In:
Angewandte Chemie International Edition, Wiley, Vol. 62, No. 29 ( 2023-07-17)
Abstract:
We demonstrate that a single polycyclic π‐scaffold can undergo sequential multistep excited‐state structural evolution along the bent, planar, and twisted conformers, which coexist to produce intrinsic multiple fluorescence emissions in room‐temperature solution. By installing a methyl or trifluoromethyl group on the ortho ‐site of N , N ′‐diphenyl‐dihydrodibenzo[ a , c ]phenazine ( DPAC ), the enhanced steric effects change the fluorescence emission of DPAC from a dominant red band to well‐resolved triple bands. The ultra‐broadband triple emissions of ortho ‐substituted DPAC s range from ≈350 to ≈850 nm, which is unprecedented for small fluorophores with molecular weight of 〈 500. Ultrafast spectroscopy and theoretical calculations clearly reveal that the above dramatic changes originate from the influence of steric hindrance on the shape of excited state potential energy surface (S 1 PES). Compared to the steep S 1 PES of parental DPAC , the introduction of ortho ‐substituent is shown to make the path of structural evolution in S 1 wider and flatter, so the ortho ‐substituted derivatives exhibit slower structural transformations from bent to planar and then to twisted forms, yielding intrinsic triple emission. The results provide the proof of concept that the bent, planar, and twisted emissive states can coexist in the same S 1 PES, which greatly expand the fundamental understanding of the excited‐state structural relaxation.
Type of Medium:
Online Resource
ISSN:
1433-7851
,
1521-3773
DOI:
10.1002/anie.202305572
Language:
English
Publisher:
Wiley
Publication Date:
2023
detail.hit.zdb_id:
2011836-3
detail.hit.zdb_id:
123227-7
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