Synthesis, characterization and molecular structures of Ni(II) complexes derived from Schiff base pyridylimine ligands J. Roberto Pioquinto-Mendoza a,⇑ , Jaime Alberto Rosas-Ortiz a , Reyna Reyes-Martínez a , Patricia Conelly-Espinosa a , Rubén A. Toscano a , Juan M. Germán-Acacio b , Alcives Avila-Sorrosa c , Oscar Baldovino-Pantaleón d , David Morales-Morales a,⇑ a Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, C.P. 04510, México b Research Support Network, Instituto Nacional de Ciencias Médicas y Nutrición SZ-Universidad Nacional Autónoma de México (CIC-UNAM), México D.F., Mexico c Departamento de Química Orgánica, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Carpio y Plan de Ayala S/N, Colonia Santo Tomás, México D.F. 11340, Mexico d UAM Reynosa Rodhe, Universidad Autónoma de Tamaulipas, Carr. Reynosa-San Fernando S/N, Reynosa, Tamaulipas 88779, México article info Article history: Received 12 July 2015 Received in revised form 16 September 2015 Accepted 18 September 2015 Available online 28 September 2015 Dedicated with great admiration to Prof. Luis Antonio Oro Giral on the Occasion of his 70 th Birthday. Keywords: Nickel complexes Pyridylimine ligands Crystal structures Supramolecular arrangements Non-covalent interactions Schiff base compounds abstract The synthesis and structural characterization of Ni(II) complexes derived from N1,N4-bis(pyridin-2-yl- methylene)butane-1,4-diamine (L1) and N1,N4-bis(1-(pyridin-2-yl)ethylidene)butane-1,4-diamine (L2) is described. The paramagnetic Ni(II) complexes NiL1 and NiL2 were fully characterized and their struc- tures unequivocally determined by single crystal X-ray diffraction techniques. The molecular structures of NiL1 and NiL2 exhibited the ligands L1 and L2 coordinated in a j 4 -N,N,N,N-tetradentate fashion. The subtle changes in the ligands defines the ionic o neutral nature of the complexes. Furthermore, in the solid state both complexes exhibit extended hydrogen-bond networks. Ó 2015 Elsevier B.V. All rights reserved. 1. Introduction Throughout the years Schiff base ligands have reached the sta- tus of privileged ligand platform [1]. In part, due to the facile man- ner in which they are prepared by condensation between aldehydes and amines. Hugo Schiff described the condensation between an aldehyde and an amine leading to a Schiff base in 1864 [2]. Schiff base ligands are able to coordinate metals through the imine nitrogen and another group, usually linked to the alde- hyde. In fact, Schiff bases are able to stabilize many different met- als in various oxidation states, controlling the performance of metals in a large variety of useful applications. This versatility in ligand design provides for the straightforward modulation of the sterics, electronics, and chirality at the central metal ion. This in turn allows for the investigation of structure– function relationships in diverse areas from catalysis to materials chemistry [3,4]. The reversibility of imine formation can also be harnessed to synthesize larger structures such as ring systems and macromolecules [5], and there is now increased interest in the study of multimetallic cooperative complexes. Metalloenzymes are one area of inspiration for the development of this area, as many sites possess multiple metal centers acting in concert to drive specific processes [6]. Numerous small molecule models have been synthesized as a means to better understand the functionality of these active sites and Schiff bases in particular, find great utility due to their excellent replication of biological coordination envi- ronments, ease of synthesis, and ability to form stable complexes with a wide variety of metal ions. In a similar manner, metallic complexes based on Schiff pyridyl imine ligands have been carried out related with cytotoxicity [7,8] antimicrobial [9] and catalytic properties in either ethylene, olefins polymerization and other potentially relevant catalytic transfor- mations [10–14]. Other reports involve Schiff pyridylimine ligands http://dx.doi.org/10.1016/j.ica.2015.09.016 0020-1693/Ó 2015 Elsevier B.V. All rights reserved. ⇑ Corresponding authors. Tel.: +52 55 56224514; fax: +52 55 56162217. E-mail address: damor@unam.mx (D. Morales-Morales). Inorganica Chimica Acta 438 (2015) 146–152 Contents lists available at ScienceDirect Inorganica Chimica Acta journal homepage: www.elsevier.com/locate/ica