Probing molecular and isotopic features of meteoritic insoluble organic matter by solid‐state nuclear magnetic resonance spectroscopy with sub‐milligram sample

Abstract

We recorded one‐ and two‐dimensional solid‐state nuclear magnetic resonance spectra of meteoric insoluble organic matter with unprecedented sensitivity and resolution permitting us to reveal unambiguous spectroscopic fingerprints relevant to its molecular and isotopic features. Two‐dimensional 1H‐1H and 1H‐13C correlation experiments have unveiled the spatial proximity between aliphatic and aromatic groups proving a highly branched character of a rigid macromolecular network composed of short aliphatic chains linking together small aromatic units. One‐dimensional 2H and two‐dimensional 1H‐2H correlation spectroscopy delivered evidence of significant reduction in the deuterium enrichment of aromatic species relevant to interstellar processes, proto‐planetary disk chemistry, and to determining the origin of the meteoritic insoluble organic matter. The experimental approach developed in this work opens new perspectives for systematic and nondestructive analysis at the molecular level of meteoritic insoluble organic matter even with a very small amount of sample from some particularly rare chondrites.

Deuteron-proton isotope correlation spectroscopy of molecular solids

“…For small organic molecules, sensitivity and resolution aspects of 2 H MAS NMR have previously been discussed. [19,[44][45][46][47][48][49] Rotational and reorientational dynamics of CD3 and ND3 moieties reduce the quadrupolar interactions, enabling narrow 2 H peaks to be detected. [46,48,50] Resolution can be substantially improved by acquiring the 2 H NMR spectra at high fields in conjunction with fast MAS, leading to 2 H chemical shifts as well as quadrupolar couplings to be measured and compared for different sites.…”