Quantitative Decoupling of Strong Mn─Mn Coupling on Photoluminescence of Zero‐Dimensional Hybrid Manganese Chlorides Single Crystals

Abstract Strong Mn─Mn coupling interactions, including dipolar and exchange interactions, significantly affect the photoluminescence quantum yields (PLQYs) in Mn 2+ ‐based luminescent materials. However, clarifying the individual effects of dipole–dipole and exchange interactions on photoluminescence (PL) is challenging because these interactions may have similar effects on PL properties, and there is a lack of materials with precisely tunable Mn─Mn distances over a wide range. In this study, the influence of dipolar and exchange coupling on PLQY is quantitatively decoupled by designing a series of hybrid manganese chlorides single crystals with a wide tuning range of Mn─Mn distances, from 6.0 to 9.5 Å. It is found that the PLQY can be enhanced from 2.1% to 57.1%, and the PL lifetime increased from 0.21 to 3.81 ms as the Mn─Mn distance increased. This enhancement is solely attributed to the decreased energy transfer dominated by dipole–dipole interactions. At the shortest Mn─Mn distance of 6 Å, exchange coupling becomes dominant, resulting in an additional red‐side PL band with negligible effects on PLQY and lifetime. This work provides valuable insights into the mechanisms underlying the regulation of PLQY in Mn 2 ⁺‐based luminescent materials.