Novel Inorganic−Organic-Layered Structures:  Crystallographic Understanding of Both Phase and Morphology Formations of One-Dimensional CdE (E = S, Se, Te) Nanorods in Ethylenediamine

A novel class of inorganic−organic-layered structures, CdE·0.5en (E = S, Se, Te; en = ethylenediamine), were obtained through reactions between elemental S, Se, or Te and Cd²⁺ at appropriate solvothermal temperatures. These compounds contain atomic sheets of inorganic CdE frameworks spaced by ethylenediamine molecules, which serve as bridged ligands between two Cd atoms in neighboring inorganic layers and also prevent these inorganic slabs from collapsing and condensing into the bulk CdE phase. From the structural viewpoint, the essential mechanism for the formation of CdE nanorods in ethylenediamine-mediated solvothermal synthesis and the unique striated morphologies of the CdE products obtained through post-hydrothermal treatment of the CdE·0.5en layered precursors were revealed. The structure-selective crystallization of II−VI compound semiconductors in ethylenediamine under conditions of direct solvothermal synthesis or during the postconversion of the layered precursors was also explained on the basis of the similarity in atomic connectivity between the inorganic slabs in the precursors and those in wurtzite or zinc-blende phases. In addition, the CdE·0.5en precursors, which possess strong quantum-confinement effects resulting from their special inorganic−organic structures with alternating CdE and ethylenediamine layers, provide further possibilities of tailoring their electronic, magnetic, and optical properties through the structural modification of either the inorganic or the organic components.