Ionic-to-Coordinate Structural Transformation of Hybrid Metal Halides with Improved Anti-Kasha's Room-Temperature Phosphorescence and Dynamic Multicolor Emission

Abstract

Hybrid metal halides (HMHs) have emerged as promising platforms for roomtemperature phosphorescence (RTP) due to their structural tunability and excited-state dynamics.However, the distinct roles of ionic versus coordinate assembly in governing RTP behavior remain unexplored. Herein, we report a thermally induced single-crystal-to-single-crystal (SCSC) transformation from ionic (DPTAH DPTA = 3,2,) and finally to coordinate (DPTAH)InCl 4 (In-3). This stepwise transition enables a systematic investigation of structure-optical properties.In detail, all three samples exhibit anti-Kasha's RTP due to the fast relaxation of excitons via T 2 →S 0 and efficient reverse internal conversion from T 1 to T 2 . Coordinate In-3 shows improved anti-Kasha's RTP performance, resulting from the synergistic effects of improved structural rigidity and heavy-atom-enhanced ISC of S 1 →T 2 , T 3 . Ionic In-1 and In-2 exhibit a higher Sb 3+ doping efficiency with a near-unity photoluminescence quantum yield due to their ionic nature.Additionally, these three samples show excitation-dependent multicolor emissions and dynamic RTP behavior because of the twisted intramolecular charge transfer of DPTA and triplet energy transfer from DPTA to Sb 3+ . These advantages enable advanced applications in white-light LED and time-resolved anti-counterfeiting. This work provides a mechanistic understanding of how assembly modes govern RTP and offers a design strategy for luminescent materials.