Halogen nuclear quadrupole resonance and structural relationships in some complex halides of zinc and copper

Abstract

X-ray diffraction and halogen nuclear quadrupole resonance (n.q.r.) methods show that Rb3ZnBr5, (NH4)3ZnBr5, and CsZnI5 are isostructural with orthorhombic (NH4)3ZnCl5, and that Rb3ZnCl5 has the tetragonal Cs3CoCl5 structure. ZnI2,2NH3 is isomorphous with the corresponding chloride and bromide diammines. Rb2ZnBr4 and (NH4)2ZnBr4 have structures of Cs2ZnBr4 type, although the rubidium salt shows some stacking faults. In the complex chlorides 35Cl n.q.r. frequencies are grouped about 9 MHz, while the bromides have 81Br frequencies grouped around 60 MHz. The � → 3/2 transitions of 127I in the iodides are in the region of 76 MHz. The diammine compounds ZnBr2,2NH3 and ZnI2,2NH3 have frequencies close to the mean values for the ZnBr42- and ZnI42- ions respectively, but in the hydrates ZnCl2,l⅓H2O,ZnBr2,2H2O, β-KZnBr3,2H2O, and KZnI3,2H2O the halogen frequencies are increased. N.q.r. and X-ray data are also reported for the compound Cs3CuCl5, formed by quenching the melt. This compound slowly disproportionates at room temperature into Cs2CuCl4 and CsCl.

Correlation of Zero Field Splittings and Site Distortions III. MnBr4 2- and Crystal Structure Refinements for Rb3ZnBr5 and Cs2ZnBr4

“…Precession photographs showed the expected orthorhombic symmetry and systematic extinctions compatible with the space group Pnma or its acen tric counterpart Pna2i for both crystals as described by Morosin and Lingafelter [8] for (1) and Asker et al [9] for (2). Complete sets of intensity data up to (sin 0)/A = 0.64 A -i were collected on a Syntex P2i four-circle diffractometer equipped with a molyb denum X-ray tube, graphite monochromator and scintillation counter (AMoKa = 0.71069 A, 2 0 -0 -scan, scan speed from 3° min-1 to 30° min-1 de pending on intensity, scan range 2° in 2 0 plus K asplitting with stationary background measurements on each side, reference reflexion every 100 reflex ions) and the unit cell parameters calculated from a least squares fit of the angular settings of 15 care fully centred high order reflexions for both crystals.…”

“…This compound was found to be isomorphous with (NH4)3ZnCl5 [9] which also has the space group Pnma with 4 formula units per unit cell [12]. The crystal structure refinement converged to R\ = 0.060.…”

Role of NH4 ions in successive phase transitions of perovskite type (NH4)2ZnX4 (X = Cl, Br) by 1H MAS NMR and 14N NMR

“…In phase I (above 432 K), the structure of (NH 4 ) 2 ZnBr 4 is orthorhombic with a o ¼ 7.649Å, b o ¼ 13.353Å, c o ¼ 9.727Å, and space group Pmcn. 21,22 Upon cooling, there is a phase transition at 432 K to an incommensurate phase II that is stable down to 395 K. The structure in phase III, between 395 K and 216 K, is monoclinic with a ¼ a o , b ¼ b o , c ¼ 4c o , b ¼ 90.00(3) , and space group P2 1 / c11. 22 The low-temperature phase IV is orthorhombic with a ¼ a o , b ¼ b o , c ¼ 3c o , and space group P2 1 cn.…”

1H NMR study of molecular dynamics and phase transition in (NH4)2ZnBr4

“…(NH4),ZnBr4 belongs to this group of compounds and is known to undergo a sequence of phase transitions as given in Table 1 (Sato, Osaka and Makita, 1983). It is found to be ferroelectric below 216.5 K, and has been studied using dielectric (Moskalev, Belbrova, Zherebtsova and Alexandrova, 1982;Osaka, Kamukae and Makita, 1982) bromine NQR (Moskalev et al, 1982), Raman and light scattering ; , X-ray diffraction (Sato et al, 1983;Asker, Scaife and Watts 1972;Osaka et al 1982), DSC (Sato et al, 1983), and photoluminescence (Madhusudan Rao and Reddy, 1984) We report here the results of our proton NMR measurements in the range 77-300 K using home-made wide-line and pulsed NMR spectrometers. The temperature of the sample was controlled by a gas flow cryostat and was measured using a copper-constantan thermocouple.…”