Remote Multiproton Storage within a Pyrrolide-Pincer-Type Ligand

Area of Science:

• Organometallic Chemistry
• Coordination Chemistry
• Ligand Design

Background:

• Chemically non-innocent ligands offer unique reactivity.
• Pyrrole-based ligands are versatile building blocks in coordination chemistry.
• Protonation of π-systems can alter ligand electronic properties.

Purpose of the Study:

• To investigate proton storage capabilities of pyrrole-based trianionic pincer ligands.
• To explore the sequential protonation of titanium and zirconium complexes.
• To characterize the protonated species and understand their electronic states.

Main Methods:

• Synthesis and characterization of titanium and zirconium complexes.
• Remote protonation using bulky borate counterions.
• X-ray diffraction and NMR spectroscopy for structural and electronic analysis.

Main Results:

• A trianionic (ONO)(3-) pincer ligand accessed dianionic and monoanionic states via protonation.
• Homoleptic zirconium complex [(3H-pyr-ONO)2 Zr] was synthesized and characterized.
• Protonation of the zirconium complex demonstrated the storage of three protons.

Conclusions:

• Pyrrole-based pincer ligands can reversibly store multiple protons.
• The electronic properties of the metal center can be tuned through ligand protonation.
• This work opens avenues for developing novel proton storage materials.