Enhancing NMR Sensitivity of Naturalâ Abundance Lowâ γ Nuclei by Ultrafast Magicâ Angleâ Spinning Solidâ State NMR Spectroscopy

Abstract

Although magicâ angleâ spinning (MAS) solidâ state NMR spectroscopy has been able to provide piercing atomicâ level insights into the structure and dynamics of various solids, the poor sensitivity has limited its widespread application, especially when the sample amount is limited. Herein, we demonstrate the feasibility of acquiring high S/N ratio naturalâ abundance 13Câ NMR spectrum of a small amount of sample (â 2.0â mg) by using multipleâ contact cross polarization (MCP) under ultrafast MAS. As shown by our data from pharmaceutical compounds, the signal enhancement achieved depends on the number of CP contacts employed within a single scan, which depends on the T1Ï of protons. The use of MCP for fast 2D 1H/13C heteronuclear correlation experiments is also demonstrated. The significant signal enhancement can be greatly beneficial for the atomicâ resolution characterization of many types of crystalline solids including polymorphic drugs and nanomaterials.Sensitive nuclei: Significant signal enhancement is achieved by multipleâ contact crossâ polarization under ultrafast magicâ angleâ spinning experiments on solids.