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.