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

Abstract

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; dmit²⁻ = 1,3-dithiole-2-thione-4,5-dithiolate), have been investigated. Complex 1 crystallizes in the monoclinic space group P2₁/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 χ ₀ = 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.

Keywords:

• Bis(1,3-dithiole-2-thione-4,5-dithiolate)nickelate monoanion
• Crystal structure
• Magnetic property

Acknowledgments

The authors thank the Science and Technology Department of Jiangsu Province and NSFC of China for financial support (Grant Nos: BK2007184, 20871068, and 10774076). X. M. Ren thanks Professor Akutagawa for the magnetic susceptibility measurements.