Integrated Paramagnetic Resonance of High-Spin Co(II) Systems

高自旋 Co(II) 系统的集成顺磁共振

• 批准号: 1152755
• 负责人: David Tierney
• 金额: $ 37.5万
• 依托单位: Miami University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-03-01 至 2015-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1152755&HistoricalAwards=false
• 关键词: Integrated; Paramagnetic; Resonance; Spin; Co

In this project, funded by the Chemistry Division's Chemical Structure, Dynamics and Mechanisms Program, Professor Tierney of the University of New Mexico will systematically investigate a large library of high-spin (hs) Co(II) coordination compounds with mixed N/O/S donor sets, encompassing 4-, 5- and 6-coordination. The work is founded on an integrated approach to paramagnetic resonance, simultaneously applying frozen-solution multi-frequency electron paramagnetic resonance (EPR) and fluid-solution nuclear magnetic resonance (NMR), to map the field- and temperature-dependence of electron-nuclear hyperfine interactions. EPR-based techniques are used to map ground state electron-nuclear hyperfine interactions onto three-dimensional structure. Excited state effects are examined in detail by UV-vis-NIR spectroscopy, by field- and temperature-dependent NMR relaxation and by NMRD. The resulting information will define the factors controlling electron dynamics in these electronically complex systems. Pulsed EPR techniques (ENDOR and ESEEM at both X- and Q-bands) and NMR of heteronuclei, including 11B in pyrazolylborate complexes and 19F incorporated into ligands, will be utilized to aid in solution speciation. The goal is to develop a deeper understanding of how excited state mixing determines ground state electronic properties and solution dynamics. Target molecules include a series of spin-crossover complexes, examining the role of structural dynamics in the magnetic hysteresis required for translation into functional materials.Complexes of high-spin cobalt(II) are important to the study of metals in biochemistry, as well as to modern magnetic materials and catalysts. For example, these complexes can be used as spectroscopic probes of the mechanisms of enzymatic reactions. Also, they can used to construct switchable magnets on the molecular or nano-scale. Such materials are at the frontier of research in modern computer miniaturization. A wide range of magnetic resonance techniques will be employed for determining the structural features of these interesting molecules. This research provides training opportunites for early-career scientists, as well as graduate and undergraduate researchers. Many students involved in this research have presented their research locally, and several have made presentations at regional and national meetings. Results from this research program have been incorporated into the undergraduate chemistry curriculum, including experiments that utilize low-temperature EPR, paramagnetic NMR, and X-ray structure determination.

在该项目中，由化学系的化学结构、动力学和机制项目资助，新墨西哥大学的 Tierney 教授将系统地研究具有混合 N/O/ 的高自旋 (hs) Co(II) 配位化合物的大型库。 S 供体集，包括 4-、5-和 6-配位。 这项工作建立在顺磁共振综合方法的基础上，同时应用冷冻溶液多频电子顺磁共振（EPR）和流体溶液核磁共振（NMR）来绘制电子-核的场和温度依赖性超精细相互作用。基于 EPR 的技术用于将基态电子-核超精细相互作用映射到三维结构上。通过 UV-vis-NIR 光谱、场和温度相关的 NMR 弛豫以及 NMRD 详细检查了激发态效应。由此产生的信息将定义控制这些电子复杂系统中电子动力学的因素。脉冲 EPR 技术（X 和 Q 波段的 ENDOR 和 ESEEM）和异核 NMR（包括吡唑基硼酸盐配合物中的 11B 和掺入配体中的 19F）将用于帮助溶液形态形成。目标是更深入地了解激发态混合如何决定基态电子特性和溶液动力学。目标分子包括一系列自旋交叉络合物，研究结构动力学在转化为功能材料所需的磁滞中的作用。高自旋钴 (II) 络合物对于生物化学中的金属研究以及现代磁性材料和催化剂。例如，这些复合物可以用作酶反应机制的光谱探针。 此外，它们还可用于构建分子或纳米尺度的可切换磁体。 此类材料处于现代计算机小型化研究的前沿。将采用广泛的磁共振技术来确定这些有趣分子的结构特征。这项研究为早期职业科学家以及研究生和本科生研究人员提供了培训机会。许多参与这项研究的学生在当地展示了他们的研究成果，还有一些学生在地区和国家会议上做了演讲。该研究项目的结果已纳入本科化学课程，包括利用低温 EPR、顺磁 NMR 和 X 射线结构测定的实验。