Fracassa Alessandro, Calogero Francesco, Pavan Giulio, Nikolaou Pavlos, Fermi Andrea, Ceroni Paola, Paolucci Francesco, Cozzi Pier Giorgio, Scattolin Thomas, Demitri Nicola, Negri Fabrizia, Gualandi Andrea, Aliprandi Alessandro, Valenti Giovanni
Dipartimento di Chimica "Giacomo Ciamician", Alma Mater Studiorum - Università di Bologna Via Gobetti 85 40129 Bologna Italy
Center for Chemical Catalysis - C3, Alma Mater Studiorum - Università di Bologna Via Gobetti 85 40129 Bologna Italy.
Chem Sci. 2024 Oct 3;15(43):17892-9. doi: 10.1039/d4sc04986a.
Thermally Activated Delayed Fluorescent (TADF) luminophores offer the potential to achieve 100% Internal Quantum Efficiency (IQE) by harvesting both singlet and triplet excitons reverse intersystem crossing from T to S. This class of molecules has therefore been embraced in the pursuit of cheaper and more efficient electrochemiluminescent (ECL) labels. The present study explores how tuning the electron-donating (D) and -accepting (A) strengths of peripheral substituents affects the ECL emission of mono- and dicyanoarene-based TADF dyes. To this end, we synthesized two series of TADF compounds, independently manipulating electron donors and acceptors by (i) halogenating electron-rich diphenylamine moieties, or (ii) mono- or di-substituting the electron-poor cyanoarene core with either fluorine or imidazole. Through a comparative analysis, we elucidate the role of each substituent in shaping the photophysics of the investigated luminophores. Despite only achieving a relative as high as 1.27%, this framework identifies several molecular features that boost the ECL efficiency to pave the way for designing highly efficient TADF-based ECL emitters. Ultimately, imidazole substituents are exploited as a platform for functionalization with triethylene glycol units. The resulting water-soluble TADF luminophores are characterized under conditions usual to commercial ECL bioanalysis, proving their potential as a cost-effective alternative replacement to [Ru(bpy)] in clinical diagnostic.
热激活延迟荧光（TADF）发光体具有通过捕获单重态和三重态激子以及从T到S的反向系间窜越来实现100%内量子效率（IQE）的潜力。因此，这类分子已被用于寻求更便宜、更高效的电化学发光（ECL）标记物。本研究探讨了调节外围取代基的给电子（D）和吸电子（A）强度如何影响基于单氰基芳烃和双氰基芳烃的TADF染料的ECL发射。为此，我们合成了两个系列的TADF化合物，通过（i）卤化富电子的二苯胺部分，或（ii）用氟或咪唑对贫电子的氰基芳烃核心进行单取代或双取代来独立操纵电子供体和受体。通过比较分析，我们阐明了每个取代基在塑造所研究发光体的光物理性质中的作用。尽管相对效率仅达到1.27%，但该框架确定了几个提高ECL效率的分子特征，为设计高效的基于TADF的ECL发射体铺平了道路。最终，咪唑取代基被用作与三甘醇单元进行功能化的平台。所得的水溶性TADF发光体在商业ECL生物分析常用的条件下进行了表征，证明了它们作为[Ru(bpy)]在临床诊断中具有成本效益的替代物的潜力。
