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

The feasibility of obtaining As-75 and Sb-121/123 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, Sb-121/123 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 As-75 and Sb-121 nuclear quadrupole coupling constants, CQ(As-75)=7.8 MHz and Cd 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 As-75 and Sb-121 NMR spectra (at 154 and 215 MHz, respectively, i.e., at Bo= 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). (C) 2014 Elsevier Inc. All rights reserved.