Metal-organic frameworks from two-dimensional copper(II) complexes bridged with N-methylpyrazine-2-carboxamide

Two kinds of mpyza-bridged copper(II) complexes, [Cu(mpyza)(2)](BF4)(2)center dot 2H(2)O (1) and [Cu(mpyza)(2)] (PF6)(2)center dot 1.5H(2)O (2) were prepared (mpyza = N-methylpyrazine-2-carboxamide). Their crystal structures have been determined, and despite the different space groups (Pc and P2(1)/c for I and 2, respectively) they exhibit a similar metal-organic framework. Four Cu ions construct rectangular arrangement providing an infinite molecular two-dimensional grid, which have an equatorial-axial-type coordinated pyrazine bridge. Compounds 1 and 2 contain two or one and a half uncoordinated water molecules in a void space. The former liberates the water at 45 degrees C, but the latter does not below 170 degrees C, being consistent with the channel of 1 loosely packed with the counter anion. The magnetic studies revealed that they involved very weak Cu---Cu superexchange antiferromagnetic interactions with J/k(B) = -0.277(5) and -0.166(5) K for 1 and 2, respectively, analyzed on the basis of a two-dimensional model. (C) 2014 Elsevier Ltd. All rights reserved.