Syntheses, characterizations and structures of NO donor Schiff base ligands and nickel(II) and copper(II) complexes Cemal S ßenol a , Zeliha Hayvali a,⇑ , Hakan Dal b , Tuncer Hökelek c a Department of Chemistry, Ankara University, Faculty of Science, 06100 Ankara, Turkey b Department of Chemistry, Anadolu University, Faculty of Science, 26470 Eskisehir, Turkey c Department of Physics, Hacettepe University, 06800 Ankara, Turkey article info Article history: Received 7 March 2011 Received in revised form 21 April 2011 Accepted 21 April 2011 Available online 28 April 2011 Keywords: Schiff bases Nickel(II) complexes Copper(II) complexes Crystal structure abstract New Schiff base derivatives (L 1 and L 2 ) were prepared by the condensation of 2-hydroxy-3-methoxybenz- aldehyde (o-vanillin) and 3-hydroxy-4-methoxybenzaldehyde (iso-vanillin) with 5-methylfurfurylamine. Two new complexes [Ni(L 1 ) 2 ] and [Cu(L 1 ) 2 ] have been synthesized with bidentate NO donor Schiff base ligand (L 1 ). The Ni(II) and Cu(II) atoms in each complex are four coordinated in a square planar geometry. Schiff bases (L 1 and L 2 ) and complexes [Ni(L 1 ) 2 ] and [Cu(L 1 ) 2 ] were characterized by elemental analyses, FT-IR, UV–vis, mass and 1 H, 13 C NMR spectroscopies. The crystal structures of the ligand (L 2 ) and com- plexes [Ni(L 1 ) 2 ] and [Cu(L 1 ) 2 ] have also been determined by using X-ray crystallographic technique. Ó 2011 Elsevier B.V. All rights reserved. 1. Introduction Schiff base ligands have played an important role in the devel- opment of coordination chemistry, especially their metal com- plexes exhibit wide applications in biological and industrial systems [1–6]. Furthermore, the Schiff bases are very important tools for the inorganic chemists as these are widely used to design molecular ferromagnets, in catalysis, in biological modeling appli- cations, as liquid crystals and as heterogeneous catalysts [7–9]. Schiff base ligands containing various donor atoms (like N, O, S, etc.) show broad biological activity and are of special interest because of the variety of ways in which they are bonded to the transition metal ions [10,11]. Schiff base nickel(II) complexes have been regarded as models for enzymes such as urease [12]. Vanilline and furfurylamine Schiff base derivatives are very useful biochem- ical materials having biological activities [13,14]. Although the oxygen atom of the furan ring could not coordinate to the transi- tion metals, the special tendency of the oxygen atom will be effec- tive on the crystal structures of the complexes [15,16]. In the previous works, we reported the syntheses and crystal structures of different Schiff base compounds and their metal com- plexes [17–20]. In this article, we have succeeded in the syntheses of new Schiff base compounds (L 1 and L 2 ) and complexes [Ni(L 1 ) 2 ], [Cu(L 1 ) 2 ] and their characterizations by elemental analyses, FT-IR, mass, 1 H and 13 C NMR, UV–vis and X-ray single crystal diffraction (Scheme 1). 2. Experimental 2.1. Reagents 2-Hydroxy-3-methoxybenzaldehyde (o-vanillin) and 3-hydro- xy-4-methoxybenzaldehyde (iso-vanillin) were purchased from Al- drich, and used without further purification. Solvents were dried and distilled before use according to the standard procedure. 2.2. Physical measurements Melting points were measured on a Thomas-Hoover apparatus using a capillary tube. 1 H and 13 C NMR spectra were recorded on a Varian Mercury, High Performance Digital FT-NMR (400 MHz) spectrometer (SiMe 4 as a internal standard). Chemical shifts for proton and carbon resonances were reported in ppm (d)( 1 H and 13 C NMR chemical shifts are given according to the numbering scheme). IR spectra were obtained from PEL-DATA spectrum 100 series spectrometer. Carbon, nitrogen and hydrogen analyses were performed on LECO CHNS-932 elemental analyzer. Mass spectro- metric analyses were performed on the Waters 2695 Allonce ZQ LC/MS spectrometer. Magnetic susceptibilities were determined on a Sherwood Scientific Magnetic Susceptibility Balance (Model MKI) at room temperature (300 K). UV–vis spectra were recorded using a Unicam UV2–100 series spectrometer. 0022-2860/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.molstruc.2011.04.037 ⇑ Corresponding author. Tel.: +90 312 2126720; fax: +90 312 2232395. E-mail address: zhayvali@science.ankara.edu.tr (Z. Hayvali). Journal of Molecular Structure 997 (2011) 53–59 Contents lists available at ScienceDirect Journal of Molecular Structure journal homepage: www.elsevier.com/locate/molstruc