Feasibility of arsenic and antimony NMR spectroscopy in solids: an investigation of some group 15 compounds.

Abstract The feasibility of obtaining 75 As and 1 21/123 Sb NMR spectra for solids at high and moderate magnetic field strengths is explored. Arsenic-75 nuclear quadrupolar coupling constants and chemical shifts have been measured for arsenobetaine bromide and tetraphenylarsonium bromide. Similarly, 121/123 Sb NMR parameters have been measured for tetraphenylstibonium bromide and potassium hexahydroxoantimonate. The predicted pseudo-tetrahedral symmetry at arsenic and the known trigonal bipyramidal symmetry at antimony in their respective tetraphenyl-bromide “salts” are reflected in the measured 75 As and 121 Sb nuclear quadrupole coupling constants, C Q ( 75 As)=7.8 MHz and C Q ( 121 Sb)=159 MHz, respectively. Results of density functional theory quantum chemistry calculations for isolated molecules using ADF and first-principles calculations using CASTEP, a gauge-including projector augmented wave method to deal with the periodic nature of solids, are compared with experiment. Although the experiments can be time consuming, measurements of 75 As and 121 Sb NMR spectra (at 154 and 215 MHz, respectively, i.e., at B 0 =21.14 T) with linewidths in excess of 1 MHz are feasible using uniform broadband excitation shaped pulse techniques (e.g., WURST and WURST-QCPMG).