Thermally Activated Delayed Fluorescence of Organic-Inorganic Hybrid Menshutkin-Type Cu-Sb Halides

Organic-inorganic hybrid metal halides have attracted much attention due to their excellent optoelectronic properties. The heterometallic structure is expected to achieve more complex luminescence centers, thereby improving the tunability of the fluorescent materials. This paper reports the synthesis of crystals [Cu(2,2'-bpy)(PPh₃)₂][CuCl₂(PPh₃)₂Sb₂OCl₄] (1, 2,2'-bpy = 2,2'-bipyridine, PPh₃ = triphenylphosphine) and (Mim)₂[Sb₂OCl₆] (2, Mim = 1-methylimidazole). Crystal 1 is a new Menshutkin-type compound with a double-layer hamburger-type structure, which is characterized by main group metal (lone pair)···π (arene) supramolecular interactions. Crystal 1 shows bright yellow light emission at room temperature and has thermally activated delayed fluorescence (TADF) characteristic with more than twice the increase of PL intensity from 170 to 320 K. The emission of crystal 1 arises from the charge transfer of the cation unit, as confirmed by the comparison study of crystals 1 and 2. Density functional theory (DFT) calculations further clarify that the enhanced PL performance and narrower bandgap are from the additional Cu(I) unit. Crystal 1 has good thermal stability and air stability, ensuring its anti-counterfeiting application. This work provides a new strategy for the construction of a Cu-Sb heterometallic compound.