Molecular spin ladders self-assembly from [Ni(dmit)2]− building blocks: Syntheses, structures and magnetic properties

Abstract

Two ion-pair compounds, consisting of 1-(4′-R-benzyl)pyridinium ([RBzPy]+, R = NO2 (1) and Br (2)) and [Ni(dmit)2]− (dmit2− = 2-thioxo-1,3-dithion-4,5-dithiolato), have been synthesized and structurally characterized. The anions of [Ni(dmit)2]− stack into dimers, which further construct into two-leg ladder through terminal S⋯S interactions in 1, lateral S⋯S interactions in 2. The weak H-bonding interactions of C–H⋯S were observed in 2, while only weak van de Waals interactions between anion and cations in 1. The magnetic susceptibilities measured in 2–300 K indicate AFM exchange interaction domination both two compounds. A peculiar magnetic transition at ∼100 K was observed in 1. An AFM ordering below ∼11 K was found in 2, and the best fit to magnetic susceptibility above 45 K in this compound, using a dimer model with s = 1/2, give rise to Δ/kB = 36.1 K, zJ = −0.91 K, C = 3.2 × 10−3 emu K mol−1 and χ0 = −4.0 × 10−6 emu mol−1 with g of 2.0 fixed.