Bis(l-tetrazolato-NN 0 ) bridged dinuclear nickel(II) Schiff base complexes: Tandem synthesis, structure and self assembly Mithun Das a , Klaus Harms b , Biswa Nath Ghosh c , Kari Rissanen c , Shouvik Chattopadhyay a,⇑ a Department of Chemistry, Inorganic Section, Jadavpur University, Kolkata 700 032, India b Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Straße, D-35032 Marburg, Germany c Department of Chemistry, Nanoscience Center, University of Jyväskylä, P.O. Box 35, 40014 Jyväskylä, Finland article info Article history: Received 30 August 2014 Accepted 12 November 2014 Available online 21 November 2014 Keywords: Nickel(II) Schiff base 1,3-Dipolar cycloaddition 5-Pyrazinyltetrazolate Dinuclear abstract Two new bis(l-tetrazolato-NN 0 ) bridged dinuclear nickel(II) Schiff base complexes [Ni 2 L 1 2 (PTZ) 2 ]2(CH 3 ) 2 SO2.69H 2 O (1) and 2[Ni 2 L 2 2 (PTZ) 2 ]3H 2 O (2)(HL 1 and HL 2 are Schiff bases, HL 1 = 2-((2-(dimethylamino) ethylimino)methyl)phenol, HL 2 = 2-((2-(methylamino)ethylimino)methyl)-6-methoxyphenol and HPTZ is 5-pyrazinyltetrazole) have been synthesized via [3+2] cyclo-addition of 2-cyanopyrazine and sodium azide in presence of nickel(II) acetate tetrahydrate and the respective Schiff bases. The structures of the complexes are confirmed by single crystal X-ray diffraction analysis. Both complexes show fluores- cence. The change in the denticity of the Schiff base blocking ligand is shown to have no effect in control- ling the molecular structures of the complexes. The supramolecular self assemblies are also explored. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Di and polynuclear complexes of nickel(II) are widely used as materials for non-linear optics [1,2], as catalysts for diverse reac- tions [3] and as suitable models for the active sites of many enzymes [4–6] and also as magnetic materials [7–9]. Several researchers have used carboxylates and pseudohalides as bridging ligands and N 2 O donor salicylaldimine Schiff bases as blocking ligands to prepare such complexes [10–15]. The ability of the phenoxo oxygen atom to bridge the metal centers and also to par- ticipate in hydrogen bonding interaction to form various supramo- lecular architectures has also inspired the researchers to use such Schiff bases in preparing new complexes [16,17]. Tetrazoles have also been used by several groups as bridging ligands [18–20]. The application of tetrazole functional groups in medicinal chemis- try as a metabolically stable surrogate for a carboxylic acid group [21–23] and in material science as high density energy materials [24–26] and also in coordination chemistry as ligands with versa- tile coordination ability through its four nitrogen atoms [27,28] are well established. However, the use of Schiff bases as blocking ligands in preparing tetrazolato bridged di and polynuclear transi- tion metal complexes is very rare. In our previous papers, we have reported three such complexes of nickel(II) [29,30]. Synthesis of few more nickel(II) complexes was also reported by a different group [31,32]. Two different methods were used in preparing the complexes. In the first case, the nickel(II) Schiff base complex with azide co-ligand was isolated in solid state followed by the reaction of this azide complex with 2-cyanopyridine to prepare the tetrazo- lato bridged dinuclear nickel(II) complexes with Schiff base block- ing ligand. In the second case, the azide complex was not isolated, instead tandem synthesis of the tetrazolato bridged nickel(II) Schiff base complexes was reported. In the present work, we have used two different Schiff bases as blocking ligands and substituted tet- razolate to prepare two bis(l-tetrazolato-NN 0 ) bridged dinuclear nickel(II) complexes by tandem synthesis using 2-cyanopyrazine, sodium azide, nickel(II) acetate and respective Schiff base ligand under stirring condition in methanol. Our intension was to exam- ine the variation in molecular architectures, if any, on changing the denticity of Schiff bases. We would also like to investigate the variation in supramolecu- lar architectures of complexes. Supramolecular systems based on coordination complexes have already received imense attention for their potential uses in various fields [33,34]. Synthesis and characterization of a large number of supramolecular systems have also been reported in last decades [35,36]. The components of a supramolecule are held together by a variety of non-covalent forces, e.g. hydrogen bonding, pp,CAHp interactions, etc. [37–40]. Herein, we report the tandem syntheses, structural features, spectroscopic characterization and supra-molecular architectures of two new bis(l-tetrazolato-NN 0 ) bridged nickel(II) complexes with two Schiff base blocking ligands. http://dx.doi.org/10.1016/j.poly.2014.11.012 0277-5387/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +91 33 24572941. E-mail address: shouvik.chem@gmail.com (S. Chattopadhyay). Polyhedron 87 (2015) 286–292 Contents lists available at ScienceDirect Polyhedron journal homepage: www.elsevier.com/locate/poly