used for QSAR modeling of dimeric pyridinium compounds as acetylcholine esterase inhibitors. QSAR model was developed for a series of 39 dimeric pyridinium compounds. QSAR models were calculated with the representation of the molecular structure by the simplified molecular-input line-entry system. One split into the training and test set have been examined. The statistical quality of the developed model is very good. The calculated model for dimeric pyridinium derivatives had following statistical parameters: r ² = 0.9477 for the training set and r ² = 0.9332 the test set. Structural indicators considered as molecular fragments responsible for the increase and decrease in the inhibition activity have been defined. The computer-aided design of new dimeric pyridinium compounds potential acetylcholine esterase inhibitors with the application of defined structural alerts has been presented.     

Molecular structure of ErCl<Subscript>3</Subscript> and YbCl<Subscript>3</Subscript> according to the data of the simultaneous electron diffraction and mass spectrometric experiment

The saturated vapors of ErCl₃ and YbCl₃ were studied in a simultaneous electron diffraction and mass spectrometric experiment at 1165 K and 1170 K, respectively. In the vapors of these compounds, we found up to 3 mol.% dimers along with the monomers. The parameters of the r _g effective configuration of the monomer molecules were determined. For ErCl₃ and YbCl₃, the internuclear distances r _g(Ln-Cl) were 2.436(5) Å and 2.416(5) Å, and the bond angles ∠_g(Cl-Ln-Cl) were 117.0(10)° and 117.2(10)°, respectively. The equilibrium configurations and vibration frequencies of the monomer and dimer molecules were calculated by the HF, B3LYP, and MP2 methods using the combination of the ECP_D energy-consistent quasirelativistic core potential, including 4f electrons [Kr4d ¹⁰4f ⁿ ], and the contracted [5s4p3d] valence basis set for Er and Yb atoms and the MIDIX [4s3p1d] basis set for Cl atoms. The parameters of the effective r _g configuration of the monomer molecules corresponding to the temperature of the experiment were calculated. The difference between the calculated equilibrium r _e(Ln-Cl) and temperature-averaged r _g(Ln-Cl) distances was found to be 0.001–0.002 Å and did not exceed the error of the r _g(Ln-Cl) parameter determined in the electron diffraction experiment. The experimental parameters of the r _g structure were shown to be consistent with the idea about the planar equilibrium geometrical configuration of ErCl₃ and YbCl₃ molecules.     

Crystal Structure of [UO<Subscript>2</Subscript>SO<Subscript>4</Subscript>{(CH<Subscript>3</Subscript>)HNCONH(CH<Subscript>3</Subscript>)}<Subscript>2</Subscript>]

The single crystals of [UO₂SO₄{(CH₃)HNCONH(CH₃)}₂] (I) were synthesized and studied by X-ray diffraction. The crystals are monoclinic, a = 6.847(1) Å, b = 14.259(3) Å, c = 14.297(3) Å, β = 93.451(4)°, space group P2₁/n, Z = 4. The main structural units of crystals I are ribbons whose composition coincides with the composition of the compound. The crystal chemical formula of the complex is AT³M ₂ ¹ (A = UO ₂ ²⁺ ).     

Synthesis and characterization of a new monophosphate (C<Subscript>6</Subscript>H<Subscript>16</Subscript>N<Subscript>2</Subscript>)(H<Subscript>2</Subscript>PO<Subscript>4</Subscript>)<Subscript>2</Subscript>

Chemical preparation, crystal structure, and NMR spectroscopy of a new trans-2,5-dimethylpiperazinium monophosphate are given. This new compound crystallizes in the triclinic system, with the space group P-1 and the following parameters: a = 6.5033(3), b = 7.6942(4), c = 8.1473(5) Å, α = 114.997(3), β = 92.341(3), γ = 113.136(3), V = 329.14(3) ų, Z = 1, and D_x = 1.565 g cm^?3. The crystal structure has been determined and refined to R = 0.030 and R _w(F ²) = 0.032 using 1558 independent reflections. The structure can be described as infinite [H₂PO₄] _n ^n? chains with (C₆H₁₆N₂)²⁺ organic cations anchored between adjacent polyanions to form columns of anions and cations running along the b axis. This compound has also been investigated by IR, thermal, and solid-state, ¹³C and ³¹P MAS NMR spectroscopies and Ab initio calculations.     

