Highly Luminescent Blue Emitter with Balanced Hybridized Locally and Charge‐Transfer Excited‐States Emission

Abstract

What prompted you to investigate this topic?The relevance of electronic excitation reaches from photobiology to molecular electronics, such as organic light emitting diodes (OLEDs). We are interested in studying intersystem crossing (ISC) in molecules and in the modulation of ISC by variation of the chemical structure and of the molecular environment. Therefore, we synthesize novel diphenylamino terphenyl emitters with increased distance between donor and acceptor moieties to study their electronic properties collaboratively within the research training group RTG 2482. What is the most significant result of this study?The designed fluorophore shows high solubility and intense blue to yellow emission in solution revealing photoluminescence quantum yields close to unity. Multi-reference quantum chemical calculations indicate a balanced hybridized local and charge-transfer excited state. Furthermore, the calculations reveal the strong involvement of the ligating p-phenylene

3‐Ligated Phenothiazinyl‐terephthalonitrile Dyads and Triads ‐ Synthesis, Electronic Properties, Delayed Fluorescence and Electronic Structure

“…Our synthetic strategy takes advantage of the one-pot brominelithium exchange-borylation-Suzuki (BLEBS) sequence, [13] which has just recently applied to the efficient syntheses of deep-blue terphenyl emitters [14] and to the synthesis of the parent diphenylamino-ortho-xylyl-terephthalonitrile TADF emitter dyad [12a] that was employed in NIR-spectroscopic and quantum chemical assignments of transitions within the excited states. [12b] Starting from 3-bromo phenothiazines 1 or 3,7-dibromo phenothiazines 4 the series of phenothiazinyl-terephthalonitrile donor-acceptor dyads 3 (Scheme 1) and terephthalonitrilephenothiazinylene-terephthalonitrile acceptor-donor-acceptor triads 5 (Scheme 2) are synthesized and obtained after chromatographic purification in good to excellent yield.…”

Molecular design of phenazine-5,10-diyl-dibenzonitriles and the impact on their thermally activated delayed fluorescence properties

“…5,6,14–17 This high efficiency can be achieved because the lowest excited singlet state (S 1 ) and lowest excited triplet state (T 1 ) are energetically sufficiently close that reverse intersystem crossing (rISC) can be thermally triggered. 18–23 The energy difference Δ E ST of both energy levels is typically less than 0.1 eV for the current highly efficient organic TADF emitters. 14,24–27 The smaller the energy gap Δ E ST between S 1 and T 1 the higher the equilibrium population of the higher excited S 1 state, which governs up to 25% of the internal quantum efficiency in cases of electric injection of charge carriers.…”