Bilayer Mott System with Cation···Anion Supramolecular Interactions Based on a Nickel Dithiolene Anion Radical: Coexistence of Ferro- and Antiferromagnetic Anion Layers and Large Negative Magnetoresistance

A novel
bilayer Mott system, (Et-4BrT)­[Ni­(dmit)2]2 (Et-4BrT
= ethyl-4-bromothiazolium; dmit = 1,3-dithiole-2-thione-4,5-dithiolate),
contains two nonequivalent Ni­(dmit)2 anion layers, where
both layers form Mott insulating states. Supramolecular Brcation···Sanion and Scation···Sanion interactions play a crucial role in constructing the
bilayer structure. The ferro- and antiferromagnetic short-range-ordering
layers coexist in the crystal, which achieves large negative magnetoresistance
(Δρ/ρ0 ≈ −75% at 70 kOe)
at 5 K under 1 GPa.