Using a Ni2+ complex as a structure-directing molecule: solvothermal synthesis and properties of [Ni(en)(tren)]4Sb14S25 featuring an unprecedented three-dimensional network architecture

Abstract

The new thioantimonate [Ni(en)(tren)]₄Sb₁₄S₂₅ (1) (tren = tris(2-aminoethyl)amine, en = ethylendiamine) was synthesized under solvothermal conditions using the complex [Ni(en)₃]Cl₂ as a structure-directing molecule in a slurry of Sb, S and tren as solvent. Under these reaction conditions two of the three en ligands in the [Ni(en)₃]Cl₂ complex are exchanged by one tren molecule. Compound 1 crystallises in the monoclinic space group P2₁/c with 4 formula units in the unit cell. Four unique Ni²⁺ complexes are chelated by one tetradentate tren and one bidentate en molecule. The three-dimensional ³_∞[Sb₁₄S₂₅]⁸⁻ anion is constructed by interconnection of [SbS₃] and [SbS₄] units forming [Sb₂S₂], [Sb₃S₃], [Sb₁₄S₁₄] and [Sb₂₀S₂₀] heterorings as the next hierarchical building groups. The two largest rings are condensed to form the three-dimensional thioantimonate(III) anions. Three different types of channels are identified with diameters of about 7 × 9, 9 × 17, and 8 × 9 Å. The Ni²⁺ complexes occupy the channels and are located above and below the [Sb₁₄S₁₄] and [Sb₂₀S₂₀] heterorings.