American Chemical Society, Journal of the American Chemical Society, 50(137), p. 15947-15956, 2015
DOI: 10.1021/jacs.5b11114
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Molecular packing in organic single crystals greatly influences their charge transport properties, but can be hardly pre-dicted and designed due to the complex intermolecular interactions. In this work, we have realized systematically fine tun-ing of the single-crystal molecular packing of five benzodifurandione-based oligo(p-phenylene vinylene) (BDOPV)-based small molecules through incorporation of electronegative fluorine atoms on the BDOPV backbone. While these molecules all exhibit similar column stacking configurations in their single crystals, the intermolecular displacements and distances are substantially modified by tuning the amounts and/or the positions of the substituent fluorine atoms. Density function-al theory (DFT) calculations showed that the subtle differences in charge distribution or electrostatic potential induced by different fluorine substitutions play an important role in regulating the molecular packing for the BDOPV compounds. Consequently, the electronic couplings for electron transfer can vary from 71 meV in a slipped stack to 201 meV in a nearly cofacial antiparallel stack, leading to the electron mobility of the BDOPV derivatives increasing from 2.6 to 12.6 cm2 V-1 s-1. The electron mobility of five molecules did not show good correlation with LUMO levels, indicating that the distinct dif-ference of charge transport properties is resulted from molecular packing. Our work not only provides a series of high electron mobility organic semiconductors, but also demonstrates that fluorination is an effective approach to finely tune single-crystal packing modes beyond simply lowering molecular energy levels.