Self-Assembly of a Three-Dimensional [Ga6(L2)6] Metal–Ligand “Cylinder”

Abstract

A near trigonal antiprism with metal-metal distances in the nanometer regime is formed by the six metal ions in the crystalline, homochiral [Ga(6)(L(2))(6)] (see structure). This metal-ligand "cylinder" is based on a threefold symmetric, beta-diketone ligand, and represents a new geometry for metal-ligand clusters.

Metallo-supramolecular capsules

“…In the broad topic of this section, transition metals are often used for templating, and significant advances in large superstructures or clusters have been made by Fujita and coworkers [12][13][14][15][16][17][18], Stang and co-workers [19,20], Raymond and co-workers [21][22][23][24][25][26][27] and Ward and co-workers [28][29][30][31][32][33][34][35][36]. Fujita has reacted pyridyl or pyrimidyl functionalised planar or near planar ligands (that are typically triangular) with cis-protected palladium in order to synthesise a substantial series of metalorganic cages [12][13][14][15][16][17][18].…”

“…Following on from these reports, Saalfrank and co-workers have also used the same tris-bidentate 4-acyl-2-pyrazolin-5-one ligand with gallium centres to assemble M 6 L 6 clusters that the authors describe as a 'cylinder' [26]. Further modification of the trigonal ligand framework so as to generate tris-malonate-based chelator ligands, followed by combination with iron chloride, resulted in the formation of tetra-and hexa-nuclear metal clusters depending on particular functionalities (O-t Bu or O-tolyl, respectively) placed on the ligand framework [27].…”

Lord of the Rings: An Octameric Lanthanum Pyrazolonate Cluster

“…[4] However, the trivalent lanthanide ions generally display variable and high (8, 9, or more) coordination numbers and the energy difference between the various coordination geometries is small; therefore they show low stereochemical preferences. This rigid threefold-symmetric ligand forms a unique supramolecular three-dimensional ring architecture with first-and second-row transition metal ions such as Ga III , [11] V III , Fe III , and In III . A better control of the coordination environment can be achieved through the use of highly predisposed ligands.…”

“…A better control of the coordination environment can be achieved through the use of highly predisposed ligands. [11,12] Based on the formation of these [M 6 L 1 6 ] three-dimensional ring structures it was reasoned that discrete supramolecular species might form with lanthanide ions, since the ligands do not necessarily have to saturate all of the coordination sites of the lanthanide ions. [4c±g] A series of poly-N donor ligands of the 2,6bisbenzimidazol-2-yl-pyridines has been studied in depth by the groups of Bünzli, Piguet, and Williams.…”

Der Herr der Ringe: ein octamerer Lanthan-Pyrazolonat-Cluster

“…Dieser starre, C 3 -symmetrische Ligand bildet mit dreiwertigen Metallionen wie Ga III , [11] V III , Fe III und In III [12] supramolekulare dreidimensionale Ringarchitekturen. [11,12] Die Bildung dieser dreidimensionalen [M 6 L 1 6 ]-Ringstrukturen gab Grund zu der Annahme, dass auch mit Lanthanoidionen diskrete supramolekulare Verbindungen gebildet werden können, da die Liganden ja nicht notwendigerweise alle Koordinationsstellen der Lanthanoidionen besetzen müssen. Die Signale der 1 H-und 13 C-NMR-Spektren der Ga III -und In III -Komplexe sind daher in charakteristischer Weise dreifach aufgespalten.…”