Experimental and theoretical study of the spin ground state of the high-spin molecular cluster [Ni II{Ni II(CH 3OH) 3} 8(μ-CN) 30{W V(CN) 3} 6] · 15CH 3OH by polarised neutron diffraction and density functional theory calculations

Abstract

Exchange mechanisms in the high-spin molecular cluster [Ni II{Ni II(CH 3OH) 3} 8(μ-CN) 30{W V(CN) 3} 6] · 15CH 3OH have been investigated by a combination of polarised neutron diffraction studies on a single crystal and theoretical calculations. The experimental spin density has been deduced from a model refinement on the basis of magnetic structure factors collected at 1.6 K under a field of 5 T. Positive spin populations were observed on both, the nickel and the tungsten sites, which provides an evidence of ferromagnetic Ni II–W V exchange interactions through the cyano bridge. A positive spin density was also observed on nitrogen atoms of the bridging cyano groups indicating a spin delocalisation mechanism. The mean experimental spin populations are in good agreement with the calculated ones, obtained by using the NBO method and the B3LYP functional. The theoretical evidence for ferromagnetic Ni II–W V interactions was also given by calculations of the exchange coupling constants on the whole complex.