Presence of Short Intermolecular Contacts Screens for Kinetic Stability in Packing Polymorphs

Abstract

Polymorphism is pervasive in molecular solids. While computational predictions of the molecular polymorphic landscape have improved significantly, identifying which polymorphs are preferentially accessed and experimentally stable remains a challenge. We report a framework that correlates short intermolecular contacts with polymorphic stability. The presence of short contacts between neighboring molecules prevents structural rearrangement and stabilizes the packing arrangement, even when the stabilized polymorph is not enthalpically favored. In the absence of such intermolecular short contacts, the molecules have added degrees of freedom for structural rearrangement, and solid-solid polymorphic transformations occur readily. Starting with a series of core-halogenated naphthalene tetracarboxylic diimides, we establish this framework with the packing polymorphs of more than 20 compounds, ranging from molecular semiconductors to pharmaceutics and biological building blocks. This framework, widely applicable across molecular solids, can help refine computational predictions by identifying the polymorphs that are kinetically stable.

Single Atom Substitution Alters the Polymorphic Transition Mechanism in Organic Electronic Crystals

“…Short-contacts exist in neighboring molecules if the measured distance between two neighboring atoms is smaller than the sum of the van der Waals radii of the atoms. 45 We note that we adopted a definition of short-contacts (given directly by Mercury 3.9) that is slightly different from the recent report by Purdum, Loo, and colleagues, 46 in that we explicitly considered hydrogen−hydrogen interactions in our analysis. The α form of diTMS contains two short-contact interactions: one intralayer and another interlayer ( Figure 3a).…”

The effect of alkyl side chain length on the formation of two semi-crystalline phases in low band gap conjugated polymers

“…22 In a recent study it has been shown that in small p-conjugated molecules short intermolecular contacts stabilize the threedimensional packing arrangement and prevent structural rearrangement to the enthalpically favored stabilized polymorph. 39 With D-PDPP4T-HD as a start, 20 it is therefore of interest to explore the underlying structural characteristics that cause polymorphism in these polymers.…”

The Effects of Chromophore Halogenation on the Stability of UV‐Absorbing Organic Solar Cells

“…We attribute these changes to cold crystallization of the films, similar to processes observed in semicrystalline polymers that are quickly quenched below and subsequently heated above their glass transition temperatures. [ 58–66 ] In contrast, TBF thin films showed no evidence of morphological instability after aging as evidenced by the AFM images in Figure S5e,f, Supporting Information. A 2017 report from Hiszpanski et al.…”