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

Abstract

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.