Synthesis of lanthanide(II) complexes of aryl chalcogenolate ligands: potential precursors to magnetic semiconductors

The synthesis of molecular precursors to semiconducting II-VI materials has attracted considerable attention since these materials are technologically important as optical materials and often difficult to synthesize by conventional methods. Among these are a class known as the diluted magnetic semiconductors, which are ternary alloys of conventional II-VI materials, such as HgTe, substituted with paramagnetic centers such as Mn{sup 2} or Fe{sup 2+}. These materials have a wide range of potential magnetooptic applications. The rare earth monochalcogenides LnQ (Ln=Yb, Eu, Sm; Q=S, Se, Te) are of interest in this area due to the great variety of dilute magnetic semiconductors they could be used to form, such as Hg{sub 1-x}Sm{sub x}Te, as well as for their range of magnetic properties. Conventional high-temperature syntheses of these materials, particularly those containing the heavier chalcogenides, are difficult and often hindered by impurities incorporated due to the high oxophilicity of the rare earth centers. The synthesis of precursor complexes to rare earth monochalcogenides, with the elements combined on a molecular level in the correct stoichiometry, allows for purification before pyrolytic cleavage and might afford the ability to process these materials at much lower temperatures. Reported complexes of the lathanide metals with heavier chalcogenide ligands (Se, Te) are very few, but some examples exist of stable compounds of trivalent lanthanide ions coordinated by selenium and tellerium-containing ligands, through divalent analogues have not been reported previously. The authors report here the synthesis of several members of a new class of compounds, lower chalogenide complexes of the divalent lanthanide metals, which the authors find to be promising precursors to rare earth monochalcogenides. 22 refs., 1 fig.