Chiral Iridium(III) Microcrystals with Mechano-Tunable Circularly Polarized Luminescence

Abstract

Multidimensional optical materials are of interest for high-security information encryption and anticounterfeiting, whereas conventional single-channel luminescent systems have low coding capacity and limited security. The combination of mechanochromic luminescence (MCL) and circularly polarized luminescence (CPL) in iridium(III) (Ir(III)) complexes has been little explored due to challenging chiral construction and inefficient chirality transfer. Herein, a pair of chiral Ir(III) complex microcrystals, Ir2((+)-CS) and Ir2((−)-CS), were constructed through a chiral anion-mediated supramolecular approach. Effective chirality transfer via C–H···O hydrogen bonding endows the microcrystals with a photoluminescence quantum yield of 61% and moderate CPL activity with luminescence dissymmetry factors (|glum|) of 1.8 × 10–2. Grinding induces crystalline-to-amorphous transition, leading to emission red-shift and CPL quenching, while CH2Cl2 vapor fuming restores the luminescence color and partially restores the CPL activity. Such dual-mode modulation of emission color and CPL activity provides an additional level of security for optical information encryption. Structural characterizations reveal that the response originates from solvent-assisted partial reconstruction of molecular packing and hydrogen-bonding networks. Rewritable devices and CPL-based encryption systems are further demonstrated. This work represents a distinct example of mechanoresponsive CPL in Ir(III) complexes, offering a route to multifunctional chiral materials for advanced information security and chiral optoelectronics.