posted on 2022-12-21, 13:06authored byNavkiran Juneja, Daniel K. Unruh, Gary C. George, Kristin M. Hutchins
The impact of intermolecular interactions and molecular
motion
on solid-state properties is an active field of interest for chemists
and materials scientists. For example, cocrystallization has been
shown to modify and/or enhance the solid-state behaviors of a molecule
when compared to the single-component solid. Here, we describe a series
of cocrystals containing bis(pyridin-4-ylmethylene)benzene-1,4-diamine
(BPDI) and ditopic or tritopic hydrogen-bond-donor molecules
that are conformationally flexible. The components in all the cocrystals
self-assemble through hydroxyl-pyridine heterosynthons to afford one-dimensional
chains due to the conformations of the donor molecules. BPDI is torsionally flexible, and in cocrystals with ditopic hydrogen-bond
donors, the molecule is almost planar, whereas in cocrystals with
tritopic hydrogen-bond donors, BPDI is significantly
twisted. This twisting in BPDI affects crystal packing
and affords higher thermal expansion coefficients. Cocrystallization
of BPDI with resveratrol, another torsionally flexible
molecule, induces molecular pedal motion in BPDI and
results in larger expansion behavior in the cocrystal.