New panchromatic dyes comprising benzothiadiazole units within a donor–acceptor π-conjugated spacer. Synthesis and photophysical properties

Four new organic dyes (D1–D4) having donor–(π-conjugated spacer(donor–acceptor))–acceptor (D–π(D–A)–A) type conjugated systems were synthesized. The dyes were studied for their photophysical and electrochemical properties. The dyes comprised electron donor bis(4-hexyloxy)triphenylamine (D), and electron acceptor cyanoacrylic acid (A) ends connected through a donor–acceptor conjugated spacer group. The conjugated spacer was designed as donor–acceptor system having thiophene to terthiophene and selenophene as donors and benzothiadiazole as acceptor. Thus, optical absorption strengths of the dyes successfully tuned by using the electron accepting property of benzothiadiazole and varying numbers of thiophenes and selenophene. Panchromatic absorption with high extinction coefficient was observed for all four dyes D1–D4.