Influence of Rare Earth Elements on Prebiotic Reaction Networks Resembling the Biologically Relevant Krebs Cycle

Rare earth elements (REEs) are not rare, but rather abundant in the earth's crust and excellent catalysts for a multitude of organic reactions. They have been recently shown to be used in the active sites of bacterial enzymes and thus essential for metabolic processes. However, these elements have so far been disregarded with respect to their possible contributions to the emergence of complex molecules. Here, we investigate the potential of REEs to act as mediators in a prebiotic reaction network resembling the biological Krebs cycle starting from glyoxylate and pyruvate. Special focus is put on a comparison between trivalent REEs and ferrous iron. Reaction products were analyzed by gas chromatography-mass spectrometry (GC-MS) and nuclear magnetic resonance (NMR) spectroscopy. Contrary to Fe²⁺, the formation of the reduced starting materials seems to be a major pathway when REEs are involved. Their high coordination numbers, flexible coordination spheres and their hard Lewis acidic properties make REEs excellent reagents in abiotic chemical reaction networks resembling conserved biochemical pathways.