scholarly journals Polar state induced by block-type lattice distortions in BaFe2Se3 with quasi-one-dimensional ladder structure

2019 ◽  
Vol 99 (24) ◽  
Author(s):  
Takuya Aoyama ◽  
Satoshi Imaizumi ◽  
Takuya Togashi ◽  
Yoshifumi Sato ◽  
Kazuki Hashizume ◽  
...  
2000 ◽  
Vol 55 (3-4) ◽  
pp. 299-316 ◽  
Author(s):  
Dagmar Henschel ◽  
Karna Wijaya ◽  
Oliver Moers ◽  
Armand Blaschette ◽  
Peter G. Jones

Abstract In a study aim ed at the „deconstruction“ of the supramolecular aggregate 3(18C6) · 2HN( SO2Me)2 (1,18C6 = 18-crown-6), which is known to display a ladder structure with two isotactic [18C6 - Me SO2N(H)SO2Me···)∞ polymers forming the uprights and symmetrically N - H···O bonded 18C6 rings providing the rungs, the following crystalline complexes were isolated and (except for 2b) characterized by low-temperature X-ray diffraction: 18C6-ClN (SO2Me)2 (2a, triclinic, space group P1̅, Z = 2), 18C6-PhN (SO2Me)2 (2b), 18C6 -MeN(SO2Me)2 (3, monoclinic, P21/c, Z = 8), Bz18C6-HN(SO2Me)2 (4, Bz18C6 = benzo-18-crown-6, monoclinic, P21/n, Z = 4), 18C6-2 MeN (SO2Me)2 (5, triclinic, P1̅, Z = 1), 18C6-Me2SO- HN( SO2Me) (SO2Ph) (13, triclinic, P1̅, Z = 2), and 18C6-H2OMe2SO·2HN(SO2Me)2 (14, triclinic, P1̅, Z = 2). Each of the one-dimensional polymers 2a (syndiotactic), 3 (disyndiotactic) and 4 (isotactic) mimics a single upright of 1; in contrast to 1 and 2a, where the intra-catemer connectivity solely relies on S - Me ··· crow n and crown ··· O = S hydrogen bonds, this bonding system is reinforced in 3 by N -Me ··· crown and in 4 by N - H ··· crown hydrogen bonds. Complex 5 is monomeric and matches a fragment formally extruded from the catemer 3; moreover, 3 and 5 represent a rare case of two structurally characterized 18C6 complexes containing the same uncharged guest species in distinct molecular ratios. The surprising structure of the quaternary adduct 14 exhibits an [18C6 ··· MeSO2N(H)SO2Me ··· ]∞ chain, which can be regarded both as an isolated, though unmodified upright from the ladder 1 and, being syndiotactic, as a stereochemical analogue of 2a; the potentially rung-forming *NH functions in the chain are blocked by hydrogenbonded side chains of the type * N - H ··· water ··· sulfoxide ··· H - N (SO2Me)2. The ternary complex 13 consists of chains [18C6 ··· Me2SO ··· H - N (SO2Ph)SO2Me···]∞ and is not closely related to the other structures


2009 ◽  
Vol 64 (11-12) ◽  
pp. 1429-1437 ◽  
Author(s):  
Andrea Schindler ◽  
Manfred Zabel ◽  
John F. Nixon ◽  
Manfred Scheer

The hexaphosphaferrocene complex [Fe(η5-P3C2tBu2)2] (1) derived from the corresponding 1,2,4-triphosphospholyl anion reacts with CuX (X = Cl, Br, I) in a 1 : 1 stoichiometry to give the isostructural, one-dimensional polymeric compounds [{Cu(μ3-X)}4{Fe(μ,η5:η1-P3C2tBu2)2}2]n (X = Cl (2), Br (3), I (4)), which display a unique sinusoidal (CuX)n ladder structure. In the reaction with CuI a second one-dimensional polymeric compound [{Cu3(μ-I)(μ3-I)2}(CH3CN){Fe(μ,η5:η1- P3C2tBu2)(μ3,η5:η1-P3C2tBu2)}]n (5) is formed. The reaction of 1 with CuX (X= Cl, Br, I) in a 1 : 2 stoichiometric ratio leads only in the case of CuCl to the formation of the new, oligomeric compound [{Cu(μ3-Cl)}4(CH3CN)2{Fe(μ,η5:η1-P3C2tBu2)2}2] (6), whereas in the case of CuBr and CuI the polymeric compounds 3 and 5 were isolated. The reaction of 1 with Ag[Al{OC(CF3)3}4] in a 1:1 stoichiometric ratio results in the formation of [Ag{Fe(μ,η5:η1-P3C2tBu2)2}2][Al{OC(CF3)3}4] (7), which shows dynamic behaviour in solution


2016 ◽  
Vol 237 (1) ◽  
Author(s):  
Shohei Kobori ◽  
Kazuki Matsui ◽  
Hideki Kuwahara ◽  
Takayuki Goto ◽  
Xiao Zhang ◽  
...  

Author(s):  
Carina Merkens ◽  
Khai-Nghi Truong ◽  
Ulli Englert

3-(4-Pyridyl)-acetylacetone (HacacPy) acts as a pyridine-type ligand towards CdX2(X= Cl, Br, I). Chain polymers with six-coordinated metal cations are obtained from CdCl2and with alternating five- and six-coordinated Cd centers from CdBr2. In either case, the formation of these compounds does not depend on the precise stoichiometry. In contrast, two different reaction products form with the heavier congener CdI2, namely a ligand-rich molecular complex CdI2(HacacPy)2and a ligand-deficient one-dimensional polymer [CdI2(HacacPy)]1∞. Interconversion between these two iodo derivatives is possibleviathermal degradation and mechanochemical synthesis. The acetylacetone moiety in HacacPy may be deprotonated and chelated to FeIII, and the resulting complex Fe(acacPy)3reacts analogously to a bridging polypyridine ligand towards the same Cd halides as the molecule HacacPy itself. With CdCl2and CdBr2, isomorphous chain polymers are obtained in which the Cd cations adopt distorted octahedral coordination and one of the peripheric pyridyl groups remains uncoordinated. With CdI2, the iron complex acts as a \mu _{{3}}-Fe(acacPy)3bridge between tetrahedral Cd centers and gives rise to a ladder structure.


Author(s):  
J.C. Bennett ◽  
F.W. Boswell ◽  
S. Ritchie ◽  
J.M. Corbett ◽  
A. Prodan

In many ways, TaTe4 and NbTe4 are nearly prototypical compounds for the study of charge-density waves (CDW). The compounds have a quasi-one-dimensional crystal structure in which chains of metal atoms are centered within extended cages of Te atoms in square antiprismatic coordination. The observed lattice distortions, involving mainly longitudinal motions of the metal atoms along the chains, correspond to that of the classic CDW model. In addition, the compounds exhibit the full spectrum of possible CDW-driven phase transitions: commensurate-to-incommensurate (C to IC), C to C and IC to IC. The subcell of TaTe4 is tetragonal with axes (a x a x c). At room temperature, the crystal is commensurately modulated giving rise to a supercell with axes (2a x 2a x 3c) and, upon heating, has been observed to undergo a C to C transition at about 450 K. In this paper, we report an additional C to IC transition occurring above 550 K. The evolution of the microstructure upon heating, including the formation of discommensuration arrays in the IC state, has been revealed by satellite dark-field (SDF) imaging.


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