Altering the Polymorphic Accessibility of Polycyclic Aromatic Hydrocarbons with Fluorination

Anna M. Hiszpanski, Arthur R. Woll, Bumjung Kim, Colin Nuckolls, Yueh Lin Loo

Research output: Contribution to journalArticle

9 Scopus citations

Abstract

Substituting hydrogen with fluorine is an extensively employed strategy to improve the macroscopic properties of compounds for use in fields as diverse as pharmaceutics and optoelectronics. The role fluorine substitution plays on polymorphism - the ability of a compound to adopt more than one crystal structure - has not been previously studied. Yet, this understanding is important as different polymorphs of the same compound can result in drastically different bulk properties (e.g., solubility, absorptivity, and conductivity). Strategies to either promote or suppress the crystallization of particular polymorphs are thus desired. Here, we show that substituting hydrogen with fluorine affects the polymorphic behavior of contorted hexabenzocoronene (cHBC). A polycyclic aromatic hydrocarbon and molecular semiconductor, cHBC exhibits two polymorphs (i.e., P21/c crystal structure which we refer to as polymorph I and a triclinic crystal structure which we refer to as polymorph II) that are accessible through postdeposition processing of amorphous films. While the same two polymorphs remain accessible in fluorinated derivatives of cHBC, fluorination appears to favor the formation of polymorph I, with progressively smaller energy barrier for transformation from polymorph II to polymorph I with fluorination.

Original languageEnglish (US)
Pages (from-to)4311-4316
Number of pages6
JournalChemistry of Materials
Volume29
Issue number10
DOIs
StatePublished - May 23 2017

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Chemical Engineering(all)
  • Materials Chemistry

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