Structure and some properties of [UO<Subscript>2</Subscript>CrO<Subscript>4</Subscript>{CH<Subscript>3</Subscript>CON(CH<Subscript>3</Subscript>)<Subscript>2</Subscript>}<Subscript>2</Subscript>]

A new complex [UO₂CrO₄{CH₃CON(CH₃)₂}₂] (I) was studied by thermal analysis, IR spectroscopy, and X-ray crystallography. The crystals are monoclinic: a = 13.8108(11) Å, b = 8.6804(7) Å, c = 13.0989(10) Å, β = 104.777(1)°, V = 1518.4(2) ų, space group P2₁/c, Z = 4, R = 2.39%. The structure of I contains infinite chains of the [UO₂CrO₄{CH₃CON(CH₃)₂}₂] composition running along [001]; the complex belongs to the AT¹¹M¹ ₂ crystal-chemical group (A = UO ₂ ²⁺ , T¹¹ = CrO ₄ ^2? , M¹ = CH₃CON(CH₃)₂) of uranyl complexes. The chains are linked into a three-dimensional framework due to hydrogen bonds between oxygen atoms of chromate ions and hydrogen atoms of methyl groups of the dimethylacetamide.     

Thermal properties,phase transitions,vibrational and reorientational dynamics of [Mn(NH<Subscript>3</Subscript>)<Subscript>6</Subscript>](NO<Subscript>3</Subscript>)<Subscript>2</Subscript>

[Mn(NH₃)₆](NO₃)₂ crystallizes in the cubic, fluorite (C1) type crystal lattice structure (Fm \( \overline{3} \) m) with a = 11.0056 Å and Z = 4. Two phase transitions of the first-order type were detected. The first registered on DSC curves as a large anomaly at T _C1 ^h  = 207.8 K and T _C1 ^c  = 207.2 K, and the second registered as a smaller anomaly at T _C2 ^h  = 184.4 K and T _C2 ^c  = 160.8 K (where the upper indexes h and c denote heating and cooling of the sample, respectively). The temperature dependence of the full width at half maximum of the band associated with the δ_s(HNH)F_1u mode suggests that the NH₃ ligands in the high temperature and intermediate phase reorientate quickly with correlation times in the order of several picoseconds and with activation energy of 9.9 kJ mol^?1. In the phase transition at T _C2 ^c probably only a some of the NH₃ ligands stop their reorientation, while the remainders continue to reorientate quickly with activation energy of 7.7 kJ mol^?1. Thermal decomposition of the investigated compound starts at 305 K and continues up to 525 K in four main stages (I–IV). In stage I, ²/₆ of all NH₃ ligands were seceded. Stages II and III are connected with an abruption of the next ²/₆ and ¹/₆ of total NH₃, respectively, and [Mn(NH₃)](NO₃)₂ is formed. The last molecule of NH₃ per formula unit is freed at stage IV together with the simultaneous thermal decomposition of the resulting Mn(NO₃)₂ leading to the formation of gaseous products (O₂, H₂O, N₂ and nitrogen oxides) and solid MnO₂.     

Molecular structure of NiO<Subscript>2</Subscript>N<Subscript>2</Subscript>C<Subscript>16</Subscript>H<Subscript>14</Subscript> from gas-phase electron diffraction and quantum chemical data

Gas-phase electron diffractometry was used to study the molecular structure of N,N′-ethylenebis(salicylaldiminato)nickel(II), NiO₂N₂C₁₆H₁₄, [hereinafter Ni(salen)] at 583(5) K. The molecule has C ₂ symmetry with a practically planar structure of the NiN₂O₂ coordination unit and with internuclear distances r _α (Ni-O) = 1.882(21) Å and r _α (Ni-N) = 1.889(22) Å. The results of B3LYP/CEP-31G molecular structure calculations are in good agreement with experimental data, whereas the RHF/CEP-31G method significantly overestimates the Ni-N internuclear distance and gives worse results for other structural parameters. According to 3LYP/CEP-31G calculations, the ¹ A low-spin state is 28 kJ/mole lower in energy than the ³ B high-spin state.     

Synthesis and X-ray investigation of Rb<Subscript>2</Subscript>[Pd(NO<Subscript>3</Subscript>)<Subscript>4</Subscript>] and Cs<Subscript>2</Subscript>[Pd(NO<Subscript>3</Subscript>)<Subscript>4</Subscript>]

Powder and single crystal X-ray diffraction studies have been performed for anhydrous nitrate complexes Rb₂[Pd(NO₃)₄] (I) and Cs₂[Pd(NO₃)₄] (II). Crystal data for I: a = 7.843(1) Å, b = 7.970(1) Å, c = 9.725(1) Å; β = 100.39(1)°, V = 597.9(1) Å ³, space group P2₁/c, Z = 2, d _calc = 2.918 g/cm³; for II: a = 10.309(2) Å, b = 10.426(2) Å, c = 11.839(2) Å; β = 108.17(3)°, V = 1209.0(4) ų, space group P2₁/c, Z = 4, d ^calc = 3.408 g/cm³. The structures are formed by isolated [Pd(NO₃)₄]^2? complex anions and alkali metal cations. The plane-square environment of the Pd atom is formed from the oxygen atoms of the monodentate nitrate groups. The geometrical characteristics of the complex anions are analyzed. Compound II has a short contact Pd...Cs 3.252 Å.     

