Precursor Engineering for the Synthesis of Mixed Anionic Metal (Cu, Mn) Chalcogenide Nanomaterials via Solvent-Less
Temidayo Oyetunde1,2, Siphamandla Masikane3, Malik Dilshad Khan3,4
1Centre for Chemical and Biochemical Research (CCBR), Redeemer's University, Ede, P.M.B. 230, Ede, Osun State 232102, Nigeria.
Abstract:
Metal-organic ligands with mixed chalcogenides are potential compounds for the preparation of mixed anionic metal chalcogenide alloys. However, only a few of such ligands are known, and their complexes are not well explored. We have prepared homo- and hetero-dichalcogenoimidodiphosphinate [(EE'PPr2NH)] (E, E' = Se, Se; S, S; S, Se) complexes of manganese and copper through metathetical reactions. The X-ray single crystal structure of [Mn{(SePPr2)2N}2] 1 revealed a triclinic crystal system, with a MnSe4 core unit, whereas the crystal structure determination of [Mn{(SPPr2)(SePPr2)N}2] 2 indicated a triclinic crystal system with a Mn(S/Se)2 unit. Both metal centers are tetrahedral, with two deprotonated bidentate ligands forming the coordination sphere. The free ligand was found to exhibit a gauche configuration in the solid state. The energies of the various rotamers of dithio-analogue were studied by DFT calculations. The decomposition behavior of complexes with homo- and heterochalcogenides was investigated, and the complexes were employed as single-source precursors to generate manganese and copper chalcogenides through solvent-less melt reactions between 500 and 550 °C. The deposited powders were characterized by powder X-ray diffraction (p-XRD), scanning electron microscopy (SEM), energy dispersive analysis of X-ray (EDAX), transmission electron microscopy (TEM), and elemental mapping. MnS, MnSe2, and MnSSe phases were obtained from the decomposition of respective manganese complexes. In contrast, the decomposition of copper-based complexes yielded Cu2-Se and the sulfur-doped Cu3Se2 phase from seleno- and mixed thio/seleno-complexes of Cu, respectively. The morphology ranged from random sheet-like structures to agglomerated platelets, while the selected area electron diffraction (SAED) revealed the crystalline nature of the materials. Depending on the nature of the complex and the temperature, different amounts of phosphorus were present as an impurity in the synthesized products.
