Synthesis and photochromic properties of triazole-bridged dithienylethene compounds with pyrene units

Three new triazole-bridged dithienylethene compounds with pyrene or benzene units were synthesized using the azide alkyne Huisgen cycloaddition reaction. Their structures were well characterized by NMR spectroscopy and mass spectrometry. UV/Vis absorption spectra and fluorescence spectra indicated that these dithienylethene compounds displayed obvious photochromism and fluorescent switch properties. The open-ring isomer of compound 1 with two pyrene subunits showed intramolecular pyrene excimer fluorescence which arises from intramolecular association of two pyrene units, in contrast to compound 2 with one pyrene subunit.