Structural complexity in indium selenides prepared using bicyclic amines as structure-directing agents

Abstract

The synthesis and characterization of five new indium selenides, [C₉H₁₇N₂]₃[In₅Se_8+x(Se₂)_1−x] (1–2), [C₆H₁₂N₂]₄[C₆H₁₄N₂]₃[In₁₀Se₁₅(Se₂)₃] (3), [C₆H₁₄N₂][(C₆H₁₂N₂)₂NaIn₅Se₉] (4) and [enH₂][NH₄][In₇Se₁₂] (5), are described. These materials were prepared under solvothermal conditions, using 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and 1,4-diazabicyclo[2.2.2]octane (DABCO) as structure-directing agents. Compounds 1–4 represent the first examples of ribbons in indium selenides, and 4 is the first example of incorporation of an alkali metal complex. Compounds 1, 2 and 4 contain closely related [In₅Se_8+x(Se₂)_1−x]³⁻ ribbons which differ only in their content of (Se₂)²⁻ anions. These ribbons are interspaced by organic countercations in 1 and 2, while in 4 they are linked by highly unusual [Na(DABCO)₂]⁺ units into a three-dimensional framework. Compound 3 contains complex ribbons, with a long repeating sequence of ca. 36 Å, and 4 is a non-centrosymmetric three-dimensional framework, formed as a consequence of the decomposition of DABCO into ethylenediamine (en) and ammonia.