pubs.acs.org/IC Published on Web 11/06/2009 r 2009 American Chemical Society Inorg. Chem. 2009, 48, 11325–11334 11325 DOI: 10.1021/ic901844j Cu II -Azide Polymers of Cu 3 and Cu 6 Building Units: Synthesis, Structures, and Magnetic Exchange Mechanism † Sandip Mukherjee, Bappaditya Gole, Rajesh Chakrabarty, and Partha Sarathi Mukherjee* Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore-560012, India Received September 18, 2009 Two new neutral copper-azido polymers [Cu 3 (N 3 ) 6 (tmen) 2 ] n (1) and [Cu 6 (N 3 ) 12 (deen) 2 ] n (2)[tmen = N, N,N 0 , N 0 -tetramethylethylenediamine and deen = N, N 0 -diethylethylenediamine] have been synthesized by using lower molar equivalents of the chelating diamine ligands with Cu(NO 3 ) 2 3 3H 2 O and an excess of NaN 3 . The single crystal X-ray structure shows that in the basic unit of the 1D complex 1, the three Cu II ions are linked by double end-on azido bridges with Cu-N EO -Cu angles on both sides of the magnetic exchange critical angle of 108°. Complex 2 is a 3D framework of a basic Cu 6 cluster. Cryomagnetic susceptibility measurements over a wide range of temperature exhibit dominant ferromagnetic behavior in both the complexes. Density functional theory calculations (B3LYP functional ) have been performed on the trinuclear unit to provide a qualitative theoretical interpretation of the overall ferromagnetic behavior shown by the complex 1. 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