Synthesis and characterization of gated photochromic diarylethene functionalized with dipicolylamine

Abstract

1,2-bis(2-methyl-1-benzothiophene-3-yl)perfluorocyclopentene (BTF6) based photochromic diarylethene functionalized with dipicolylamine (DPA), BTF-DPA has been synthesized, and its photochromic properties have been determined. The photoconversion reaction of o-BTF-DPA was prohibited due to the electronic effect originated from electron donation from DPA to the diarylethene BTF6 framework. The addition of Cu2+ gave rise to dramatically increase the conversion yield of o-BTF-DPA from 0 to 23.86% (for o-BTF-DPA-Cu2+) due to diminishing the electron donation ability of DPA. The addition of EDTA removed Cu2+ from BTF-DPA-Cu2+, which result in suppressing the conversion yield o-BTF-DPA. We also synthesized BTF-DMA and BTF-TMA to examine the mechanism of gated photochromism in diarylethenes. We found that the electron donation ability of DPA plays a critical role in the modulation of photochromic reactivity. The results demonstrated that BTF-DPA could be applicable as a “molecular lock” that requires Cu2+ “key” and EDTA “hand” to unlatch the key. We believe this strategy can be further extended to develop the gated photochromic systems by controlling the electronic state via non-bonding nitrogen-containing ligands.