Structure, phase transition and properties of the one-dimensional antiferromagnet Cu(2,6-dimethylpyrazine)Br2.

Fei Ding,Bingying Pan,Dehua Wang,Hui Zheng,Xiangnan Gong,Lingli Li,Chuanlu Yang,Lichun Zhang,Xiaoyu Zhou

doi:10.1039/d1ra02318g

Abstract

We report the crystal structure and properties of the one-dimensional S = 1/2 antiferromagnet Cu(2,6-dimethylpyrazine)Br2 with strong intra-chain exchange. At room temperature, its linear spin chains are formed by Cu2+ ions via the non-bonding Br⋯Br contacts. Interestingly, a phase transition from Pmmn to P21/n structure occurs at TS ≈ 248 K below which the [CuBr2]n spin chains become non-linear and the magnetic susceptibility abruptly increases, reflecting the weakening of antiferromagnetic exchange strength. This result evidences the Goodenough–Kanamori rules which claim that a linear super-exchange pathway produces stronger antiferromagnetic coupling. From magnetic susceptibility measurements we find the average intra-chain exchange strength is J/kB ≈ −88.18 K in the low temperature phase. Both magnetic and specific measurements show the absence of magnetic ordering down to 2 K, implying the excellent magnetic one-dimensionality of Cu(2,6-dimethylpyrazine)Br2. We also performed ultra-violet (UV) absorption and photoluminescence measurements which give a semiconducting band gap Δ ≈ 2.79 eV which is consistent with theoretical calculations.

Highlights

A phase transition from Pmmn to P21/n structure occurs at TS z 248 K below which the [CuBr2]n spin chains become non-linear and the magnetic susceptibility abruptly increases, reflecting the weakening of antiferromagnetic exchange strength
From magnetic susceptibility measurements we find the average intra-chain exchange strength is J/kB z À88.18 K in the low temperature phase
The synthesis and physical properties of coordination polymer complexes with the chemical formula LCuX2 (L 1⁄4 organic ligand, X 1⁄4 halide ions) is an important subject of inorganic chemistry, because these materials play a crucial role for understanding the pathway of magnetic interactions

Summary

Introduction

The synthesis and physical properties of coordination polymer complexes with the chemical formula LCuX2 (L 1⁄4 organic ligand, X 1⁄4 halide ions) is an important subject of inorganic chemistry, because these materials play a crucial role for understanding the pathway of magnetic interactions. We report the crystal structure and properties of the one-dimensional S 1⁄4 1/2 antiferromagnet Cu(2,6dimethylpyrazine)Br2 with strong intra-chain exchange.

Results

Conclusion