Symmertrical and unsymmetrical donor-acceptor benzothiadiazoles

Abstract

In recent years research on benzothiadiazole (BTD) based molecular system with enhanced π-electron delocalization has gained significant attention of the scientific community due to their diverse photonic, and electronic applications. BTD is strong acceptor and its donor–acceptor (D–A) derivatives exhibit strong absorption, high fluorescence quantum yield, and excellent thermal and photochemical stability. The electronic and photonic properties of BTD based D–A system is a function of their HOMO–LUMO gap. The HOMO–LUMO gap of D––A systems can be tuned either by altering the strength of D/A units or by varying the -bridge. The D–A molecules with strong intramolecular charge-transfer and low HOMO–LUMO gap are potential candidates for organic photovoltaics. A wide variety of donors (triphenylamine, carbazole, ferrocene, etc.) and acceptors (TCNE, TCNQ, BODIPY, etc.) have been explored in the design and synthesis of donor–acceptor systems.Substitution of the donors and acceptors at 4- and 7-position of the BTD perturbs the photonic properties of these molecular systems significantly. In order N S 1 N 2 3 4 6 5 7 xii to tune the HOMO–LUMO gap, the BTD unit was functionalized with various donors, acceptors and linkers in symmetrical and unsymmetrical fashion. The effect of substitution of various D/A units on the photonic, thermal and electrochemical properties were studied.