A simple and general method to determine reliable pseudocontact shifts in lanthanide complexes

Area of Science:

• Nuclear Magnetic Resonance (NMR) Spectroscopy
• Structural Biology
• Computational Chemistry

Background:

• Pseudocontact shifts (PCS) in paramagnetic NMR provide crucial geometric insights for solution-state molecular structure determination.
• Separating PCS from Fermi contact (FC) shifts traditionally requires linearization methods dependent on isostructurality and Bleaney's constants, often limiting applicability.
• Existing methods struggle with labile sites and lower symmetry complexes.

Purpose of the Study:

• To generalize a recently developed model-free method for separating PCS and FC shifts.
• To overcome the reliance on isostructurality and Bleaney's constants for geometric analysis.
• To enable accurate geometric determinations in solution for a broader range of molecular systems, including those with lower symmetry.

Main Methods:

• Generalization of a model-free linearization method for PCS/FC shift separation.
• Application to complexes with reduced symmetry beyond axial symmetry.
• Validation against established ab initio computational approaches.

Main Results:

• Successful generalization of the model-free method to lower symmetry complexes.
• Demonstrated independence from structural hypotheses and assumptions like isostructurality.
• High agreement between the proposed method's results and accurate ab initio calculations.

Conclusions:

• The developed model-free method offers a robust and versatile approach for accurate geometric determination using paramagnetic NMR.
• This advancement expands the utility of NMR spectroscopy for structural analysis, particularly for challenging systems.
• The method provides a reliable alternative to traditional techniques, enhancing structural biology and chemical research.