A comparison of X-ray crystal structures including methyl 3,5-bis(hydroxymethyl)benzoate, its phenylethynyl extended derivative in polymorphous forms and the corresponding carboxylic acids

Different supramolecular interactions mediated by Br atoms in the crystal structures of three anisole derivatives

Three anisole building blocks featuring bis(hydroxymethyl) or bis(bromomethyl) pendants have been analyzed with regard to their molecular structures and packing behaviour. The compounds are ethyl 3,5-bis(hydroxymethyl)-4-methoxybenzoate, C12H16O5, (I), [5-bromo-3-(hydroxymethyl)-2-methoxyphenyl]methanol [or 4-bromo-2,6-bis(hydroxymethyl)anisole], C9H11BrO3, (II), and 5-bromo-1,3-bis(bromomethyl)-2-methoxybenzene [or 4-bromo-2,6-bis(bromomethyl)anisole], C9H9Br3O, (III). A typical supramolecular pattern involved C—H...π interactions generating molecular stacks, while π–π interactions were only observed in the absence of bromine, indicating a striking influence on the distances between adjacent aromatic moieties. When comparing bis(hydroxymethyl) compound (II) with bis(bromomethyl) compound (III), we found that the strong O—H...O hydrogen bonds in a zigzag arrangement in the first are replaced by C—H...Br interactions in the second without a change in the general packing.

5,5′-(Ethyne-1,2-diyl)diisophthalic acid dimethyl sulfoxide tetrasolvate

In the title compound, C₁₈H₁₀O₈·4C₂H₆OS, the mid-point of the triple bond of the main mol­ecule is located on a special position, i.e. about an inversion center. The carboxyl groups are twisted slightly out of the planes of the aromatic rings to which they are attached, making dihedral angles of 24.89 (1) and 7.40 (2)°. The cystal packing features strong O—H⋯O hydrogen bonds, weaker C—H⋯O inter­actions and O⋯S contacts [3.0981 (11) Å] and displays channel-like voids extending along the a-axis direction which contain the dimethyl sulfoxide solvent mol­ecules.

Redetermination of tetra-methyl tetra-thia-fulvalene-2,3,6,7-tetra-carboxyl-ate

An improved crystal structure of the title compound, C₁₄H₁₂O₈S₄, is reported. The structure, previously solved using the heavy-atom method (R = 7.1%), has now been solved using direct methods. Due to the improved quality of the data set an R value of 2.06% could be achieved. In the crystal, C—H⋯S and C—H⋯O contacts link the mol­ecules.