Two spin systems based on [Ni(dmit) ₂] ^- building blocks exhibiting 1-D chain and 2-D sheet structures: Crystal structures and magnetic properties

The crystal structures and magnetic properties for two ion-pair complexes, [MG][Ni(dmit) ₂] (1) and [RhB][Ni(dmit) ₂] (2) (MG ⁺ = N-(4-((4-(dimethylamino)phenyl)(phenyl)methylene)cyclohexa-2,5-dienylidene)-N-methylmethanaminium, RhB ⁺ = 9-(2-carboxyphenyl)-3,6-bis(diethylamino)xanthylium; dmit ^2- = 1,3-dithiole-2-thione-4,5-dithiolate), have been investigated. Complex 1 crystallizes in the monoclinic space group P2 ₁/c, the stacking interactions between the GM ⁺ and [Ni(dmit) ₂] ^- lead to the anion exhibiting a banana-shaped molecular geometry; the neighboring anions form a 1-D alternating chain along the crystallographic [1 1 0] direction via intermolecular lateral-to-lateral and head-to-head S · · · S contacts. The temperature dependence of magnetic susceptibility from 2-350 K does not display the magnetic character of a 1-D chain; the magnetic susceptibility data were fit to the Curie-Weiss equation to give C = 0.351(15) emu K mol ^-1, θ = -3.51(28) K, and χ0 = 8.00(3) × 10 ^-5 emu mol ^-1. Complex 2 belongs to the triclinic space group P-1 with two crystallographic inequivalent [Ni(dmit) ₂] ^- anions, which exhibit perfect planar geometry. Two ethyl groups of RhB ⁺ are disordered over two positions at 296 K, and one becomes ordered at 150 K. The [Ni(dmit) ₂] ^- anions form a 2-D molecular layer via intermolecular lateral-to-lateral and head-to-lateral S · · · S interactions with the anionic layer parallel to the crystallographic (0 1 -1) plane. The temperature variation of magnetic susceptibility from 2 to 350 K shows that antiferromagnetic coupling dominates in the anionic layer, and the disorder-order changes of cationic structure are not coupled to magnetic property.