Fluorination‐Induced Evolution of Columnar Packing in Fluorous Triphenylenes and Benzotriphenylenes

Abstract

What is the main focuso fy our research?We develop "top-down" synthetic methodologies for organic electron-acceptor materials that become components in aw ide variety of organic optoelectronic devices. Our syntheses are based on one-step, high-temperature, gas-or solution-phase reactions between polycyclic aromatic hydrocarbons (PAHs) and perfluoroalkyl or -aryl halides. While dozens of PAH(RF)n derivatives with electron affinities that range from 1.0 to 3.3 eV have been prepared in this manner in our lab, optimizing these reactions to produce primarily as ingle product has remained challenging until now.T his paper provides the first examples of highly selective syntheses of polysubstituted fluorous triphenylenes. Our finding that copper metal promotes specific substitution sites on triphenylene can now be applied to other PAHs ubstrates that have triphenylene-like structural elements to achieve higher selectivity in the preparation of particular PAH(RF/ArF) n targets of interest. With the myriad of fluorous PAHs at hand, we also study how various types and various numbers of fluorous groups affect their solid-state packing, which can greatly influence charge transport kinetics and thermodynamics. An unanticipated example of this is reported in this paper:r eplacing one Fa tom with an Ha tom in ac yclo-C 4 F 8 substituent resulted in ashift in columnar stacking of 508.Invited for thism onth'sc over are the groupso fS tevenS trauss/Olga Boltalina at Colorado State University,a nd Yu-Sheng Chen at the NSF'sC hemMatCARS. The cover pictures hows the evolution of fluorous triphenylenec rystalp ackingm otifs against the backdrop of the Very Large Array near Magdalena in New Mexico, where scientists studyt he evolution of the universe. The stepwise structural evolution in columnar packingo bserved was possible because of the development of a one-stepselectives ynthesis for triphenylene(C 4 F 8 ) n derivatives (n = 1-3). These compounds are expected to find application in liquid crystal displaysa nd organic electronics. Read the fulltext of the article at

Gas-Phase Synthesis of Perfluoroalkyl-Functionalized Graphene and Its Desensitization Effect on 1,3,5,7-Tetranitro-1,3,5,7-Tetraazacyclooctane

“…Some polycyclic aromatic hydrocarbons have been fluorinated by reacting with perfluoroalkyl iodides to achieve specific molecular functions. 29,30 1,4-C 4 F 8 I 2 is an ideal reagent for the fluorination modification of aromatic systems. It can react with two adjacent C atoms on the aromatic ring to form a stable sixmembered ring structure.…”

“…Therefore, in this study, perfluoroalkyl-functionalized graphene (PFG) was synthesized by the reaction of graphene with 1,4-C 4 F 8 I 2 . Since graphene is insoluble, the reaction was carried out in sealed quartz tube at 360 °C. − Air was removed under vacuum, and the gas-phase reaction proceeded at an inert atmosphere. PFGs with varying fluorine contents were obtained by adjusting the amount of 1,4-C 4 F 8 I 2 used, and their structures were characterized.…”

“…Perfluoroalkyl iodides are excellent fluorination reagents since they can easily generate free radicals when exposed to heat or UV light. Some polycyclic aromatic hydrocarbons have been fluorinated by reacting with perfluoroalkyl iodides to achieve specific molecular functions. , 1,4-C 4 F 8 I 2 is an ideal reagent for the fluorination modification of aromatic systems. It can react with two adjacent C atoms on the aromatic ring to form a stable six-membered ring structure. − Graphene belongs to the category of polycyclic aromatic hydrocarbons, and thus perfluoroalkyl could theoretically be grafted on its surface using the same method.…”

Stabilization of Columnar Liquid Crystal Phases via Arene-Perfluoroarene Interactions

“…Arenes and perfluoroarenes are well-known to engage in 1:1 cofacial π-stacking interactions. Since the first report of the alternating stacking of benzene and hexafluorobenzene in the solid state by Patrick and Prosser, arene perfluoroarene interactions have been used extensively in crystal engineering to control the positioning of molecules in crystalline solids through these predictable π-stacking interactions. − For example, arene–perfluoroarene interactions have been used to direct topochemical reactions in crystalline solids. , Several studies have also shown that partially fluorinated polycyclic aromatic hydrocarbons also stack predictably such that the fluorinated ring and the nonfluorinated ring are positioned on top of one another. − Despite the effectiveness of arene–perfluoroarene interactions in promoting π-stacking, this motif has not been widely used in the design of columnar liquid crystalline materials . In one example, Grubbs and co-workers showed that a 1:1 mixture of a liquid crystalline hexa­alkoxy­triphenylene with perfluorotriphenylene led to a significantly higher clearing point, suggesting a stabilization of the columnar phase through arene–perfluoroarene interactions .…”

“…The geometry-optimized structure shows an antiparallel stacking of the dibenzo­pentacene­quinone cores with an intermolecular distance of 3.5 Å, consistent with typical π-stacking distances observed in crystalline solids and columnar mesophases (Figure ). Furthermore, the molecules engage in slightly offset π-stacking, which is consistent with reported crystal structures of partially fluorinated polycyclic aromatic hydrocarbons. − Overall, the calculations show that antiparallel π-stacking interactions in model dimers are favorable, which supports the idea that the mesophase is stabilized by a similar stacking.…”