Synthesis, crystal structure and biological activity of the nickel(II) complex of 2,6-diacetylpyridinedihydrazone A. Dilek Azaz*, Selma Celen, Hilmi Namli, Onur Turhan and Raif Kurtaran Department of Biology and Chemistry, Balikesir University Art & Science Faculty, Cagis, 10145 Balikesir, Turkey Canan Kazak and N. Burcu Arslan Department of Physics, Faculty of Arts and Sciences, Ondokuz Mayis University, TR-55139 Samsun, Turkey Received 15 January 2007; accepted 13 March 2007 Abstract A complex of Ni II with 2,6-diacetylpyridinedihydrazone (L) towards nickel(II) has been prepared and characterized by means of elemental analyses, IR, electronic spectra and single crystal X-ray analyses. [NiL 2 ](NO 3 ) was crys- tallized in the tetragonal space group P-4 21 c. The complex exhibits the expected coordination sphere with six nitrogen atoms coordinated to the central Ni II with a deformation from pseudo-octahedral geometry. Antimicrobial activities of the ligand and its complex were investigated. Introduction Schiff bases with hydrazone-based functional groups are of interest owing to their versatility in coordinating metals as well as their pharmacological and biological activities [1]. It is well established that some drugs have increased activity when administered as metal com- plexes, as compared to the free ligand [2, 3]. Condensa- tion of 2,6-diacetylpyridine with hydrazine hydrate is one example of compounds, which acts as a planar tridentate ligand analogues to terpyridine. Divalent transition metals (iron, cobalt, copper) complexes with 2,6-diacetylpyridinedihydrazone (Figure 1a) and its derivatives have been prepared and characterized by Curry et al. [4]. Subsequently, one crystal structure of a nickel complex related to the title complex has been published by Sproul and Stucky [5] (Figure1b). According to this study, the nickel (IV) ion is coordi- nated to two 2,6-diacetylpyridine dioximato ligands via the six nitrogen atoms of these ligands. Radecka- Paryzek et al. [1] described the synthesis, spectral characterization and X-ray crystal structure of a 2,6- diacetylpyridinedihydrazone complex with lead(II) nitrate. In this complex, one lead ion is surrounded by nine ligating atoms, three nitrogen atoms from the or- ganic ligand and six oxygen atoms from nitrate anions. In this study, we report the synthesis and X-ray crystal structure of a mononuclear nickel(II) com- pound of 2,6-diacetylpyridinedihydrazone, whose structure is shown in Figure 1c. The antimicrobial activity of the ligand (L) and its metal complex towards common bacteria and fungi was investigated in vitro. Experimental All reagents and solvents were purchased from Merck, Aldrich or Carlo Erba and used without further purifi- cation. Elemental analyses were carried using Eurovec- tor 3018 CHNS analyzer. FTIR spectra were obtained by using IR grade KBr disks on a Perkin-Elmer 1600 Series FTIR spectrophotometer in the range of 4000–250 cm )1 . Electronic spectra were obtained using a Varian Cary |1E| UV-Visible Spectrophotometer. 2,6-diacetylpyridinedihydrazone was prepared by reacting an EtOH solution of 2,6-diacetylpyridine with hydrazine hydrate as described in the literature [1]. Synthesis of the complex To a solution of Ni(NO 3 ) 2 Æ 6H 2 O (1 mmol in 25 ml EtOH), 2,6-diacetylpyridinedihydrazone (2 mmol in 30 cm 3 MeCN) was added in one portion and the mixture was heated to boiling point. The mixture was stirred for 10 min. at the boiling point and then left to stand for 2 or 3 days. The light brown crystalline pre- cipitate was filtered off and dried in air. Yield: 68%, Found: C, 37.8; H, 4.2; N, 29.1, Cal. C 18 H 26 N 12 Ni O 6 : C, 38.2; H, 4.6; N, 29.7. Crystals were suitable for X-ray crystallography. Crystal structure determination The data collection was performed at 293 K on a Stoe-IPDS-2 diffractometer equipped with a graphite * Author for correspondence: E-mail: azaz@balikesir.edu.tr Transition Metal Chemistry (2007) 32:884–888 Ó Springer 2007 DOI 10.1007/s11243-007-0242-2