New insights into the structure and chemistry of Titan%26apos;s tholins via C-13 and N-15 solid state nuclear magnetic resonance spectroscopy

作者：Derenne S^*; Coelho C; Anquetil C; Szopa C; Rahman A S; McMillan P F; Cora F; Pickard C J; Quirico E; Bonhomme C

来源：Icarus, 2012, 221(2): 844-853.

DOI：10.1016/j.icarus.2012.03.003

• Cosmochemistry
• Exobiology
• Titan
• Atmospheres, Chemistry

Tholins are complex C,N-containing organic compounds produced in the laboratory. They are considered to provide materials that are analogous to those responsible for the haze observed in Titan%26apos;s atmosphere. These compounds present an astrobiological interest due to their ability to release amino acids upon hydrolysis. Their chemical structure has been investigated using a large number of techniques. However, to date no detailed nuclear magnetic resonance (NMR) study has been performed on these materials despite the high potential of this technique for investigating the environment of given nuclei. Here C-13 and N-15 solid state NMR spectroscopy was applied to obtain new insights into the chemical structure of tholins produced through plasma discharge in gaseous N-2-CH4 mixtures designed to simulate the atmosphere of Titan. Due to the low natural abundance of these isotopes, a C-13 and N-15-enriched tholin sample was synthesized using isotopically enriched gas precursors. Various pulse sequences including C-13 and N-15 single pulse, H-1-C-13 and H-1-N-15 cross-polarisation and H-1-N-15-C-13 double cross-polarisation were used. These techniques allowed complete characterisation of the chemical and structural environments of the carbon and nitrogen atoms. The NMR assignments were supplemented and confirmed by ab initio electronic structure calculations for model structures and molecular fragments.

• 出版日期2012-12