Single crystal X-ray diffraction studies on [(CH3)nNH4–n]3[Sb2Cl9] (, 3) chloroantimonates(III) in their low-temperature ferroelectric phases—structures and phase transitions

Isostructural Inorganic–Organic Piperazine-1,4-diium Chlorido- and Bromidoantimonate(III) Monohydrates: Octahedral Distortions and Hydrogen Bonds

Halogenidoantimonate(III) monohydrates of the (C₄H₁₂N₂)[SbX₅]·H₂O (X = Cl, 1 or Br, 2) formula, crystallizing in the same monoclinic space group of P2₁/n, are isostructural, with an isostructurality index close to 99%. The single crystal X-ray diffraction data do not show any indication of phase transition in cooling these crystals from room temperature to 85 K. Both hybrid crystals are built up from [SbX₆]^3– octahedra that are joined together by a common edge forming isolated bioctahedral [Sb₂X₁₀]^4– units, piperazine-1,4-diium (C₄H₁₂N₂)²⁺ cations and water of crystallization molecules. These structural components are joined together by related but somewhat different O/N/C–H···X and N–H···O hydrogen bonded systems. The evolution of structural parameters, notably the secondary Sb–X bonds along with the associated X/Sb–Sb/X–X/Sb angles and O/N/C–H···X hydrogen bonds, as a function of ligand exchange and temperature, along with their influence on the irregularity of [SbX₆]^3– octahedra, was determined. The comparison of packing features and hydrogen bond parameters, additionally supported by the Hirshfeld surface analysis and data retrieved from the Cambridge Structural Database, demonstrates the hierarchy and importance of hydrogen bond interactions that influence the irregularity of single [SbX₆]^3– units.

Crystal structure of a new hybrid anti-mony-halide-based compound for possible non-linear optical applications

The hybrid title compound, catena-poly[[[bis-(1,4-diazo-niabi-cyclo-[2.2.2]octa-ne) [tetra-achlorido-anti-monate(III)]-μ-chlorido-[tetra-chlorido-anti-monate(III)]-μ-chlorido]] monohydrate], {(C6H14N2)2[Sb2Cl10]·H2O} n , is self-assembled into alternating organic and inorganic layers parallel to the bc plane. The anionic inorganic layer consists of infinite zigzag chains of corner-sharing [SbCl6](3-) octa-hedra running along the b axis. The organic part is made up of 1,4-diazo-niabi-cyclo-[2.2.2]octane dications (dabcoH2 (2+)). The water mol-ecules in the structure connect inorganic and organic layers. Hydrogen-bonding inter-actions between the ammonium groups, water mol-ecules and Cl atoms ensure the structure cohesion.

catena-Poly[N,N,N',N'-tetra-methyl-ethylendi-ammonium [[tetra-bromido-antimonate(III)]-μ-bromido] hemihydrate]

The asymmetric unit of the title compound {(C₆H₁₈N₂)₂[Sb₂Br₁₀]·H₂O}_n, consists of two tetra­methyl­ethylendi­ammonium cations that are located on centres of inversion, as well as one tetra­methyl­ethylendi­ammonium cation, one water mol­ecule, one distorted octahedral [SbBr₆]³⁻anion and one bisphenoidal [SbBr₄]⁻ anion in general positions. The [SbBr₆]³⁻ and [SbBr₄]⁻ anions are linked together by two long Sb—Br bonds of 3.2709 (8) and 3.5447 (7) Å into {[Sb₂Br₁₀]⁴⁻}_n chains along [001]. One of the three tetra­methyl­ethylendi­ammonium cations is disordered and was refined using a split model (occupancy ratio 0.58:0.42). The cations and the water mol­ecule are connected to the {[Sb₂Br₁₀]⁴⁻}_n polymeric anions by weak N—H ⋯Br and O(water)—H ⋯Br hydrogen bonding.

Tris(N,N-dimethylanilinium) tri-μ-bromido-bis[tribromidoantimonate(III)]

In the title compound, (C₈H₁₂N)₃[Sb₂Br₉], two of the three unique N,N-dimethyanilinium cations exhibit flip–flop disorder with an occupancy ratio of 0.58 (1):0.42 (1). N—H⋯Br hydrogen bonds link the organic cations and bioctahedral face-sharing anions into a three-dimensional network.

