Search for a Predicted Hydrogen Bonding Motif - A Multidisciplinary Investigation into the Polymorphism of 3-Azabicyclo[3.3.1]nonane-2,4-dione
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- 作者：Ashley T. Hulme ; Andrea Johnston ; Alastair J. Florence ; Phillipe Fernandes ; Kenneth Shankland ; Colin T. Bedford ; Gareth W. A. Welch ; Ghazala Sadiq ; Delia A. Haynes ; W. D. Samuel Motherwell ; Derek A. T
- 刊名：Journal of the American Chemical Society
- 出版年：2007
- 出版时间：March 28, 2007
- 年：2007
- 卷：129
- 期：12
- 页码：3649 - 3657
- 全文大小：688K
- 年卷期：v.129,no.12(March 28, 2007)
- ISSN：1520-5126
文摘
The predictions of the crystal structure of 3-azabicyclo[3.3.1]nonane-2,4-dione submitted in the2001 international blind test of crystal structure prediction (CSP2001) led to the conclusion that crystalstructures containing an alternative hydrogen bonded dimer motif were energetically competitive with theknown catemer-based structure. Here we report an extensive search for a dimer-based crystal structure.Using an automated polymorph screen a new catemer-based metastable polymorph (form 2) and two newcatemer-based solvates were found, and concurrent thermal studies reproduced form 2 and identified aplastic phase (form 3), whose powder X-ray diffraction pattern was consistent with the cubic space groupI23 (a = 7.5856(1) Å). Computational studies on the monomer showed that the imide N-H was a weakhydrogen bond donor, rationalizing the occurrence of the plastic phase which involved the breaking of allhydrogen bonds, and modeling of small clusters showed that dimers could easily reorganize to give thecatemer. FTIR spectra confirmed the weakness of the hydrogen bond, with the solute showing no self-assembly in solution. It is concluded that the weakness of the N-H donor, coupled with the globular shapeof the molecule, allows unusually facile transformation between alternative hydrogen bonding motifs duringaggregation and nucleation.