Synthesis, characterization and magnetic properties of head-to-head stacked vanadocenes

Abstract

In order to design magnetically active molecular materials, it is desirable to arrange paramagnetic molecules in one dimension, which may lead to a molecular bar magnet. For this purpose, vanadocenyl units with three unpaired electrons each can be stacked in a head-to-head fashion. The target compound in this work is 1,8-bisvanadocenyl naphthalene, where the naphthalene backbone serves as a clamp keeping two vanadocene units together. The target compound in this work is obtained through the reaction of the disodium salt of 1,8-biscyclopentadiendiylnaphthalene with the cyclopentadienyl vanadium (CpV) transfer reagent [V(μ₂-Cl)(η⁵-Cp)(thf)]₂. The 1,8-bisvanadocenyl naphthalene is fully characterized. In addition, variable temperature ¹H NMR spectroscopy, X-ray structure analysis, magnetic measurements and DFT calculations have been performed. In both experiment and theory, a weak antiferromagnetic coupling between the spin centers is found, with the spin highly localized on the V(II) ions.