Self-assembly of the tetrachlorido(oxalato)rhenate(iv) anion with protonated organic cations: X-ray structures and magnetic properties

Anders H Pedersen,Miguel Julve,Euan K Brechin,José Martínez-Lillo

doi:10.1039/c6ce02025a

Anders H Pedersen, Miguel Julve + Show 2 more

Open Access

https://doi.org/10.1039/c6ce02025a

Copy DOI

Abstract

Two novel ReIV compounds of formulae [H2bpy][ReIVCl4(ox)] (1) and [H3biim]2[ReIVCl4(ox)] (2) [H2bpy2+ = 4,4′-bipyridinium dication, H3biim+ = 2,2′-biimidazolium monocation, and ox2− = oxalate dianion] have been synthesised and magneto-structurally characterised. 1 crystallises in the monoclinic system with space group C2/c, and 2 crystallises in the triclinic system with space group P. The ReIV ion in 1 and 2 is six-coordinate, bonded to four chloride ions and two oxalate-oxygen atoms in a distorted octahedral geometry. Short intermolecular ReIV–Cl⋯Cl–ReIV contacts, Cl⋯π type interactions and hydrogen bonds are present in the crystal lattice of both compounds, generating novel supramolecular structures based on the highly anisotropic [ReIVCl4(ox)]2− species. Examination of the magnetic properties of 1 and 2 reveals significant antiferromagnetic coupling between ReIV ions propagated primarily through the ReIV–Cl⋯Cl–ReIV interactions, as evidenced by the occurrence of maxima in the magnetic susceptibility at ca. 12 (1) and 17 K (2).

Highlights

The synthesis and development of new magnetic materials based on building blocks containing paramagnetic 4d and 5d metal ions is an emerging research topic in the field of molecular magnetism.[1,2,3]
Among the 5d metal ions, the paramagnetic ReIV ion is very appealing to magnetochemists: it is a 5d3 metal ion whose ground electronic state is a 4A2g term with three unpaired electrons and a high value of the spin-orbit coupling constant
Because of the relatively large degree of spin delocalization that is spread from the ReIV ion onto its coordinated ligands,[3,30,31,32,33,34,35,36] significant magnetic interactions can be mediated by bridging ligands in polynuclear compounds, but by intermolecular contacts, even at relatively large metal-metal distances

Summary

Introduction

The synthesis and development of new magnetic materials based on building blocks containing paramagnetic 4d and 5d metal ions is an emerging research topic in the field of molecular magnetism.[1,2,3] In comparison with 3d analogues, compounds involving 4d and 5d metal ions have been scarcely investigated, despite often exhibiting significantly stronger magnetic exchange interactions on account of their more diffuse magnetic orbitals. Among the 5d metal ions, the paramagnetic ReIV ion is very appealing to magnetochemists: it is a 5d3 metal ion whose ground electronic state is a 4A2g term with three unpaired electrons and a high value of the spin-orbit coupling constant Because of the relatively large degree of spin delocalization that is spread from the ReIV ion onto its coordinated ligands,[3,30,31,32,33,34,35,36] significant magnetic interactions can be mediated by bridging ligands in polynuclear compounds, but by intermolecular contacts, even at relatively large metal-metal distances.

Methods

Results

Conclusion