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Mechanofluorochromism of D–π–A‐Type Difluoroboron β‐Carbonyl Cyclic Ketonate Complexes that Contain a Carbazole Unit
Author(s) -
Zhang Fushuang,
Liu Qingwen,
Chen Yuannan,
Zhai Lu,
Liu Mingyang,
Sun Jingbo,
Mi Wenhua,
Sun Meng,
Lu Ran
Publication year - 2017
Publication title -
asian journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.846
H-Index - 44
eISSN - 2193-5815
pISSN - 2193-5807
DOI - 10.1002/ajoc.201700380
Subject(s) - carbazole , chemistry , steric effects , molecule , grinding , photochemistry , stereochemistry , organic chemistry , materials science , composite material
Four new D–π–A‐type difluoroboron β‐carbonyl cyclic ketonate complexes that contain carbazole units ( TCCH , TCCP , CCH , and CCP ) have been synthesized that exhibited reversible mechanofluorochromic (MFC) behaviors. Interestingly, TCCH and TCCP , which contained a tert ‐butyl carbazole group, exhibited high‐contrast mechanofluorochromism compared with CCH and CCP , which just contained a carbazole group. For example, shifts of Δ δ =49 and 20 nm were detected during the mechanofluorochromism of TCCH and CCH , respectively. We found that tert ‐butyl carbazole derivatives existed as isolated molecules in the as‐synthesized crystals, on account of the steric hindrance of the tert ‐butyl groups, and that J ‐aggregates were formed upon grinding. Transformation between the isolated and aggregated molecules, which was stimulated by mechanical force, led to clear changes in the emission properties. However, J ‐aggregates were formed in the as‐synthesized crystals of carbazole derivatives, and grinding only weakened the strength of the π–π interactions, thereby resulting in low‐contrast mechanofluorochromism. Therefore, this approach provides a useful strategy for the design of MFC dyes with high performance.