Lanthanide clusters with chalcogen encapsulated Ln: NIR emission from nanoscale NdSe(x)

Ln(SePh)(3) (Ln = Ce, Pr, Nd) reacts with elemental Se in the presence of Na ions to give (py)(16)Ln(17)NaSe(18)(SePh)(16), a spherical cluster with a 1 nm diameter. All three rare-earth metals form isostructural products. The molecular structure contains a central Ln ion surrounded by eight five-coordinate Se(2-) that are then surrounded by a group of 16 Ln that define the cluster surface, with additional μ(3) and μ(5) Se(2-), μ(3) and μ(4) SePh(-), and pyridine donors saturating the vacant coordination sites of the surface Ln, and a Na ion coordinating to selenolates, a selenido, and pyridine ligands. NIR emission studies of the Nd compound reveal that this material has a 35% quantum efficiency, with four transitions from the excited state (4)F(3/2) ion to (4)I(9/2), (4)I(11/2), (4)I(13/2), and (4)I(15/2) states clearly evident. The presence of Na(+) is key to the formation of these larger clusters, where reactions using identical concentrations of Nd(SePh)(3) and Se with either Li or K led only to the isolation of (py)(8)Nd(8)Se(6)(SePh)(12).