Coordination Polymers Containing Manganese(II)-Azido Layers Connected by Dipyridyl-tetrazine and 4,4′-Azobis(pyridine) Linkers

Two new polynuclear manganese­(II) complexes [Mn­(dptz)­(N3)2]n (1) and [Mn­(azpy)­(N3)2]n (2) (where dptz = dipyridyl-tetrazine and azpy = 4,4′-azobis­(pyridine)) have been synthesized by self-assembly of the ligand azide, together with dptz and azpy as secondary spacers. The compounds are characterized by single-crystal X-ray diffraction analyses and variable-temperature magnetic measurements. The structural analyses reveal that in complex 1, which is the first reported Mn­(II) complex with the ligand dptz, two μ1,3 bridging azides connect neighboring manganese ions in a zigzag manner to generate a neutral two-dimensional (2D) sheet which is further connected by the dptz ligands to form a three-dimensional (3D) framework. By contrast, complex 2 contains dimeric [Mn2(μ1,1-N3)2]2+ fragments linked to four identical motifs by means of four single μ1,3-N3 bridges, that generates a neutral 2D MnII–azide sheet which is further interconnected by azpy ligands to neighboring manganese ions forming an unprecedented 3D network. Variable-temperature (2–300 K) magnetic susceptibility measurements show the presence of predominantly antiferromagnetic coupling for both complexes that has been reproduced with a regular antiferromagnetic S = 5/2 chain (J) with interchain interactions (j) modeled with the molecular field approximation with J = −7.1 cm–1 and j′ = −0.8 cm–1 for 1 and J = −4.2 cm–1 and j′ = 0.1 cm–1 for 2.

本研究通过叠氮配体与联吡啶四嗪（dipyridyl-tetrazine，dptz）、4,4'-偶氮二吡啶（4,4′-azobis(pyridine)，azpy）作为次级桥联配体的自组装反应，成功合成了两种新型多核锰(II)配合物：[Mn(dptz)(N₃)₂]ₙ（记为1）与[Mn(azpy)(N₃)₂]ₙ（记为2）。
通过单晶X射线衍射分析与变温磁性测试对所合成的两种配合物进行了结构与物性表征。
结构分析表明，配合物1是首例以dptz为配体的锰(II)配合物，其结构中两个μ-1,3桥联叠氮根以锯齿形方式连接相邻锰离子，形成中性二维（two-dimensional，2D）层状结构；随后该二维层又通过dptz配体进一步桥联，构筑出三维（three-dimensional，3D）骨架结构。
与之相对，配合物2含有二聚体[Mn₂(μ-1,1-N₃)₂]²+结构单元，该单元通过四个单μ-1,3-N₃桥联与四个相同的结构单元相连，形成中性二维锰(II)-叠氮根层状结构；随后该二维层又通过azpy配体与相邻锰离子相互连接，最终构筑出前所未有的三维网络。
变温（2~300 K）磁化率测试结果显示，两种配合物均主要表现出反铁磁耦合相互作用；通过正则反铁磁自旋S=5/2链（耦合常数J）结合分子场近似模拟链间相互作用（j），可很好地复现测试结果，其中配合物1的J = −7.1 cm⁻¹、j' = −0.8 cm⁻¹，配合物2的J = −4.2 cm⁻¹、j' = 0.1 cm⁻¹。