Weak nuclear spin singlet relaxation mechanisms revealed by experiment and computation

Area of Science:

• Nuclear Magnetic Resonance (NMR) Spectroscopy
• Quantum Information Science
• Computational Chemistry

Background:

• Nuclear spin singlet states offer potential for long-lived nuclear magnetization storage.
• Applications in spectroscopy, imaging, and dynamic processes are hindered by difficulty in predicting polarization lifetimes.
• Understanding factors influencing singlet state lifetimes is crucial for harnessing their potential.

Purpose of the Study:

• To investigate and accurately predict proton singlet lifetimes in ethyl-d5-propyl-d7-maleate.
• To validate the use of molecular dynamics (MD) simulations and ab initio calculations for determining NMR relaxation mechanisms.
• To identify key factors limiting singlet state lifetimes.

Main Methods:

• Combined experimental and computational approach.
• Utilized molecular dynamics simulations and ab initio calculations.
• Studied proton singlet lifetimes in ethyl-d5-propyl-d7-maleate dissolved in deuterated chloroform.

Main Results:

• Achieved precise correspondence between experimental and simulated proton singlet lifetimes without adjustable parameters.
• Identified dipolar couplings to low-gamma solvent nuclei as a significant lifetime-limiting factor.
• Highlighted the role of residual paramagnetic species in reducing singlet state lifetimes.

Conclusions:

• Molecular dynamics simulations and ab initio calculations can accurately predict NMR singlet lifetimes.
• Unusual mechanisms, including solvent couplings and paramagnetic impurities, are critical determinants of singlet state longevity.
• MD simulations provide powerful insights into under-explored NMR relaxation mechanisms.