The structure, phase transition and molecular dynamics of [C(NH₂)₃]₃[Sb₂Br₉]

Abstract

The crystal structures of [C(NH 2 ) 3 ] 3 [Sb 2 Br 9 ] (Gu 3 Sb 2 Br 9 ) at 300 K and of [C(NH 2 ) 3 ] 3 [Sb 2 Cl 9 ] (Gu 3 Sb 2 Cl 9 ) at 90 and 300 K are determined. The compounds crystallize in the monoclinic space group: C2/c. The structure is composed of Sb 2 X 3− 9 (X = Cl, Br) ions, which form two-dimensional layers through the crystal, and guanidinium cations. In Gu 3 Sb 2 Br 9 the structural phase transformation of the first-order type is detected at 435/450 K (on cooling/heating) by the DSC and dilatometric techniques. The dielectric relaxation process in the frequency range between 75 kHz and 5 MHz over the low temperature phase indicates reorientations of weakly distorted guanidinium cations. The proton 1 H NMR second-moment and spin-lattice relaxation time, T 1 , temperature runs for the polycrystalline Gu 3 Sb 2 Br 9 sample indicate a complex cation motion. A significant dynamical non-equivalence of two guanidinium cations was found. The possible mechanism of the phase transition in Gu 3 Sb 2 Br 9 is discussed on the basis of the results presented.

Structural Diversity and Magnetic Properties of Hybrid Ruthenium Halide Perovskites and Related Compounds

“…[57] Several hybrid A 3 M 2 X 9 compounds (A = organic monocation; M = trivalent metal ions and X = halides) of the main group elements have been studied previously,i ncluding MA 3 Sb 2 X 9 (X = Br or I), [58,59] [C(NH 2 ) 3 ] 3 M 2 I 9 (M = Sb or Bi), [60] MA 3 Bi 2 X 9 (X = Br or I). [61] Some of these hybrids adopt A 3 M 2 X 9 -type layered structures [62,63] of the type shown in Figure 1, while others contain dimeric M 2 X 9…”

Structural Diversity and Magnetic Properties of Hybrid Ruthenium Halide Perovskites and Related Compounds

“…[57] Several hybrid A 3 M 2 X 9 compounds (A = organic monocation; M = trivalent metal ions and X = halides) of the main group elements have been studied previously,i ncluding MA 3 Sb 2 X 9 (X = Br or I), [58,59] [C(NH 2 ) 3 ] 3 M 2 I 9 (M = Sb or Bi), [60] MA 3 Bi 2 X 9 (X = Br or I). [61] Some of these hybrids adopt A 3 M 2 X 9 -type layered structures [62,63] of the type shown in Figure 1, while others contain dimeric M 2 X 9 3À anions comprising two face-sharing MX 6 octahedra.…”

Phase Transitions Mechanism and Distortion of SbCl6 3– Octahedra in Bis(n-butylammonium) Pentachloroantimonate(III) (C4H9NH3)2[SbCl5]

“…The C7 atom is split between two positions with occupancy factors of 0.64 for C7 and 0.36 for C7A. The same type of disorder for the nbutylammonium cation was found in the structure of (n-C 4 H 9 NH 3 ) 2 [BiCl 5 ] [11]. It is suggested that the ethyl group of the alkylammonium chain undergoes a reorientation around the C5-C7 bond [11].…”

“…The lone electron pair may be easily deformed from the initial symmetry as a result of a formation of M-X-M (M = Bi, or Sb; X = Cl, Br or I) bonds. When two octahedra are joined together having common (X) halogen atoms the bridging M-X bond length is increased, whereas the oppo- 3 Cl 9 ], where in the octahedral configuration of the antimony atom there are three bridging Sb-Cl bonds, the length of which is 2.915(10)Å, whereas the three terminal ones, have a length of 2.446(1)Å [11]. It should be noted that the increase of bond lengths compared to not deformed octahedron in this case is 0.27Å, whereas the decrease in length of the opposite bonds is 0.20Å.…”