title: Carboxylic Acid Functionalized Clathrochelate Complexes: Large, Robust, and Easy-to-Access Metalloligands.
abstract: Polycarboxylate ligands are among the most important building blocks for the synthesis of metal-organic frameworks (MOFs). The ability to access these ligands in an efficient way is of key importance for future applications of MOFs. Here, we demonstrate that mono- and dinuclear clathrochelate complexes are versatile scaffolds for the preparation of polytopic carboxylate ligands. The largely inert clathrochelate complexes have a trigonal-bipyramidal shape. The synthesis of functionalized clathrochelates with two, three, four, or five carboxylic acid groups in the ligand periphery can be achieved in a few steps from simple starting materials. Apart from being easily accessible, the metalloligands display interesting characteristics for applications in metallasupramolecular chemistry and materials science: they are rigid, large (up to 2.2 nm), and robust and they can show additional functions (e.g., fluorescence or extra charge) depending on the metal ion that is present in the clathrochelate core. The utility of these new metalloligands in MOF chemistry is demonstrated by the synthesis of zinc- and zirconium-based coordination polymers. The combination of Zn(NO3)2 with clathrochelates having two or three carboxylic acid groups gives MOFs in which the clathrochelate ligands are connected by Zn4O clusters or zinc paddlewheel links. The structures of the resulting two- and three-dimensional networks could be established by single-crystal X-ray crystallography. The reaction of carboxylic acid functionalized clathrochelates with ZrCl4 gives amorphous powders that display permanent porosity after solvent removal.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Marmier
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Wise
authors.affiliation: GZG, Department of Crystallography, Georg-August-Universität Göttingen , 37077 Göttingen, Germany.
authors.forename: Julian J
authors.initials: JJ
authors.lastname: Holstein
authors.affiliation: Swiss-Norwegian Beamline, ESRF , Grenoble, France.
authors.forename: Philip
authors.initials: P
authors.lastname: Pattison
authors.forename: Kurt
authors.initials: K
authors.lastname: Schenk
authors.forename: Euro
authors.initials: E
authors.lastname: Solari
authors.forename: Rosario
authors.initials: R
authors.lastname: Scopelliti
authors.forename: Kay
authors.initials: K
authors.lastname: Severin