Octacyanotungstate (V)-based square [W2Mn2] complexes: Effect of intermolecular interaction on molecule-based magnetism

In this research, the synthesis, structure and magnetic properties of an ion-pair complex {[MnII(hmp)2]2(Cl)2}{[MnII(hmp)2WV(CN)8]2} (1) (hmpH = 2-hydroxymethylpyridine) are reported. Complex 1 was prepared by [W (CN)8]3− reacting with Mn(II) salt and hmpH in MeCN solution. Single-crystal X-ray diffraction shows that 1 is crystallized in triclinic system with a space group of P-1 and its structure consists of four parts of two chlorine-bridged [Mn2] cations and two tetrameric [Mn2W2] anionic clusters. The cationic [Mn2] and anionic [Mn2W2] moieties each are connected by π–π stacking to form their own layer. The packing of cations and anions layer by layer via molecular electrostatic potential, Van der Waals force and hydrogen bonding constructs a three-dimensional supramolecular framework. The magnetic analyses show the antiferromagnetic coupling interaction between MnII and WV or MnII and MnII in both parts. No evidence of single-molecule magnet or long-range ordering is observed in the data. By comparing to an analog with spin glass properties, we draw a conclusion that the differences of crystal packing mode, especially the π–π stacking within each layer, could be a key factor for the distinct magnetic properties.

Graphical abstractIon-pair complex of {[MnII(hmp)2]2(Cl)2}{[MnII(hmp)2WV(CN)8]2} (hmpH = 2-hydroxymethylpyridine) with square construction was synthesized by [W(CN)8]3− reacting with Mn(II) salt and hmpH in MeCN solution. The magnetic analyses show the antiferromagnetic coupling between metal ions and the influence of π–π stacking on the magnetic properties was investigated.Figure optionsDownload full-size imageDownload as PowerPoint slide