Heterometallic coordination framework by sodium carboxylate subunits and cobalt (III) centers obtained from a highly hydrogen bonding stabilized cobalt (II) monomeric complex Jesús A. Arenzano a,b , Jorge O. Virues b , Raúl Colorado-Peralta a , Pedro I. Ramirez-Montes c , Rosa Santillán c , Mario Sanchez d , José María Rivera a, ⁎ a Facultad de Ciencias Químicas, Universidad Veracruzana, Prolongación Oriente 6, No. 1009, Colonia Rafael Alvarado, C.P. 94340 Orizaba, Ver., Mexico b Facultad de Ingeniería Mecánica y Eléctrica, Universidad Veracruzana, Circuito Gonzalo Aguirre Beltrán S/N, Zona Universitaria, C.P. 91000 Xalapa, Ver., Mexico c Departamento de Química, Centro de Investigación y de Estudios Avanzados del IPN, Apartado P.O. Box 14-740, CP 07360 México DF, Mexico d Centro de Investigación en Materiales Avanzados, S.C. Alianza Norte 202, PIIT, Carretera Monterrey-Aeropuerto Km. 10, C.P. 66600 Apodaca, N.L., Mexico abstract article info Article history: Received 1 July 2014 Received in revised form 29 October 2014 Accepted 30 October 2014 Available online 31 October 2014 Keywords: Pseudosymmetry Metal–organic frameworks Hydrogen bonding Theoretical calculations Crystal engineering Crystal packing Coordination cobalt and nickel complexes (1) and (2) were obtained serendipitously by the reaction of M(NO 3 ) 2 ·6H 2 O (M = Co and Ni) and methyliminodiacetic acid (H 2 L) in a mixture of solvents. The X-ray diffraction showed the unusual structures with Z′ = 4 of (1) and (2), showing the four monomers highly stabilized by hy- drogen bonding interactions which corresponds to the tris-(aqua)-(N-methyliminodiacetato)-cobalt (II) and nickel (II) respectively. The Wiberg Bond Indices (WBIs) were computed on (1) and (2) to evaluate the stability of the hydrogen bonding interactions and showed a good correlation with the experimental X-ray diffraction data. Finally, the complex [Co (L) 2 Na] n (3) corresponds to the heterometallic coordination framework which was obtained by addition of a second equiv. of methyliminodiacetic acid (H 2 L) in basic sodium hydroxide media. The oxidation of the cobalt atom in (3) was confirmed by the experimental coordination bond distances observed by XRD, which are in the range from 1.882 to 1.957 Å. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Structures with Z′ N 1 have attracted great attention because of the deep knowledge they can offer into crystal nucleation and packing [1–3]. The frequency of Z′ N 1 reported by Steed gave a value of 11.5% for organic structures and 8.8% for the Cambridge Structural Database (CSD) as a whole [4], while Bond gave a value of 12.3% for organic struc- tures, 9.2% for metal-containing structures and 10.9% for the CSD as a whole [5]. Factors contributing to this increase may include improve- ments in techniques for structure determination. The fact that some crystals take more than one symmetry independent molecules is still under study [6–8]. For example, nucleosides and nucleotides possess an array of strong hydrogen bonding, they have low intrinsic molecular symmetry, and they have normally chiral centers and hence crystallize in chiral space groups. All of these factors have been identified as imparting a tendency toward crystallization with more than one inde- pendent molecule in the asymmetric unit Z′ N 1. Structures exhibiting saturated hydrogen bonding are of particular interest because they rep- resent cases in which all the crystal packing requirements of the system have been met, often at the expense of increasing Z′. Combination of one or more competing synthons can lead to structures where the asymmetric unit contains more than one molecule [9]. Also, alcohols and phenols form stable clusters in solution because of strong hydrogen bonding and have a higher tendency to form Z′ N 1 [10,11]. The study of polymorphic systems seems to be another key to understand the secrets of high Z′ structures [12]. The analysis of the electron density distri- bution function ρ(r) in a crystal is another approach to the study of Z′ N 1 [13–15]. In this paper we could study by X-ray diffraction and theoretical calculations the intermolecular hydrogen bonding in- teractions between the four monomers present in the asymmetric unit, Z′ = 4 of the cobalt and nickel complexes 1 and 2. Also, we could demonstrate that the addition of sodium hydroxide to a solu- tion prepared to obtain the cobalt complex 1 with Z′ = 4 led to the heterometallic complex 3, which results because the three water molecules in complex 1 are replaced by a second more reactive deprotonated methyliminodiacetato ligand (L − ), consequently the hydrogen bonding interactions disappear and the free carboxylate units coordinate to sodium atom Scheme 1. Inorganic Chemistry Communications 51 (2015) 55–60 ⁎ Corresponding author. E-mail address: chemax7@yahoo.com.mx (J.M. Rivera). http://dx.doi.org/10.1016/j.inoche.2014.10.037 1387-7003/© 2014 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Inorganic Chemistry Communications journal homepage: www.elsevier.com/locate/inoche