Amphiphilic paramagnetic neutral gold dithiolene complexes

Abstract

The sulfiding of benzils with P₄S₁₀ in 1,3-dimethyl-2-imidazolidinone (DMI) as solvent allows for a direct synthesis of neutral radical, gold dithiolene complexes based on 1,2-bis-(4-alkoxy-phenyl)ethylene-1,2-dithiolate ligands with n-butyl, n-octyl and n-dodecyl chains. The three neutral and soluble complexes Au-OC₄, Au-OC₈ and Au-OC₁₂ exhibit a near infrared (NIR) absorption band around 1.5 μm and EPR characteristics which confirm a strong delocalization of the spin density on the electron-rich dithiolene ligands. X-Ray crystal structures of Au-OC₄ and Au-OC₁₂ are compared with those of the corresponding nickel complexes. They are characterised by segregation of the alkyl chains into layered structures with a stacking of the radical complexes into alternated spin chains, confirmed by the temperature dependence of the magnetic susceptibility which attests for antiferromagnetic interactions and a singlet ground state. Observations under polarising microscope and DSC experiments do not reveal a thermotropic behaviour for Au-OC₁₂.