Metallocenium Salts of Radical Anion Bis(Dichalcogenate) Metalates

Abstract

For the last 30 years metal-bis(1,2-dichalcogenate) anionic complexes have been extensively used as building blocks for the preparation of both conducting and magnetic molecular materials. Several of these materials show remarkable features and have made a significant contribution to the development of molecular materials science. It is worth mentioning some examples of the molecular materials based on metalbis(1,2-dichalcogenate) anionic complexes based that have made a significant contribution to the field of molecular material science, in the last decades. A large number of molecular conductors and even superconductors based on metal-bis(1,2dichalcogenate) anionic acceptors have been obtained [1] and Me4N[Ni(dmit)2]2 (dmit = 1,3-dithiol-2-thione-4,5-dithiolate) was the first example of a π acceptor superconductor with a closed-shell donor [2]. The spin-Peierls transition was observed for the first time in the linear spin chain system TTF[Cu(tdt)2] [3] (TTF = tetrathiafulvalene; tdt = 1,2-ditrifluoromethyl-1,2-ethylenedithioate). The coexistence of linear spin chains and conducting electrons, was observed for the first time in the compounds Per2[M(mnt)2] (M = Ni, Pd, Pt) [4] (mnt = 1,2-dicyano1,2-ethylene-dithiolato), presenting competing spin-Peierls and Peierls instabilities of the spin chains and 1D conducting electronic systems. A purely organic system with a spin-ladder configuration was observed for the first time in the compound DT-TTF2[Au(mnt)2] [5] (DT-TTF = dithiophentetrathiafulvalene). A spin transition was observed in the compound [Fe(mnt)2rad] [6], where rad = 2-(p-N-methylpyridinium)4,4,5,5-tetramethylimidazoline-1-oxyl. Ferromagnetic ordering was reported for NH4[Ni(mnt)2]H2O [7]. The discovery of the first molecule-based material exhibiting ferromagnetic ordering, the electron-transfer (ET) salt [Fe(Cp*)2]TCNE (TCNE = tetracyanoethylene), with TC = 4.8 K, in 1986 [8, 9], was a landmark in molecular magnetism and gave a significant impulse to this field. Since then among the strategies followed to obtain cooperative magnetic properties, considerable attention has been given to the linear-chain electron-transfer salts based on metallocenium donors and on planar acceptors. [10, 11]. Besides [Fe(Cp*)2]TCNE, bulk ferromagnetism was reported