The mechanically induced color change from UV to visible region

The branched amidoamine molecule 1 with different chromophores of a rhodamine B and two pyrenyl moieties at each side was synthesized. The luminescent properties of 1 with the color change from bright blue (UV region) to reddish (visible region) under mechanical stimulus were observed, which was attributed to the emission of pyrene excimer II, with a sandwich packing mode, and the chemical reaction of rhodamine B from a spirolactam to a ring opened amide.