Isolated versus Condensed Anion Structure II; the Influence of the Cations (1,3-propanediammonium, 1,4-phenylendiammonium, and n-propylammonium) on Structures and Phase Transitions of CdBr2- 4Salts A 79,81Br NQR and X-ray Structure Analysis

Abstract

Abstract The influence of the cations on the condensation of anions CdBr4 2- in salts (A')CdBr4 (II) and (A)2CdBr4 (II) is studied by 79,81Br NQR and X-ray crystal structure determinations. (A')CdBr4 : A' = [H3N(CH2)3NH3]2+ (1) crystallizes with a layer-type anion structure at 298 K and A' = [1,4-(H3N)2C6H4]2+ (2) crystallizes with a chain-type anion structure at 298 K. (A)2 CdBr4 : A = [n-H3C(CH2)2NH3]+ (3) crystallizes with a layer-type anion structure at 293 K. (1) shows successive phase transitions at 328, 363, and 495 K according to the NQR and DSC measurements. Phase IV of (1): at 298 K orthorhombic, Pnma, Z = 4,a = 772.1 (4), b = 1905.4(9), c = 789.8(4) pm. 81Br NQR spectrum showed a doublet at 77 K (phase IV) with ν1= 61.177 and ν2 = 45.934 MHz and also a doublet at 350 K (phase III) with ν1= 57.581 and ν2 = 48.747 MHz. (2): at 295 K orthorhombic, Pnma, Z = 4, a = 802.5(3), b = 1775.1(6), c = 881.9(3) pm; the five-coordinated Cd atom and one-dimensional [CdBr4]2- anion chain structure was observed. This coordination and chain structure are very rare for (A')CdX4 (II) or (A)2CdX4 (II). Two 81Br NQR lines were observed at 77 K: ν1= 70.159 and ν3 = 40.056 MHz. One more line appeared at 85 K: ν2 = 53.622 MHz. A 81Br NQR triplet was observed at 273 K: ν1 = 67.919, ν2 = 56.317, and ν3 = 40.907 MHz. (3) shows successive phase transitions at 121, 135, 165, and 208 K according to the NQR, DSC, and DTA measurements. Phase I of (3): at 293 K orthorhombic, Cmca, Z = 4, a = 783.4(4), b = 2480.2(10), c = 806.5(4) pm. 81Br NQR doublet was observed at 77 K (phase V) and at 300 K (Phase I) with ν1 = 61.060 and ν2 = 54.098 MHz (77 K); v1 = 55.835 and ν2 = 55.964 MHz (373 K). No NQR line could be observed in phases II, III, and IV.