Mixed bridged dinuclear Ni(II) complex incorporating 2-pyridinealdoxime ligand: Synthesis, crystal structure and magnetic property Lina Zheng a , Suyun Zhang a , Kai Li a , Wenqian Chen a , Yanmei Chen b , Bin Xu b , Bin Hu b , Yahong Li a,b,c,⇑ , Wu Li b a Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry and Chemical Engineering, Soochow University, Suzhou 215123, China b Key Laboratory of Salt Lake Resources and Chemistry, Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining 810008, China c State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou 730000, China article info Article history: Received 20 May 2010 Received in revised form 18 September 2010 Accepted 20 September 2010 Available online 25 September 2010 Keywords: Pyridine-2-carbaldehyde oxime Mixed bridged In situ reaction Magnetic property abstract A complex of the composition [Ni 2 (Hpyco) 2 (epa)(EtOH)Cl 3 ](1) (Hpyco = pyridine-2-carbaldehyde oxime; Hepa = 3-(ethoxycarbonyl)picolinic acid) has been synthesized via solvothermal synthetic reaction, and fully characterized by X-ray single crystal diffraction, IR and elemental analysis. Crystal structure revealed that 1 contains carboxylic oxygen atom bridged and chloro bridged dinuclear core with each Ni(II) exhibiting pseudo-octahedral geometry. An ester was formed in situ by the reaction of solvent ethanol with one carboxylic group of pyridine-2,3-dicarboxylic acid. Low-temperature magnetic suscep- tibility measurement for the solid sample of 1 revealed the ferromagnetic Ni II Ni II interactions. Ó 2010 Elsevier B.V. All rights reserved. 1. Introduction High-nuclearity paramagnetic complexes continue to attract in- tense attention in several fields because of their aesthetically pleasing structures [1], bioactivity [2–6], catalytic [7–10] and sin- gle-molecular magnetic properties [11–14]. Many synthetic strate- gies have been developed to this synthesis, and one of the most efficient approaches is the use of suitable bridging ligands, e.g., car- boxylic acids [15,16], oximates [17], pyridones [18,19], oxalate [20,21], oxamides [22], etc., for the assembly of many metal ions into a single molecular entity. It has been proved that combination of different bridging ligand in one synthetic system is a fertile route for the preparation of polynuclear cluster. We are interested in the coordination chemistry of combination of pyridine-2-carbaldehyde oxime ((Py)C(H)NOH) with carboxylic acid. Carboxylato anions can bind toward metal cations in various ways: monodentate, chelate, monoatomic bridges and multiply bridges [15,16,23]. The diverse coordination modes of carboxylato anions largely contribute to the formation of the high-nuclearity clusters. The anionic form of pyridine-2-carbaldehyde oxime ((Py)C(H)NO  ) is a key ligand in the area of single-molecule magnetism [24,25]. The use of the anionic ligand (Py)C(H)NO  had previously given a handful of Ni II [26–29], Ni II Mn II [30], Mn II [31,32], Zn II [33] and Co III [34] polynuclear compounds, but only a few of them contained ancillary carboxylate ligands. We have recently reported that combination of (Py)C(H)NO  with (4-Cl) PhCO 2 H and PhCO 2 H resulted in the formations of wheel like Mn 6 and Ni 6 molecules [35]. We suspected that there might be a number of other high-nuclearity Ni/(Py)C(H)NO  /R 0 CO  2 species available by changing aromatic carboxylic acid to pyridyl car- boxylic acid. With this consideration in mind, we explored the solvothermal reaction involving (Py)C(H)NOH, pyridine-2,3-dicar- boxylic acid, and NiCl 2 6H 2 O. A novel complex of formula [Ni 2 (Hpyco) 2 (epa)(EtOH)Cl 3 ] (1) (Hpyco = pyridine-2-carbaldehyde oxime; Hepa = 3-(ethoxycarbonyl)picolinic acid) was synthesized. Herein, we report the preparation, structural characterization and magnetic study of 1. To the best of our knowledge, complex 1 is the first chloro and carboxylic oxygen atom bridged dinuclear Ni(II) complex. 2. Results and discussion 2.1. Synthesis and IR spectrum The complex 1 was prepared under solvothermal condition in EtOH (Scheme 1). Treatment of NiCl 2 6H 2 O with (Py)C(H)NOH li- gand and pyridine-2,3-dicarboxylic acid in EtOH led to the forma- tion of 1. Complex 1 was readily isolated as a cyan crystal with 0022-2860/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.molstruc.2010.09.020 ⇑ Corresponding author at: Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry and Chemical Engineering, Soochow University, Suzhou 215123, China. Tel.: +86 512 65880323; fax: +86 512 65880089. E-mail address: liyahong@suda.edu.cn (Y. Li). Journal of Molecular Structure 984 (2010) 153–156 Contents lists available at ScienceDirect Journal of Molecular Structure journal homepage: www.elsevier.com/locate/molstruc