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Scale-up Chemical Synthesis of Thermally-activated Delayed Fluorescence Emitters Based on the Dibenzothiophene-S,S-Dioxide Core
Published on: October 24, 2017
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Thermally activated delayed fluorescence (TADF) emitters: sensing and boosting spin-flipping by aggregation
Ashish Kumar Mazumdar1, Gyana Prakash Nanda1, Nisha Yadav1
1Materials Research Centre, Indian Institute of Science, C. V. Raman Road, Bangalore, Karnataka, 560012, India.
Beilstein Journal of Organic Chemistry
|September 21, 2022
Summary
New metal-free organic emitters with thermally activated delayed fluorescence (TADF) show promise for optoelectronics and sensing. Tailoring donor units influences aggregation-induced emission and fluorescence switching, enabling applications in solid-phase sensing.
Area of Science:
- Materials Science
- Organic Chemistry
- Photophysics
Background:
- Metal-free organic emitters with Thermally Activated Delayed Fluorescence (TADF) are crucial for optoelectronic devices and sensing.
- Donor-acceptor (D-A) compounds are key to achieving TADF properties.
- Controlling molecular structure is vital for tuning photophysical properties.
Purpose of the Study:
- To synthesize and characterize novel (4-bromobenzoyl)pyridine (BPy)-based D-A compounds with varying donor units.
- To investigate the impact of donor size and strength on TADF properties, aggregation-induced enhanced emission (AIEE), and solid-phase sensing capabilities.
- To explore the potential of these emitters for fluorescence-based acid-base sensing.
Main Methods:
- Synthesis of BPy-based D-A compounds: BPy-pTC (tert-butylcarbazole donor) and BPy-p3C (tricarbazole donor).
- Photophysical characterization in solution and solid phase, including emission spectra and TADF properties.
- Investigation of aggregation-induced enhanced emission (AIEE) in THF/water mixtures.
- Analysis of singlet-triplet energy gap (ΔEST) and reverse intersystem crossing rate (kRISC).
- Evaluation of fluorescence switching in response to acid (trifluoroacetic acid, TFA) and base (triethylamine, TEA) vapors.
Main Results:
- Both BPy-pTC and BPy-p3C exhibited prominent TADF properties in solution and solid states.
- BPy-p3C showed stronger excited-state charge transfer and a more twisted D-A geometry, leading to AIEE.
- A reduced ΔEST and faster kRISC were observed in the aggregated state, enhancing delayed fluorescence.
- Solid-phase fluorescence switching with fatigue resistance was achieved upon exposure to acid and base vapors.
Conclusions:
- Donor strength and size significantly influence ΔEST in the aggregated state.
- The synthesized compounds demonstrate potential for photon upconversion and enhanced delayed fluorescence.
- The sensitivity of pyridinyl nitrogen to protons enables effective fluorescence-based acid-base sensing.
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