Application of Electron Paramagnetic Resonance Spectroscopy for Studies of Prebiotic Metals and Complexes

Metals and metal-organic mixtures are hypothesized to have played a crucial role in life’s emergence, particularly at metal-rich geological settings such as hydrothermal vents. Electron paramagnetic resonance (EPR) is an important tool in chemical analysis of materials or complexes with unpaired electrons. Owing to its sensitivity to spin-orbit coupling, electron-electron magnetic interactions systems with multiple unpaired electrons, and hyperfine interactions with nuclear magnetic moments, this spectroscopic technique provides detailed information regarding the spatial arrangement of coordinating ligand fields and the hydration environments of paramagnetic species. Herein, we introduce EPR methods relevant for prebiotic chemistry studies, particularly to examine organo-metallic interactions relevant to prebiotic and early biological systems. We report on the analysis of metal–organic mixtures using primarily continuous wave EPR spectroscopy with some supplementary pulsed EPR approaches, identifying what impacts organics have on mineral analysis under early Earth relevant conditions, and examine specific ligand coordination (amino acids and quinones, among others) of three abundant paramagnetic ions of relevance to prebiotic geochemical origins of life (Fe2+, Fe3+, Mn2+). We conclude with a detailed discussion of the impacts and implications of this work on the use of EPR with laboratory-scale origins of life studies, while suggesting future directions of research within the field.