Ab initio molecular dynamics study of sodium NMR chemical shifts in the methylamine solution of [Na+ [2.2.2]cryptand Na−]. Issue 1 (22nd December 2020)

• Record Type: Journal Article
• Authors: Abella, Laura; Philips, Adam; Autschbach, Jochen
• Is Part Of: Physical chemistry chemical physics. Volume 23:Issue 1(2020)
• Page Start: 339
• Page End: 346
• Publication Date: 2020-12-22
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/d0cp06012g
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : NMR shielding constants for Na − and Na + are computed and analyzed based on ab initio molecular dynamics of [Na + [2.2.2]cryptand Na − ] in methylamine. The analysis shows why solvated sodite ions exhibit free ion-like behavior in NMR experiments. Abstract : The sodium anion (Na − ) was once thought to behave like a 'genuine' anion, with both the [Ne] core and the 3s valence shell interacting very weakly with their environments. In the present work, following a recent study of the surprisingly small quadrupolar line widths of Na −, NMR shielding calculations were carried out for the Na − /Na + [2.2.2]cryptand system solvated in methylamine, based on ab initio molecular dynamics simulations, followed by detailed analyses of the shielding constants. The results confirm that Na − does not act like a quasi-free ion that interacts only weakly with its surroundings. Rather, the filled 3s shell of Na − interacts strongly with its chemical environment, but only weakly with the ion's own core and the nucleus, and it isolates the core from the chemical environment. As a consequence, the Na − ion appears in NMR experiments like a free ion.