We have synthesized a series of lanthanide dithiocarbamate precursors for the synthesis of lanthanide sulfide materials and nanoparticles. Three dithiocarbamate complexes with europium, [Eu(S 2 CNRR′) 3 L], where L ) 1,10-phenanthroline, and R ) methyl, R′ ) ethyl (1), R ) R′ ) n Propyl (2), and R ) R′ ) i Butyl (3), as well as the lanthanide complexes, [Ln(S 2 CNR 2 ) 3 L], where R ) ethyl, L ) 1, 10-phenanthroline, and Ln ) Nd (4), Sm (5), Gd (6), Ho (7), and Er (8), were synthesized and characterized by single-crystal X-ray diffraction, infrared, NMR, and UV-visible spectroscopy. We have used thermal analysis coupled with GC-MS and X-ray powder diffraction to determine the mechanism of decomposition. With R ) Et, smaller Ln ions give lower precursor decomposition temperatures, consistent with the higher lattice energies of the product Ln sulfides. Because they are monomeric, and water-and air-stable, these compounds should be ideal precursors for forming LnS as nanoparticles and bulk materials.

We have discovered room temperature photoluminescence in Sm3+ and Pr3+ dithiocarbamate complexes. Surprisingly, these complexes exhibit more intense emission than those of the Eu3+, Tb3+, and Dy3+ analogues. The electronic absorption, excitation, and emission spectra are reported for the complexes [Ln(S2CNR2)3L] and NH2Et2[Ln(S2CNEt2)4], where Ln = Sm, Pr; R = ethyl, ibutyl, benzyl; and L = 1,10-phenanthroline, 2,2'-bipyridine, and 5-chloro-1,10-phenanthroline. The lowest ligand-localized triplet energy level (T1) of the complexes are determined from the phosphorescence spectra of analogous La3+ and Gd3+ chelates. The luminescence decay curves were measured to determine the excited-state lifetimes for the Pr3+ and Sm3+ complexes. X-ray crystal structures of Sm(S2CNiBu2)3phen, Pr(S2CNEt2)3phen, and Pr(S2CNiBu2)3phen are also reported.

EuS nanoparticles were synthesized by solution-phase thermolysis of the diethylammonium salt of the anionic europium dithiocarbamate complex, [Eu(S 2 CNEt 2 ) 4 ] -. Oleylamine and triphenylphosphine were used as surfactants to prevent nanoparticle agglomeration and stabilize particle growth. By varying the synthetic parameters such as reaction temperature, heating time, and the [surfactant]:[precursor] ratio, nanoparticles of different sizes were obtained. The size-dependent magnetic properties of these nanoparticles were studied, and it was observed that a decrease in the ferromagnetic ordering temperature occurs with decreasing particle size.

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To understand the importance of the band gap to the magnetic ordering in magnetic semiconductors, we have studied the effect of particle size on the ferromagnetic Curie temperature in semiconducting EuS. We have synthesized capped approximately 20 nm EuS nanoparticles using a single-source precursor, [Eu(S(2)CN(i)()Bu(2))(3)Phen] decomposed in trioctylphosphine. The nanoparticles have been characterized by X-ray powder diffraction, TEM, and magnetic susceptibility measurements as a function of temperature and field. The Curie temperature, based on Arrott plots, is depressed by 1-2 K from the bulk value.