TY - JOUR
T1 - Altering the Polymorphic Accessibility of Polycyclic Aromatic Hydrocarbons with Fluorination
AU - Hiszpanski, Anna M.
AU - Woll, Arthur R.
AU - Kim, Bumjung
AU - Nuckolls, Colin
AU - Loo, Yueh Lin
N1 - Funding Information:
The authors thank Dr. Matthew Bruzek and Prof. John Anthony (University of Kentucky, Lexington, KY) for providing the fluorinated pentacene quinone precursor used in the synthesis of fluorinated cHBC derivatives (NSF DMR-103527). The authors also thank Aaron and Wesley Sattler of the Parkin Group (Columbia University) for solving the 8F-cHBC crystal structure. This work was supported by the NSF MRSEC program through the Princeton Center for Complex Materials (DMR-0819860 and DMR-1420451) and the SOLAR Initiative at the NSF (DMR-10135217). GIXD experiments were conducted at CHESS, which is supported by NSF and NIH/NIGMS under award DMR-1332208. A.M.H. acknowledges support through the National Defense Science and Engineering Graduate (NDSEG) Fellowship (Air Force Office of Scientific Research 32 CFR 168a). B.K. and C.N. acknowledge support from the Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, U.S. Department of Energy (DOE), under Award No. DE-FG02-01ER15264. Lawrence Livermore National Laboratory is operated by Lawrence Livermore National Security LLC, for the U.S. Department of Energy, National Nuclear Security Administration under Contract DE-AC52-07NA27344. LLNL-JRNL-713258.
Publisher Copyright:
© 2017 American Chemical Society.
PY - 2017/5/23
Y1 - 2017/5/23
N2 - 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.
AB - 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.
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U2 - 10.1021/acs.chemmater.7b00627
DO - 10.1021/acs.chemmater.7b00627
M3 - Article
AN - SCOPUS:85019692167
SN - 0897-4756
VL - 29
SP - 4311
EP - 4316
JO - Chemistry of Materials
JF - Chemistry of Materials
IS - 10
ER -