Synthesis,structural, and electrochemical properties of NaCo(PO<Subscript>3</Subscript>)<Subscript>3</Subscript> cathode for sodium-ion batteries

A new Co-base sodium metaphosphate compound, NaCo(PO₃)₃, has been synthesized here by solid-state method. The crystal structure is refined by the Rietveld method, and the results reveal that NaCo(PO₃)₃ has an orthorhombic structure with the space group of P2 ₁ 2 ₁ 2 ₁ and lattice parameters of a = 14.2453(2) Å, b = 14.2306(1) Å, and c = 14.2603(2) Å. Its typical morphology and chemical composition are confirmed by scanning electron microscopy (SEM) and energy-dispersive spectrometry (EDS). The valence states of all elements and the internal/external vibrational modes of NaCoP₃O₉ compound are measured by X-ray photoelectron and vibrational spectrum, where a typical feature of the (PO₃)^? polyanion group is observed. Meanwhile, the electrochemical properties of NaCo(PO₃)₃ cathode for sodium-ion batteries are also elevated and an initial discharge capacity of 33.8 mAh/g can be obtained at 0.05 C within 1.5–4.2 V. After 20 cycles, a discharge capacity of 26.7 mAh/g can be obtained and a well-kept oxidation–reduction plateau is still observed for NaCo(PO₃)₃ cathode, indicating the good reversibility of this metaphosphate electrode.     

High-temperature heat capacity and thermodynamic properties of pyrovanadate Pb<Subscript>2</Subscript>V<Subscript>2</Subscript>O<Subscript>7</Subscript> and orthovanadate Pb<Subscript>3</Subscript>(VO<Subscript>4</Subscript>)<Subscript>2</Subscript>

The heat capacities of Pb₂V₂O₇ and Pb₃(VO₄)₂ as a function of temperature in the range 350–965 K have been studied by the differential scanning calorimetry method. The C_P = f(T) curve for Pb₂V₂O₇ is described by the equation C_p = (230.76 ± 0.51) + (73.60 ± 0.50)×10^-3T ? (18.38 ± 0.54)×10⁵T^-2 in the entire temperature range. For Pb₃(VO₄)₂, there is a well-pronounced extreme point in the C_P = f(T) curve at T = 371.5 K, which is caused by the existence of a structural phase transition. The thermodynamic properties of the oxide compounds have been calculated.     

The thermodynamic properties of the [(Me<Subscript>3</Subscript>Si)<Subscript>7</Subscript>C<Subscript>60</Subscript>]<Subscript>2</Subscript> fullerene complex

The temperature dependence of the heat capacity C _p ^o of the [(Me₃Si)₇C₆₀]₂ fullerene complex was measured for the first time using precision adiabatic vacuum calorimetry over the temperature range 6.7–340 K and high-accuracy differential scanning calorimetry at 320–635 K. For the most part, the error in the C _p ^o values was about ±0.5%. An irreversible endothermic effect caused by the splitting of the dimeric bond between fullerene fragments and the thermal decomposition of the complex was observed at 448–570 K. The thermodynamic characteristics of this transformation were calculated and analyzed. Multifractal analysis of the low-temperature (T < 50 K) heat capacity was performed, and conclusions were drawn concerning the character of the heterodynamicity of the structure. The experimental data obtained were used to calculate the standard thermodynamic functions C _p ^o (T), H ^o (T) ? H ^o (0), S ^o (T) ? S ^o (0), and G ^o (T) ? H ^o (0) over the temperature range from T → 0 to 445 K and estimate the standard entropy of formation of the compound from simple substances at 298.15 K. The standard thermodynamic properties of [(Me₃Si)₇C₆₀]₂ are compared with those of the (C₆₀)₂ dimer, the [(η⁶-Ph₂)₂Cr]⁺[C₆₀]^?? fulleride, and the initial C₆₀ fullerene.     

