Efficient Intersystem Crossing and Long-lived Charge-Separated State Induced by Through-Space Intramolecular Charge Transfer in a Parallel Geometry Carbazole-Bodipy Dyad

Hui Liang; Manlin Lu; Zafar Mahmood; Zheng Li; Zeduan Chen; Guowei Chen; Ming-De Li; Yanping Huo; Shaomin Ji

doi:10.1002/anie.202312600

Efficient Intersystem Crossing and Long-lived Charge-Separated State Induced by Through-Space Intramolecular Charge Transfer in a Parallel Geometry Carbazole-Bodipy Dyad

Angew Chem Int Ed Engl. 2023 Oct 26;62(44):e202312600. doi: 10.1002/anie.202312600. Epub 2023 Sep 26.

Authors

Hui Liang¹, Manlin Lu², Zafar Mahmood¹, Zheng Li¹, Zeduan Chen¹, Guowei Chen¹, Ming-De Li², Yanping Huo¹, Shaomin Ji¹

Affiliations

¹ School of Chemical Engineering and Light Industry, Guangdong University of Technology, Guangzhou, 510006, P. R. China.
² College of Chemistry and Chemical Engineering, and Key Laboratory for Preparation and Application of Ordered Structural Materials of Guangdong Province, Shantou University, Shantou, 515063, P. R. China.

PMID: 37654187
DOI: 10.1002/anie.202312600

Abstract

The design of efficient heavy atom-free triplet photosensitizers (PSs) based on through bond charge transfer (TBCT) features is a formidable challenge due to the criteria of orthogonal donor-acceptor geometry. Herein, we propose using parallel (face-to-face) conformation carbazole-bodipy donor-acceptor dyads (BCZ-1 and BCZ-2) featuring through space intramolecular charge transfer (TSCT) process as efficient triplet PS. Efficient intersystem crossing (Φ_Δ =61 %) and long-lived triplet excited state (τ_T =186 μs) were observed in the TSCT dyad BCZ-1 compared to BCZ-3 (Φ_Δ =0.4 %), the dyad involving TBCT, demonstrating the superiority of the TSCT approach over conventional donor-acceptor system. Moreover, the transient absorption study revealed that TSCT dyads have a faster charge separation and slower intersystem crossing process induced by charge recombination compared to TBCT dyad. A long-lived charge-separated state (CSS) was observed in the BCZ-1 (τ_CSS =24 ns). For the first time, the TSCT dyad was explored for the triplet-triplet annihilation upconversion, and a high upconversion quantum yield of 11 % was observed. Our results demonstrate a new avenue for designing efficient PSs and open up exciting opportunities for future research in this field.

Keywords: Charge Separation; Heavy Atom-Free Triplet Photosensitizer; Intersystem Crossing; TTA-Upconversion; Through Space Intramolecular Charge Transfer.

Abstract

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