Aryl-Substituted Unsymmetrical Benzothiadiazoles: Synthesis, Structure, and Properties

A family of unsymmetrical donor–acceptor, ferrocenyl-substituted benzothiadiazoles of types D₁–π–A−π–D₂, D₁–π–A₁–π–A₂, D₁–A−π–D₂, and D₁–A₁–A₂–D₂, bearing a variety of electron-donating and electron-withdrawing groups, were designed and synthesized. Their photophysical, electrochemical, and computational properties were explored, which show strong donor–acceptor interaction. The presence of electron-rich units anthracene (<b>6f</b>) and triphenylamine (<b>6h</b>), and an electron-deficient unit 1,1,4,4-tetracyanobuta-1,3-diene (TCBD) (<b>9b</b>) results in lowering of the band gap, which leads to a red shift of the absorption spectrum in these benzothiadiazole systems. The single crystal structures of <b>6c</b>, <b>6g</b>, <b>7a</b>, and <b>7b</b> are reported, which show marvelous supramolecular interactions