X-ray crystallographic studies and molecular calculations on 1∶1 inclusion complexes of cholic acid with acetophenone and its derivatives

Molecular calculations were applied to four channel-type inclusion complexes of cholic acid (CA) with acetophenone or its derivatives (3-, 4-fluoroacetophenone and 2-chloroacetophenone). According to the calculated results, both the total and van der Waals interaction energies between channel and included guests depend on the channel form determined by the guest species. Similarly, the channel form is responsible for the dipole moment of the channel. Further examination of the results suggests that dipole-dipole interaction does not play an important role in the determination of the guest orientation. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82193 (26 pages).     

X-ray quality geometries of geodesic polyarenes from theoretical calculations: what levels of theory are reliable?

[structure: see text] Computational methods for calculating molecular geometries have not been well calibrated heretofore against X-ray data for bowl-shaped polycyclic aromatic hydrocarbons (PAHs). The analysis presented here capitalizes on a rare opportunity provided by corannulene to account explicitly for molecular distortions from crystal packing forces. Within the error limits of an extensive X-ray data set, B3LYP/6-31G* calculations were found to correctly reproduce all of the experimental bond distances and bond angles. The reliability and shortcomings of geometry calculations at other levels of theory are enumerated.     

Novel rhenium oxocomplexes of indazole-3-carboxylic acid – Synthesis,X-ray studies,spectroscopic characterization and DFT calculations

Three novel rhenium oxocomplexes incorporating indazole-3-carboxylate ligand: cis-[ReOCl₂(Ind-3-COO)(PPh₃)]·OPPh₃ (1a), cis-[ReOCl₂(Ind-3-COO)(PPh₃)] (1b) and cis-[ReOBr₂(Ind-3-COO)(PPh₃)]·OPPh₃ (2) have been synthesized and characterised spectroscopically and structurally (by single-crystal X-ray diffraction). The 1a and 2 are isostructural in solid state. The electronic spectrum of 1a was investigated at the TDDFT level employing B3LYP functional in combination with LANL2DZ. Additional information about binding in the complex 1a was obtained by NBO analysis.     

The structure of β-diketones related to curcumin determined by X-ray crystallography,NMR (solution and solid state) and theoretical calculations

Structural Chemistry - Structural data are reported on sixteen ketoenols of β-diketones: solution NMR, solid-state NMR (CPMAS and MAS) and X-ray crystallography (four compounds, where three...     

Dipole moment and self-association of cyclohexylsulfamic acid in 1,4-dioxane solution at 298.15?K

Abstract  

The density, refractive index, and electrical permittivity of cyclohexylsulfamic acid in 1,4-dioxane solutions were measured at 298.15 K. The limiting apparent specific volume, refraction, and polarization were calculated from the experimental data. The electrical dipole moment of cyclohexylsulfamic acid was estimated using the Debye, Onsager, and Kirkwood equations. The dipole association of cyclohexylsulfamic acid was treated with the assumption that the dipole moment of dimeric species is zero. The dimerization constant and dipole moment of monomeric species were evaluated.     

Limiting Partial Molar Volumes of Water in 1-Hexanol, 1-Octanol, 1-Decanol, and Cyclohexanol at 298.15?K

From the density of solutions of water in 1-hexanol, 1-octanol, 1-decanol, and cyclohexanol, measured at 298.15K, the limiting partial molar volume and the excess limiting partial molar volume of water was estimated. The limiting partial molar volume of water in alcohols was discussed in terms of the void space created by the addition of water to alcohol and by the packing density of water. On the basis of the Kirkwood-Buff theory and the activity of water in alcohols an average aggregation number of water molecules, as well as the number of the excess alcohol molecules in the surroundings of the water molecule was calculated. The solvation ability of the investigated alcohols was estimated as the difference in the solvation Gibbs energy of an alcohol molecule in solution relative to the pure alcohol. The observed difference was mainly ascribed to an indirect effect caused by water molecules on the alcohol structure and to a lesser extent to the hydrogen bonding of water to alcohol molecules. The limiting partial molar volume of water was also interpreted in terms of scaled particle theory and the various volume contributions arising from dispersion, dipole–dipole, and inductive interactions between water and an alcohol molecule were calculated.     

X-ray structure and thermal analysis of a 1∶1 complex between sulfathiazole andβ-cyclodextrin

An inclusion complex with the formula (-cyclodextrin) (sulfathiazole) 8.3 H₂O has been crystallized and characterized by physicochemical methods including single crystal X-ray analysis. The complex crystallizes in the monoclinic system, space group P2₁, witha=15.264(4),b= 16.500(6),c=15.559(5) Å,=117.29(3)^o andZ=2. The structure was solved using published co-ordinates for-cyclodextrin in an isomorphous complex. Refinement by block-diagonal leastsquares yieldedR=0.061 for 4706 unique observed reflections. Inclusion of sulfathiazole produces a slight ellipticity in the host conformation, but the guest adopts a conformation similar to that observed in its polymorphs. The guest is held in the macrocyclic cavity predominantly by hydrophobic forces, with the phenyl ring near the host primary hydroxyl side and the thiazole ring near the secondary hydroxyl side. The complex packs in layers parallel to theac-plane. Layers are linked by hydrogen bonding to water molecules which are located outside the cyclodextrin cavity. An extensive network of hydrogen bonds mediated chiefly by water molecules stabilizes the crystal structure.     

Solution and fluorous phase synthesis of β,β-difluorinated 1-amino-1-cyclopentane carboxylic acid derivatives

An efficient protocol for the preparation of β,β-difluorinated 1-amino-1-cyclopentane carboxylic acid derivatives was developed. 2,2-Difluro-4-phenyl-3-butenoic acid 6 was used as substrate for the preparation of the starting vinyl difluoro imino esters 8. The key steps of this methodology rely on the chemo- and diastereoselective addition of allylzinc bromides over the iminic functionality of 8 and subsequent RCM reaction. This synthetic sequence was successfully applied to fluorous synthesis.     

