Highly Efficient Electrochemiluminescence from Imidazole‐Based Thermally Activated Delayed Fluorescence Emitters

Abstract

A family of novel Thermally Activated Delayed Fluorescence (TADF) emitters have been synthetized by a straightforward and metal‐free synthesis, and structurally characterized. In this work we keep fixed the acceptor moiety, 4‐(1H‐imidazol‐1‐yl)benzonitrile, and systemically tested different donors to correlate their photophysical and electrochemical properties with their performance in electrochemiluminescence using both benzoyl peroxide as coreactant and coreactant free (annihilation) conditions. Some compounds exceed the efficiency of the standard [Ru(bpy)3]Cl2 up to 28 times with benzoyl peroxide and 38 times in annihilation. Interestingly, we found that the efficiency is mainly dictated by the electrochemical reversibility of redox processes rather than by the photophysical properties in terms of photoluminescence quantum yield or excited state lifetime. In addition, the annihilation electrochemiluminescence efficiency strongly depend on the pulse sequence. The imidazole moiety can be conveniently alkylated allowing the insertion of functional groups, such a carboxylic acid, enabling practical applications.

One-Pot N-α-C(sp3)–H Bond Functionalisation Cascade for the Synthesis of Polysubstituted Imidazoles

“…31 32 33 34 35 36 37 38 These nitrogen-containing molecules also have photophysical properties. 39 40 41 42 43 In this context, progress in designing imidazole molecules by simple and eco-friendly methods has turned out to be a main attraction in organic synthesis.…”

Designing thermally activated delayed fluorescence emitters with through-space charge transfer: a theoretical study

“…Organic thermally activated delayed fluorescence (TADF) materials have been extensively investigated as next-generation organic light-emitting diodes (OLEDs), which can utilize 100% of excitons by triplet-to-singlet upconversion without the need for heavy metals. 1–9 The photophysical performance of organic molecules depends highly on their excited state properties. 10–12 By designing TADF molecules with twisted donor (D) and acceptor (A) configurations, the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) can be effectively separated, leading to a reduction in the singlet–triplet energy gap (Δ E ST ) and an increase in the reverse intersystem crossing rate ( K RISC ).…”