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The first indirectly detected 13C−H solid-state NMR correlation spectra of species bound to a surface are reported. The experiments were performed at 14.1 T under fast (40 kHz) MAS. The sensitivity gain was demonstrated on a mesoporous silica sample containing approximately 300 μg of covalently bound allyl groups, in the absence of templating molecules and without isotope enrichment. A well-resolved two-dimensional spectrum was acquired in 15 min, which is more than 10 times faster than using direct detection of 13C nuclei.

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Solid state 13C−1H 2D HETeronuclear CORrelation spectra (Caravatti, P.; Bodenhausen, G.; Ernst, R. R. Chem. Phys. Lett. 1982, 89, 363−367. Roberts, J. E.; Vega, S.; Griffin, R. G. J. Am. Chem. Soc. 1984, 106, 2506−2512) are reported for many amino acids and peptides with 13C isotopic composition at natural abundance. These HETCOR spectra often have multiple proton cross peaks for each carbon, and these cross peaks can be extremely helpful for assigning the spectrum. Apart from peaks due to groups that have a lot of motion, the peak volumes correlate with C−H distance and can be used to estimate distances with standard derivation of 0.2 Å; the longest distances for which cross peaks are visible is 3 Å. The HECTOR pulse sequence also appears to be very useful for studying hydrogen bonding interactions, since the distances for most of C−O···H−X hydrogen bond pairs are within the range that is observable by HETCOR.

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