Synergistic Chirality in Spiro‐Fused Chiral Conjugated Helices

Abstract

ABSTRACT This study presents the design and synthesis of novel spiro‐fused chiral conjugated helices via a bilateral bent‐π‐extension strategy to elucidate chirality synergy across mixed chiral centers. Notably, six stereoisomers of SDPD6H , including three enantiomeric pairs, were successfully obtained and fully resolved. Single‐crystal structural analysis reveals that helicene fusion onto the spirodiperylenetetraimide ( SDP ) skeleton induces significant bending of the originally planar perylene diimide subunits into bowl‐shaped geometries, breaking molecular symmetry and thus raising the isomerization barrier. Furthermore, the stereoisomers exhibit distinct chiroptical responses, with P , S , P ‐ 6 showing the strongest chiroptical activity (Cotton effects: |Δ ε | reaching 310 M −1 cm −1 ). Through in‐depth theoretical analysis of rotatory strength ( R ), we elucidate the origin of the circular dichroism (CD) behavior in the 425–600 nm region. In homochiral bishelicene configurations ( P , P or M , M ), the magnetic transition dipole moments ( m ) from the two molecular fragments differ significantly in magnitude, leading to non‐canceling R 3 and R 4 , and thus pronounced CD signals. In contrast, heterochiral configurations ( P , M ) produce magnetic dipoles of similar magnitude but opposite sign, resulting in near‐complete cancellation and a suppressed CD response. This work provides a mechanistic understanding of stereochemical interplay in hybrid multi‐chiral‐centers systems and establishes a new design strategy for advanced chiroptical materials.