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

Different structural types of copper(II) furan- and thiophencarboxylates: X-ray structural, EPR, spectral and magnetic analyses

Petra Bertová, Vladimír Kuchtanin, Zdeňka Růžičková, Ján Moncoľ, Jozef Švorec, and Peter Segľa

Department of Inorganic Chemistry, Faculty of Chemical and Food Technology, Slovak Technical University in Bratislava, 81237 Bratislava, Slovakia

E-mail: peter.segla@stuba.sk

Abstract: Synthesis and characterization of eight new complexes of various structural types are reported. With 5-nitro-2-furancarboxylic acid (5-NO₂-2-fucH), two monomeric complexes, [Cu(5- NO₂-2-fuc)₂(H₂O)₂] (II ) and [Cu(5-NO₂-2-fuc)₂(H₂O)₄] (III ), as well as a dimeric complex with ethylnicotinate (Etnic), [Cu(5-NO₂-2-fuc)₂(Etnic)₂]₂ (V), were prepared. With other acids: 2,5- dimethyl-3-furancarboxylic acid (2,5-Me₂-3-fucH), 2-thiophencarboxylic acid (2-tpcH), 3-methyl- 2-thiophencarboxylic acid (3-Me-2-tpcH) or 5-methyl-2-thiophencarboxylic acid (5-Me-2-tpcH), only dimeric complexes [Cu(2,5-Me₂-3-fuc)₂(H₂O)]₂ (I ), [Cu(2,5-Me₂-3-fuc)2(Etnic)]₂ (IV ), [Cu(2- tpc)₂(Etnic)]₂ (VI ), [Cu(3-Me-2-tpc)₂(Etnic)]₂ (VII) and Cu(5-Me-2-tpc)₂ (Etnic)]₂ (VIII) have been synthesised. Characterizations of the complexes were based on elemental analysis and infrared, electronic, EPR and magnetic measurements. Moreover, complexes III, V, VII and VIII were also studied by X-ray structural analysis. Two structural types of dimeric complexes were observed differing in the number of carboxylate bridges. Most of the dinuclear complexes exhibit the common “paddle-wheel” structural motif while the molecular structure of V contains two pentacoordinated copper(II) ions bridged by two carboxylate groups of two 5-nitro-2-furancarboxylate ligands resulting in the intramolecular copper-copper distance of 4.4960(8) Å. Magnetic properties (monomeric EPR signal and isotropic exhchange constant (J of approximately 0 cm⁻¹) of V confirmed a very weak magnetic interaction between copper centres.

Keywords: copper(II) compexes – furancarboxylate – thiophencarboxylate – ethylnicotinate – EPR of copper(II)

Full paper is available at www.springerlink.com.

DOI: 10.1515/chempap-2015-0204

Chemical Papers 70 (1) 114–125 (2016)