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Cooling-rate dependent single-crystal-to-single-crystal phase transition in an organic co-crystal
- Crawford, Adam W., Groeneman, Ryan H., Unruh, Daniel K., Hutchins, Kristin M.
- Chemical communications 2019 v.55 no.22 pp. 3258-3261
- chemical reactions, cooling, olefin, phase transition
- 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.