Mechanofluorochromism of D–π–A‐Type Difluoroboron β‐Carbonyl Cyclic Ketonate Complexes that Contain a Carbazole Unit. Issue 11 (9th October 2017)

• Record Type: Journal Article
• Authors: Zhang, Fushuang; Liu, Qingwen; Chen, Yuannan; Zhai, Lu; Liu, Mingyang; Sun, Jingbo; Mi, Wenhua; Sun, Meng; Lu, Ran
• Is Part Of: Asian journal of organic chemistry. Volume 6:Issue 11(2017)
• Page Start: 1659
• Page End: 1666
• Publication Date: 2017-10-09
• Subjects: carbazoles -- charge transfer -- donor–acceptor systems -- mechanofluorochromism -- nitrogen heterocycles; Chemistry, Organic -- Periodicals; Organic compounds -- Synthesis -- Periodicals; 547.005
• DOI: 10.1002/ajoc.201700380
• Languages: English
• ISSNs: 2193-5807

Abstract

Abstract: Four new D–π–A‐type difluoroboron β‐carbonyl cyclic ketonate complexes that contain carbazole units (TCCH, TCCP, CCH, andCCP ) have been synthesized that exhibited reversible mechanofluorochromic (MFC) behaviors. Interestingly, TCCH andTCCP, which contained a tert ‐butyl carbazole group, exhibited high‐contrast mechanofluorochromism compared withCCH andCCP, which just contained a carbazole group. For example, shifts of Δ δ =49 and 20 nm were detected during the mechanofluorochromism ofTCCH andCCH, 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. Abstract : Compare and contrast : High‐contrast mechanofluorochromism has been achieved through the introduction of tert ‐butyl carbazole into difluoroboron β‐diketone complexes.