Bromide anion-triggered visible responsive metallogels based on squaramide complexes

Abstract

Driven by the cooperation of metal coordination and multiple hydrogen bonds, a squaramide-based bisimidazole ligand forms structurally novel metallogels involving one-dimensional (1D) nanofibrils with linearly and infinitely extended Cl–Cu or Br–Cu bonds wrapped up with organic ligands. The resulting soft material enables us to discriminate bromides from other salts and, of special significance, from other halides both in aqueous solutions and in powder forms by the naked-eye. Raman spectroscopy clearly unravels the discrimination mechanism associated with a key step of anion ligand exchange, which has witnessed the exceptional ability of Raman spectroscopy in the investigation of metallogels.