Complex three-dimensional lanthanide metal–organic frameworks with variable coordination spheres based on pyrazine-2,3,5,6-tetracarboxylate

Abstract

Metal-organic frameworks {[Ln 4 IJpztc) 3 IJH 2 O) 11 ]·10IJH 2 O)} n (Ln = GdIJ1), TbIJ2); pztc = pyrazine-2,3,5,6tetracarboxylate) containing variable coordination spheres and with a complex and unusual three dimensional structure, were synthesized by the reaction of H 4 pztc with the respective LnIJIII) salt in water under hydrothermal conditions. The compounds were characterized by single crystal X-ray crystallography, elemental and thermal analysis, and FTIR spectroscopy. The asymmetric units in these compounds have four symmetry-independent LnIJIII) ions and these are octa-and nona-coordinate centers, with irregular coordination polyhedra from ijLnIJpztc) 2 IJH 2 O) 6 ], ijLnIJpztc) 2 IJH 2 O) 4 ], ijLnIJpztc) 3 IJH 2 O) 3 ], ijLnIJpztc) 3 IJH 2 O)], and ijLnIJpztc) 4 ] cluster units. The fully deprotonated ligand, pztc, coordinates to the Ln 3+ ions through seven or through ten of its atoms (i.e., the maximum coordination number for this ligand). The three-dimensional open framework contains irregular channels along the [001] crystallographic direction. The channels are approximately 12 Å wide at their largest dimension and contain strongly hydrogen bonded water molecules of crystallization which further stabilize the structure. The solvent accessible volume is 20% of the total volume. The structures exhibit magnetic behavior that is characteristic of the respective isolated paramagnetic lanthanide ions. CrystEngCommThis journal is

Solvent Influence in Obtaining Diverse Coordination Symmetries of Dy(III) Metal Centers in Coordination Polymers: Synthesis, Characterization, and Luminescent Properties

“…The rational design of LnCPs is quite complicated owing to the higher coordination numbers and flexible coordination spheres exhibited by the lanthanide metal centers. − Flexible linkers offer various conformations to meet the coordination requirements imposed by lanthanide coordination spheres. , The final coordination architectures based on flexible linkers are cooperatively influenced by the conformation of the linker as well as the coordination sphere of the metal center. , Hence, the utilization of flexible linkers has proven to be one of the successful strategies to explore the structural diversity of LnCPs . In addition, the solvent also plays a vital role in the self-assembly process of coordination polymers directly by coordinating with the metal center or indirectly templating the crystal growth process. , When solvents are directly involved in the coordination assembly by coordinating with the metal centers depending upon the bulkiness and steric hindrance of the solvent, it influences the symmetry of the metal coordination sphere thereby affecting the self-assembly process. , …”