A stimuli-responsive double-stranded digold(i) helicate

Abstract

We report herein a stimuli-responsive dinuclear double stranded [Au₂L₂]²⁺ helicate assembled from gold(I) atoms and phenyl-substituted diphosphine ligands derived from a xanthene-type backbone (L). The conformational flexibility of the dinuclear [Au₂L₂]²⁺ helicate allows a diversity of molecular conformations and packing arrangements that lead to different solid-state emission colours. Blue (I_B), bluish green (II_G) and yellow (III_Y) emitting crystalline and red emitting (IV_R) amorphous forms of this double stranded [Au₂L₂]²⁺ helicate have been obtained by slight modification of the crystallization conditions. Different molecular conformations and packing arrangements of dinuclear double stranded [Au₂L₂]²⁺ helicates that result in different non-covalent interactions played the most significant role in tailoring the solid-state luminescence properties. On the basis of the single crystal structural data and photophysical studies, we found that an increasing number of intra- and mainly intermolecular noncovalent interactions locked and rigidified the twisted conformation of the double stranded [Au₂L₂]²⁺ helicate, and enhanced π-stacking between its aromatic units induced the red-shift in solid-state luminescence emission. The solid-state luminescence colour of this double stranded [Au₂L₂]²⁺ helicate can be switched reversibly from blue to red by external (mechanical and chemical) stimuli.