Novel, predicted patterns of supramolecular self-assembly, afforded by tetrameric R_4^4(12) rings of C 2 symmetry in the crystal structures of 2-hydroxy-1-cyclopentanecarboxylic acid, 2-hydroxy-1-cyclohexanecarboxylic acid and 2-hydroxy-1-cycloheptanecarboxylic acid

Abstract

Determination of the crystal structures of the homologous (1R*,2R*)-trans-2-hydroxy-1-cyclopentanecarboxylic acid (5T), (1R*,2S*)-cis-2-hydroxy-1-cyclohexanecarboxylic acid (6C) and (1R*,2S*)-cis-2-hydroxy-1-cycloheptanecarboxylic acid (7C) proved a predicted pattern of supramolecular close packing. The prediction was based on the common features observed in the crystal structures of six related 2-hydroxy-1-cyclopentanecarboxylic acids and analogous carboxamides [Kálmán et al. (2001). Acta Cryst. B57, 539–550]. This pattern is characterized by tetrameric R_4^4(12) rings of C 2 symmetry formed from dimeric R_2^2(12) rings. The C 2 symmetry of such tetramers is not common in the literature, usually they have Ci symmetry. Both types of tetramers are formed from dimers with similar or opposite orientation. The R_2^2(12) dimers differ in their hydrogen bonds. In 5T the monomers are joined by a pair of O1—H...O2=C bonds, whereas in 7C they are joined by a pair of O3—H...O1-H bonds. In 6C 60% of the disordered R_2^2(12) dimers are similar to those in 7C, while 40% resemble those in 5T. Apart from these hydrogen-bonding differences and the ring-size differences, the three crystals exhibit isostructurality.