Designing Threefold π-Surfaces Through Peripheral Halogenation to Shape Multidirectional Molecular Packing

Controlling the interaction landscape of threefold π-surfaces offers a promising strategy for directing multidirectional molecular packing. Triptycene-tribenzoquinone, with its rigid three-bladed framework, provides a suitable platform for exploring this concept. Here we report the synthesis of new fluoro-, bromo-, and iodo-substituted triptycene-tribenzoquinones, which, together with the previously reported chloro-substituted derivative, constitute the complete series of hexahalogenated triptycene-tribenzoquinones (TT_X; X = F, Cl, Br, and I). Using this series, we systematically investigate the effects of peripheral halogenation on their electronic properties and solid-state molecular packing. All derivatives exhibit reversible three-step reduction with first reduction potentials comparable to those of the corresponding tetrahalogenated benzoquinones. Increasing halogen size enhances the anisotropy of the electrostatic surface potential, leading to progressively stronger σ-hole character. Upon crystallization, different packing modes emerge depending on the interplay between the intrinsic threefold π-surface geometry, halogen size, and σ-hole character, with TT_F, TT_Cl, and TT_Br, and TT_I forming non-layered packing, layered rectangular 2D sheets, and a porous 3D network, respectively. These results demonstrate that peripheral halogenation reshapes the interaction landscape of threefold π-surfaces while preserving their intrinsic redox properties, providing a design strategy for organizing molecular building blocks with multidirectional π-surfaces into desired supramolecular architectures.