Ultra-Wideline 2D Correlations Among Low-γ Species in Solid-State NMR via the Progressive Saturation of a Common...

Ultra-wideline nuclear magnetic resonance (NMR) spectra arising from large chemical shift anisotropy and/or quadrupolar broadening can span several MHz, rendering two-dimensional (2D) correlations between low-γ nuclei subject to these interactions exceptionally challenging. The limited pulse excitation bandwidth, poor sensitivity, and weak internuclear couplings make correlations between such spins nearly impossible in practice. To deal with such cases, this study introduces the PROgressive Saturation of the Protons Enhanced Correlation Technique (PROSPECT) experiment. PROSPECT correlates the powder spectra of low-γ nuclei through their independent dipolar interactions with a common ¹H reservoir, without requiring direct coupling between the correlated spins. 2D homonuclear and heteronuclear correlations are demonstrated experimentally using this method between ¹⁹⁵Pt and ¹⁴N spins, dealing with resonances that span over 1 MHz. Spin dynamic numerical simulations reproduce very well the experimental 2D line shapes, and support our physical description of the method. In this way, PROSPECT extends multidimensional solid-state NMR to regimes previously considered inaccessible, enabling correlations between ultra-wideline anisotropic interactions.