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.