Strategic modification of ligands for remarkable piezochromic luminescence (PCL) based on a neutral Ir(III) phosphor

A new aggregation-induced emission (AIE)-active neutral Ir(III) complex has been rationally designed and synthesized by introducing carboxyl and F substituents into the ancillary and cyclometalating ligands, respectively, to construct different kinds of intermolecular interaction, leading to excellent piezochromic luminescence (PCL) properties. The emission colours are tunable by a grinding–fuming/heating process with good reversibility in the solid state. A combination of powder X-ray diffraction, differential scanning calorimetry, 1H NMR, X-ray photoelectron and Fourier-transform infrared spectroscopy unambiguously confirm that the mechanism of PCL involves disruption of the intermolecular π–π interactions and hydrogen bonding. The combined AIE and PCL properties have enabled an efficient re-writable data recording device to be fabricated using the Ir(III) complex as the active material.