Structure determinations of the low-temperature phases of the copper pyridine N-oxide complexes Cu(C/sub 5/H/sub 5/NO)/sub 6/X/sub 2/ by neutron diffraction and EPR: influence of solvent and anion on the nature of the cooperative Jahn-Teller coupling

Journal Article · Wed Dec 01 04:00:00 EST 1982 · Inorg. Chem.; (United States)

DOI:https://doi.org/10.1021/ic00142a032· OSTI ID:6800349

Keijzers, C P ^[1]; McMullan, R K; Wood, J S; van Kalkeren, G; Srinivasan, R; de Boer, E

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1. Univ. of Nijmegen, Netherlands

The hexakis(pyridine N-oxide)copper fluoborate and perchlorate complexes have been examined by single-crystal neutron diffraction, electron paramagnetic resonance, and magnetic susceptibility measurements, in order to elucidate the nature of the cooperative Jahn-Teller effect (CJTE) exhibited by these salts and its dependence on the nature of the anion and the solvent used for crystal growing. Neutron diffraction studies between 298 and 20 K on crystals of the fluoborate salt and of the perchlorate salt grown from acetonitrile solution confirm the loss of the high-temperature 3 symmetry of the crystals and the formation of three domains associated with static Jahn-Teller-distorted structures at temperatures of ca. 60 K, as was earlier indicated by EPR results. The structure has been refined with use of 1938 neutron reflection intensities ((sin theta)/lambda less than or equal to 0.79 A/sup -1/) recorded at 20 K, the final R(F/sup 2/) and R/sub w/(F/sup 2/) values being 0.041 and 0.047, respectively. The analysis indicates that DMF molecules are incorporated statistically into the complex, to the extent of approximately 1 molecule to 40 pyridine N-oxide molecules. The DMF molecules occupy tetragonal distortion sites about the copper, with Cu-O distances of 2.67 A, and the presence of these tetragonally distorted complexes in samples grown from DMF solution explains the appearance of the static sites in the earlier reported room-temperature EPR spectra of doped crystals containing Cu(C/sub 5/H/sub 5/NO/sub 6//sup 2 +/. Single crystals and powders of mixed salts with varying ClO/sub 4//sup -//BF/sub 4//sup -/ ratios and heavily doped single crystals of the isostructural zinc complexes have been examined by EPR techniques to assess the relative stabilities of the low-temperature ferrodistortive and antiferrodistortive forms characteristic respectively of the BF/sub 4//sup -/ and ClO/sub 4//sup -/ salts. 9 figures, 5 tables.

• OSTI ID: 6800349
• Journal Information: Inorg. Chem.; (United States), Journal Name: Inorg. Chem.; (United States) Vol. 21:12; ISSN INOCA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
AZINES
BOND ANGLE
BOND LENGTHS
COHERENT SCATTERING
COMPLEXES
COPPER COMPLEXES
CRYSTAL STRUCTURE
DIFFRACTION
DIMENSIONS
ELECTRON SPIN RESONANCE
HETEROCYCLIC COMPOUNDS
JAHN-TELLER EFFECT
LENGTH
MAGNETIC PROPERTIES
MAGNETIC RESONANCE
MAGNETIC SUSCEPTIBILITY
NEUTRON DIFFRACTION
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHYSICAL PROPERTIES
PYRIDINES
RESONANCE
SCATTERING
TRANSITION ELEMENT COMPLEXES