RESUMO
The structure of the complex of beta-cyclodextrin (cyclomaltoheptaose) with beta-naphthyloxyacetic acid was studied in solid state by X-ray diffraction and in aqueous solution by 1H NMR spectroscopy. The complex crystallizes in the channel mode, space group C2, with a stoichiometry of 2:1; two beta-cyclodextrin molecules related by a twofold crystal axis form dimers, in the cavity of which one guest molecule is found on average. The above stoichiometry indicates one guest per beta-CD dimer statistically oriented over two positions or two guest molecules in pi-pi interactions in half of the beta-CD dimers and the rest of the beta-CD dimers empty. In addition, occupancy of 0.5 for the guest per every beta-CD dimer is in accord with the occupancy of the two disordered primary hydroxyls. These two hydroxyl groups, to which the carboxylic oxygen atoms of the guest are hydrogen bonded, point towards the interior of the beta-CD cavity. In aqueous solution, the 1H NMR spectroscopic study indicated that there is a mixture of complexes with host-guest stoichiometries both 1:1 and 2:1.
Assuntos
Ciclodextrinas/química , Glicolatos/química , Naftalenos/química , Reguladores de Crescimento de Plantas/química , beta-Ciclodextrinas , Apium/efeitos dos fármacos , Cristalografia por Raios X , Modelos Moleculares , Ressonância Magnética Nuclear Biomolecular , SoluçõesRESUMO
A new development of the TWIN algorithm is described and used for phase extension/refinement in supramolecular complexes. A small number of phased reflections at low resolution are sufficient for the quasi-automated determination of all atomic coordinates, including disordered atoms.
Assuntos
Algoritmos , Cristalografia por Raios X/métodos , Conformação MolecularRESUMO
The crystal structure of the 1:1 complex of beta-cyclodextrin (cyclomaltoheptaose) with trans-cinnamic acid was studied by X-ray diffraction. Two beta-cyclodextrin molecules related by a twofold crystal axis form dimers in the hydrophobic cavity of which, two guest molecules are entirely buried. The complex crystallizes in the monoclinic C2 space group with channel-type molecular packing. The oxygen atoms of the carboxylate group of the trans-cinnamic acid molecule form strong hydrogen bonds with two water molecules lying in the interdimeric space of the hydrophobic channel.
