首页 | 本学科首页   官方微博 | 高级检索  
   检索      


Topography of cyclodextrin inclusion complexes : Part II. The iodine-cyclohexa-amylose tetrahydrate complex; its molecular geometry and cage-type crystal structure
Authors:RK McMullan  W Saenger  J Fayos  D Mootz
Institution:Abteilung Röntgenstrukturanalyse, Institut für Moiekulare Biologie, 3301 Stöckheim über Braunschweig Deutschland
Abstract:Iodine-cyclohexa-amylose tetrahydrate (C6H10O5)6 ·I2·d4H2O] crystallizes in the orthorhombic space-group P212121, a  14.240 Å, b  36.014 Å, c  9.558 Å. The structure was solved by heavy-atom techniques and refined by least-squares methods to a conventional discrepancy index R  0.148 for the 2872 observed data. The six d-glucose residues are in the C1 chair conformation; the conformational angles vary in magnitude from 45 to 66°, the angles O(5)-C(5)-C(6)-O(6) are close to · 70°, and the six O(4) atoms are almost coplanar (r.m. s. displacement 0.13 Å). Only four of the six O(2) ?O(3) intramolecular hydrogen bonds have formed, which renders the molecule less symmetrical and more conical-shaped than in the previously determined α-cyclodextrin-potassium acetate complex. The iodine molecule is coaxial with the cyclohexa-amylose molecule. The I-I distance is a conventional 2.677 Å. Close interactions between the iodine atoms and the host molecule comprise carbon atoms C(5) and C(6) and oxygen atoms O(4), with interatomic distances all equal to or greater than van der Waals contacts. Intermolecular, almost-linear, short contacts O ? I-I?O with I?O distances of 3.22 and 3.07 Å indicate attractive interaction.The molecules are arranged in herring-bone “cage-type” fashion, with the four water molecules as space-filling mediators; the structure is held together by an intricate network of hydrogen bonds.
Keywords:Present address: Max-Planck-Institut für experimentelle Medizin  Abteilung Chemie  34 Göttingen  Hermann-Rein-Str  3  Deutschland  to whom correspondence should be addressed  
本文献已被 ScienceDirect 等数据库收录!
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号