Click synthesis, aggregation-induced emission, E/Z isomerization, self-organization, and multiple chromisms of pure stereoisomers of a tetraphenylethene-cored luminogen

J Am Chem Soc. 2012 Jun 20;134(24):9956-66. doi: 10.1021/ja208883h. Epub 2012 Jun 6.

Abstract

It has been difficult to decipher the mechanistic issue whether E/Z isomerization is involved in the aggregation-induced emission (AIE) process of a tetraphenylethene (TPE) derivative, due to the difficulty in the synthesis of its pure E and Z conformers. In this work, pure stereoisomers of a TPE derivative named 1,2-bis{4-[1-(6-phenoxyhexyl)-4-(1,2,3-triazol)yl]phenyl}-1,2-diphenylethene (BPHTATPE) are successfully synthesized. Both isomers show remarkable AIE effect (α(AIE) ≥ 322) and high fluorescence quantum yield in the solid state (Φ(F) 100%). The conformers readily undergo E/Z isomerization upon exposure to a powerful UV light and treatment at a high temperature (>200 °C). Such conformational change, however, is not observed under normal fluorescence spectrum measurement conditions, excluding the involvement of the E/Z isomerization in the AIE process of the TPE-based luminogen. The molecules of (E)-BPHTATPE self-organize into ordered one-dimensional nanostructures such as microfibers and nanorods that show obvious optical waveguide effect. BPHTATPE shows rich chromic effects, including mechano-, piezo-, thermo-, vapo-, and chronochromisms. Its emission peak is bathochromically shifted by simple grinding and pressurization and the spectral change is reversed by fuming with a polar solvent, heating at a high temperature, or storing at room temperature for some time. The multiple chromic processes are all associated with changes in the modes of molecular packing.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Click Chemistry*
  • Fluorescent Dyes / chemical synthesis*
  • Fluorescent Dyes / chemistry
  • Hot Temperature
  • Isomerism
  • Nanostructures / chemistry
  • Nanostructures / ultrastructure
  • Spectrometry, Fluorescence
  • Stilbenes / chemical synthesis*
  • Stilbenes / chemistry

Substances

  • Fluorescent Dyes
  • Stilbenes