Probing Jahn-Teller distortions in Mn(acac)₃ through paramagnetic interactions in solid-state MAS NMR

Area of Science:

• Solid-state chemistry
• Coordination chemistry
• Materials science

Background:

• Solid coordination compounds possess diverse applications.
• Transition metals with unpaired spins influence local structural environments.
• Solid-state Nuclear Magnetic Resonance (NMR) is sensitive to these environments.

Purpose of the Study:

• To demonstrate the utility of solid-state NMR for characterizing paramagnetic coordination compounds.
• To elucidate the structural and electronic properties of tris(acetylacetonato)manganese(III) (Mn(acac)3).
• To explore the relationship between electronic structure, crystal structure, and NMR spectral shifts.

Main Methods:

• Magic Angle Spinning (MAS) NMR spectroscopy (13C and 1H) was employed.
• Density-functional theory (DFT) calculations were used for spectral assignment.
• Analysis of spin-density distribution through NMR probing.

Main Results:

• NMR spectra of Mn(acac)3 showed enhanced resolution due to paramagnetic interactions.
• Spectral assignments were successfully established using combined theoretical and experimental approaches.
• NMR analysis provided insights into the molecular electronic structure and spin-density distribution.

Conclusions:

• Solid-state NMR is a powerful tool for probing local structures in paramagnetic coordination compounds.
• The paramagnetic interaction in Mn(acac)3 acts as a spectral fingerprint.
• Jahn-Teller distortions in Mn(acac)3 correlate with electron occupancy, crystal structure, and 13C NMR shifts.