Yoshihiro Furukawa

35Cl NQR and 1H NMR studies of [C(NH2)3]AuCl4, [C(NH2)3]2PtCl4, and [C(NH2)3]2PdCl4

Abstract The temperature dependence measurements of 35 Cl NQR frequencies and 1 H NMR spin-lattice relaxation time T 1 were carried out for guanidinium tetrachloro-aurate(III), -platinate(II), and -palladate(II). The gold(III) complex showed four NQR lines at various temperatures between 77 and 344 K, while the platinum-(II) and palladium(II) complexes gave two NQR lines in the temperature ranges 77–169 K and 77–220 K, respectively. An unusual phase transition was located at 363 K for the gold(III) complex. The high-temperature phase was easily supercooled. All the complexes studied yielded a T 1 minimum attributable to the reorientation of the planar cation about its C 3 axis. The motional parameters were evaluated. The Zeeman-quadrupole cross relaxation between protons and chlorine nuclei was observed for the platinum(II) and palladium(II) complexes at various temperatures below room temperature, while it was also detected for the high-temperature phase of the gold(III) complex.

Phase transitions and ionic motions in ammonium potassium hexafluoroaluminates(III) with compositions of (NH4)3−xKx[AlF6] (x = 1,2) as studied by 1H, 19F, and 27Al nuclear magnetic resonance

Abstract Phase transitions and ionic motions in ammonium potassium hexafluoroaluminates (III) with compositions of (NH4)3−xKx[AlF6] (x = 1,2) were characterized by means of differential thermal analysis (DTA) and NMR of 1H, 19F, and 27Al nuclei. It was found by powder X-ray diffraction that the x = 2 composition ( a = 8.64 2 A ) as well as the x = 1 composition crystallize in a face-centered cubic structure at room temperature. From DTA experiments, phase transitions were located at 250 and 186 K for the x = 1 composition and at 170 K for the x = 2 composition. The temperature dependences of the spin-lattice relaxation times T1 of 1H, 19F, and 27Al NMR were well interpreted in terms of overall reorientations of NH+4 and [AlF6]3− ions. The phase transition mechanisms are briefly discussed in relation to the crystal structures and the molecular motions of the NH4+ and [AlF6]3− ions. Preliminary results of DTA and powder X-ray diffraction are reported for several nonstoichiometric compositions of (NH4)3−xKx[AlF6](0

Electrical conductivity due to ammonium ion transport in (NH4)3[MF6] (M:Al, Ga, In) and (NH4)2K[AlF6] crystals

Abstract The electrical conductivity σ of (NH 4 ) 3 [AlF 6 ] and (NH 4 ) 2 K[AlF 6 ] was measured from room temperature to ca. 400 K by an ac complex impedance analysis. The conductivity of each complex obeyed the Arrhenius relation, σT = σ 0 exp (−E a RT ) . The σ value at 320 K and the E a value are 3.0×10 −4 and 29 and 1.0×10 −6 S m −1 and 69 kJ mol −1 , respectively, in the order given above. 1 H and 19 F NMR second moment and spin-lattice relaxation time measurements on (NH 4 ) 3 [AlF 6 ] confirmed that the electrical conduction is attributable to the self-diffusion of NH + 4 ions. The results obtained are compared with those of (NH 4 ) 3 [GaF 6 ] and (NH 4 ) 3 [InF 6 ] recently reported. The high σ values for these complexes are related to their crystal structures and anionic reorientational motions.