First Order Temperature Dependent Phase Transition in a Monoclinic Polymorph Crystal of 1,6-Hexanedioic Acid: An Interpretation Based on the Landau Theory Approach

Molecules

Hoong-Kun Fun¹  Suchada Chantrapromma² 

[1] X-ray Crystallography Unit, School of Physics, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia;Department of Chemistry, Faculty of Science, Prince of Songkla University, Hat-Yai, Songkhla 90112, Thailand

关键词: adipic acid;    crystal structure;    Landau theory;    phase-transition;   

DOI  :  10.3390/molecules190710137

来源: mdpi

【 摘 要 】

Crystals of 1,6-hexanedioic acid (I) undergo a temperature-dependent reversible phase transition from monoclinic P2₁/c at a temperature higher than the critical temperature (T_c) 130 K to another monoclinic P2₁/c at temperature lower than T_c. The phase transition is of first order, involving a discontinuity and a tripling of the b-axis at T_c whereas the other unit cell parameters vary continuously. The transition is described by the phenomenological Landau theory. The crystal structure analyses for data collected at 297(2) K and 120.0(1) K show that there is half of a molecule of (I) in the asymmetric unit at 297(2) K whereas there are one and a half molecules of (I) in the asymmetric unit at 120.0(1) K. At both temperatures, 297(2) and 120.0(1) K, intermolecular O-H···O hydrogen bonds link the molecules of I into infinite 1D chains along [101] direction. However there are significantly more O-H···O hydrogen bonds presented in the 120.0(1) K polymorph, thereby indicating this phase transition is negotiated via hydrogen bonds. The relationship of the conformational changes and hydrogen bonding for these two polymorphs are explained in detail.

【 授权许可】

CC BY   
© 2014 by the authors; licensee MDPI, Basel, Switzerland.