Effect of High Pressure on the Crystal Structures of Polymorphs of Glycine
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- 作者：Alice Dawson ; David R. Allan ; Scott A. Belmonte ; Stewart J. Clark ; William I. F. David ; Pamela A. McGregor ; Simon Parsons ; Colin R. Pulham ; and Lindsay Sawyer
- 刊名：Crystal Growth & Design
- 出版年：2005
- 出版时间：July 2005
- 年：2005
- 卷：5
- 期：4
- 页码：1415 - 1427
- 全文大小：761K
- 年卷期：v.5,no.4(July 2005)
- ISSN：1528-7505
文摘
The effect of high pressure on the crystal structures of 
-, 
-, and 
-glycine has been investigated. Anew polymorph, 
-glycine, is obtained from glycine. -Glycine is monoclinic, P21/a, a = 11.156(4), b = 5.8644(11),c = 5.3417(17) Å, = 125.83(4)
at 1.9 GPa. The transition, which occurs between 0 and 0.8 GPa, proceeds from asingle crystal of -glycine to a single crystal of -glycine, resulting in an equal number of NH···O hydrogen bondsbut an increase in the number and strength of CH···O hydrogen bonds, which act to close-up "holes" that are formedwithin the layers of -glycine in the centers of R-type hydrogen-bonded motifs. Trigonal -glycine begins to undergoa transition to another high-pressure phase, 
-glycine, at 1.9 GPa, but the transformation is destructive; it isessentially complete at 4.3 GPa. The structure is monoclinic Pn, a = 4.8887(10), b = 5.7541(11), c = 5.4419(11) Å, = 116.682(10) at 4.3 GPa. The structure consists of layers similar to those observed in -glycine with interlayerseparations of 2.38 and 3.38 Å and CH···O interactions formed between the layers. Monoclinic -glycine is knownto be stable to 23 GPa, and we have obtained a single-crystal structure of this polymorph at 6.2 GPa. Super-shortNH···O hydrogen bonds are not formed up to 6.2 GPa, and they only shorten significantly if they are formed parallelto CH···O hydrogen bonds, which strengthen, or vectors across holes which close-up, under pressure.
-, -, and -glycine has been investigated. Anew polymorph, -glycine, is obtained from glycine. -Glycine is monoclinic, P21/a, a = 11.156(4), b = 5.8644(11),c = 5.3417(17) Å, = 125.83(4) at 1.9 GPa. The transition, which occurs between 0 and 0.8 GPa, proceeds from asingle crystal of -glycine to a single crystal of -glycine, resulting in an equal number of NH···O hydrogen bondsbut an increase in the number and strength of CH···O hydrogen bonds, which act to close-up "holes" that are formedwithin the layers of -glycine in the centers of R-type hydrogen-bonded motifs. Trigonal -glycine begins to undergoa transition to another high-pressure phase, -glycine, at 1.9 GPa, but the transformation is destructive; it isessentially complete at 4.3 GPa. The structure is monoclinic Pn, a = 4.8887(10), b = 5.7541(11), c = 5.4419(11) Å, = 116.682(10) at 4.3 GPa. The structure consists of layers similar to those observed in -glycine with interlayerseparations of 2.38 and 3.38 Å and CH···O interactions formed between the layers. Monoclinic -glycine is knownto be stable to 23 GPa, and we have obtained a single-crystal structure of this polymorph at 6.2 GPa. Super-shortNH···O hydrogen bonds are not formed up to 6.2 GPa, and they only shorten significantly if they are formed parallelto CH···O hydrogen bonds, which strengthen, or vectors across holes which close-up, under pressure.