First fluorescein liquid crystals: synthesis, mesomorphic and fluorescence properties of fluorescein-triphenylene dimers

ABSTRACT

This paper reported not only the first fluorescein liquid crystals but also revealed the influence of peripheral alkyl chains on mesomorphic properties and photophysical properties. Novel fluorescein-triphenylene dimers 4a–4f with different alkyl chains were designed and synthesised in yields of 76–83%. Samples 4a, 4b, 4c and 4d with CH₃ and C₄H₉ exhibited the columnar mesophase but samples 4e and 4f with C₈H₁₇ showed no mesophase. The longer alkyl chains on fluorescein units resulted in the lower phase transition temperature. The too long alkyl chain destroyed the liquid crystalline behaviour. Their fluorescence quantum yields were as high as 0.78–0.87 in CH₂Cl₂ solution and 0.11–0.17 in solid states. The longer alkyl chains leaded to the higher emission efficiencies.

GRAPHICAL ABSTRACT

KEYWORDS:

• Triphenylene
• fluorescein
• fluorecence
• columnar
• mesophase

Acknowledgments

Financial support from the National Natural Science Foundation of China (No: 21406036), Fujian Natural Science Foundation of China (No. 2017J01571), Fujian Science and Technology Project (No. 2019N0010), Fuzhou science and technology project (2018-G-44), and the National Undergraduate Innovation Program in Fujian Normal University (2020) were greatly acknowledged.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

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Additional information

Funding

This work was supported by the National Natural Science Foundation of China [21406036].