Lithium makes the difference: A simple strategy for the synthesis of lithium-doped porous metal-organic frameworks (MOFs) is developed (see structure; C black, O red, AlO(6) blue octahedra), thus paving the way for the facile preparation of lithium-doped MOFs. Moreover, the significant increase in hydrogen adsorption predicted by theoretical calculations is observed.

Improving the hydrogen-adsorption properties of a hydroxy-modified MIL-53(Al) structural analogue by lithium doping.

The solubility of salicylic acid has been investigated in methanol, acetonitrile, acetic acid, acetone, water, and ethyl acetate from (10 to 50) °C. No new polymorphs or solvates of salicylic acid were found. The melting properties of salicylic acid were determined by differential scanning calorimetry. A correlation was observed between the solubility and the van't Hoff enthalpy of solution. A higher solubility was related to a lower van't Hoff enthalpy of solution. Water differed from the organic solvents in terms of solubility and its correlation to the van't Hoff enthalpy of solution. In addition, the morphology of salicylic acid crystals recrystallized from water differed from the other solvents.

Solubility and Melting Properties of Salicylic Acid

Caffeine, a pharmaceutical model compound, generally forms cocrystals with carboxylic acids that involve an O−H···N hydrogen bond between the carboxylic acid group of the acid and the caffeine imidazole moiety. Such solids are typically based on a single heterosynthon. To examine the facility of introducing additional supramolecular heterosynthons to the caffeine-carboxylic-acid cocrystal system, structural isomers of aromatic carboxylic acids (i.e., hydroxy- and dihydroxybenzoic acids) with additional hydrogen-bonding functional groups (i.e., hydroxy group) were screened for cocrystal formation. For this purpose, a highly efficient screening method based on thermodynamically driven solution-mediated phase transformation was utilized. This method enabled the rapid discovery of nine new solid phases involving caffeine. These caffeine phases were identified using single-crystal X-ray diffraction and FT-IR spectroscopy as cocrystals based on 2-, 3-, 4-hydroxybenzoic- and 2,3-, 2,4-, 2,5-, 3,4-, and 3,5-dihyd...

Cocrystals of Caffeine and Hydroxybenzoic Acids Composed of Multiple Supramolecular Heterosynthons: Screening via Solution-Mediated Phase Transformation and Structural Characterization

Neutron-diffraction studies of salicylic acid and α resorcinol*

The experimental and theoretical study on the structures and vibrations of 5-fluoro-salicylic acid and 5-chloro-salicylic acid (5-FSA and 5-ClSA, C7H5FO3 and C7H5ClO3) is presented. The Fourier transform infrared spectra (4000–400 cm−1) and the Fourier transform Raman spectra (4000–50 cm−1) of the title molecules in the solid phase were recorded. The molecular structures, vibrational wavenumbers, infrared intensities, Raman intensities and Raman scattering activities were calculated for a pair of molecules linked by the intermolecular OH···O hydrogen bond. The geometrical parameters and energies of 5-FSA and 5ClSA were obtained for all eight conformers/isomers from density functional theory (DFT) (B3LYP) with 6-311++G(d,p) basis set calculations. The computational results identified the most stable conformer of 5-FSA and 5-ClSA as the C1 form. The complete assignments were performed on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method. The spectroscopic and theoretical results were compared with the corresponding properties for 5-FSA and 5-ClSA monomers and dimer of C1 conformer. The optimized bond lengths, bond angles and calculated wavenumbers showed the best agreement with the experimental results. Copyright © 2010 John Wiley & Sons, Ltd.

W. Cochran

Papers

The crystal and molecular structure of salicylic acid