Spin Control in Oxamato-Based Manganese(II) Copper(II) Coordination Polymers with Brick-Wall Layer Architectures

Two new heterobimetallic manganese(II) copper(II) coordination polymers of formulas [Mn2Cu2-(Me(3)mpba)(2)(H2O)(6)]center dot 8H(2)O (1) and [Mn2Cu2(Me(4)ppba)(2)(H2O)(6)] center dot 8H(2)O (2) [Me(3)mpba = 2,4,6-trimethyl-N, N'-1,3-phenylenebis(oxamate) and Me(4)ppba = 2,3,5,6-tet-ramethyl-N,N'-1,4-phenylenebis(oxamate)] have been synthesized following a molecular-programmed self-assembly method from the corresponding dicopper(II) complexes acting as metalloligands toward Mn-II ions. 1 and 2 consist of neutral Mn-2(II) Cu-2II layers with a brick-wall structure made up of oxamato-bridged (MnCuII)-Cu-II chains connected through double meta-(1) and para-substituted (2) permethylated phenylene spacers. Overall magnetic (1) and nonmagnetic (2) layer ground states result from the ferro- and antiferromagnetic interchain interactions between the oxamato-bridged Mn-II Cu-II ferrimagnetic chains across m-and p-phenylene spacers, respectively. Interestingly, compound 1 exhibits a long-range ferromagnetic ordering with a rather high Curie temperature (T-C) of 20.0 K.