Nuclear magnetic resonance chemical shifts in alkali iodides, cuprous halides and silver halides

Abstract

NMR chemical shifts of 63Cu, 65Cu, 35Cl, 79Br and 127I nuclei in cuprous halides (CuCl, CuBr and CuI) and silver halides (AgCl, AgBr and AgI) were determined accurately at 294 K using magic-angle-spinning of the sample. The mechanisms of the chemical shifts are discussed qualitatively in terms of the ionic radii and electronegativities. We propose four factors determining the chemical shifts; the nearest neighbor interaction, the next nearest neighbor interaction, isolation and the covalency effect. Temperature dependences of the metal and halogen chemical shifts in alkali iodides, cuprous halides and silver halides were measured for static samples. Positive temperature dependences are observed in LiI ( 7Li and 127I), NaI ( 23Na and 127I), cuprous halides (halogen nuclei), and AgI ( 127I). On the other hand, the dependence is negative in KI ( 39K and 127I), RbI ( 87Rb and 127I), CsI ( 133Cs and 127I), cuprous halides ( 63Cu), AgCl ( 35Cl), and AgBr ( 79Br). These temperature dependences are interpreted qualitatively in terms of lattice vibration, lattice expansion and cation motion.