摘要
Revealing structural isomerization in metal clusters would bridge a huge structural gap between small molecular isomerization and solid–solid phase transformation.However,genuine structural isomerism in metal clusters is still rare.In this work,we report the first example of structural isomerismin Cu clusters.By utilizing the coordination flexibility of alkyne to enable the migration of partial Cu atoms in Cu metal cores,two Cu_(15)cluster complexes(Cu_(15)-a and Cu_(15)-c)possessing identical composition but different metal core structures have been successfully isolated.Interestingly,although the structure of Cu_(15)-a can be retained in CH_(2)C_(l2)solution below 27°C,it will gradually change to give an intermediate state,Cu_(15)-b,as the temperature rises(at about 31°C)before it eventually transforms into Cu_(15)-c(at 40∼65°C).Significantly,atomically precise Cu_(15)-b clearly provides footprints for tracing the thermal migration process of Cu atoms during the thermal transformation from Cu_(15)-a to Cu_(15)-c.In addition,Cu_(15)-a and Cu_(15)-c exhibit diverse crystallization-induced emission enhancement phenomena.Crystalline Cu_(15)-c displays redshifted photoluminescence(820 nm)compared with Cu_(15)-a(726 nm)due to the shorter mean Cu···Cu distance in Cu_(15)-c.Notwithstanding,crystalline Cu_(15)-a exhibits much more intense photoluminescence at room temperature than that in Cu_(15)-c,which might be attributed to the stronger intermolecular C–H⋯πinteractions in Cu_(15)-a.These results indicate that cluster isomerism provides valuable opportunities for insight into the structure–property relationships and understanding the complex evolution of phase transformation in nanometallic solids.
基金
supported by the National Natural Science Foundation of China(grant nos.22101048,22005054,and 21975044)
the Natural Science Foundation of Fujian Province(grant no.2021J01150).
