Synthesis, Structural Characterization, and Monte Carlo Simulation of the Magnetic Properties of Two New Alternating MnII Azide 2-D Honeycombs. Study of the Ferromagnetic Ordered Phase below 20 K

Reaction of MnII and pyridine derivatives such as 4-methylpyridine (4-Mepy) and 4-ethylpyridine (4-Etpy) led to the new two-dimensional systems trans-[Mn(4-Mepy)2(N3)2]n (1) and trans-[Mn(4-Etpy)2(N3)2]n (2). Compound 1 crystallizes in the triclinic system, P1 group (a = 9.269(2) A, b = 9.635(3) A, c = 18.860(4) A, Z = 4), and compound 2 crystallizes in the monoclinic system, P2(1)/c group (a = 14.416(3) A, b = 8.515(2) A, c = 15.728(4) A, Z = 4). The two compounds show honeycomb structures based on dinuclear Mn-(mu-N3)2-Mn subunits linked to the four nearest-neighbor similar subunits by four end-to-end single azido bridges, but whereas the subunits of compound 1 show the end-to-end Mn-(mu 1,3-N3)2-Mn kind of bridges, compound 2 prefers the end-on Mn-(mu 1,1-N3)2-Mn fragment. Magnetically, compound 1 is an alternating 2-D system with two different antiferromagnetic interactions, whereas compound 2 corresponds to a two-dimensional ferro-antiferromagnetic system showing spin canting and permanent magnetization below 20 K. The coupling constant parameters J1 = -10.1 cm-1, J2 = -4.7 cm-1, and g = 2.019 for 1 and J1 = -5.3 cm-1, J2 = 2.9 cm-1, and g = 2.016 for 2 have been obtained from calculations using the Monte Carlo method based on the Metropolis algorithm.