ORIGINAL PAPER Nickel(II) polypyridyl Complexes of 2,4,6-Tris(2-pyridyl)- 1,3,5-triazine Hassan Hadadzadeh • Mahbobeh Maghami • Jim Simpson • Aliakbar Dehno Khalaji • Khatereh Abdi Received: 18 October 2011 / Accepted: 14 February 2012 / Published online: 2 March 2012 Ó Springer Science+Business Media, LLC 2012 Abstract The synthesis, purification, characterization, electrochemical properties, and fluorescence quenching of two new mononuclear Ni(II) complexes, [Ni(tptz) (CH 3 OH)Cl 2 ](1) and [Ni(tptz) 2 ](PF 6 ) 2 CH 3 CN (2), con- taining the ligand 2,4,6-tris(2-pyridyl)-1,3,5-triazine (tptz) are described. Solid state structures of both complexes have been determined by single crystal X-ray crystallography. In (1) and (2), the Ni(II) metal centers use the major coordi- nation site of the tptz ligand and the coordination geometry around the Ni(II) is a distorted octahedron. The free tptz ligand has three emission bands that are assigned to the 1 (p–p * ) and 1 (n–p * ) states. The fluorescence spectra of (1) and (2) show that the fluorescence quenching of the tptz fluorophore proceeds via an energy transfer process. Magnetic susceptibility data derived from paramagnetic NMR revealed effective magnetic moments of 2.75 l B for (1), and 2.91 l B for (2) at room temperature. Cyclic vol- tammetry of (1) shows that the Ni(III/II) reduction couple is quasi-reversible whereas in complex (2), the Ni(II/I) couple indicates an electrochemical (EC) mechanism. Keywords 2,4,6-Tris(2-pyridyl)-1,3,5-triazine (tptz)  X-ray crystallography  Nickel(II) complexes  Cyclic voltammetry  Fluorescence quenching  Fluorophore Introduction 2,4,6-Tris(2-pyridyl)-1,3,5-triazine (tptz) is a bulky het- erocyclic organic compound featuring three 2-pyridyl rings and a 1,3,5-triazine ring [1] with an extended conjugated p system, that was first synthesized by Case and Koft in 1959 [2]. Among the polypyridyl ligands, tptz has drawn much attention because of its multiple coordination sites (major, middle, and minor) [3] (scheme 1) and large stabilizing p systems [4–6]. At first, it has been used as an analytical reagent for various metals. There is considerable interest in the coordination chemistry of tptz as a complexant for the separation and extraction of trivalent lanthanide(III) and actinide(III) ions [3, 7, 8], as a rigid strained ligand for catalytic transition metal centers [5], the potential antitumor characteristics of its platinum-group metal complexes [9], and the prepara- tion of DNA cleaving agents [10]. It acts as a building block to form polynuclear complexes and the coordination networks of huge supramolecular architectures [11–15]. Also its rigidity and trigonal geometry can lead to the formation of porous frameworks enclosing cavities and channels with different metals [16, 17]. Transition metal complexes of tptz also have gained much attention because of their biological activity and their physical, magnetic, and photoluminescence properties [18–22]. These complexes can also be used in a variety of electrocatalytic and pho- tocatalytic reactions [5]. In addition, several mononuclear complexes with the tptz ligand are known including Cu 2? H. Hadadzadeh (&)  M. Maghami  K. Abdi Department of Chemistry, Isfahan University of Technology, Isfahan 84156-83111, Iran e-mail: hadad@cc.iut.ac.ir J. Simpson Department of Chemistry, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand A. D. Khalaji Department of Chemistry, Faculty of Science, Golestan University, Gorgan, Iran 123 J Chem Crystallogr (2012) 42:656–667 DOI 10.1007/s10870-012-0296-7