Construction of a Two-Dimensional Molecular Slab with a π-Extended Hexaarylbenzene Molecule

We demonstrate a unique approach to a 2D molecular slab in the solid state by designing a π-extended hexaarylbenzene molecule, hexa(naphthothiophene diimide)-substituted benzene (NTI6). The six naphthothiophene diimide (NTI) moieties of NTI6 were found to stand almost perpendicularly to the central benzene core both in solution and in the solid state, realizing a 3D shape-persistent molecular structure. In the solid state, four of the six NTI units participated in π-stacking intermolecular interactions in two different directions (the crystallographic a- and b-axis directions). In addition, the remaining two NTI units interacted with neighboring molecules in an edge-to-edge manner in the crystallographic (110) direction. Theoretical calculations showed that the intra- and intermolecular overlaps of LUMOs efficiently spread within the 2D molecular slab, ensuring the formation of a 2D interactive electronic structure suitable as the active channel of organic field-effect transistors (OFETs). Indeed, the NTI6-based solution-processed OFETs exhibited electron mobility on the order of 10^-2 cm² V^-1 s^-1, corroborating the presence of a 2D electronic structure within the molecular slab.