Lanthanide Chelation Complexes and Their Solvent Clusters Probed by Cryogenic Ion Spectroscopy

Professor Mathias Weber at the University of Colorado at Boulder is investigating the molecular properties of complexes consisting of lanthanide ions and chelating agents to obtain detailed information on the structures and intermolecular forces governing the chelation of lanthanide ions. Lanthanides are of strategic importance regarding their potential applications as luminescent biomarkers as well as in spintronics and molecular qubits. However, the separation of lanthanide ions from other metals and each other after extraction from ore or electronic waste is challenging due to the similarities in their coordination chemistry. Professor Weber and his students will measure the infrared spectra of lanthanide ion-chelator complexes and their clusters with solvent molecules in the gas phase, and carry out quantum chemical calculations to determine how the presence of solvents affects the structures of the chelator complexes. The experimental data will serve as benchmarks for the quality of the description of lanthanide chemistry by quantum chemical methods. This work will advance the fundamental understanding of lanthanide chemistry and could help in developing predictive methods for the design of more selective and lanthanide chelators. Such new chelators could significantly reduce the cost of lanthanide separation and recovery. The program will provide training for graduate students in advanced instrumentation, and interpretation of the results requires the application of quantum chemistry methods. Lanthanide-chelator complexes and their solvent clusters will be studied using cryogenic ion vibrational spectroscopy. The ions are generated by electrospray ionization and cooled in a cryogenic ion trap. After cooling and nitrogen tagging, their infrared spectra are measured using photodissociation spectroscopy in a reflectron time-of-flight mass spectrometer. Representatives of early, mid, and late lanthanides, e.g., La, Eu, and Tm, respectively, will be studied with two types of chelators. The first chelator family is based on cyclen macrocycles, with tetraazacyclododecane tetraacetic acid as the main target. The second chelator group consists of polypeptides that mimic the binding pockets of lanthanide sequestering proteins, which are more selective than traditional macrocyclic chelators. Preliminary density functional theory calculations show that single solvent molecules such as water interact with both the metal ion and the chelator, and they may be crucial for the binding behavior. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria. NSF Award ID: 2619835 | Program: 01002627DB NSF RESEARCH & RELATED ACTIVIT | Principal Investigator: J Mathias Weber | Institution: University of Colorado at Boulder, BOULDER, CO | Award Amount: $560,000 View on NSF Award Search: https://www.nsf.gov/awardsearch/show-award/?AWD_ID=2619835 View on Research.gov: https://www.research.gov/awardapi-service/v1/awards/2619835.html