State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Collaborative Innovation Center of Advanced Microstructures , Nanjing University , Nanjing 210023 , China.
Department of Chemistry , University of Nebraska , Lincoln , Nebraska 68588 , United States.
J Am Chem Soc. 2018 Jun 27;140(25):7820-7826. doi: 10.1021/jacs.8b02415. Epub 2018 Jun 18.
One-dimensional (1D) spin-1 ( S = 1) chain of organic radicals with low local magnetic anisotropy may provide a better understanding of the low-dimensional magnetism. We report solid-state studies, including single crystal X-ray crystallography, of air-stable tetraazacyclophane diradical dication salt 1·2[Al(OC(CF)CH)] with a triplet ground state (Δ E ≈ 0.5 kcal mol). The magnetic behavior for 1 at low temperature is best modeled by 1D spin S = 1 Heisenberg chain with intrachain antiferromagnetic coupling of J'/ k = -5.4 K, which is associated with the interaryl C···C contacts, including π-π interactions. Zero-field splitting value, | D/ hc| ≈ 5.6 × 10 cm, for 1 is rather small; thus, the 1D chains are characterized by the high degree of isotropicity | D/2 J'| ≈ 7.5 × 10. The diradical dication salt possesses extraordinary stability with onset of decomposition at temperature of about 180 °C (∼450 K), based on thermogravimetric analysis and EPR spectroscopy.
一维（1D）自旋-1（S=1）有机自由基链具有较低的局域各向异性，可能为低维磁性提供更好的理解。我们报告了固态研究，包括单晶 X 射线晶体学，对具有三重基态（ΔE≈0.5 kcal mol）的空气稳定四氮杂环十六烷双自由基二阳离子盐 1·2[Al(OC(CF)CH)]。在低温下，1 的磁行为最好通过具有内链反铁磁耦合 J'/k=-5.4 K 的 1D 自旋 S=1 Heisenberg 链来建模，这与芳基间 C···C 接触有关，包括π-π相互作用。1 的零场分裂值|D/hc|≈5.6×10 cm 相当小；因此，1D 链的各向同性程度很高，|D/2J'|≈7.5×10。基于热重分析和 EPR 光谱，双自由基二阳离子盐具有非凡的稳定性，在约 180°C（约 450 K）时开始分解。
