Isolated versus Condensed Anion Structure III: The Influence of the Cations 1,3-propanediammonium, 1,4-butanediammonium, /t-propylammonium, /i-butylammonium and /i-pentylammonium on Structures and Phase Transitions of ZnBrJ" Salts. A Br NQR and X-ray Structure Analysis
چکیده
The influence of the cations on the condensation of the anions in the salts (A')Zn(II) Br4 and (A)2Zn(II)Br4 is studied by 81 Br NQR and X-ray crystal structure analysis. (A')Zn(II)Br4(A' = [H3N(CH2)3NH3] + ) (1) shows a phase transition at 474 K. The phase II of (1) crystallizes with isolated [ZnBrJ " tetrahedra: monoclinic P2 t/«, Z = 4, a = 1108.4 (5), b = 1096.8 (2), c = 1118.5 (6) pm, and ß= 117.07(4)° at 296 K. A quartet was observed in the Br NQR spectrum of phase II: 61.634, 58.062, 56.675, and 53.673 MHz (77 K); 59.193, 57.448, 56.015, and 52.515 MHz (301 K). (A)2ZnBr4(A = [«-H3C(CH2)2NH3] (2) and [«-H3C(CH2)3NH3] (3)) also show structures with isolated [ZnBrJ 2 tetrahedra. The compound (2) crystallizes with P2Jc, Z = 4, a = 771.8(3), 6 = 1061.9(4), c = 2054.2 (7) pm, and /?= 106.75(1)° at 291 K. The compound (3) crystallizes with P2j/c, Z = 4, a = 768.9(4), 6 = 2229.6(10), c = 1071.6(5) pm, and 0 = 91.70(3)° at 295 K. Br NQR and DSC measurements on [H3N(CH2)4NH3]ZnBr4 (4), and [n-H3C(CH2)4NH3]2ZnBr4 (5) were also performed. The compound (4) shows several phase transitions at 349 K and higher temperatures, and a quartet in the 81 Br NQR spectrum could be observed between 77 and 330 K: 65.992, 65.544, 59.900, and 50.162 MHz (77 K); 63.787, 62.963, 59.928, and 50.364 MHz (320 K). The compound (5) shows also a phase transition at 244 K, and a quartet of 8 'Br lines could be observed in the NQR spectrum between 77 and 244 K: 61.279, 58.933, 57.869, and 56.485 MHz (77 K); 59.712, 56.936, 57.409, and 54.793 MHz (240 K). The various influences of the cations, such as size and hydrogen bonds on the condensation of [ M X J 2 (M = Zn, Cd; X = C1, Br) are discussed.