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(Me3mpba)2(H2O)6]·8H2O (1) and [Mn2Cu2(Me4ppba)2(H2O)6]·8H2O (2) [Me3mpba = 2,4,6-trimethyl-N,N′-1,3-phenylenebis(oxamate) and Me4ppba = 2,3,5,6-tetramethyl-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 MnII ions. 1 and 2 consist of neutral MnII2CuII2 layers with a brick-wall structure made up of oxamato-bridged MnIICuII 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 MnIICuII ferrimagnetic chains across m- and p-phenylene spacers, respectively. Interestingly, compound 1 exhibits a long-range ferromagnetic ordering with a rather high Curie temperature (TC) of 20.0 K.本研究合成了两种新型异双金属二价锰-二价铜配位聚合物，其化学式分别为[Mn₂Cu₂(Me₃mpba)₂(H₂O)₆]·8H₂O（1）与[Mn₂Cu₂(Me₄ppba)₂(H₂O)₆]·8H₂O（2）；其中Me₃mpba=2,4,6-三甲基-N,N′-1,3-苯双(草酰胺)，Me₄ppba=2,3,5,6-四甲基-N,N′-1,4-苯双(草酰胺)，合成采用分子调控自组装法，以相应的二铜(II)配合物作为金属配体（metalloligand）与Mn(II)离子进行配位反应。配合物1与2均由中性的Mn(II)₂Cu(II)₂层构成，该层呈现砖墙型结构，由草酰胺桥连的Mn(II)Cu(II)链通过双间位（1）和双对位（2）全甲基化苯撑间隔基相互连接而成。整体而言，配合物1与2分别具有铁磁层基态与非磁层基态，这分别源于草酰胺桥连的Mn(II)Cu(II)亚铁磁链通过间位和对位苯撑间隔基发生的链间铁磁相互作用与反铁磁相互作用。值得关注的是，配合物1表现出长程铁磁有序现象，其居里温度（T_C）高达20.0 K。