Computational NMR spectroscopy of organoarsenicals and the natural polyarsenic compound arsenicin A

The (1)H and (13)C NMR chemical shifts and coupling constants of a series of organoarsenic compounds were calculated with DFT methods and compared with available experimental spectra. We show that non-relativistic methods successfully model the NMR spectra of these molecules; relativistic spin-orbit effects are small but appreciable for (13)C shifts, and their inclusion is beneficial. Application of the same methods of calculation to the intriguing natural polyarsenic compound arsenicin A allowed several viable alternative structures to be ruled out and thereby confirmed the previously suggested adamantane-like structure of arsenicin A. These results not only reinforce the known predictive power of DFT NMR calculations, but also open the way for the investigation of other naturally occurring molecules with unusual structures outside the scope of empirical methods.