Cationic dinuclear Ir(III) complexes based on acylhydrazine ligands: Reversible piezochromic luminescence and AIE behaviours

Abstract To comprehensively understand the structure-property correlations is of fundamental importance for the development of desirable piezochromic luminescence (PCL) materials. Keeping this in mind, two new cationic dinuclear metal Ir(III) complexes containing same acylhydrazone ancillary ligands and easily tunable cyclometalated ligands have been rationally designed and synthesized. Both luminophores show excellent aggregation-induced emission (AIE) behaviours and high-contrast PCL properties. The powder X-ray diffraction (PXRD) studies suggest that the emission changes of complexes before and after grinding derive from effective transformation between crystalline and amorphous phase. Fourier Transform Infrared (FT-IR) spectra further indicate that PCL effect of complexes could be ascribed to the disorder of hydrogen bonds between N–H and C O groups. Importantly, the principle of introducing hydrogen-bonding sites into Ir(III) complexes provides a feasible method for designing smart PCL materials. Based on the fascinating PCL properties of complexes 1 and 2, the efficient proof-of-concept data encryption and re-writable devices are successfully obtained, respectively.