Molecular structure of SmBr<Subscript>3</Subscript> and DyBr<Subscript>3</Subscript> according to the data of simultaneous electron diffraction and mass spectrometric experiment

The saturated vapors of samarium and dysprosium tribromides were investigated for the first time by electron diffraction with mass spectrometric monitoring at temperatures of 1151(10) K and 1141(10) K. Dimer molecules (up to 2 mole %) were found in vapors along with monomer molecules. The SmBr₃ and DyBr₃ molecules have a pyramidal effective configuration with bond angles ∠_gBr-Sm-Br=115.1(9)° and ∠_gBr-Dy-Br=115.3(7)°. The difference between the internuclear distances of SmBr₃ and DyBr₃ (r _g(Sm-Br) = 2.653(6) Å and r _g(Dy-Br) = 2.609(5) Å) coincides with the difference between the ionic radii of Sm³⁺ and Dy³⁺. The insignificant pyramidality of the r _g configuration and the low deformation vibration frequencies of SmBr₃ and DyBr₃ may be indicative of a planar equilibrium geometry of D _3h symmetry. The equilibrium distances r _e(Sm-Br) and r _e(Dy-Br) have been evaluated and compared with the values obtained by quantum chemical calculations.     

<Emphasis Type="Italic">cis</Emphasis>-Dioxomolybdenum(VI) complexes of sterically encumbered phenol-based tetradentate N<Subscript>2</Subscript>O<Subscript>2</Subscript> ligands: Structural,spectroscopic, and electrochemical studies

Two cis-dioxomolybdenum(VI) complexes [MoO₂L] (L: L ¹, 2 and L: L ², 3) in a phenol-based sterically encumbered N₂O₂ ligand environment have been synthesized, and their crystallographic characterizations are reported. The orange crystals of 2 are monoclinic, space group P2₁/a with unit cell dimensions as a=16.2407(17) Å, b=7.2857(8) Å, c=18.400(2) Å, β=98.002(9)°, Z=4, and d _cal=1.486 g cm^?3. The light orange crystals of 3, however, are orthorhombic, space group, Pbcn, with unit cell dimensions a=8.3110(12) Å, b=12.637(3) Å, c=34.673(5) Å, Z=4, and d _cal=1.187 g cm^?3. The structures were refined by a full-matrix least-squares procedure on F ² to a final R=0.046 (0.055 for 3) using 4944 (3677) all independent data. In both the cases, the Mo atom exists in a distorted octahedral geometry defined by a N₂O₄ donor set, which features a cis-Mo(–O)₂ and a trans-Mo(OPh)₂ arrangement. Compound 2 undergoes a quasireversible one-electron reduction at ?1.3 V vs Ag/AgCl reference due to Mo^VIO₂/Mo^VO₂ electron transfer and thus providing a rare example of steric solution to the comproportionation–dimerization problem encountered frequently in the development of valid biomimetic models for the active sites of oxomolybdenum enzymes.     

Thermolysis of [Pt(NH<Subscript>3</Subscript>)<Subscript>4</Subscript>][ReHlg<Subscript>6</Subscript>] (Hlg = Cl,Br). Structure refinement for [Pt(NH<Subscript>3</Subscript>)<Subscript>4</Subscript>][ReCl<Subscript>6</Subscript>]

Thermal decomposition of [Pt(NH₃)₄][ReHlg₆] binary complex salts (Hlg = Cl, Br) in a hydrogen atmosphere has been studied. Polycrystal X-ray diffractometry indicated that two-phase metallic systems are the final products of thermolysis. Structure refinement was performed for [Pt(NH₃)₄][ReCl₆] by the combined technique involving decomposition of the diffractogram into individual reflections, isolation of reflections most sensitive to the position of separate light atoms, and full-profile analysis. Crystal data for PtReN₄Cl₆H₁₂: a = 11.616(1) Å, b = 10.998(1) Å, c = 10.377(1) Å, V = 1148.1 ų, space group Cmca, Z = 4, d _x = 3.831 g/cm³. The indices are R_p = 5.48%, R_wp = 10.01%, R(F²) = 12.62%. The coordination polyhedron of Re is an almost regular octahedron: Re-Cl 2.34–2.36 Å, ∠ Cl-Re-Cl 86.9–90.3°; the coordination polyhedron of Pt is a square: Pt-N 2.04 Å, ∠N-Pt-N 90.4°.     

Study of variation in thermophysical properties of RE<Subscript>6</Subscript>UO<Subscript>12</Subscript>(s) along the lanthanide series

The novel ligand N,N,N′′′′,N′′′′-tetrabutyl-N′′′,N′′′-(N″,N″-diethyl)-ethidene bisdiglycolamide (TBEE-BisDGA) and other eight analogous extractants have been synthesized and characterized by NMR and HRMS. The solvent extraction of Th⁴⁺, UO₂ ²⁺ and Eu³⁺ from nitric acid solution using the above BisDGA extractants was investigated in 1-dodecanol at 30 ± 1 °C. The extractants exhibited higher affinity toward Th⁴⁺ than UO₂ ²⁺ and Eu³⁺ in the present system. The maximum value of separation factor SF _Th(IV)/U(VI) and SF _{Th(IV)/Eu(III)} is 78.5 and 53.3 respectively for TBEE-BisDGA, 88.1 and 69.5 respectively in the case of TB ^i-PE-BisDGA at 3 M HNO₃ solution.     

