ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Synthesis, crystal structures, spectral, electrochemical and magnetic properties of di-µ-phenoxido-bridged dinuclear copper(II) complexes with N-salicylidene-2-hydroxybenzylamine derivatives: axial coordination effect of dimethyl sulphoxide molecule

Yoshihisa Kakuta, Naoyuki Masuda, Michihiro Kurushima, Takashi Hashimoto, Daisuke Yoshioka, Hiroshi Sakiyama, Yuya Hiraoka, Makoto Handa, and Masahiro Mikuriya

Department of Chemistry and Research Centre for Coordination Molecule-based Devices, School of Science and Technology, Kwansei Gakuin University, 2-1 Gakuen, Sanda, 669-1337, Japan

E-mail: junpei@kwansei.ac.jp

Abstract: The template reaction of salicylaldehyde and its substituted derivatives and 2-hydroxy-5-bromobenzylamine or 2-hydroxy-5-chlorobenzylamine with copper(II) acetate in dimethyl sulphoxide (dmso) afforded eight dinuclear Cu(II) complexes, [Cu₂(L)₂(dmso)₂] (H₂ L = N-salicylidene-2-hydroxy-5-bromobenzylamine, N-salicylidene-2-hydroxy-5-chlorobenzylamine and their 5-bromo, 5-nitro and 5-methyl-substituted salicylidene derivatives). These Cu(II) complexes were characterised by IR and UV-VIS-NIR spectroscopy, electric conductivity, cyclic voltammetry, and temperature dependence of magnetic susceptibilities (4.5–300 K). In the THF solution, the complexes are nonelectrolytes and exhibit a characteristic CT band due to phenoxido-bridging at 360–384 nm. In the cyclic voltammograms, an irreversible reduction process was observed at −1.18–1.54 V vs Fc/Fc⁺. Single-crystal X-ray crystallography revealed that two Cu(II) ions were bridged by the two phenoxido-oxygen atoms of the two Schiff-base ligands with axial coordination of dmso molecules forming a square pyramid with a Cu-Cu distance of 3.0628(8)–3.0931(6) °A. In accordance with the crystal structures, the magnetic interaction between the two Cu(II) ions is relatively anti-ferromagnetic with −2J value of 386–575 cm⁻¹. The axial coordination effect of the dmso molecule was discussed in relation to the correlation between the Cu-O-Cu angle and the −2J value.

Keywords: dinuclear copper(II) complex – phenoxido-bridged complex – magnetic properties – crystal structure – dimethyl sulphoxide

Full paper is available at www.springerlink.com.

DOI: 10.2478/s11696-013-0528-0

Chemical Papers 68 (7) 923–931 (2014)