Improving the performance of J-modulated ADEQUATE experiments through homonuclear decoupling and non-uniform sampling

Area of Science:

• Nuclear Magnetic Resonance Spectroscopy
• Organic Chemistry
• Analytical Chemistry

Background:

• Measuring homonuclear ¹³ C-¹³ C couplings at natural abundance is crucial for structural elucidation.
• The Adequate DoublE QUAntumTransfer Experiment (ADEQUATE) is a key technique for this purpose.
• Existing methods face challenges with F₁ digitization requirements and data acquisition efficiency.

Purpose of the Study:

• To evaluate the combined efficacy of non-uniform sampling and homonuclear decoupling (HD) for acquiring homonuclear ¹³ C-¹³ C coupling constants.
• To introduce and assess an HD technique analogous to previous 1,1-HD-ADEQUATE and 1,n-HD-ADEQUATE experiments.
• To optimize the measurement of both ¹ J_CC and ⁿ J_CC coupling constants.

Main Methods:

• Implementation of a scaling factor in the ADEQUATE pulse sequence to reduce F₁ digitization demands.
• Application of non-uniform sampling (NUS) to accelerate data acquisition.
• Introduction and integration of homonuclear decoupling (HD) into the ADEQUATE experiment.
• Testing the combined NUS and HD approach using ibuprofen as a model compound.

Main Results:

• The combination of non-uniform sampling and homonuclear decoupling significantly facilitates the acquisition of homonuclear ¹³ C-¹³ C coupling data.
• Both one-bond (¹ J_CC) and multiple-bond (ⁿ J_CC) couplings were successfully measured with improved efficiency.
• Ibuprofen served as an effective model compound for validating the enhanced experimental approach.

Conclusions:

• The integration of non-uniform sampling and homonuclear decoupling represents a significant advancement in measuring homonuclear ¹³ C-¹³ C couplings.
• This optimized ADEQUATE experiment enhances efficiency and accessibility for obtaining vital coupling constant information.
• The methodology holds promise for broader applications in structural analysis of organic molecules.