Charge-transfer salts of M(mnt)2 (M=Ni, Pd, Pt, Au) with BDNT: ferromagnetic interactions in conductive (BDNT)2–[Ni(mnt)2]

Abstract

Charge-transfer salts between BDNT and M(mnt)₂ (M=Ni, Pd, Pt, and Au) have been prepared by mixing BDNT–(SbCl₆)₂ and (TBA)₂ –[M(mnt)₂ ] and by electrochemical oxidation of BDNT in TBA–[M(mnt)₂ ] solution. Almost all powdery samples of (1:1) salts show high electrical conductivity. The valence of M(mnt)₂ was determined to be –1 by the CN stretching mode, which means that the valence of BDNT is +0.5, +1, or +2. Their crystal structures are not known except for the low-conductive BDNT–[Au(mnt)₂ ]₂ , in which Au(mnt)₂ forms dimers which are arranged in crisscross stacks. Among these compounds, (BDNT)₂–[Ni(mnt)₂ ] exhibits a ferromagnetic interaction with |J|=3.4 K. It is concluded from the EPR experiment that [Ni(mnt)₂ ]^– is responsible for the ferromagnetic interaction.