Solid-state NMR studies of 17O-enriched pyrophosphates

Area of Science:

• Solid-state inorganic chemistry
• Nuclear Magnetic Resonance spectroscopy

Background:

• Pyrophosphates are crucial inorganic compounds with diverse applications.
• Understanding the local atomic environment in crystalline pyrophosphates is essential for material science.
• Previous studies lacked detailed oxygen-17 (17O) NMR analysis in these materials.

Purpose of the Study:

• To investigate the local structure and electronic environment of oxygen atoms in crystalline pyrophosphates using advanced NMR methods.
• To characterize the differences between bridging and terminal oxygen atoms.
• To explore the influence of cations on oxygen environments.

Main Methods:

• 17O NMR spectroscopy was employed on 17O-enriched crystalline samples.
• High-field (17.6 T) experiments utilized triple-quantum magic-angle spinning (3QMAS) and double-rotation (DOR) techniques.
• Analysis focused on quadrupole coupling constants and chemical shifts.

Main Results:

• Distinct signals were observed for bridging (P-OB-P) and terminal (P-OT) oxygen atoms.
• Bridging oxygen atoms exhibited significantly higher quadrupole coupling constants.
• A positive correlation was found between the cationic radius and the chemical shift of terminal oxygen atoms.

Conclusions:

• 17O NMR, particularly 3QMAS and DOR, provides detailed insights into pyrophosphate structures.
• The electronic environment of oxygen atoms is strongly influenced by their bonding and neighboring cations.
• This research establishes a foundation for further solid-state NMR studies of phosphate materials.