Lanthanide-Centered Polyoxoalkoxide Complexes Provide a Platform for Systematic Room- and Variable-Temperature...

Area of Science:

• Inorganic Chemistry
• Materials Science
• Supramolecular Chemistry

Background:

• Lanthanide (Ln) containing polyoxometalates are of interest for their unique electronic and magnetic properties.
• Previous Ln-containing polyoxometalate series often exhibit structural variations across the lanthanide series.
• The development of isostructural Ln-polyoxometalates is crucial for systematic studies and applications.

Purpose of the Study:

• To synthesize a complete series of lanthanide-containing polyoxoalkoxide sandwich-type complexes.
• To investigate the structural and spectroscopic properties of these complexes.
• To explore the potential of these complexes for 17O NMR thermometry.

Main Methods:

• High-yielding synthesis of (TBA)3[M{Mo5O13(OMe)4NO}2] complexes (M = La-Lu, except Pm).
• Characterization using solution-state 1H/17O NMR, IR spectroscopy, cyclic voltammetry, and electronic absorption spectroscopy.
• Single crystal X-ray diffraction for new derivatives (Tm, Yb, Lu, Y).

Main Results:

• All synthesized (TBA)3[M{Mo5O13(OMe)4NO}2] complexes are isostructural in the solid-state, a unique feature attributed to the large tetrabutylammonium cations.
• Solution-state NMR revealed significant lanthanide-induced shifts (100-2000 ppm) for 17O nuclei directly bound to the Ln center.
• Variable temperature 17O NMR spectroscopy demonstrated a notable temperature dependence of these chemical shifts.

Conclusions:

• The synthesized lanthanide polyoxometalate series offers a structurally uniform platform for fundamental studies.
• The observed temperature-dependent 17O NMR signals present a promising avenue for developing 17O NMR thermometers.
• This work expands the scope of lanthanide-containing polyoxometalates and their potential applications in sensing.