Oxoclusters of the Lanthanides Begin to Resemble Solid-State Materials at Very Small Cluster Sizes: Structure and NIR Emission from Nd(III)

The reaction of Nd(SePh)3 with SeO2 and Hg in pyridine gives the dodecanuclear cluster
[(py)18Nd12O6Se4(Se2)4(SePh)4(Se2Ph)2Hg2(SePh)4][(Hg(SePh)3]2. In this compound the 12 Nd(III) ions are
stacked in four sets of Nd3, with pairs of tetrahedral oxo ligands separating the Nd3 planes and Se, SeSe,
SePh, pyridine, and HgSePh groups encapsulating the oxo core. Both the Nd−O bond lengths and the
geometries about the oxo ions are remarkably similar to those found in solid-state Nd2O3. Near-IR emission
experiments indicate that the cluster emission properties are less intense than those of highly emissive
(DME)2Nd(SC6F5)3 or (THF)8Nd8O2Se2(SePh)16 but brighter than the nonemissive solid-state compound
Nd2O3. Intensity variations are interpreted in terms of concentration quenching and phonon relaxation.