Acta Crystallographica Section B

Structural Science

Volume 58, Part 3 Number 2 (June 2002)

research papers

Acta Cryst. (2002). B58, 494-501 [ doi:10.1107/S0108768102001854 ]

Novel, predicted patterns of supramolecular self-assembly, afforded by tetrameric rings of C₂ symmetry in the crystal structures of 2-hydroxy-1-cyclopentanecarboxylic acid, 2-hydroxy-1-cyclohexanecarboxylic acid and 2-hydroxy-1-cycloheptanecarboxylic acid

A. Kálmán, L. Fábián, G. Argay, G. Bernáth and Z. Gyarmati

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 rings of C₂ symmetry formed from dimeric rings. The C₂ symmetry of such tetramers is not common in the literature, usually they have C_i symmetry. Both types of tetramers are formed from dimers with similar or opposite orientation. The dimers differ in their hydrogen bonds. In 5T the monomers are joined by a pair of O1-HO2=C bonds, whereas in 7C they are joined by a pair of O3-HO1-H bonds. In 6C 60% of the disordered 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.

Keywords: supramolecular self-assembly; hydrogen bonds; isostructurality.