Unprecedented and Differently Applicable Pentagonal Units in a Dynamic Library: A Keplerate of the Type {(W)W₅}₁₂{Mo₂}₃₀

Abstract

Dedicated to Professor Peter Day on the occasion of his 70th birthdayIn the field of polyoxometalate chemistry, porous spherical molybdenum oxide-based clusters of the type {(Mo VI )Mo VI 5 } 12 (linker) 30 , [1] called Keplerates, [2a,b] are notable not only from an aesthetic point of view [2c] but also because they show properties of interest for different areas of science. Some of these clusters can act as artificial cells exhibiting gated pores while interacting specifically with their environments; others are of interest for several aspects of materials science. [3][4][5] In detail, of interest are a) solution properties in connection with a new type of assembly process leading to vesicles, including magnetic ones, [6a,b] b) the option to employ the characteristic interactions with amphiphiles for the generation of monolayers and Langmuir-Blodgett films [6c] as well as highly ordered honeycomb nanostructures at airwater interfaces, [6d] c) the integration into sol-gel-derived silica to obtain unprecedented hybrids, [6e] and d) the discovery of novel magnetic properties, [6f]

Porous Capsules {(M)M5}12FeIII30 (M=MoVI, WVI): Sphere Surface Supramolecular Chemistry with 20 Ammonium Ions, Related Solution Properties, and Tuning of Magnetic Exchange Interactions

“…The obtained results (see title) could be anticipated for the following reasons: First, the presence of the expected 20 crown ether type {Fe 3 W 3 O 6 } pores leads (especially because of the high negative cluster charge, and in the context of sphere surface supramolecular chemistry) to the fixation of 20 NH 4 + ions through hydrogen bonds. Second, the magnetic properties of 1 a showed the expected difference to those of the spherical antiferromagnet {Mo 72 Fe 30 }, exhibiting frustration properties with model character for KagomØ lattices (see below).…”

“…Though the principle of the high formation tendency of the present type of spherical Keplerate skeleton has been discussed before [14] (also with respect to the necessary presence of the basic pentagonal units in the reaction medium), [4,5] a useful identification of the pentagonal units integrated into a spherical species through a basic simple physical method has not been described to date. This point is [19] of the dynamic light-scattering study on a 0.5 mg mL À1 aqueous solution of 1 (pH 4.6; see the Experimental Section).…”

“…[3e] It is important for synthetic aspects that the capsules basic parts, that is, the 12 metal oxide based pentagonal units, are present in a dynamical library; [4] interestingly, pentagonal units are also the central elements of important spherical structures, such as the C 60 buckyball, icosahedral viruses, and geodesic domes.…”

Polyoxometallate als Bausteine für funktionelle Nanosysteme

“…[30] der auf zwei grundsätzlichen Strukturmotiven beruht, die als Baueinheiten für größere Cluster und ausgedehnte Strukturen dienen können: kondensierte {Nb 6 }-Oktaeder und ein offener {Nb 6 }-Ring. [31] Kürzlich haben wir die Polyoxoniobate [HNb 27 . [33] Dieser "Über-Lindqvist"-Cluster enthält 6 Nb-Zentren an den Spitzen eines Oktaeders und 12 Ti-Atome an den Kantenmitten.…”

Oxo‐Metalate Building Blocks: Conceptual Competitors for Tetravalent Carbon?

“…The metal-oxide based structures result from sophisticated control over reactions based on the simplest tetrahedral oxoanions of the type MO 4 nÀ or on larger ones like the important pentagonal building blocks. [30] These developments offer options for controlling structure and function-in principle analogous to activities in organic chemistry. This is nicely demonstrated by the contributions included in this special issue, entitled, "Frontiers in Metal Oxide Cluster Science".…”