Abstract
We have prepared two dmit-based salts with a stable organic radical-substituted ammonium cation, (PO-CONH-C2H4N(CH3)3)[Ni(dmit)2]2·CH3CN and (PO-CONH-C2H4N(CH3)3)[Pd(dmit)2]2 where PO is 2,2,5,5-Tetramethyl-3-pyrrolin-1-oxyl and dmit is 2-Thioxo-1,3-dithiol-4,5-dithiolate. The salts are not isostructural but have similar structural features in the anion and cation packing arrangements. The acceptor layers of both salts consist of tetramers, which gather to form 2D conducting layers. Magnetic susceptibility measurements indicate that the Ni salt is a Mott insulator and the Pd salt is a band insulator, which has been confirmed by band structure calculations. The cationic layers of both salts have a previously unreported polar structure, in which the cation dipoles order as ➚➘➚➘ along the acceptors stacking direction to provide dipole moments. The dipole moments of nearest neighbor cation layers are inverted in both salts, indicating no net dipole moments for the whole crystals. The magnetic network of the [Ni(dmit)2] layer of the Ni salt is two-dimensional so that the magnetic susceptibility would be expected to obey the 1D or 2D Heisenberg model that has a broad maximum around T ≈ θ. However, the magnetic susceptibility after subtraction of the contribution from the PO radical has no broad maximum. Instead, it shows Curie–Weiss behavior with C = 0.378 emu·K/mol and θ = −35.8 K. The magnetic susceptibility of the Pd salt obeys a Curie–Weiss model with C = 0.329 emu·K·mol−1 and θ = −0.88 K.
Highlights
Over the past two decades, organic magnetic conductors that combine electrical conductivity with magnetic moments have attracted great interest [1,2,3]. This is due to reports of unique and interesting properties that emerge from the interplay between itinerant and localized electrons
Λ-(BETS)2 FeCl4 (BETS = bis(ethylenedithio)tetraselenafulvalene) and its derivatives show unique physical properties such as a transition to antiferromagnetic order coupled to a metal-insulator transition, colossal magnetoresistance, field-induced superconductivity and a superconductor-to-insulator transition [1]
We report organic magnetic conductors consisting ofas salts have a dipole moment, which cancels that of the anionic layers
Summary
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