Octahedral distortion caused by hydrogen bonding in tris(diethylammonium) hexachloridoantimonate(III)

The factors influencing the distortion of inorganic anions in the structures of chloridoantimonates(III) with organic cations, in spite of numerous structural studies on those compounds, have not been clearly described and separated. The title compound, [(C(2)H(5))(2)NH(2)](3)[SbCl(6)], consisting of isolated distorted [SbCl(6)](3-) octahedra that have C(3) symmetry and [(C(2)H(5))(2)NH(2)](+) cations, unequivocally shows the role played by hydrogen bonding in the geometry variations of inorganic anions. The organic cations, which are linked to the inorganic substructure through N-H...Cl hydrogen bonds, are clearly responsible for the distortion of the octahedral coordination of Sb(III) in terms of differences (Delta) in both Sb-Cl bond lengths [Delta = 0.4667 (6) A] and Cl-Sb-Cl angles [Delta = 9.651 (17) degrees].

Dielectric critical slowing down in pentakis(imidazolium) undecabromodibismuthate(III): (C(3)N(2)H(5))(5)Bi(2)Br(11)

Low frequency dielectric dispersion studies have been carried out for the ferroelectric pentakis(imidazolium) undecabromodibismuthate(III)- (C(3)N(2)H(5))(5)Bi(2)Br(11)-single crystal in the paraelectric phase in the radio-frequency region (100 Hz-1 MHz). The dielectric dispersion, observed for an electric field along the a-axis (P 2(1)/n space group), is characterized by a polydispersive nature close to the Curie temperature (T(c) = 155 K). The dielectric dispersion findings were analyzed accurately with the Cole-Cole formula. In the vicinity of the Curie temperature the process of the dielectric critical slowing down is clearly observed. Such a dynamic dielectric response is characteristic of ferroelectric crystals classified as 'order-disorder' type.

Dielectric critical slowing down in ferroelectric (C(3)N(2)H(5))(5)Sb(2)Br(11)

Dielectric dispersion studies have been carried out on the pentakis(imidazolium) undecabromodiantimonate(III), (C(3)N(2)H(5))(5)Sb(2)Br(11), single crystal in the audio-frequency region. It is found that low-frequency dielectric dispersion, observed for the field along the a-axis of the monoclinic symmetry (P 2(1)/n), reveals a polydispersive nature near the paraelectric-ferroelectric phase transition temperature (T(c) = 145 K). The dielectric dispersion results can be fitted with the Cole-Cole formula. Unexpectedly, the mean relaxation frequency obeys the Vogel-Fulcher law with freezing temperature of 143 K. Near the ferroelectric phase transition temperature, the process of dielectric critical slowing down was observed. Such a dynamic dielectric response is characteristic of ferroelectrics with an 'order-disorder' transition mechanism.

High-Pressure- and Low-Temperature-Induced Changes in [(CH3)2NH(CH2)2NH3][SbCl5]

The structure of N,N-dimethylethylenediammonium pentachloroantimonate(III), [(CH3)2NH(CH2)2NH3][SbCl5], NNDP, was investigated at 100 and 15 K at ambient pressure, as well as at pressures up to 4.00 GPa at room temperature in the diamond-anvil cell. The stable structure at low temperatures and low pressures consists of isolated [SbCl5]2- anions and [(CH3)2NH(CH2)2NH3]2+ cations. The inorganic anions have a distorted square pyramidal geometry. They are arranged in linear chains parallel to the c axis. In contrast to the low-temperature studies, where no phase transition was detected, pressure induces a P2(1)/c --> P2(1)/n phase transition between 0.55 and 1.00 GPa, accompanied by a doubling of the a unit-cell parameter. This solid-solid transition results from changes in the electron configuration of the Sb(III) atom and formation of the Sb-Cl bridging bonds between inorganic polyhedra to form, at approximately 1.0 GPa, isolated [Sb2Cl10]4- units consisting of [SbCl6]3- octahedra and [SbCl5]2- square pyramids connected by a common corner. The intermolecular distances continuously decrease with further increase in pressure, and at approximately 3.1 GPa, zigzag [{SbCl5}n]2n- chains containing corner-sharing [SbCl6]3- octahedra are formed. The unit-cell volume of NNDP decreases by 18.15% between room pressure and 4.00 GPa. The linear distortions of the [SbCl5]2- and [SbCl6]3- polyhedra decrease with increasing pressure and decreasing temperature and indicate a reduction in the stereochemical activity of the lone electron pair on the Sb(III) atom.