Cluster based copper(II)-azide polymer: Synthesis, structure and magnetic study Sandip Saha a,⇑ , Debabrata Biswas a , Partha Pratim Chakrabarty a , Atish Dipankar Jana b , Athanassios K. Boudalis c , Saikat Kumar Seth d,e , Tanusree Kar d a Department of Chemistry, Acharya Prafulla Chandra College, New Barrackpur, Kolkata 700 131, India b Department of Physics, Behala College, Parnashree, Kolkata 700 060, India c Institute of Materials Science, NCSR ‘‘Demokritos”, 153 10, Aghia Paraskevi Attikis, Greece d Department of Materials Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032, India e Department of Physics, M.G. Mahavidyalaya, Bhupatinagar, Midnapore(E), West Bengal 721425, India article info Article history: Received 15 August 2010 Accepted 9 September 2010 Available online 22 September 2010 Keywords: Ethylene diamine Azides Copper(II) 1D coordination polymers Crystal structure Magnetic properties abstract The reaction of ethylene diamine with Cu(NO 3 ) 2 3H 2 O and an excess of NaN 3 (1:2:4 molar ratio) lead to the formation of copper-azido based polymer [Cu 4 (N 3 ) 8 (en) 2 ] n (1), which has been successfully character- ized by elemental analyses, IR spectroscopy, single-crystal X-ray diffraction and variable temperature magnetic study. X-ray crystal structure determination of 1 reveals that the structure consists of 1D chains of a centrosymmetric tetranuclear copper(II)-azido cluster, connected through double azido end-to-end bridges. Variable-temperature magnetic studies (between 2 and 300 K) suggest dominant antiferromag- netic interactions in this complex, although ferromagnetic interactions have been observed in all other copper-azido based polymers produced with ethylene diamine reported so far. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction Azides are very useful for constructing magnetically coupled sys- tems exhibiting a variety of behaviors such as antiferromagnetism [1–7], ferromagnetism [1–3,8–19], alternating ferro and antiferro- magnetism [20,21], ferrimagnetism [22,23], metamagnetism [24– 27], spin-canting [28], spin-flop [29], spin-glass [30], single-mole- cule magnetism [31–33] and single-chain magnetism [34,35]. The azido ligand is suitable bridging ligand due to its versatile binding modes and its capacity to mediate different types of magnetic ex- change interactions [36–42]. In a majority of the cases, the investi- gations of metal-azido systems have been mainly focused on the low dimensionalities [4–7]. High-dimensional networks of metal- azido derivatives are of particular interest because of their novel topology and enhancement of bulk magnetic properties, as well as their magnetostructural correlations. In recent times the most com- mon strategy employed for the synthesis of high-dimensional me- tal-azido systems is the further extension of metal-azido assemblies, using neutral organic blocking diamine co-ligands [43–47]. The simple, small diamine ligands are important in the synthesis of copper-azido cluster based polymers because they have relatively small volume. In this strategy most of the complexes were prepared by the use of blocking amine co-ligands in less than one equivalent with respect to the metal in conjunction with the azido ligand. Thus decreasing the molar amount of blocking diamine co-li- gands opens more sites for the bridging azido ligand to link the me- tal centers and it predominantly helps by the extension of metal- azido assemblies to synthesize high-dimensional materials. An- other interesting feature is that a simple change in the substitution on the diamine ligand dramatically changes the structure and mag- netic behavior of the metal-azido systems [43–47]. In a systematic study Mondal and Mukherjee have synthesized three Cu(II)-azido polymers [Cu 5 (N 3 ) 10 (en) 2 ] n (I), [Cu 6 (N 3 ) 12 (en) 4 ] n (II) and [Cu 4 (- N 3 ) 8 (en) 4 ] n (III) (where en = ethylenediamine) using ethylenedia- mine as a blocking co-ligand and they have established that the amount of the blocking amine co-ligand has a major and significant role on the structural diversity and magnetic behavior of these poly- mers [44]. The first two complexes are 3D polymers and the third complex is a 2D polymer. Variable-temperature magnetic studies in the temperature range 300–2 K reveal the existence of dominant ferromagnetic behavior in all three cases, with a metamagnetic type behavior in the first complex. In an another study Gu et al. have syn- thesized [Cu 8 (N 3 ) 16 (en) 4 ] n H 2 O(IV) using the same diamine as blocking co-ligand [45]. This complex is also a 3D coordination poly- mer and shows weak ferromagnetic coupling within the copper-azi- do cluster units. Therefore, these systems still remain a challenging scientific endeavor. Here, we extend the examples of polymeric copper(II) azide complexes bearing ethyenediamine as a blocking co-ligand, report- 0277-5387/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.poly.2010.09.012 ⇑ Corresponding author. Tel.: +91 33 2416 0354; fax. +91 33 2537 8797. E-mail address: sandipsaha2000@yahoo.com (S. Saha). Polyhedron 29 (2010) 3342–3348 Contents lists available at ScienceDirect Polyhedron journal homepage: www.elsevier.com/locate/poly