Benzo‐Extended Thiaquasi[7]Circulenes: Strategic Scholl‐Type Synthesis, Tunable Electronic, and Stimuli‐Responsive Properties

Thia-quasi[7]circulenes (TQCs) are a novel class of π-conjugated molecules exhibiting unique electronic, optical, and electrochemical properties. We report a highly efficient bottom-up synthesis of TQCs via Scholl oxidative cyclization, achieving exceptional yields and structural precision. Single-crystal X-ray analysis confirms their negatively curved geometry, featuring a central antiaromatic heptagonal core and a surrounding aromatic rim, leading to bifacial electronic properties. TQCs demonstrate stable redox behavior with tunable Highest Occupied Molecular Orbital (HOMO)-Lowest Unoccupied Molecular Orbital (LUMO) energy levels. Their remarkable electrochemical stability highlights potential as redox-active materials. TQCs exhibit blue-shifted fluorescence compared to carbo-quasi[7]circulenes, with enhanced quantum yields upon benzoannulation. Additionally, they display mechanochromic luminescence upon grinding, revealing tunable molecular characteristics. These findings establish TQCs as versatile molecular frameworks, bridging fundamental chemistry and next-generation functional materials, making them promising candidates for organic electronics, energy storage, and optoelectronic applications.