Disorder as adaptation of the crystal structure to increase the crystallization temperature. X-ray crystal structure of the host-guest complexes between 1,1′-binaphthyl-2,2′-dicarboxylic acid and dimethyl sulphoxide obtained at 50 and 60 °C

The complex formation of 1,1′-binaphthyl-2,2′-dicarboxylic acid (BNDA) with dimethyl sulphoxide (DMSO) at different temperatures was investigated. The crystal structures of the α- and β-form [triclinic, P1, a = 9.614(2), b = 11.743(2), c = 12.029(2) Å, α = 99.35(3), β = 93.58(3), γ = 110.51(3)°, V = 1244.5(4) Å3, Z = 2, R = 0.053 for 4879 reflections] host–guest complexes obtained at 50 and 60 °C, respectively, were determined by x-ray structure analysis (the crystal structure of the α-form obtained at room temperature was studied previously). There is disorder of the guest molecules characteristic of the α-form of the 1:1 BNDA·DMSO complex obtained at 50 °C and the host carboxylic groups in the β-form of the 1:2 BNDA·DMSO, considered a consequence of the changed conditions for crystal preparation. By disordering of the crystal structure the interaction of the solvent molecule with its environment, especially with nearest BNDA molecules, is improved. The new orientation leads to the formation of a more compact host–guest associate which resists the escape of the guest molecules from the growing crystal during crystallization and may exist even in the nucleation step. Thus disordering of the solvent molecules (α-form) and disordering of the carboxyl groups of the host molecules (β-form) are the two modes of operation in this system. Copyright © 1999 John Wiley & Sons, Ltd.

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