Heavy‐Atom‐Induced Narrow Emission in Chalcogen‐Coordinating Lanthanide Cerium(III) Complexes

Luminescent lanthanide cerium(III) compounds have gathered increasing research interest in both inorganic phosphors and functional molecular complexes. Cerium(III) exhibits broad double‐peak emission originating from 5 d excited state 2 D 3/2 to 4 f ground states 2 F 7/2 and 2 F 5/2 . It is vital to adjust the bandwidth of the emission for different applications like lighting and display, while no regulation between these two peaks in Ce(III) emitters has been reported hitherto. In this work, novel heavy‐atom‐induced narrow emission is observed in luminescent Ce(III) complexes by adopting imidodiphosphinate ligand with different chalcogen‐coordinating sites from O to S, Se, and Te. Not only a new Ce(III) complex with orange–red emission beyond the traditional emission color regions of Ce(III) was obtained, but also the ratio of the two peaks was systematically tuned to achieve the narrowest emission from Ce(III) with a full width at half maximum of 42 nm. Time‐dependent density functional theory calculations ascribe the tuning of emission spectra to centroid shift and simultaneously provide the orbital contribution values of different chalcogen atoms to the emission excited state. By extending the coordination atoms from classic oxygen and nitrogen to heavier and softer elements, these results give new insight into luminescence properties and mechanisms of Ce(III) emission.