Derivation of saddle shaped cyclooctatetrathiophene: increasing conjugation and fabricating pentamer

With cyclooctatetrathiophene (COTh) as building block, two α,α,α,α-tetraaryl COThs, COThP and COThTh have been efficiently synthesized. Phenyl and thienyl were employed as end-capping groups to introduce to COTh and increase its conjugation. For enlarging the special ‘saddle’ shaped structure, a pentamer of COTh was synthesized via Negishi reaction and CuCl2-promoted oxidative coupling reaction. The pentamer (COThF) is a new type of dendrimer with COTh as dendron, which presents an artistic configuration possessing a large saddle shape. All compounds were fully characterized by 1H NMR, 13C NMR, HRMS and IR. The crystal structures of COThP and COThTh were confirmed by X-ray analysis. The molecular configuration of COThF was optimized by theoretical calculations. Their UV–vis properties, electrochemical behaviours and thermo-gravimetric analysis of COThP, COThTh and COThF were also described.