IDENTIFICATION OF TRANSITION METAL ION COMPOUNDS BY ESR SPECTROSCOPY

这个子项目是利用资源的许多研究子项目之一。 由NIH/NCRR资助的中心拨款提供。对子项目的主要支持 子项目的首席调查员可能是由其他来源提供的， 包括美国国立卫生研究院的其他来源。为子项目列出的总成本可能 表示该子项目使用的中心基础设施的估计数量， 不是由NCRR赠款提供给次级项目或次级项目工作人员的直接资金。 奇里克教授感兴趣的是研究低价过渡金属离子化合物(Ti、Zr、Hf、Nb)用于固氮。为此，他合成和研究了许多化合物，如双(环戊二烯)锆络合物，并使用了包括电子自旋共振在内的各种方法进行鉴定。作为中心活动的重要服务/培训部分，Acert的工作人员培训了Chirik团队的一些研究生使用Bruker EMX ESR机器，并帮助他们分析频谱。ESR光谱清楚地表明，反应产物由两个氮原子组成，每个原子带有一个自由电子。~(13)C取代化合物的合成和通过~(13)C核进行的额外ESR谱分裂的分析提供了进一步的结构细节。除了主要产品外，ESR还检测到大量其他产品。根据它们的g-因子及其各向异性、同位素卫星谱线等，确定了产物为Zr(III)化合物。ESR也被用来定量反应产物的比率(自由基与非自由基，Zr(IV)与Zr(III))，并帮助选择有利于所需反应路线的条件。目前，针对Nb有机化合物的类似工作也在进行中。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Prof Chirik is interested in studying low-valence transition metal ion compounds (Ti, Zr, Hf, Nb) for nitrogen fixation. For this purpose he synthesized and studied a number of compounds, such as bis(cyclopentadienyl)zirconium complexes and used a variety of methods including ESR for their identification. As an important service/training component of the center activity, ACERT staff trained a number of graduate students from Chirik's group to use the Bruker EMX ESR machine and helped them with analyzing the spectra. ESR spectroscopy clearly demonstrated that the reaction products consisted of two nitrogen atoms each bearing a free electron. Synthesis of 13C substituted compounds and analysis of the additional ESR spectral splitting via 13C nuclei provided further structural details. Along with the main product, ESR detects substantial amounts of other products. Based on their g-factors and their anisotropy, isotope satellite lines etc. the products were identified as Zr(III) compounds. ESR was also used to quantify the ratio of reaction products (radical vs. non-radical, Zr(IV) vs. Zr(III)) and helped in choosing conditions favoring the desired reaction path. Similar work is now in progress for niobium organic compounds.