A phase transition from monoclinic C2 with Z '=1 to triclinic P1 with Z '=4 for the quasiracemate L-2-aminobutyric acid-D-methionine (1/1)

作者：Gorbitz Carl Henrik^*; Wragg David S; Bakke Ingrid Marie Bergh; Fleischer Christian; Gronnevik Gaute; Mykland Maria; Park Yoomin; Trovik Kristian Wiedicke; Serigstad Halvard; Sundsli Bard Edgar Vestheim

来源：Acta Crystallographica Section C-Structural Chemistry, 2016, 72(7): 536-+.

DOI：10.1107/S2053229616008858

• L-2-aminobutyric acid
• D-methionine
• disorder
• steric conflict
• phase transition
• quasiracemate
• crystal structure

Racemates of hydrophobic amino acids with linear side chains are known to undergo a unique series of solid-state phase transitions that involve sliding of molecular bilayers upon heating or cooling. Recently, this behaviour was shown to extend also to quasiracemates of two different amino acids with opposite handedness [Gorbitz & Karen (2015). J. Phys. Chem. B, 119, 4975-4984]. Previous investigations are here extended to an l-2-aminobutyric acid-D-methionine (1/1) co-crystal, C4H9NO2 center dot C5H11NO2S. The significant difference in size between the -CH2CH3 and -CH2CH2SCH3 side chains leads to extensive disorder at room temperature, which is essentially resolved after a phase transition at 229 K to an unprecedented triclinic form where all four D-methionine molecules in the asymmetric unit have different side-chain conformations and all three side-chain rotamers are used for the four partner L-2-aminobutyric acid molecules.

• 出版日期2016-7