Electronic and molecular structure of high-spin d4 complexes: Experimental and theoretical study of the [Cr(D2O)6]2+ cation in Tutton's salts

Dobe, Christopher, Noble, Christopher, Carver, Graham, Tregenna-Piggott, Philip L. W., McIntyre, Garry J., Barra, Anne-Laure, Neels, Antonia, Janssen, Stefan and Juranyi, Fanni (2004) Electronic and molecular structure of high-spin d4 complexes: Experimental and theoretical study of the [Cr(D2O)6]2+ cation in Tutton's salts. Journal of the American Chemical Society, 126 50: 16639-16652.


Author Dobe, Christopher
Noble, Christopher
Carver, Graham
Tregenna-Piggott, Philip L. W.
McIntyre, Garry J.
Barra, Anne-Laure
Neels, Antonia
Janssen, Stefan
Juranyi, Fanni
Title Electronic and molecular structure of high-spin d4 complexes: Experimental and theoretical study of the [Cr(D2O)6]2+ cation in Tutton's salts
Journal name Journal of the American Chemical Society   Check publisher's open access policy
ISSN 0002-7863
Publication date 2004
Sub-type Article (original research)
DOI 10.1021/ja046095c
Volume 126
Issue 50
Start page 16639
End page 16652
Total pages 14
Place of publication Washington, D.C., U.S.A.
Publisher American Chemical Society
Language eng
Subject 100702 Molecular and Organic Electronics
1099 Other Technology
Abstract Variable-temperature spectroscopic and crystallographic studies on the chromium(II) Tutton’s salts, (MI)2Cr(X2O)6(SO4)2, where MI ) ND4+, Rb+, or Cs+, and X ) H or D, are reported. Inelastic neutron scattering (INS) and multifrequency EPR experiments facilitate a rigorous definition of the ground-state electronic structure from 1.5 up to 296 K, which is unprecedented for a high-spin d4 complex. Modeling of the INS data using a conventional S ) 2 spin Hamiltonian reveals a dramatic variation in the axial and rhombic zero-field-splitting parameters. For the ammonium salt, D and E are -2.454(3) and 0.087(3) cm-1 at 10 K and -2.29(2) and 0.16(3) cm-1 at 250 K, respectively. A temperature variation in the stereochemistry of the [Cr(D2O)6]2+ complex is also identified, with an apparent coalescence of the long and medium Cr-O bond lengths at temperatures above 150 K. The corresponding changes for the rubidium and cesium salts are notable, though less pronounced. The experimental quantities are interpreted using a 5EXe Jahn-Teller Hamiltonian, perturbed by anisotropic strain. It is shown that good agreement can be obtained only by employing a model in which the anisotropic strain is itself temperature dependent. A new theoretical approach for calculating variable-temperature EPR spectra of high-spin d4 complexes, developed within the 5EXe coupling model, is described. Differences between spin-Hamiltonian parameters determined by INS and EPR are consistent with those of the different time scales of the two techniques.
Keyword Tutton’s salts
Chromium(II)
Ammonium salt
Rubidium salt
Cesium salt
Jahn-Teller Hamiltonian
High-spin d4 complexes
Q-Index Code C1

Document type: Journal Article
Sub-type: Article (original research)
Collections: Excellence in Research Australia (ERA) - Collection
Centre for Advanced Imaging Publications
 
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