Lumpe H, Menke A, Haisch C, Mayer P, Kabelitz A, Yusenko KV, Buzanich AG, Block T, Pöttgen R, Emmerling F, Daumann L
Chemistry – A European Journal (04 June 2020)
Lanthanides (Ln) are critical raw materials, however, their mining and purification have a considerable negative environmental impact and sustainable recycling and separation strategies for these elements are needed. In this study, we present the precipitation and solubility behavior of Ln complexes with Pyrroloquinoline quinone (PQQ), the cofactor of recently discovered lanthanide (Ln) dependent methanol dehydrogenase (MDH) enzymes. In this context, we have been able to elucidate the molecular structure of a bio‐relevant europium PQQ complex for the first time outside a protein environment. The complex crystallizes as an inversion symmetric dimer, Eu 2 PQQ 2 , with binding of Eu in the biologically relevant pocket of PQQ. LnPQQ and Ln1Ln2PQQ complexes are characterized using Inductively Coupled Plasma Mass Spectrometry (ICP‐MS), Infrared (IR) spectroscopy, 151 Eu‐Mössbauer spectroscopy, X‐ray total scattering, and Extended X‐ray Absorption Fine Structure (EXAFS). We show that a natural enzymatic cofactor is capable to achieve separation by precipitation of the notoriously similar, and thus difficult to separate, lanthanides to some extent.