Conversion of Metal Pyrazolate/(Hydr)oxide Clusters into Nanojars: Solution vs Solid-State Structure and Magnetism

Area of Science:

• Supramolecular Chemistry
• Coordination Chemistry
• Materials Science

Background:

• Nanojars are supramolecular metal-organic complexes ([Cu(μ-OH)(μ-pz)]n) acting as anion binding and extraction agents.
• Unlike traditional agents, nanojars self-assemble around target anions and cannot be isolated in a guest-free state.
• They exhibit extraordinary binding strength, even for highly hydrophilic anions like carbonate and sulfate, resisting precipitation by Ba2+ ions.

Purpose of the Study:

• To provide further evidence for the superior robustness of the nanojar framework.
• To characterize the structure and properties of nanojars encapsulating new anions.
• To explore the formation of molybdate-incarcerating nanojars.

Main Methods:

• Competition experiments with other transition metal complexes.
• Mass spectrometry.
• Variable-temperature nuclear magnetic resonance (NMR) studies, including analysis of paramagnetic Cu2+ influence on 1H hyperfine shifts.
• X-ray crystallography of two polymorphs of carbonate-containing nanojars.
• Magnetism studies.

Main Results:

• Demonstrated superior robustness of the nanojar framework through competition experiments.
• Characterized nanojar structures, including the highest cubic symmetry crystal lattice to date.
• Presented the first evidence of molybdate-incarcerating nanojars, formed via rearrangement of a polyoxometalate precursor in the presence of Cu2+ ions.
• Investigated the influence of paramagnetic centers on NMR spectra.

Conclusions:

• Nanojars possess a highly robust framework capable of binding and extracting various anions.
• The study expands the scope of nanojar chemistry to include molybdate anions.
• Nanojars represent a promising class of materials for anion recognition and sequestration.