Self-assembled monolayers of polyoxovanadates with phthalocyaninato lanthanide moieties on gold surfaces

The two first representatives of phthalocyaninato (Pc) lanthanide-ligated polyoxovanadate cages {[V12O32(Cl)](LnPc)n}n-5 (n = 1 or 2, Ln = Yb3+) were synthesised and fully characterised. These magnetic complexes form two-dimensional self-assembled monolayers exhibiting electrical conductivity on gold substrate surfaces, as assessed by using an EGaIn tip

Exploring the Ligand Functionality, Electronic Band Gaps, and Switching Characteristics of Single Wells–Dawson‐Type Polyoxometalates on Gold

The miniaturization, high performance, energy efficiency, and new added functionalities are the essential drivers of modern information data storage and processing technologies. Polyoxometalates (POMs) characterized by atomically well-defined structures with discrete energy levels and the ability to undergo redox transformations are viewed as promising active components for the integration into the next-generation (beyond-CMOS) hybrid nanoelectronics. Herein, new fundamental insights into the application of organically augmented POMs on conducting surfaces are offered. Three key findings resulting from scanning probe investigations combined with integral spectroscopic methods used to explore tris(alkoxo)-ligated, vanadium-containing Wells-Dawson-type POM structures on Au(111) are reported on. First, it is shown how the (OCH2)3C–R ligands, depending on the structurally exposed R group (R = CH2SMe and NHCOC6H4SMe), influence the self-assembly behavior of the synthesized POMs on gold. Second, the impact of the employed (OCH2)3C–R ligands and the determined assembly characteristics on the relative position of POM's electronic band structure against the Fermi level of the gold surface are explained. Third, the on-surface conductance switching of single POM structures due to external electrical stimuli is demonstrated. The author's experimental efforts enable to discover highly sought-after multi-level resistive switching orchestrated by electrically accessible V(3d) states in the POM single-molecules at room temperature in a narrow voltage range

Interplay between the amphipathic polyoxometalate interactions in solution and at solid–liquid interfaces: a toolbox for the technical application

The far-reaching interplay between the speciation of polyoxometalates (POMs) in the liquid phase and the POM adsorption characteristics on substrate surfaces yet remains to be understood. The significance of this interplay is however paramount because it indicates the degree of technical applicability of solvent-processable POM molecules. Herein, we target this fundamentally important issue, shedding light on the “POM–counterion–solvent” and “POM–counterion–solvent–substrate” processes. We effectively combine the results from small-angle X-ray scattering in solution with surface sensitive scanning tunneling microscopy and X-ray photoelectron spectroscopy measurements and present on this basis a semi-quantitative analysis which provides an excellent correlation between both approaches. The MeCN-solution speciation of a tris(alkoxo)-ligated Wells–Dawson-type polyoxoanion – explored as a representative of commonly negatively charged POM-based inorganic–organic nanostructures – is strikingly connected with the growth of porous two-dimensional molecular layers on highly oriented pyrolytic graphite (HOPG). Low water amounts dramatically transform intermolecular relationships toward hierarchical agglomeration that inhibits the layer formation on HOPG. The obtained findings lay the groundwork for a mechanistic study of controlled nucleation and growth of POM nanostructures on weakly interacting surface

CCDC 1950769: Experimental Crystal Structure Determination

Related Article: Ricarda Pütt, Xinkai Qiu, Piotr Kozłowski, Hans Gildenast, Oliver Linnenberg, Stefan Zahn, Ryan C. Chiechi, Kirill Yu. Monakhov|2019|Chem.Commun.|55|13554|doi:10.1039/C9CC06852

CCDC 1950768: Experimental Crystal Structure Determination

Related Article: Ricarda Pütt, Xinkai Qiu, Piotr Kozłowski, Hans Gildenast, Oliver Linnenberg, Stefan Zahn, Ryan C. Chiechi, Kirill Yu. Monakhov|2019|Chem.Commun.|55|13554|doi:10.1039/C9CC06852