EPR spectroscopy: A versatile tool for exploring transition metal complexes in organometallic and bioinorganic chemistry

Paramagnetic molecules, such as main-group radicals and transition metal complexes, play crucial roles in catalytic and enzymatic reactions in organometallic and bioinorganic chemistry. Electron paramagnetic resonance (EPR) spectroscopy emerges as a powerful tool for probing the intricate electronic and geometric structures of these molecules. The application of EPR spectroscopy spans a wide spectrum of chemical entities, from simple radicals to transition metal complexes, metalloproteins, and metal clusters, emphasizing its versatility across various fields of chemistry. This review introduces the EPR spectra of transition metal complexes, offering a comprehensive theoretical foundation along with illustrative examples from both bioinorganic and organometallic chemistry. These examples highlight the effectiveness of EPR spectroscopy in characterizing transition metal complexes, reinforcing our understanding of their structure and reactivity.