Novel dense organic–lanthanide hybrid architectures: syntheses, structures and magnetic properties

Abstract

Six novel three-dimensional (3D) dense organic–lanthanide(III) frameworks with formula {[Ln(HBPTCA)(H₂O)]·3H₂O}_n [Ln = La (1), Ce (2), Sm (3)] and [Ln₄(BPTCA)₃(H₂O)₄]_n [Ln = Tb (4), Dy (5), Ho (6)] were obtained by reactions of the corresponding lanthanide nitrate salt with 4,4′-bipyridine-2,2′,6,6′-tetracarboxylic acid (H₄BPTCA) under different conditions. Complexes 1–3 have the same structure with (4, 6²)₂(4², 6¹⁰, 8³) topology, which is rare binodal (3, 6)-connecting rutile structure, while the complexes 4–6 also with the same structure have different topology of (4², 6)₄(6, 8²)₄(4³, 6³)₄(4², 6⁴)₆(4⁴, 6⁵, 8⁵, 10). The results indicate that the reaction conditions have great influence on the structure of the resulted complexes in this system. In addition, the H₄BPTCA was found to be an effective bridging ligand for construction of novel lanthanide-based dense hybrids, and two new coordination modes of the BPTCA⁴⁻ were found in the complexes. The photoluminescent property of 4 and magnetic properties of 2, 5 and 6 were also investigated.