Coordination Polymers of Lanthanide(III): Toward Encapsulation of Well-Defined Assembly of Guest Molecules

A series of lanthanide(III) coordination polymers [{La(Ben)3(H2O)2}·(4,4′-BPNO)0.5·HBen·DMF]n (1), [{Ce(Ben)3(4,4′-BPNO)(H2O)2}·DMF]n (2), [Tb(Ben)3(4,4′-BPNO)0.5(H2O)]n (3), [{Ln(Ben)3(4,4′-BPNO)(H2O)2}·HBen]n [Ln = La (4), Eu (5), Gd (6), Tb (7)] are synthesized and structurally characterized (where Ben = benzoate; HBen = benzoic acid; 4,4′-BPNO = 4,4′-bipyridyl-N,N′-dioxide; DMF = dimethylformamide). The metal centers in 1 have nine coordinated geometry, while the metal centers in all other coordination polymers are eight coordinated. Polymer 1 comprises one-dimensional chains of lanthanum(III) benzoate that encapsulate hydrogen-bonded assemblies formed by HBen···4,4′-BPNO···HBen interactions in its interstitial space. The polymer 2 and 3 are eight coordinated with square antiprism geometry around the metal node. The other four coordination polymers 4−7 have the same general composition and possess three-dimensional honeycomb like structures that encapsulates benzoic acid molecules in the interstices. The complex 5 (solid) exhibits a strong red luminescence emission characteristic of Eu(III). Magnetic susceptibility of 6 revealed weak antiferromagnetic interactions between the Gd(III) ions.

本研究合成并结构表征了一系列镧系(III)配位聚合物（lanthanide(III) coordination polymers）：[{La(Ben)₃(H₂O)₂}·(4,4′-BPNO)₀.₅·HBen·DMF]ₙ (1)、[{Ce(Ben)₃(4,4′-BPNO)(H₂O)₂}·DMF]ₙ (2)、[Tb(Ben)₃(4,4′-BPNO)₀.₅(H₂O)]ₙ (3) 以及[{Ln(Ben)₃(4,4′-BPNO)(H₂O)₂}·HBen]ₙ [Ln = La (4)、Eu (5)、Gd (6)、Tb (7)]。其中，Ben为苯甲酸根（benzoate），HBen为苯甲酸（benzoic acid），4,4′-BPNO为4,4′-联吡啶-N,N′-二氧化物（4,4′-bipyridyl-N,N′-dioxide），DMF为N,N-二甲基甲酰胺（dimethylformamide）。配合物1中的金属中心为九配位几何构型，而其余所有配位聚合物的金属中心均为八配位几何构型。聚合物1由一维苯甲酸镧(III)链构成，其间隙空间封装了由HBen···4,4′-BPNO···HBen氢键相互作用形成的组装体。配合物2与3的金属节点周围为八配位四方反棱柱几何构型。其余四种配位聚合物4~7具有相同的通式组成，且均呈现三维类蜂窝状结构，其间隙空间封装有苯甲酸分子。固态配合物5表现出Eu(III)特征的强红色发光发射。配合物6的磁化率测试结果显示，Gd(III)离子之间存在弱反铁磁相互作用。