Elucidation of the structural and magnetic properties of the anion-radical salt (Et-3,5-diMe-Pz)(TCNQ)2

Abstract

The intriguing structural and magnetic properties of the low-dimensional, chain-like anion-radical salt (Et-3,5-diMe-Pz)[TCNQ]₂, where Et-3,5-diMe-Pz is N-ethyl-2,6-dimethylpyrazinium and TCNQ is 7,7,8,8-tetracyanoquinodimethane, are reported. The nature of the low-temperature transition near 164 K, which may be misidentified as a traditional spin-Peierls event, is clarified with X-ray diffraction, magnetometry, specific heat studies, and numerical calculations. Specifically, this complex is identified as a spin-Peierls-like system due to a subtle intrinsic magnetic dimerisation present at room temperature. The dimerisation of the antiferromagnetic spin chains in (Et-3,5-diMe-Pz)[TCNQ]₂ predicted by DFT calculations is much stronger in the low-temperature phase (α = 0.087) than in the high-temperature phase (α = 0.628), as observed in the magnetic properties.