M2(N3)4(hmt)(H2O) (M = Co2+ and Ni2+, hmt = hexamethylenetetramine): mixed azide-hmt bridged 3D metal frameworks with long-range magnetic ordering.

Two mixed azide-hmt bridged compounds were obtained with neutral 3D networks, Co2(N3)4(hmt)(H2O) (1) and Ni2(N3)4(hmt)(H2O) (2), hmt = hexamethylenetetramine. In 1, the azide ions present three kinds of coordination modes in the connection of two unique Co2+ions. Each Co1 is connected by trans-EE-azide ions and hmt into extended (4,4) layers, and each Co2 is connected by EO-azide ions into dimers which are located between the neighboring (4,4) layers. The cis-EE-azide ions connect the dimers to the neighboring layers to form rare 3D networks. The Co12+and Co22+ions have four and three connections through azide bridges to the neighboring Co2+ions, respectively. Twisted torsion angles of cis/trans-EEazide bridges are observed in 1, with a value of 83.39 and 117.43°, respectively. The Ni analogue 2is isostructural with 1revealed by IR, elemental analysis and Powder X-ray diffraction. Magnetic investigation shows that 1is a weak ferromagnet below Tc= 15.0 K, with a large coercivity of 1 T at 2 K, while 2is a soft ferromagnet below Tc= 10.0 K. [ABSTRACT FROM AUTHOR]