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

Abstract

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 1 [Ru(dbm) 2 (acac-I)] (dbm = dibenzoylmethanate ion, acac- I = 3-iodo-2,4-pentanedionate ion), the complex 2 [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 2 was characterized by elemental analysis, IR, 1 H NMR, 13 C NMR, UV–vis, cyclic voltammetry, mass spectroscopy as well as X-ray single-crystal diffraction. It crystallized with empirical formula of C 46 H 49 O 6 Ru 1 Si 1 in a monoclinic crystal system and space group P 2 1 / c with a = 21.077(3) Å, b = 9.5130(7) Å, c = 21.8790(12) Å, β = 94.125(7)°, V = 4375.5(7) Å 3 and Z = 4. Additionally, scanning tunneling microscopy measurements at liquid He temperature and in an ultrahigh vacuum (UHV-STM) were conducted on complex 2 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.