Exploring the Symmetry, Structure, and Self‐Assembly Mechanism of a Gigantic Seven‐Fold Symmetric {Pd₈₄} Wheel

Abstract

The symmetry, structure and formation mechanism of the structurally self-complementary {Pd84} = [Pd84O42(PO4)42(CH3CO2)28](70-) wheel is explored. Not only does the symmetry give rise to a non-closest packed structure, the mechanism of the wheel formation is proposed to depend on the delicate balance between reaction conditions. We achieve the resolution of gigantic polyoxopalladate species through electrophoresis and size-exclusion chromatography, the latter has been used in conjunction with electrospray mass spectrometry to probe the formation of the ring, which was found to proceed by the stepwise aggregation of {Pd6}(-) = [Pd6O4(CH3CO2)2(PO4)3Na(6-n)H(n)](-) building blocks. Furthermore, the higher-order assembly of these clusters into hollow blackberry structures of around 50 nm has been observed using dynamic and static light scattering.

Investigating the Formation of Giant {Pd72}Prop and {Pd84}Gly Macrocycles Using NMR, HPLC, and Mass Spectrometry

“…13 To address this issue, we decided to target systems that form gigantic structures but assemble more slowly. 14,15 The first of these is a smaller {Pd 72 (Figure 1). This structural analogue contains 28 glycolate ligands in place of acetate.…”

“…The peak at 18.8 min corresponds to {Pd 84 } Gly and can be seen to shift gradually to a lower retention time from day 1 through day 4. Interestingly, the peak at 19.3 min, which is between the sizes of those of {Pd 15 H NMR experiments were conducted on the mother liquor to explore the self- Figure 4. This is similar to that found for the inclusion guests within the spherical {Mo 132 }.…”

Overcoming the Crystallization Bottleneck: A Family of Gigantic Inorganic {Pdx}L (x=84, 72) Palladium Macrocycles Discovered using Solution Techniques

“…[11,12] Most large inorganic nanostructures are discovered in as imilar way,r equiring reactions not just to proceed, but to also produce pure diffraction-quality crystals. Where no such crystals are produced, no structure is determined and no compound is discovered;t hat is,a"crystallization bottleneck".…”

“…Where no such crystals are produced, no structure is determined and no compound is discovered;t hat is,a"crystallization bottleneck". Herein, we demonstrate how new metal oxide macrocycles can be discovered without the need for diffraction-quality crystals.I nstead, we exploit solution sizing techniques [12] to screen reactions for the presence of new nanoscale species,e ven where no crystals are observed. Data suggesting new species ("leads"), discovered either by screening or crystallization, are then structurally characterized from crude solution.…”

“…Despite alack of crystalline products suitable for XRD,it was clear from observing color changes and performing gel electrophoresis [12] that palladate cluster products were being formed in the reaction solutions.Inthe course of our previous studies on the formation of {Pd 84 } Ac ,w ed eveloped as ize exclusion chromatography (SEC) method in which POPd clusters of different sizes are resolved;i ns od oing we were able to show that macrocycles are present in reactions even when no crystals are formed. [12] Knowing there to be products in the reaction mixtures,w es creened crude solutions of reactions incorporating aw ide variety of carboxylate ligands for the synthesis of large species.That is,instead of setting up many reactions and waiting for serendipitous crystallization, our new approach screened for the formation of large species as leads to be further characterized.…”