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 (6f) and triphenylamine (6h), and an electron-deficient unit 1,1,4,4-tetracyanobuta-1,3-diene (TCBD) (9b) 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 6c, 6g, 7a, and 7b are reported, which show marvelous supramolecular interactions.