The Electron and Spin Distributions and Magnetic Anisotropy in Mixed-Valent Diruthenium(V) Tetracarboxylates from Crystallography and Theory

Abstract

The determination of the electron and spin density distributions of the tetracarboxylato mixed-valent diruthenium(II,III) complex (NBu₄)[Ru₂^VBr₂(O₂CC₃H₇)₄] was carried out using high-resolution X-ray diffraction and polarized neutron diffraction (PND) on single crystals. Experimental and theoretical spin distributions show that the spin density is predominantly localized on the ruthenium atoms with some delocalization onto bromide and carboxylate ligands. The charge-density analysis supports these findings, showing charge accumulation on the metal centres and typical donor–acceptor ligand–metal interactions. Experimental topological analysis of the Ru---Ru bond confirm an open-shell metal-metal interaction. The local magnetic anisotropy was explored through angle-resolved magnetic susceptibility measurements and PND. Magnetic data reveals significant magnetic anisotropy with an easy axis along the crystallographic c axis and the hard magnetization axis along the b crystallographic axis. Local magnetic susceptibility tensors derived from PND highlight pronounced planar magnetic anisotropy oriented along the equatorial Ru-O plane. The experimentally determined anisotropy parameters are in excellent agreement with ab initio calculations.