EaStCHEM School of Chemistry and Centre of Magnetic Resonance, University of St Andrews, St Andrews, Fife, KY16 9ST, Scotland, UK.
Sasol UK Ltd, St Andrews, Fife, KY16 9ST, Scotland, UK.
Dalton Trans. 2018 Aug 21;47(31):10473-10479. doi: 10.1039/c8dt00977e. Epub 2018 Apr 26.
The presence of multiple paramagnetic species can lead to overlapping electron paramagnetic resonance (EPR) signals. This complication can be a critical obstacle for the use of EPR to unravel mechanisms and aid the understanding of earth abundant metal catalysis. Furthermore, redox or spin-crossover processes can result in the simultaneous presence of metal centres in different oxidation or spin states. In this contribution, pulse EPR experiments on model systems containing discrete mixtures of Cr(i) and Cr(iii) or Cu(ii) and Mn(ii) complexes demonstrate the feasibility of the separation of the EPR spectra of these species by inversion recovery filters and the identification of the relevant spin states by transient nutation experiments. We demonstrate the isolation of component spectra and identification of spin states in a mixture of catalyst precursors. The usefulness of the approach is emphasised by monitoring the fate of the chromium species upon activation of an industrially used precatalyst system.
多种顺磁物种的存在可能导致电子顺磁共振（EPR）信号的重叠。这种复杂性可能是使用 EPR 来阐明机制和帮助理解地球丰富金属催化的关键障碍。此外，氧化还原或自旋交叉过程可能导致不同氧化态或自旋态的金属中心同时存在。在本研究中，对含有离散的 Cr(i) 和 Cr(iii) 或 Cu(ii) 和 Mn(ii) 配合物混合物的模型系统进行了脉冲 EPR 实验，证明了通过反转恢复滤波器分离这些物种的 EPR 谱以及通过瞬态摆动实验确定相关自旋态的可行性。我们证明了在催化剂前体混合物中分离组分谱并鉴定自旋态。通过监测工业用前催化剂体系激活后铬物种的命运强调了该方法的有用性。
