A variable temperature structural study of the Jahn–Teller distortion in Ba2CuUO6

For about a decade, we have systematically investigated thermally-accessible lattice strain and local pseudo Jahn-Teller distortion of [CuL2]3[M(CN)6]2·4H2O (L = (1R, 2R)-cyclohexanediamine; M = Cr, Co, and Fe). In mononuclear Cu(II) complexes, (pseudo) Jahn-Teller effect plays an important role in flexible distortion of crystal structures especially Cu(II) coordination environment. Beside Jahn-Teller distortion, we have dealt with some factors for example, metal substitution as bimetallic assemblies, chirality of ligands, and H/D isotope effect to vary intermolecular interaction and crystal packing. According to the course work using variable temperature PXRD, we have found that anisotropy of crystal strain distortion did not corporate with Jahn-Teller distortion around local coordination environment because of the discrepancy of the crystallographic axes and molecular alignment. In order to elucidate the anisotropic control of lattice strain and Jahn-Teller distortion closely, we have employed transition metal oxide with orthogonal or layered structures to prepare composite materials with the chiral metal complexes for discussion of thermally-accessible PXRD changes and IR shift due to adsorption. At first, we have employed chiral one-dimensional zig-zag Cu-Cr bimetallic assemblies and their oxides prepared by burining. Based on variable temperature XRD patterns, a linear correlation (lnK = a/T + b) of K (=d(T)-d(0)/d(T)) values, where d(T) and d(0) are spacing of lattice plane (d = nλ/(2sinθ)) at T K and 0 K (extrapolated), respectively, and its deviation from ideal correlation indicates degree of anisotropic lattice distortion of the composite materials. For example, we could observe LiMnO2, typical material of lithium ion battery, was enhanced anisotropic lattice strain along the b axis or the (011) plane added by [CuL2(H2O)2](NO3)2 complexes. Which may prevent from breaking down regular crystal structures during charge-discharge of secondary battery.

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Change in electronic structure in a six-coordinate copper(II) complex accompanied by an anion order/disorder transition

Acta Crystallographica Section B Structural Science ◽

10.1107/s0108768110003678 ◽

2010 ◽

Vol 66 (2) ◽

pp. 206-212 ◽

Cited By ~ 4

Author(s):

Colin A. Kilner ◽

Malcolm A. Halcrow

Keyword(s):

Electronic Structure ◽

Room Temperature ◽

Variable Temperature ◽

Copper Ion ◽

Coordination Geometry ◽

Teller Distortion ◽

Crystallographic Study ◽

Jahn Teller ◽

Ligand Coordination ◽

Jahn Teller Distortion

A variable-temperature crystallographic study of [Cu(L OH)2][ClO4]2·2(CH3)2CO [L OH = 2,6-bis(hydroxyiminomethyl)pyridine] between 30 and 300 K is presented. The complex exhibits an unusual electronic structure at room temperature with a {d_{z^2}}1 ground state, corresponding to an axially compressed ligand coordination geometry about the copper ion. This reflects a suppression of the pseudo-Jahn–Teller distortion that is normally shown by copper(II) compounds with this ligand geometry [Halcrow et al. (2004). New J. Chem. 28, 228–233]. On cooling the compound undergoes an abrupt structural change at 157 ± 3 K, that does not involve a change in the space group (P\bar 1), but causes significant changes to c and the unit-cell angles. This reflects a conformational rearrangement of the complex dication, towards a more typical pseudo-Jahn–Teller elongated coordination geometry. This occurs concurrently with a crystallographic ordering of one of the two perchlorate anions, and a significant displacement of the two lattice acetone molecules. The transformation involves displacements of up to 0.5 Å in the non-H atoms of the structure at 30 K, compared with their positions at 300 K. The change in coordination geometry of the complex around 157 K is reflected in a small reduction in its magnetic moment near that temperature.

