Field-Induced Single-Ion Magnet Phenomenon in Hexabromo- and Hexaiodorhenate(IV) Complexes

• Main Authors: Carlos Rojas-Dotti, Adrián Sanchis-Perucho, Marta Orts-Arroyo, Nicolás Moliner, Ricardo González, Francesc Lloret, José Martínez-Lillo
• Format: Article
• Language: English
• Published: MDPI AG 2020-04-01
• Series: Magnetochemistry
• Subjects: rhenium; crystal structures; AC/DC measurements; molecular magnetism; single-ion magnets
• Online Access: https://www.mdpi.com/2312-7481/6/2/20

Two mononuclear Re^IV complexes of general formula (PPh₄)₂[ReX₆] [PPh₄⁺ = tetraphenylphosphonium cation, X = Br (<b>1</b>) and I (<b>2</b>)] have been prepared and structurally and magnetically characterised. Both compounds crystallise in the triclinic system with space group <i>P</i>ī. Their structures are made up of hexahalorhenate(IV), [ReX₆]²⁻, anions, and bulky PPh₄⁺ cations. Each Re^IV ion in <b>1</b> and <b>2</b> is six-coordinate and bonded to six halide ions in a quasi regular octahedral geometry. In their crystal packing, the [ReX₆]²⁻ anions are well separated from each other through the organic cations, generating alternated anionic and cationic layers, and no intermolecular Re−X···X−Re interactions are present. Variable-temperature dc magnetic susceptibility measurements performed on microcrystalline samples of <b>1</b> and <b>2</b> show a very similar magnetic behaviour, which is typical of noninteracting mononuclear Re^IV complexes with <i>S</i> = 3/2. Ac magnetic susceptibility measurements reveal the slow relaxation of the magnetisation in the presence of external dc fields for <b>1</b> and <b>2</b>, hence indicating the occurrence of the field-induced single-ion magnet (SIM) phenomenon in these hexabromo- and hexaiodorhenate(IV) complexes.