Solid-phase polymorphism of p-n-hexyloxy- and p-n-heptyloxybenzoic acids

The solubility of p-n-hexyloxy- and p-n-heptyloxybenzoic acids in nonaqueous solvents of different polarities was determined over the temperature range from ?20 to 60°C. Acid polymorphs were obtained by crystallization from solutions and melts and by the thermal shock method. The temperatures and enthalpies of phase transitions and X-ray characteristics of the new polymorphs were determined.     

Crystal Structure of 3,4-Dihydro-2-methoxy-2-methyl-4-phenyl-2H,5H-pyrano[3,2-c]chromen-2-one

Crystallography Reports - A new polymorph of 3,4-dihydro-2-methoxy-2-methyl-4-phenyl-2H,5H-pyrano[3,2-c]chromen-2-one (pyranocoumarin) was studied by X-ray diffraction. The crystallographic...     

Study of phase behavior in a system of linear hydrogen-bonded carboxylic acid homologues

The system of hydrogen-bonded liquid crystals formed from binary mixtures p-n-heptyloxybenzoic (I) acid and p-n-undecloxybenzoic (II) acid has been investigated by polarizing optical microscopy, differential scanning calorimetry, X-ray diffraction, and scattering and dielectric measurements. The T–X phase diagram was obtained for this system. All mixtures show enantiotropic smectic and nematic phases. The crystalline phase represents a (α, β) solid solution. At the 2:1 ratio of I to II, an intermediate phase – co-crystal γ – is formed. The co-crystal γ possesses a much wider mesophase range than the corresponding initial components. In contrast to mixtures based on the solid solutions having a positive anisotropy, the co-crystal shows a negative dielectric anisotropy in the mesophase.     

Crystal Structure and Properties of [Co(NH3)6][PdCl4]Cl

Russian Journal of Coordination Chemistry - Complexes [Co(NH3)6][PdCl4]Cl (I) and [Co(NH3)6]2[PtCl4]3 (II) are synthesized and characterized. Complex I is isolated for the first time. The...     

Phase Diagram and Dielectric Studies in Hydrogen-Bonded Liquid Crystal System

The thermal and dielectric behaviors of mixtures were investigated for systems of p-n-hexyloxybenzoic acid (6OBA) and p-n-octyloxybenzoic acid (8OBA) by differential scanning calorimetry, polarized optical microscopy, and dielectric measurements. The T-X phase diagram was obtained for this system. Eutectic composition was calculated and received experimentally. Enthalpies of mixing were calculated to describe phase transitions physically. All mixtures show enantiotropic smectic and nematic phases. Dielectric permittivity has higher value for the mixture with fractional proportion of 30 to 70% mol for 8OBA than that for initial acid. It is assumed that co-crystallization of initial compound occurs when the ratio of components is close to equimolar ratio.     

Mesomorphic and dielectric properties of the p-n-hexyloxybenzoic acid-p-n-heptyloxybenzoic acid liquid crystal system

Thep-n-hexyloxybenzoic acid (I)-p-n-heptyloxybenzoic acid (II) system was investigated by thermal and X-ray phase analyses and dielcometry. Solid solutions of three types were found in the low-temperature region of the system, namely, solid solution based on I (up to 15 mol % II); solid solution based on a compound with the equimolar ratio of the components (γ); and solid solution based on II (>15 mol % II). The range of the two-phase equilibrium (N + I) was 2°–4°; a continuous nematic solution (N) formed in the system. The temperature and composition dependences of dielectric anisotropy Δ? were characterized. The γ compound showed negative dielectric anisotropy, Δ? = ?1.4, which was constant over the whole temperature range of the nematic phase.