Unusual 2:3:2 complex of DABCO mono-betaine with HCl and H2O studied by X-ray diffraction, DFT calculations and spectroscopic methods

The preparation, characterization, structure and dissolution analysis of apremilast solvatomorphs

Apremilast (AP) {systematic name: (S)-2-[1-(3-ethoxy-4-methoxyphenyl)-2-(methylsulfonyl)ethyl]-4-acetamidoisoindoline-1,3-dione} is an inhibitor of phosphodieasterase-4 (PDE4) and is indicated for the treatment of adult patients with active psoriatic arthritis. The ability of AP to form solvates has been investigated and three solvatomorphs of AP, namely, the AP ethyl acetate hemisolvate, C22H24N2O7S·0.5C4H8O2, the AP toluene hemisolvate, C22H24N2O7S·0.5C7H8, and the AP dichloromethane monosolvate, C22H24N2O7S·CH2Cl2, were obtained. The three AP solvatomorphs were characterized by X-ray powder diffraction, thermogravimetric analysis and differential scanning calorimetry. Single-crystal X-ray diffraction was used to analyze the structures, crystal symmetry, packing modes, stoichiometry and hydrogen-bonding interactions of the solvatomorphs. In addition, dissolution analyses were performed to study the dissolution rates of different AP solvatomorph tablets in vitro and to make comparisons with commercial apremilast tablets (produced by Celgene); all three solvatomorphs showed similar dissolution rates and similar values of the similarity factor f2 in a comparison of their dissolution profiles.

1-Carboxymethyl-3-methyl-1H-imidazol-3-ium chloride 2-(3-methyl-1H-imidazol-3-ium-1-yl)acetate monohydrate: a crystal stabilized by imidazolium zwitterions

The title compound, C6H9N2O2(+)·Cl(-)·C6H8N2O2·H2O, contains one 2-(3-methyl-1H-imidazol-3-ium-1-yl)acetate inner salt molecule, one 1-carboxymethyl-3-methyl-1H-imidazol-3-ium cation, one chloride ion and one water molecule. In the extended structure, chloride anions and water molecules are linked via O-H···Cl hydrogen bonds, forming an infinite one-dimensional chain. The chloride anions are also linked by two weak C-H···Cl interactions to neighbouring methylene groups and imidazole rings. Two imidazolium moieties form a homoconjugated cation through a strong and asymmetric O-H···O hydrogen bond of 2.472 (2) Å. The IR spectrum shows a continuous D-type absorption in the region below 1300 cm(-1) and is different to that of 1-carboxymethyl-3-methylimidazolium chloride [Xuan, Wang & Xue (2012). Spectrochim. Acta Part A, 96, 436-443].

A novel cadmium(II) coordination polymer containing two kinds of independent one-dimensional chain

The structure of the title compound, catena-poly[[cadmium(II)-di-μ-chlorido-μ-(1,4-diazoniabicyclo[2.2.2]octane-1-carboxylato)] [[aquachloridocadmium(II)]-di-μ-chlorido] dihydrate], {[Cd(C₈H₁₅N₂O₂)Cl₂][CdCl₃(H₂O)]·2H₂O}n, contains two kinds of independent one-dimensional chain, viz. {[Cd(C₈H₁₅N₂O₂)Cl₂]⁺}n and {[CdCl₃(H₂O)]⁻}n, and uncoordinated water molecules. Each CdII cation in the {[Cd(C₈H₁₅N₂O₂)Cl₂]⁺}n chain is octahedrally coordinated by two pairs of bridging chloride ligands and two O atoms from different bridging carboxylate groups. CdII cations in the {[CdCl₃(H₂O)]⁻}n chain are also octahedrally surrounded by four bridging chloride ligands, one terminal chloride ligand and one coordinated water molecule. Hydrogen bonds between solvent water molecules and these two independent chains generate a three-dimensional framework containing two-dimensional zigzag layers.