锰（II）和铜（II）的六氟乙酰丙酮1:1配合物与5-（4-[N-叔丁基-N-氨氧基]苯基）嘧啶：自由基和顺磁阳离子之间配合物交换行为的区域化学奇偶性分析

Manganese(II) and copper(II) hexafluoroacetylacetonate 1:1 complexes with 5-(4-[N-tert-butyl-N-aminoxyl]phenyl)pyrimidine: regiochemical parity analysis for exchange behavior of complexes between radicals and paramagnetic cations.

作者信息

Field Lora M, Lahti Paul M, Palacio Fernando, Paduan-Filho Armando

机构信息

Department of Chemistry, University of Massachusetts, Amherst, MA 01003, USA.

出版信息

J Am Chem Soc. 2003 Aug 20;125(33):10110-8. doi: 10.1021/ja0343813.

DOI:10.1021/ja0343813

PMID:12914475

Abstract

Mn(hfac)(2) and Cu(hfac)(2) form coordination complexes with 5-(4-[N-tert-butyl-N-aminoxyl]phenyl)pyrimidine, PyrimPh-NIT. (MnPyrimPh-NIT(2))(2) and (CuPyrimPh-NIT(2))(2), 1 and 2, respectively, are cyclic M(2)L(2) dimers that exhibit strong exchange coupling between the coordinated paramagnetic dication (M) and nitroxide (NIT) unit. The M-NIT exchange is strongly antiferromagnetic (AFM) in 1 and strongly ferromagnetic (FM) in 2. Magnetic susceptibility measurements for 1 were fitted to an AFM spin pairing model with J/k = -0.25 K between Mn-NIT spin sites units. Complex 2 also exhibits AFM spin pairing between S = 1 Cu-NIT spin units that is somewhat field dependent at low temperature. The fit of corrected paramagnetic susceptibility chi(T) to an AFM spin pairing model at 200 Oe yields J/k = (-)3.8 K, quite similar to earlier measurements at 1000 Oe yielding J/k = (-)5.0 K. At 1.40 K, the magnetization of 2 does not approach saturation until somewhat above 170 kOe, giving an S-shaped curve; at 0.55 K, the magnetization curve shows steps characteristic of field-induced crossover between the S = 0 ground state and excited spin states. From the steps in the 0.55 K data, we estimate J/k = (-)3.8-4.0 K for 2, in good agreement with the analysis of chi(T).

摘要

Mn(hfac)₂ 和 Cu(hfac)₂ 与 5-(4-[N-叔丁基-N-氨氧自由基]苯基)嘧啶（PyrimPh-NIT）形成配位络合物。(MnPyrimPh-NIT₂)₂ 和 (CuPyrimPh-NIT₂)₂，分别为 1 和 2，是环状 M₂L₂ 二聚体，在配位的顺磁性二价阳离子（M）和氮氧化物（NIT）单元之间表现出强烈的交换耦合。M-NIT 交换在 1 中为强反铁磁性（AFM），在 2 中为强铁磁性（FM）。对 1 的磁化率测量结果符合 Mn-NIT 自旋位点单元之间 J/k = -0.25 K 的反铁磁自旋配对模型。配合物 2 在 S = 1 的 Cu-NIT 自旋单元之间也表现出反铁磁自旋配对，在低温下有点依赖于磁场。在 200 Oe 下将校正后的顺磁磁化率 χ(T) 拟合到反铁磁自旋配对模型，得到 J/k = (-)3.8 K，与早期在 1000 Oe 下测量得到的 J/k = (-)5.0 K 非常相似。在 1.40 K 时，2 的磁化强度直到略高于 170 kOe 才接近饱和，给出一条 S 形曲线；在 0.55 K 时，磁化曲线显示出 S = 0 基态和激发自旋态之间场诱导交叉的特征台阶。根据 0.55 K 数据中的台阶，我们估计 2 的 J/k = (-)3.8 - 4.0 K，与 χ(T) 的分析结果吻合良好。