Magneto−Structural Correlations in 2D and 3D Extended Structures of Manganese(II)−Malonate Systems

Two polymeric malonato-bridged manganese(II) complexes of formula [Mn(mal)(H2O)2]n (1) and [Mn2(mal)2(4,4‘-bipy)(H2O)2]n (2) have been synthesized and characterized (mal = malonate dianion; 4,4‘-bipy = 4,4‘-bipyridine).
The crystal structure of complex 1 was already known. Complex 2 crystallizes in monoclinic space group P21/n, Z
= 2, with unit cell parameters of a = 7.2974(10) Å, b = 18.7715(10) Å, c = 7.514(3) Å, and β = 91.743(12)°.
The structure determination reveals that the complex [Mn2(mal)2(4,4‘-bipy)(H2O)2]n (2) is a 3D network being composed
of Mn−malonate sheets which are pillared by bidentate 4,4‘-bipy spacer forming small voids. The Mn−Mn distances
through Mn−μ-(O3−C8−O4)−Mn, Mn−μ-(O1−C6−O2)−Mn, and Mn−μ-4,4‘-bipy−Mn bridges are 5.561, 5.410, and
11.723 Å, respectively. The magnetic behaviors of complexes 1 and 2 in the temperature range 300−2 K are very
close, corresponding to a weak antiferromagnetic coupling. The magnetic pathways of complex 1 are through two
Mn−O−C−O−Mn with anti-anti conformation and two Mn−O−C−O−Mn with syn-anti conformations and in complex
2 through all Mn−O−C−O−Mn with syn-anti conformations. Both syn-anti and anti-anti conformations create weak
antiferromagnetic coupling, and the susceptibility data are fitted by the expansion series of Lines and the Curély
formula for an S = 5/2 antiferromagnetic quadratic layer, based on the exchange Hamiltonian H = −ΣnnJSiSj. The
best fit is given by the superexchange parameters J = −0.32 cm-1 and g = 2.00 for complex 1 and J = −0.14
cm-1, Jinter = −0.031 cm-1, and g = 2.00 for complex 2. Finally, in both the complexes there is a magnetic
pathway Mn−O−C−C−C−O−Mn, and this pathway through the three carbon atoms of the malonato-bridging ligand
could be considered negligible.

两种由多聚马来酸桥连的锰(II)配合物，其化学式分别为[Mn(mal)(H2O)2]n（1）和[Mn2(mal)2(4,4'-bipy)(H2O)2]n（2），已成功合成并进行了表征（mal代表马来酸二阴离子；4,4'-bipy代表4,4'-联吡啶）。已知配合物1的晶体结构。配合物2以单斜晶系P21/n空间群结晶，晶胞参数为a = 7.2974(10) Å，b = 18.7715(10) Å，c = 7.514(3) Å，以及β = 91.743(12)°。结构解析表明，配合物[Mn2(mal)2(4,4'-bipy)(H2O)2]n（2）构成一个三维网络，该网络由锰-马来酸片层组成，这些片层被双齿的4,4'-bipy间隔物支撑，形成小的空腔。通过Mn-μ-(O3-C8-O4)-Mn，Mn-μ-(O1-C6-O2)-Mn，和Mn-μ-4,4'-bipy-Mn桥连接的Mn-Mn距离分别为5.561 Å，5.410 Å，和11.723 Å。在300-2 K的温度范围内，配合物1和2的磁性行为非常接近，对应于弱反铁磁性耦合。配合物1的磁通路是通过两个反反式构象的Mn-O-C-O-Mn和两个顺反式构象的Mn-O-C-O-Mn实现的，而配合物2则是通过所有顺反式构象的Mn-O-C-O-Mn实现的。顺反式和反反式构象均产生弱反铁磁性耦合，磁化率数据通过Lines展开系列和Curély公式拟合，适用于S = 5/2反铁磁性二次层，基于交换哈密顿量H = −ΣnnJSiSj。最佳拟合值由配合物1的交换参数J = −0.32 cm-1和g = 2.00，以及配合物2的J = −0.14 cm-1，Jinter = −0.031 cm-1和g = 2.00给出。最后，在这两种配合物中均存在Mn-O-C-C-C-O-Mn的磁通路，且通过马来酸桥连配体的三个碳原子的该通路可视为可忽略不计。