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Issue 14, 2012
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CuN6 Jahn–Teller centers in coordination frameworks comprising fully condensed Kuratowski-type secondary building units: phase transitions and magneto-structural correlations

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Abstract

The metal–organic framework [Cu(ta)2] (Hta = 1H-1,2,3-triazole), containing Jahn–Teller active Cu(II) ions and 1,2,3-triazolate ligands, is prepared under solvothermal reaction conditions. The compound shows a reversible phase transition from the tetragonal crystal system (α-[Cu(ta)2]: space group I41/amd (no. 141), a = 11.8447(7) Å, c = 18.9782(13) Å, V = 2662.6(3) Å3) to the cubic crystal system (β-[Cu(ta)2]: space group Fd[3 with combining macron]m (no. 227), a = 17.4416(15) Å, V = 5305.9(8) Å3) within the temperature range of 120–160 °C. Both [Cu(ta)2] polymorphs have identical bonding topologies that might be described as fully condensed Kuratowski-type pentanuclear secondary building units of local Td point group symmetry in which four Cu(II) ions occupy the vertices of an imaginary tetrahedron. α-[Cu(ta)2], as opposed to the high-temperature β-phase, shows a strong tetragonal Jahn–Teller distortion of CuN6 coordination octahedra. The compounds are characterized by elemental and thermogravimetric analyses, single crystal and powder X-ray diffraction, FTIR-, UV-vis and fluorescence spectroscopy. Magnetic susceptibility investigations reveal two different Cu(II) sites at a ratio of 1 : 2, in agreement with the solid state structure of [Cu(ta)2]. At low temperatures the formation of antiferromagnetically coupled Cu(II) dimers is observed, leading to a spin frustration of roughly 1/3 of all magnetically active Cu(II) sites.

Graphical abstract: CuN6 Jahn–Teller centers in coordination frameworks comprising fully condensed Kuratowski-type secondary building units: phase transitions and magneto-structural correlations

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Supplementary files

Article information


Submitted
01 Dec 2011
Accepted
27 Jan 2012
First published
02 Mar 2012

Dalton Trans., 2012,41, 4239-4248
Article type
Paper

CuN6 Jahn–Teller centers in coordination frameworks comprising fully condensed Kuratowski-type secondary building units: phase transitions and magneto-structural correlations

M. Grzywa, D. Denysenko, J. Hanss, E. Scheidt, W. Scherer, M. Weil and D. Volkmer, Dalton Trans., 2012, 41, 4239
DOI: 10.1039/C2DT12311H

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