A Series of Metal–Organic Frameworks Constructed From a V‑shaped Tripodal Carboxylate Ligand: Syntheses, Structures, Photoluminescent, and Magnetic Properties

Six novel complexes, namely, {[Zn_1.5(L)­(bix)_1.5(H₂O)]·H₂O}_<i>n</i> (<b>1</b>), {[Co_1.5(L)­(bix)_1.5(H₂O)]·H₂O}_<i>n</i> (<b>2</b>), {[Co₃(L)₂(4,4′-bpy)₃]·5H₂O}_<i>n</i> (<b>3)</b>, {[Cd₃(L)₂(4,4′-bpy)₃]·4.5H₂O}_<i>n</i> (<b>4</b>), {[Cu₃(L)₂(4,4′-bpy)₃]·3H₂O}_<i>n</i> (<b>5)</b>, and {[Ni_1.5(L)­(4,4′-bpy)_1.5(H₂O)₃]·2H₂O}_<i>n</i> (<b>6)</b> have been synthesized by the hydrothermal reaction of 5-(4-carboxy-2-nitrophenoxy)­isophthalic acid (H₃L) with different transition metal ions in the presence of ancillary ligands, 1,4-bis­(imidazol-1-ylmethyl)­benzene (bix) and 4,4′-bipyridine (4,4′-bpy). Complexes <b>1</b> and <b>2</b> are isostructural, possessing a (3,8)-connected <b>tfz</b>-d type topology with the Schläfli symbol of {4³}₂{4⁶·6¹⁸·8⁴}. The 3D structures of complexes <b>3</b>–<b>5</b> are very similar to complex <b>1</b> with only a little difference of the H₃L coordination motif in complexes <b>4</b> and <b>5.</b> Meanwhile, we use 4,4′-bpy instead of bix as the ancillary ligand in all three complexes. Complex <b>6</b> is a mixed one-dimensional chain and two-dimensional sheet structure, which are further linked to each other in a three-dimensional framework by H-bond interactions. All the complexes are characterized by single crystal X-ray diffraction, IR spectroscopy, thermogravimetry analysis, and elemental analysis. In addition, the luminescent properties of complexes <b>1</b> and <b>4</b> are discussed, and the magnetic properties of complexes <b>2</b> and <b>3</b> are also investigated