Solvothermal synthesis, structure and properties of a new 3-D Cu(I)–Gd(III) heterometallic coordination framework

A novel (3,6)-connected CdII coordination polymer based on an ether-linked tricarboxylate ligand: synthesis, topology and luminescence sensing properties in aqueous solution

A novel three-dimensional coordination polymer, namely, poly[[diaquabis(μ-4,4'-bipyridine)bis{μ₃-5-[(2-carboxyphenoxy)methyl]isophthalato}tricadmium(III)] dimethylformamide monosolvate 2.5-hydrate], {[Cd₃(C₁₆H₉O₇)₂(C₁₀H₈N₂)₂(H₂O)₂]·2C₃H₇NO·5H₂O}_n, was obtained by the reaction of ether-linked 5-[(2-carboxyphenoxy)methyl]isophthalic acid (H₃L) with Cd^II salts in the presence of 4,4'-bipyridine (bpy) under solvothermal conditions. In this complex, the Cd^II centres are connected by the carboxylate ligands to form two-dimensional wave-like layers, which are pillared by bpy ligands and extended into a rare three-dimensional (3,6)-connected sqc27 framework. The complex demonstrated good water stability and strong luminescence emissions. It not only possesses excellent luminescence sensing activities toward Fe³⁺ and Cr₂O₇^2- in aqueous solution, but can also distinguish between Cr₂O₇^2- and CrO₄^2- by luminescence. Furthermore, it could be simply and quickly regenerated at least five times. A study of the sensing mechanism indicated that luminescence quenching may be related to the energy competition between the complex and sensing analytes.

Poly[[tetra-aqua-tetra-kis-[μ(3)-5-(pyridine-4-carboxamido)-isophthalato]cobalt(II)dierbium(III)] tetra-hydrate]

In the centrosymmetric polymeric title compound, {[CoEr₂(C₁₄H₈N₂O₅)₄(H₂O)₄]·4H₂O}_n, the Er^III cation has a coordination number of eight and is surrounded by seven carboxyl­ate O atoms from four 5-(pyridine-4-carboxamido)­isophthalate (L) ligands and one water mol­ecule, forming a distorted square-anti­prismatic arrangement. The Co^II cation is located on an inversion center and is coordinated by two pyridine N atoms, two carboxyl­ate O atoms and two water mol­ecules in a distorted octa­hedral geometry. The asymmetric unit contains two anionic L ligands. One bridges two Er^III cations and one Co^II cation through two carboxyl­ate groups and one pyridine N atom, while the other bridges two Er^III cations and one Co^II cation through two carboxyl­ate groups. Extensive O—H⋯O, O—H⋯N and N—H⋯O hydrogen-bonding inter­actions are present in the crystal, involving all uncoordinated water mol­ecules and the uncoordinated pyridine N atom of one of the ligands bonded to an adjacent coordinated water mol­ecule. The title compound is isotypic with the gadolinium analogue.