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Spin, Orbital and Lattice Coupling in the Double Perovskite Ba2154SmMoO6

MRS Proceedings ◽

10.1557/proc-1148-pp04-02 ◽

2008 ◽

Vol 1148 ◽

Author(s):

Abbie Mclaughlin

Keyword(s):

Degrees Of Freedom ◽

Variable Temperature ◽

Double Perovskite ◽

Neutron Diffraction Study ◽

Antiferromagnetic Transition ◽

Spin Orbital ◽

Teller Distortion ◽

Jahn Teller ◽

Lattice Coupling ◽

Jahn Teller Distortion

AbstractAn unexpectedly high antiferromagnetic transition temperature (TN = 130 K) has been observed in the double perovskite Ba2154SmMoO6 as a result of a strong interplay between spin, orbital and lattice degrees of freedom. A variable temperature neutron diffraction study of Ba2154SmMoO6 demonstrates that the orbital order below TN is as a result of a Jahn-Teller distortion of the MoO6 octahedra.

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The Interplay of Open-Shell Spin-Coupling and Jahn-Teller Distortion in Benzene Radical Cation Probed by X-ray Spectroscopy

10.26434/chemrxiv.12799922.v2 ◽

2020 ◽

Author(s):

Marta L. Vidal ◽

Michael Epshtein ◽

Valeriu Scutelnic ◽

Zheyue Yang ◽

Tian Xue ◽

...

Keyword(s):

High Harmonic ◽

Open Shell ◽

Spin Coupling ◽

High Symmetry ◽

Teller Distortion ◽

Spectral Window ◽

X Ray ◽

Jahn Teller ◽

X Ray Absorption ◽

Jahn Teller Distortion

We report a theoretical investigation and elucidation of the x-ray absorption spectra of neutral benzene and of the benzene cation. The generation of the cation by multiphoton ultraviolet (UV) ionization as well as the measurement of the carbon K-edge spectra of both species using a table-top high-harmonic generation (HHG) source are described in the companion experimental paper [M. Epshtein et al., J. Phys. Chem. A., submitted. Available on ChemRxiv]. We show that the 1sC -> pi transition serves as a sensitive signature of the transient cation formation, as it occurs outside of the spectral window of the parent neutral species. Moreover, the presence of the unpaired (spectator) electron in the pi-subshell of the cation and the high symmetry of the system result in significant differences relative to neutral benzene in the spectral features associated with the 1sC ->pi* transitions. High-level calculations using equation-of-motion coupled-cluster theory provide the interpretation of the experimental spectra and insight into the electronic structure of benzene and its cation. The prominent split structure of the 1sC -> pi* band of the cation is attributed to the interplay between the coupling of the core -> pi* excitation with the unpaired electron in the pi-subshell and the Jahn-Teller distortion. The calculations attribute most of the splitting (~1-1.2 eV) to the spin coupling, which is visible already at the Franck-Condon structure, and estimate the additional splitting due to structural relaxation to be around ~0.1-0.2 eV. These results suggest that x-ray absorption with increased resolution might be able to disentangle electronic and structural aspects of the Jahn-Teller effect in benzene cation.

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Jahn-Teller Effect in Hexahydroxocuprate(II) Complexes

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19951429 ◽

1995 ◽

Vol 60 (9) ◽

pp. 1429-1434

Author(s):

Martin Breza

Keyword(s):

Hydrogen Bonding ◽

Quantum Chemical ◽

Potential Surface ◽

Hydroxyl Group ◽

Chemical Calculation ◽

Teller Distortion ◽

Jahn Teller ◽

Jahn Teller Effect ◽

Extremal Values ◽

Jahn Teller Distortion

Using semiempirical CNDO-UHF method the adiabatic potential surface of 2[Cu(OH)6]4- complexes is investigated. The values of vibration and vibronic constants for Eg - (a1g + eg) vibronic interaction attain extremal values for the optimal O-H distance. The Jahn-Teller distortion decreases with increasing O-H distance. The discrepancy between experimentally observed elongated bipyramid of [Cu(OH)6]4- in Ba2[Cu(OH)6] and the compressed one obtained by quantum-chemical calculation is explainable by hydrogen bonding of the axial hydroxyl group.

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