Structure of radical cations of saturated heterocyclic compounds with two heteroatoms as studied by electron paramagnetic resonance, electron-nuclear double resonance, and density functional theory calculations

Kirill B Nuzhdin; Sergej V Nesterov; Daniil A Tyurin; Vladimir I Feldman; Liu Wei; Anders Lund

doi:10.1021/jp051440l

Structure of radical cations of saturated heterocyclic compounds with two heteroatoms as studied by electron paramagnetic resonance, electron-nuclear double resonance, and density functional theory calculations

J Phys Chem A. 2005 Jul 21;109(28):6166-73. doi: 10.1021/jp051440l.

Authors

Kirill B Nuzhdin¹, Sergej V Nesterov, Daniil A Tyurin, Vladimir I Feldman, Liu Wei, Anders Lund

Affiliation

¹ Department of Chemistry, Moscow State University, 119992 Moscow Russia. krill.nuzhdin@rad.chem.msu.ru

PMID: 16833956
DOI: 10.1021/jp051440l

Abstract

The radical cations of piperazine, morpholine, thiomorpholine, and thioxane were investigated by electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) spectroscopy in a solid Freon matrix. Optimized geometry and magnetic parameters of the radical cations were calculated using a density functional theory (DFT)/Perdew-Burke-Ernzerhof (PBE) method. Both experimental and theoretical results suggest that all the studied species adopt chair (or distorted chair) conformations. No evidence for the boat conformers with intramolecular sigma-bonding between heteroatoms were obtained. In the cases of morpholine and thioxane, the oxygen atoms are characterized by relatively small spin populations, whereas a major part of spin density is located at N and S atoms, respectively. The thiomorpholine radical cation exhibits nearly equal spin population of N and S atoms. In most cases (except for thioxane), the calculated magnetic parameters agree with the experimental data reasonably well.