Synthesis of Indolocarbazole‐Diketopyrrolopyrrole Dyads and Investigation of Their Photoinduced Electron Transfer Properties

ABSTRACT Electron transfer (ET) dyads comprising electron‐donating as well as electron‐accepting chromophores are highly useful in various opto‐electronic applications. Thus, design and synthesis of efficient ET dyads is a highly demanding area of research. Here, we designed three dyads by connecting electron donating indolocarbazole (ICZ) moiety with three different electron accepting diketopyrrolopyrrole (DPP) moieties. A facile methodology for the synthesis of these ICZ‐DPP dyads was developed using the Suzuki–Miyaura cross‐coupling reaction of boronated‐ICZ and bromo‐DPPs. Detailed characterizations of the dyads were done using NMR, optical spectroscopy, and mass spectrometry. All the dyads exhibited broad and strong visible light absorption and displayed interesting solvent‐dependent photophysical properties. Interestingly, significant quenching of fluorescence in polar solvents due to non‐radiative deactivation of excited states was also observed for all the dyads. Femtosecond transient absorption measurements were done, which showed ultrafast electron transfer from ICZ donor to DPP acceptor, leading to charge separated state in polar solvents. This study showed that ICZ‐DPP dyads with broad visible light absorption and efficient photoinduced charge separation could be useful for various applications, including organo‐electronics, photocatalysis, sensing/imaging, and so on.