Synthesis, structural characterization, and Monte Carlo simulation of the magnetic properties of two new alternating Mn-II azide 2-D honeycombs. Study of the ferromagnetic ordered phase below 20 K

Reaction of Mn-II 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)(N-3)(2)], (1) and trans-[Mn(4-Etpy)(2)(N-3)(2)](n) (2) Comp ound 1 crystallizes in the triclinic system, P (1) over bar group (a = 9.26 9(2) Angstrom, b = 9.635(3) Angstrom, c = 18.860(4) Angstrom, Z = 4), and c ompound 2 crystallizes in the monoclinic system, P2(1)/c group (a = 14.416( 3) Angstrom, b = 8.515(2) Angstrom, c = 15.728(4) Angstrom, Z = 4). The two compounds show honeycomb structures based on dinuclear Mn-(mu -N-3)(2)-Mn subunits linked to the four nearest-neighbor similar subunits by four end-t o-end single azido bridges, but whereas the subunits of compound 1 show the end-to-end Mn-(mu (1,3)-N-3)(2)-Mn kind of bridges, compound 2 prefers the end-on Mn-(mu (1,1)-N-3)(2)-Mn fragment. Magnetically, compound 1 is an al ternating 2-D system with two different antiferromagnetic interactions, whe reas compound 2 corresponds to a two-dimensional ferro-antiferromagnetic sy stem showing spin canting and permanent magnetization below 20 K. The coupl ing constant parameters J(1) = -10.1 cm(-1). J(2) = -4.7 cm(-1) and g = 2.0 19 for 1 and J(1) = -5.3 cm(-1), J(2) = -2.9 cm(-1), and g = 2.016 for 2 ha ve been obtained from calculations using the Monte Carlo method based on th e Metropolis algorithm.