Observation of metal ion dependent packing structures and magnetic behaviors of metal-bis-1, 2-dithiolene complexes

Abstract

The crystal structures and magnetic properties were investigated experimentally and theoretically for two S = ½ spin chain complexes, which consist of [M(mnt)₂]⁻ (M = Pt for 1 or Pd for 2) with 1-(4′-bromo-2′-flurobenzyl)-4-aminopyridinium (1-BrFBz-4-NH₂Py⁺). The 1-BrFBz-4-NH₂Py⁺ cations exhibit different molecular conformations and arrangements in 1 and 2; the [M(mnt)₂]⁻ anions form regular stacks in 1, whereas they form irregular stacks in 2. In addition, the intermolecular interactions between the [M(mnt)₂]⁻ anions and cations are also different from each other in the crystals of 1 and 2. Complex 1 shows the magnetic characteristics of a low-dimensional antiferromagnetic coupling spin system with a spin-Peierls-type transition around 7 K, and complex 2 exhibits diamagnetism over the temperature range of 5–300 K. Theoretical analyses, based on the calculations for the charge density distributions of [Pt(mnt)₂]⁻ and [Pd(mnt)₂]⁻ anions and the magnetic exchange constants within the anion spin chains, addressed the diverse molecular alignments in the crystals of 1 and 2 and distinct magnetic behaviors between 1 and 2.