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Three New Cu−Azido Polymers and Their Systematic Interconversion: Role of the Amount of the Blocking Amine on the Structural Diversity and Magnetic Behavior

American Chemical Society
Publication Date
  • Inorganic & Physical Chemistry
  • Physics


Three new coordination polymers $[Cu_5(N_3)_{10}(en)_2]_n$ (1), $[Cu_6(N_3)_{12}(en)_4]n$ (2), and $[Cu_4(N_3)_8(en)_4]_n$ (3) have been synthesized in a controlled manner by treatment of a 1:2 mixture of $Cu(NO_3)_2$ and $NaN3$ with varying amount of ethylenediamine (en). Single-crystal structure analyses clearly indicated that the puckered $Cu_4$ biscubane unit in 1 gradually opens to a slightly more open $Cu_4$ macrocyclic unit in 2 when more en approaches to the $Cu_4$ core. Upon addition of further en, an open $Cu_4$ linear secondary building unit was obtained in complex 3. Complex 1 contains four different kinds of bridging modes of the azide anion and is a complicated 3D polymer. Similarly, complexes 2 and 3 are 3D and 2D polymers, respectively, containing three different kinds of bridging azides. Complex 3 contains two very rare cis end-to-end (EE) and single-end-on (EO) azido modes. Structural transformation from 1 to 3 was monitored and explained qualitatively. Variable-temperature magnetic studies in the temperature range of 300−2 K reveal the existence of dominant ferromagnetic behavior in all the three cases with a metamagnetic-type behavior in complex 1 with the critical field of transition at 0.8 T. The purity of all the complexes were established by elemental analyses, as well as by the powder XRD patterns that matched well with the expected patterns from the single-crystal structure analysis.

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