Diarylethene-based imines and amines: Synthesis, photochromic properties and effects of substitution

Condensation of dialdehyde 1 with different aromatic amines gave a series of symmetrical diarylethenes containing Schiff-base moieties, which were reduced with NaBH4 to give the corresponding diarylethene amines. The structures of all new compounds were confirmed by NMR spectroscopy, mass spectrometry, X-ray diffraction and elemental analysis. Their photochromic properties were also investigated, revealing that diarylethene imines displayed better photochromic properties in solution than their amine analogues. Furthermore, we found that by varying the aromatic amine precursor, diarylethenes with different polychromic behavior could be obtained. A number of different aromatic amines were investigated, including different carbon skeletons and substitution with different halogens in various positions, to tune the polychromic behavior.