Face-to-Face Helical Columns with Permanent Polarity Consisting of Homochiral End-Functionalized Helicenes.

Chiral π-conjugated molecules hold great potential for applications in spin-selective organic semiconductors and chiroptical electronic devices that respond to circularly polarized light. Their performance is anticipated to be strongly influenced by how they assemble in the solid state. However, strategies for controlling the packing structure─particularly in helically twisted π-conjugated molecules─remain limited. In this work, we achieved a homochiral face-to-face columnar packing arrangement for helicene derivatives by modifying their helical ends with 2,1,3-thiadiazole and phenanthrene-fused ring structures. Theoretical calculations suggested significantly strong intermolecular interactions in the face-to-face columnar arrangement (e.g., Etotal = -113.9 kJ·mol-1), comparable to those observed in planar π-conjugated molecules, likely due to the large overlap area between adjacent helical molecules. Thiadiazole-fused derivative (P)-TD[7]H and phenanthrene-fused derivative (M)-1, with face-to-face columnar arrangements in the solid state, exhibited a photoconductivity maximum of ΦΣμmax = 1 × 10-5 cm2·V-1·s-1 as determined by the flash-photolysis time-resolved microwave conductivity method, confirming its potential as an organic semiconductor.