Two‐Step Mechanochromic Luminescence of N,N′‐Bis‐Boc‐3,3′‐di(pyren‐1‐yl)‐2,2′‐biindole

Abstract Despite recent advances in the development of mechanochromic luminescent organic molecules, the mechano‐responsive properties of intramolecularly stacked fluorophores are not well documented. Herein, the synthesis and emission properties of three N , N′ ‐bis‐Boc‐3,3′‐diaryl‐2,2′‐biindole (Boc= tert ‐butoxycarbonyl) derivatives as a new class of solid‐state emissive fluorophores are described. For a 3,3′‐dipyrenyl derivative in the crystalline state, partial intramolecular stacking of the dipyrenyl groups was observed, which results in a two‐step mechanochromic luminescence from blue ( λ em =462 nm) to green ( λ em =516 nm) and yellow ( λ em =535 nm).