Structural properties of mixed (NH4)2−xRbxZnCl4 (x=0, 1, and 2) crystals studied by 1H and 87Rb nuclear magnetic resonance

The structures of mixed (NH4)2−xRbxZnCl4 (x=0, 1, and 2) single crystals were determined by x-ray diffraction. In addition, the nuclear magnetic resonance (NMR) spectra and spin–lattice relaxation times of the 1H and 87Rb nuclei in the three crystals were determined using NMR spectroscopy. We analyzed the crystallographic structures of these crystals by considering the occupation probabilities (NH4 or Rb) of the two cationic sites. Our NMR results confirm that there are two crystallographically inequivalent NH4 sites, NH4(1) and NH4(2), in (NH4)2ZnCl4, and two crystallographically inequivalent Rb sites, Rb(1) and Rb(2), in Rb2ZnCl4. However, only one NH4 site and two Rb sites were observed in NH4RbZnCl4. The NH4 and Rb occupation rates of each of the two available sites, A1 and A2, were determined from the NMR signals.