[Cu₂(en)₂(N₃)₄]_n – A new member in the family of copper(II)-azido assemblies: structural and magnetic studies

Abstract

A copper(II) complex with ethylene diamine and azide, viz., [Cu₂(en)₂(N₃)₄]_n has been isolated under self-assembling conditions and characterized both structurally and magnetically in order to probe the role of reactant molar ratios in generating supramolecular assemblies with strong magnetic interactions toward achieving molecule-based magnets as a long-term objective. The title structure with ferromagnetic interactions is an intermediate member in the family of copper-azido assemblies involving ethylene diamine, obtained by systematic modifications in the reactant molar ratios, highlighting the inherent difficulty in controlling the final solid formation and potential of the delicate equilibrium conditions in directing supramolecular structures, which may display interesting structure-correlated properties. The structure is a chain of μ-1,1 bridged dimers of Cu2, connected to Cu1 through μ-1,3 azide bridges, leading to a rail-road arrangement of polymeric chains. Two such parallel chains are further linked to each other through Cu3, which is connected to Cu2′ of the dimer, through asymmetric end-on μ-1,1 azide bridges, resulting in a 2-D network in the unit cell. The magnetic behavior revealed ferromagnetic interactions in Cu(II) pairs and is dominated by overall antiferromagnetic interactions within the network.

Keywords:

• Copper-azides
• ethylene diamine
• magnetic properties

Acknowledgements

Financial assistance from DST (SR/WOS-A/CS-04/2007) New Delhi, India is gratefully acknowledged. The authors also thank DST for the single crystal X-ray diffraction facility installed in the Department of Chemistry, BHU. BK acknowledges UGC for the Rajiv Gandhi National Fellowship. JPS acknowledges CEFIPRA/IFCPAR (Indo-French Center for the Promotion of Advanced Research) for support. PP, BK and SSS acknowledge Prof. R.J. Butcher, Howard University, Washington, DC, USA for helpful crystallographic discussions.