Spin Canting and Metamagnetism in 2D and 3D Cobalt(II) Coordination Networks with Alternating Double End-On and Double End-to-End Azido Bridges

By employing an N,N'-ditopic spacer 2-amino-pyrazine (ampyz), two-dimensional (2D) (1) and three-dimensional (3D) (2) azido-bridged cobalt(II) coordination networks with the identical formula [Co(N-3)(2)(ampyz)](n) have been synthesized and characterized structurally and magnetically. Compound 1 was prepared by the layer diffusion method in ambient temperature and crystallized in the high symmetric space group Immm. The 2D square-grid structure of 1 contains the perfect symmetric linear of alternating double end-on (EO) and double end-to-end (EE) azido-bridged Co-II chains which are linked together by an ampyz spacer in trans-arrangement. The intra-layer pi-pi stacking interactions among ampyz spacers additionally stabilize this layer. The adjacent 2D layers are assembled by the intermolecular hydrogen bonding between the NH2 of the ampyz and the EE azido ligands building a 3D structure. Compound 2 was prepared by a hydrothermal technique and shows a 3D framework containing a zigzag chain of similarly alternating double EO and double EE azido-bridged Co-II center. In contrast, this chain is linked by two ampyz spacers in cis-fashion giving rise to a 3D structure. The magnetic investigation of 1 shows the coexistence of a big spin canting angle and metamagnetism having magnetic ordering at 10 K, whereas the magnetic behavior of 2 simply exhibits spin-canted antiferromagnetism below T-N of 16 K.