Hydrogen-Bonded Tapes Based on Symmetrically Substituted Diketopiperazines: A Robust Structural Motif for the Engineering of Molecular Solids
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- 作者：Serge Palacin ; Donovan N. Chin ; Eric E. Simanek ; John C. MacDonald ; George M. Whitesides ; Mary T. McBride ; and G. Tayhas R. Palmore
- 刊名：Journal of the American Chemical Society
- 出版年：1997
- 出版时间：December 10, 1997
- 年：1997
- 卷：119
- 期：49
- 页码：11807 - 11816
- 全文大小：280K
- 年卷期：v.119,no.49(December 10, 1997)
- ISSN：1520-5126
文摘
A series of eight symmetrically substituted diketopiperazines(DKPs) derived from 1-amino-1-carboxycycloalkanes (n = 3-7; 3,3,5,5-tetramethylcyclohexane;4,4-dimethylcyclohexane; 2-indan) were synthesized andtheir crystal structures determined. In the solid state, all eightcompounds form two pairs of hydrogen bonds withtwo adjacent molecules to form a one-dimensional structure that werefer to as "tapes". These molecules representa range of volumes and shapes that contain a common molecular fragment(DKP ring). We examined this series ofcompounds with three objectives in mind: (i) to establish the abilityof the hydrogen-bonded "tape" motif to persistthrough these differences in volume and shape; (ii) to provide a seriesof structurally related compounds to use totest computational methods of predicting crystal structure frommolecular structure; (iii) to search for qualitativecorrelations between molecular structure and crystal packing. Allcompounds form tapes and with one exception,all tapes pack with their long axes parallel. When viewed downtheir long axis, two types of tapes emerge:planarand nonplanar. The type of tape that forms reflects theconformation adapted by the DKP ring-planar or boat.Planar tapes form when the angle (
) between the two planesdefined by the cis-amides in the DKP ring is180
;nonplanar tapes form when < 180. Five of the eightcompounds studied form planar tapes, the remaining threecompounds form nonplanar tapes. Despite the variability in volumeand shape represented by this series of molecules,the persistence of the tape motif in their crystalline solids suggeststhat the hydrogen-bonding interactions betweenDKPs dominate the packing arrangement of these molecules. Voidspace in the crystalline solid is minimized byparallel alignment of tapes that pack in a manner that permits theinterdigitation of substituents on adjacent tapes.
) between the two planesdefined by the cis-amides in the DKP ring is180;nonplanar tapes form when < 180. Five of the eightcompounds studied form planar tapes, the remaining threecompounds form nonplanar tapes. Despite the variability in volumeand shape represented by this series of molecules,the persistence of the tape motif in their crystalline solids suggeststhat the hydrogen-bonding interactions betweenDKPs dominate the packing arrangement of these molecules. Voidspace in the crystalline solid is minimized byparallel alignment of tapes that pack in a manner that permits theinterdigitation of substituents on adjacent tapes.