Anomalous Pressure‐Induced Blue‐Shifted Emission of Ionic Copper‐Iodine Clusters: The Competitive Effect between Cuprophilic Interactions and Through‐Space Interactions

Abstract

AbstractDeveloping ionic copper‐iodine clusters with multiple emitting is crucial for enriching lighting and display materials with various colors. However, the luminescent properties of traditional ionic copper‐iodine clusters are often closely associated with low‐energy cluster‐centered triplet emission, which will redshift further as the Cu⋅⋅⋅Cu bond length decreases. This article utilizes a pressure‐treated strategy to achieve an anomalous pressure‐induced blue‐shifted luminescence phenomenon in ionic Cu4I6(4‐dimethylamino‐1‐ethylpyridinium)2 crystals for the first time, which is based on dominant through‐space charge‐transfer (TSCT). Herein, we reveal that the more advantageous through‐space interactions in the competition between cuprophilic interactions and through‐space interactions can lead to a blue‐shifted luminescence. High‐pressure angle‐dispersive X‐ray diffraction and high‐pressure infrared experiments show that the enhanced through‐space interactions mainly originate from forming new intermolecular C−H⋅⋅⋅I hydrogen bonds and the enhancement of van der Waals interactions between organic cations and anionic clusters. Theoretical calculations and experimental studies of excited‐state dynamics confirm that the blue‐shifted emission is due to the increased energy gap between the excited triplet and ground states caused by the electron delocalization under stronger through‐space interactions. This work deepens previous understanding and provides a new avenue to design and synthetic ionic copper‐iodine clusters with high‐energy TSCT emission.