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Crystal structure of beta-cyclodextrin-benzoic acid inclusion complex.
Thammarat Aree1, Narongsak Chaichit
1Department of Chemistry, Faculty of Science, Chulalongkorn University, Phyathai Road, Pathumwan, 10330, Bangkok, Thailand. mam@atc.atccu.chula.ac.th
Carbohydrate Research
|February 1, 2003
Summary
This study details the crystal structure of a beta-cyclodextrin and benzoic acid complex, revealing how these molecules form channels for guest inclusion via hydrogen bonding and water bridges.
Area of Science:
- Supramolecular Chemistry
- Crystal Engineering
- Materials Science
Background:
- Cyclodextrins are cyclic oligosaccharides with a hydrophobic cavity and hydrophilic exterior, widely used in host-guest chemistry.
- Benzoic acid is a common organic compound with applications in various industries.
- Understanding the co-crystallization behavior of beta-cyclodextrin and benzoic acid is crucial for designing novel inclusion complexes.
Purpose of the Study:
- To elucidate the crystallographic structure of the inclusion complex formed between beta-cyclodextrin (beta-CD) and benzoic acid (BA).
- To investigate the intermolecular interactions, including hydrogen bonding and water-mediated interactions, that stabilize the crystal lattice.
- To characterize the arrangement of guest molecules within the beta-CD framework.
Main Methods:
- Single-crystal X-ray diffraction analysis was employed to determine the three-dimensional structure of the co-crystal.
- Anisotropic refinement of atomic parameters was performed using collected diffraction data.
- Hydrogen bonding networks and guest molecule positioning were analyzed.
Main Results:
- The co-crystal structure [2(C(6)H(10)O(5))(7).2(C(7)H(6)O(2)).0.7(C(2)H(6)O).20.65H(2)O] was determined in the triclinic space group P1.
- Beta-cyclodextrin molecules form dimers stabilized by intradimer and interdimer hydrogen bonds, creating channels for guest inclusion.
- Benzoic acid molecules are positioned with their carboxyl groups extending towards the O-6 sides of beta-CD, stabilized by hydrogen bonds with beta-CD and water molecules.
Conclusions:
- The study provides a detailed crystallographic insight into the beta-cyclodextrin-benzoic acid inclusion complex.
- The formation of beta-CD dimers and subsequent channel structures is key to the inclusion of guest molecules.
- The precise arrangement and stabilization of benzoic acid within the complex offer valuable information for host-guest chemistry applications.