Long-Range Rigidity Induced Ultralong Cluster-Centered Phosphorescence

Ultralong phosphorescence of organic or coordination compounds has been a hot topic recently, and the relationship between the lifetime and local rigidity of the molecules has been an intensive focus. We present here a new effective strategy to regulate the phosphorescence lifetime only via controlling the long-range rigidity. The coordination compound [Cu6I6(HMTA)2] (CuIU, HMTA = hexamethylenetetramine) has two phases or polymorphic isomers, namely, cubic C-CuIU and trigonal T-CuIU with fully disordered and very slightly disordered [Cu6I6] clusters, respectively. In the trigonal lattice of T-CuIU, [Cu6I6] clusters are bridged by HMTA, resulting in a more rigid framework with a largely reduced disorder degree. Notably, with no significant change of the [Cu6I6] emission center, such long-range rigidity of the framework can obviously enhance the phosphorescent afterglow performance to a fairly high phosphorescence quantum yield of 59% and a long lifetime of 1.1 s, keeping similar emission color. The lifetime (0.2∼1.1 s) can be simply tuned by adjusting the rigidity of the framework through changing the content of T-CuIU with the reaction time alteration in the synthesis of mixed-phase CuIU. Moreover, the material can be scaled up to kilograms by a simple synthetic method and used for ultralong phosphorescent textile with a steady photophysical property.