Novel rhenium oxocomplexes of 2-hydroxymethylbenzimidazole – Synthesis,X-ray studies,spectroscopic characterization and DFT calculations

Three novel rhenium oxocomplexes of biologically relevant ligand 2-hydroxymethylbenzimidazole: cis-[ReOCl₂(hmbzim)(PPh₃)] (1), cis-[ReOBr₂(hmbzim)(PPh₃)] and [ReO(hmbzim)₂(PPh₃)](ReO₄)·CH₃OH (3) have been synthesized and characterized spectroscopically and structurally (by single-crystal X-ray diffraction). The electronic spectra of 1 and 3 were investigated at the TDDFT level employing B3LYP functional in combination with LANL2DZ. Additional information about binding in the complexes 1 and 3 was obtained by NBO analysis.     

Comparative theoretical and experimental analysis of hydrocarbon σ-radical cations

The structures of σ-radical cations formed by ionization of adamantane, twistane, noradamantane, cubane, 2,4-dehydroadamantane, and protoadamantane were optimized at the B3LYP, B3LYP-D, M06-2X, B3PW91, and MP2 levels of theory using 6-31G(d), 6-311+G(d,p), 6-311+G(3df,2p), cc-PVDZ, and cc-PVTZ basis sets. On the whole, single-configuration approximations consistently describe the structure and transformations of the examined σ-radical cations. The best correlations (r = 0.97–0.98) between the calculated adiabatic ionization potentials and experimental oxidation (anodic) potentials of hydrocarbons were obtained in terms of B3PW91 approximation.     

The synthesis of (−)-cis- and (−)-trans-crobarbatic acid

The synthesis of both cis- and trans-crobarbatic acid is reported. The five-step sequence proceeds in high yield and with control of both relative and absolute stereochemistry. The key step in the synthesis is the Birch reductive alkylation of a chiral furoic acid which sets the absolute stereochemistry of the products. The stereochemistry of the compounds described was proven unambiguously by X-ray crystallography on one synthetic intermediate and on trans-crobarbatic acid.     

Densities, Viscosities, Speeds of Sound, FT-IR and 1H-NMR Studies of Binary Mixtures of n-Butyl Acetate with Ethanol, Propan-1-ol, Butan-1-ol and Pentan-1-ol at?298.15, 303.15, 308.15 and 313.15?K

Densities, viscosities and speeds of sound of binary mixtures of ethanol, propan-1-ol, butan-1-ol and pentane-1-ol with n-butyl acetate have been measured over the entire range of composition at temperatures of 298.15, 303.15, 308.15 and 313.15 K and atmospheric pressure. From the experimental densities, viscosities and speeds of sound, the excess molar volumes V ^E, deviations in viscosity ????, and deviations in isentropic compressibility ???? _S have been calculated. The excess molar volumes and deviations in isentropic compressibility are positive for all the binary systems studied over the whole composition, while deviations in viscosities are negative for all of the binary mixtures. The excess molar volumes, deviations in viscosity, and deviations in isentropic compressibility have been fitted to a Redlich?CKister type polynomial equation. FTIR and ¹H-NMR studies of these mixtures are also reported.     

Synthesis,X-ray, 1H-NMR and DFT analysis of the phthalimide–hydrazone probes as selective anion sensor

Two simple phthalimide–hydrazone probes with nitro groups were synthesised and characterised by NMR, FT-IR, HR-MS and single crystal X-ray crystallography. The synthesised receptors were evaluated for application in anion sensing. The receptors displayed strong, sensitive and selective colouration in the presence of cyanide ions by forming a stable complex with cyanide ion. The use of variable nitro groups helped in the elucidation of the mechanism of the complex formation. The ¹H NMR spectroscopy was used to support the mechanism of the complex formation. DFT methods were used to understand the stability of the complex with respect to the reactant. The absorbance data were also compared with the TD-DFT calculated excitation parameters. The experimental results were found to correlate well with the theoretical data.     

A theoretical analysis and its application of the second order EC'''' reactions at microelectrodes under steady-state conditions

With a new approach,the general current expressions of two typical second ordercatalytic reactions are obtained for disk,hemispherical and spherical microelectrodes understeady-state conditions.This approach is based on the concept of reaction layer.For thesecond order EC' reactions,we also discussed how it is possible to observe pseudo-first orderor second order behavior.This consideration allows the study of the fast chemical reactionsand systems where the bulk concentrations of the reactants are nearly equal.Regenerationof Fe~(3+)(EDTA) with H_2O_2 was selected as an example of a rapid catalytic reaction.     

Novel theoretical analyses of some features of X-ray spectrometry—I: Tertiary effects in XRF analysis

Given good concentration correction equations, which take first order matrix effects into account, and for either monochromatic or polychromatic excitation, it is possible to derive simple concentration correction equations that take into account third order effects. These improvements are fully additive to the common concentration correction equations. However, any incorporation of third order improvements into fundamental equations distorts their precise theoretical basis.     

Potentiometric determination of the ionization constants of ethylenediamine-N,N′-diglutaric acid at 298.15 K

Step ionization constants of ethylenediamine-N,N′-diglutaric acid at 298.15 K and ionic strength values of 0.1, 0.5, and 1.0 (KNO₃) are determined by means of potentiometry. The resulting data are extrapolated to zero ionic strength using an equation with one individual parameter, and the thermodynamic ionization constants are calculated. A correlation is made between the obtained results and the corresponding data for related compounds.