Decafluorinated and Perfluorinated Warped Nanographenes: Synthesis, Structural Analysis, and Properties

Abstract

Fluorination is a useful approach for tailoring the physicochemical properties of nanocarbon materials. However, owing to the violent reactivity of fluorination, achieving edge-perfluorination of nanographene while maintaining its original π-conjugated structure is challenging. Instead of using traditional fluorination, here, we employed a bottom-up strategy involving fluorine preinstallation and synthesized decafluorinated and perfluorinated warped nanographenes (DFWNG and PFWNG, respectively) through a 10-fold Suzuki–Miyaura coupling followed by a harsh Scholl reaction, whereby precisely edge-perfluorinated nanographene with an intact π-conjugated structure was achieved for the first time. X-ray crystallography confirmed the intact π-conjugated structure and more twisted saddle-shaped geometry of PFWNG compared to that of DFWNG. Dynamic study revealed that the 26-ring carbon framework of PFWNG is less flexible than that of DFWNG and the pristine WNG, enabling chirality resolution of PFWNG and facilitating the achievement of CD spectra at −10 °C. The edge-perfluorination of PFWNG resulted in improved solubility, lower lowest unoccupied molecular orbital, and a surface electrostatic potentials/dipole moment direction opposite those of the pristine WNG. Likely owing to its intact π-conjugated structure, PFWNG exhibits comparable electron mobility with well-known PC₆₁BM. Furthermore, perfluorination improves thermal stability and hydrophobicity, making PFWNG suitable for use as a thermostable/hydrophobic n-type semiconductor material. In the future, this fluorination strategy can be used to synthesize other perfluorinated nanocarbon materials, such as perfluorinated graphene nanoribbons and porous nanocarbon.