Solid State EPR Studies on Bis(1,2-dithiosquarato) cuprates(II): a Structure – Spectroscopy Relationship

Katja Bellin,a Duha Jawad,b Barbara Wenzelc and Peter Strauchb,*

a GKSS-Research Center, Institute of Polymer Research; Kantstr. 55, D-14513 Teltow
b University of Potsdam, Institute of Chemistry, Karl-Liebknecht-Str. 24-25, 14476 Golm;
c Institute of Interdisciplinary Isotope Research e. V. (IIF), Permoserstraße 15, D-04318 Leipzig
* Corresponding author: E-mail: ps@chem.uni-potsdam-de

1,2-Dithiosquaratometalates (M = Cu, Ni) are available by direct synthesis from metal salts with dipotassium-1,2-dithiosquarate and the appropriate counter cations. For EPR measurements in solid state (powder or single crystals) a diamagnetic dilution of the paramagnetic centers by isostructural host lattices is necessary to separate the magnetic centers from each other to prevent interactions. The X-ray structures of two potential diamagnetic hosts (Ph4P)2[Ni(dtsq)2] 1 and [(Ph3P)2N]2[Ni(dtsq)2] 2 as well as the structures of two paramagnetic[Cu(dtsq)2]2– complexes with sterically demanding counter cations [(Ph3P)2N]2[Cu(dtsq)2] 4 and [p–C6H4(CH2Ph3)2] [Cu(dtsq)2] 5 are discussed. The copper complexes 4 and 5 as well as (Ph4P)2[Cu(dtsq)2] 3 were studied by solid state EPR spectroscopy as powders or single crystals and the parameters are compared to those of related complexes in diamagnetic host lattices. Metal-metal distances of 11–13 Å in the copper complexes separate the paramagnetic centres sufficiently and reduce the interactions to enable a well resolved hyperfine structure and to determine the tensor parameters of the magnetic g- and ACu-tensors.

Keywords: 1,2-dithiosquarate, X-ray, EPR, copper(II), nickel(II)