Orientational disorder in crystal structures of (NH<Subscript>4</Subscript>)<Subscript>3</Subscript>ZrF<Subscript>7</Subscript> and (NH<Subscript>4</Subscript>)<Subscript>3</Subscript>NbOF<Subscript>6</Subscript>

Crystal structures of (NH₄)₃ZrF₇ (I) and (NH₄)₃NbOF₆ (II) are refined by X-ray diffraction at room temperature. The compounds are isostructural and belong to the structural type of elpasolite: space group F23; a(I) = 9.4185(3) Å, a(II) = 9.3371(5) Å; V(I) = 835.50(5) ų, V(II) = 814.02(8) ų; Z = 4; R(I) = 0.0145, and R(II) = 0.0138. The refinement of the structures in the space group Fm3m yields abnormally short X-X distances in the pentagonal bipyramid MX₇ (X = F, O). The oxygen atom in II is identified by Nb-X distances and occupies one of the axial vertices of the bipyramid. The Nb atom in II is statistically distributed over the position 24f, while Zr in I resides in the symmetry center. The pentagonal bipyramid MX₇ has six independent orientations in I and twelve in II. One of three crystallographically independent ammonium groups of the structures is disordered over six or twelve equivalent orientations.     

Synthesis and crystal structure of (<Emphasis Type="Italic">o</Emphasis>-Diaminobenzene)<Subscript>2</Subscript> Zn(OAc)<Subscript>2</Subscript>

The treatment of o-diaminobenzene with Zn ( OAc )₂ · 2H₂O in alcohol results in the formation of mononuclear bis(o-diaminobenzene)diacetate Zinc, Zn[C₈H₁₁N₂O₂]₂. Its structure was determined by X-ray diffraction analysis. The complex is also characterized by elemental analysis, ¹H NMR and IR. The crystal is monoclinic space group C2, parameters: a = 16.297(5), b = 4.775(3), c = 11.664(5) Å, β = 97.646(5)°, λ = 1.54184 Å, V = 899.6(7) ų, Z = 2, ρ _c = 1.476 g/cm³, M _r = 399.75, F(000) = 416.0, R ₁ = 0.0594, wR ₂ = 0.1439 for 995 observed reflections with I > 2σ(I).     

Synthesis,structure, and properties of the thermolysis products of [Os(NH<Subscript>3</Subscript>)<Subscript>5</Subscript>Cl][ReCl<Subscript>6</Subscript>]

The crystal structure of [Os(NH₃)₅Cl][ReCl₆] has been refined by X-ray powder analysis: a = 11.645(3) Å, b = 8.3788(2) Å, c = 15.277(4) Å, β = 91.029(6)°, V = 1490(1) ų, d _x = 3.163 g/cm³, space group P2₁/m, Z = 4. The thermolysis product of the salt in a hydrogen atmosphere is a solid substitution solution Os_0.5Re_0.5: a = 2.753(2) Å, c = 4.366(3) Å, space group P6₃/mmc; coherent scattering region (CSR) is ～230 Å.     

New Hybrid Material: (C<Subscript>3</Subscript>H<Subscript>6</Subscript>N<Subscript>3</Subscript>)<Subscript>4</Subscript>Bi<Subscript>2</Subscript>Cl<Subscript>10</Subscript>. Synthesis,Structural Study and Spectroscopic Behavior

The structure of (C₃H₆N₃)₄Bi₂Cl₁₀ was determined by single crystal X-ray diffraction at room temperature. It crystallizes in the orthorhombic space group Pcmn, with a = 9.430 (1) Å, b = 17.426 (3) Å, c = 19.883(5) Å, V = 3267.3 (11) ų and Z = 4. The structure consists of discrete binuclear [Bi₂Cl₁₀]^4– anions and 3-aminopyrazolium cations. The crystal packing is governed by weak N–H···Cl hydrogen bonds, π–π and electrostatic Cl···Cl interactions. Infrared spectrum is used to gain more information on the title compound. An assignment of the observed vibration modes is reported. The crystal morphology is studied using the BFDH laws. The calculated HOMO and LUMO energies show that charge transfer occur within organic and inorganic molecules. The optical absorption of the zero-dimensional hybrid was also investigated.