Effect of high pressure on the crystal structures of polymorphs of glycine

By A. Dawson, D. Allan, S. A. Belmonte, S. Clark, W. David, P. A. Mcgregor, S. Parsons, C. Pulham, L. Sawyer. 2005

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The effect of high pressure on the crystal structures of α-, β-, and γ-glycine has been investigated. A new polymorph, δ-glycine, is obtained from β glycine. δ-Glycine is monoclinic, P21/a, a = 11.156(4), b = 5.8644(11), c = 5.3417(17) A, β = 125.83(4)° at 1.9 GPa. The transition, which occurs between 0 and 0.8 GPa, proceeds from a single crystal of β-glycine to a single crystal of δ-glycine, resulting in an equal number of NH···O hydrogen bonds but an increase in the number and strength of CH···O hydrogen bonds, which act to close-up “holes” that are formed within the layers of β-glycine in the centers of R-type hydrogen-bonded motifs. Trigonal γ-glycine begins to undergo a transition to another high-pressure phase, e-glycine, at 1.9 GPa, but the transformation is destructive; it is essentially complete at 4.3 GPa. The structure is monoclinic Pn, a = 4.8887(10), b = 5.7541(11), c = 5.4419(11) A, β = 116.682(10)° at 4.3 GPa. The structure consists of layers similar to those observed in α-glycine with inte...

Subfields: Materials Chemistry, Organic Chemistry, Physical and Theoretical Chemistry

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