UHV-STM Investigations and Numerical Calculations of a Ruthenium β-Diketonato Complex with Protected Ethynyl Ligand: [Ru(dbm)₂(acac-TIPSA)]

The quest of molecular electronic devices necessitates addressing model molecular systems as starting points. Among the targeted functions, electron transfer between specific moieties inside a molecule is expected to play a fundamental role for ultimate logical gates. Here we propose a coordination complex exhibiting two inorganic centers (Ru and Si) that constitutes a step toward a more complex architecture. Starting from the complex <b>1</b> [Ru­(dbm)₂(acac-I)] (dbm = dibenzoylmethanate ion, acac-<i>I</i> = 3-iodo-2,4-pentanedionate ion), the complex <b>2</b> [Ru­(dbm)₂(acac-TIPSA)] (acac-TIPSA = 3-(triisopropylsilyl)­acetylene-2,4-pentanedionate ion) was obtained through Sonogashira cross coupling reaction under classical conditions. This complex <b>2</b> was characterized by elemental analysis, IR, ¹H NMR, ¹³C NMR, UV–vis, cyclic voltammetry, mass spectroscopy as well as X-ray single-crystal diffraction. It crystallized with empirical formula of C₄₆H₄₉O₆Ru₁Si₁ in a monoclinic crystal system and space group <i>P</i>2₁/<i>c</i> with <i>a</i> = 21.077(3) Å, <i>b</i> = 9.5130(7) Å, <i>c</i> = 21.8790(12) Å, β = 94.125(7)°, <i>V</i> = 4375.5(7) ų and <i>Z</i> = 4. Additionally, scanning tunneling microscopy measurements at liquid He temperature and in an ultrahigh vacuum (UHV-STM) were conducted on complex <b>2</b> on a Ag(111) surface. The STM images, supported by adsorption and STM image calculations, demonstrate that the molecules exist in two stable forms when adsorbed on the metallic surface

Effect of Interlayer Spacing on the Activity of Layered Manganese Oxide Bilayer Catalysts for the Oxygen Evolution Reaction

We investigated the dependence of the electrocatalytic activity for the oxygen evolution reaction (OER) on the interlayer distance of five compositionally distinct layered manganese oxide nanostructures. Each individual electrocatalyst was assembled with a different alkali metal intercalated between two nanosheets (NS) of manganese oxide to form a bilayer structure. Manganese oxide NS were synthesized via the exfoliation of a layered material, birnessite. Atomic force microscopy was used to determine the heights of the bilayer catalysts. The interlayer spacing of the supported bilayers positively correlates with the size of the alkali cation: NS/Cs⁺/NS > NS/Rb⁺/NS > NS/K⁺/NS > NS/Na⁺/NS > NS/Li⁺/NS. The thermodynamic origins of these bilayer heights were investigated using molecular dynamics simulations. The overpotential (η) for the OER correlates with the interlayer spacing; NS/Cs⁺/NS has the lowest η (0.45 V), while NS/Li⁺/NS exhibits the highest η (0.68 V) for OER at a current density of 1 mA/cm². Kinetic parameters (η and Tafel slope) associated with NS/Cs⁺/NS for the OER were superior to that of the bulk birnessite phase, highlighting the structural uniqueness of these nanoscale assemblies