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Published on: November 7, 2016
Cooling-rate dependent single-crystal-to-single-crystal phase transition in an organic co-crystal
Adam W Crawford1, Ryan H Groeneman2, Daniel K Unruh1
1Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409, USA. kristin.hutchins@ttu.edu.
Abstract:
We investigate a previously unobserved phase transition in an organic co-crystal containing the olefin trans-1,2-bis(4-pyridyl)ethylene. The olefin undergoes molecular motion in the crystalline state, and converts from a disordered to ordered phase upon cooling. Ordering causes a unit cell change to occur via a reversible single-crystal-to-single-crystal (SCSC) transformation. The ordered phase is only accessed via slow cooling; flash cooling locks the crystal in a kinetically trapped, disordered state, and SCSC reversibility is lost. The common practice of flash cooling may inhibit access to thermodynamic products and unique phases.
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