A Series of Cu^II–Ln^III Metal–Organic Frameworks Based on 2,2′-Bipyridine-3,3′-dicarboxylic Acid: Syntheses, Structures, and Magnetic Properties

A series of Cu^II–Ln^III heterometallic metal–organic frameworks (HMOFs), displaying three types of structures with the formulas of {[Ln₂Cu­(BDPC)₄­(H₂O)₆]­·9H₂O}_<i>n</i> (Ln = La, <b>1</b>; Pr, <b>2</b>; Nd, <b>3</b>; BPDC^2– = 2,2′-bipyridine-3,3′-dicarboxylate), {[Ln₂Cu₂(BPDC)₅­(H₂O)₆]­·9H₂O}_<i>n</i> (Ln = Pr, <b>4</b>; Nd, <b>5</b>; Sm, <b>6</b>; Eu, <b>7</b>; Gd, <b>8</b>; Tb, <b>9</b>) and [DyCu₃(BPDC)₄­(NO₃)­(H₂O)₆]_<i>n</i> (<b>10</b>), have been successfully synthesized and well characterized. Single crystals available for X-ray diffraction measurements were carried out for MOFs <b>3</b>, <b>7</b>, <b>9</b>, and <b>10</b>. Powder X-ray diffraction and Fourier transform infrared analysis demonstrate the isomorphism for MOFs <b>1</b>–<b>3</b>, as well as MOFs <b>4</b>–<b>9</b>. The BPDC^2– ligand herein exhibits seven different coordination modes to link metal centers for the construction of different three-dimensional structures. The structures of the three types of Cu^II-Ln^III HMOFs can be described topologically with the Schläfli symbol {3·6²}­{3²·6⁶·7³·8³·9}­{6²·7}, {4·6²}₂{4²·6⁴·8⁶·10³}­{6·8²}₂, and {4·8·9}₂­{6·8·9}₂­{6·8²·9³}­{8²·9}₂, of which the latter two are new topologies. The static magnetic properties of the 10 HMOFs and dynamic magnetic properties of <b>9-Tb</b>_<b>2</b><b>Cu</b>_<b>2</b> and <b>10-DyCu</b>_<b>3</b> have been studied