Charge Localization in Isolated Mixed-Valence Complexes: An STM and Theoretical Study

Abstract

{Cp*(dppe)Fe(C≡C-)}(2)(1,3-C(6)H(4)) is studied both as a neutral molecule, Fe(II)-Fe(II), and as a mixed-valence complex, Fe(II)-Fe(III). Scanning tunneling microscopy (STM) is used to image these species at 77 K under ultrahigh-vacuum conditions. The neutral molecule Fe(II)-Fe(II) has a symmetric, "dumbbell" appearance in STM images, while the mixed-valence complex Fe(II)-Fe(III) demonstrates an asymmetric, bright-dim double-dot structure. This asymmetry results from localization of the electron to one of the iron-ligand centers, a result which is confirmed through comparison to theoretical STM images calculated using constrained density-functional theory (CDFT). The observation of charge localization in mixed-valence complexes outside of the solution environment opens up new avenues for the control and patterning of charge on surfaces, with potential applications in smart materials and molecular electronic devices.

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

“…[33][34][35] Among molecules with magnetic centres, ruthenium complexes may be of particular interest to study charge transfer or transport phenomena at the nanometer scale. [36][37][38][39][40][41][42] In a previous paper, we reported the investigation of a series of ruthenium tris( -diketonato)complexes by UHV-STM. 43 Here, the synthesis and characterization of a new ruthenium -diketonato complex with Scheme 1.…”

Synthesis and Characterization of a Series of Ruthenium Tris(β‐diketonato) Complexes by an UHV‐STM Investigation and Numerical Calculations

“…[21][22][23] A recent review also appeared on STM spectroscopy of magnetic molecules. [24] Several studies have been reported on ruthenium compounds measured by STM [25][26][27][28][29][30][31][32][33][34][35][36] and also on ruthenium and tris(diketonato) ligands, [37][38][39][40][41][42] but very few on adsorption of ruthenium or metal acetylacetonate (acac) complexes and their derivatives.…”

1,2-Diethynylbenzene-Bridged [Cp*(dppe)Fe]n+ Units: Effect of Steric Hindrance on the Chemical and Physical Properties

“…2,3 In particular, the wire-like performance of linear species has been investigated in detail by means of various physical methods 4 including scarce measurements at the molecular level. 3,5,6 Previous reports from our laboratory have described several series of this type of molecule containing the redox-active Cp*(dppe)Fe−CC− (dppe = 1,2-bis(diphenylphosphino)-ethane, Cp* = C 5 Me 5 ) termini linked to π-conjugated polyynediyl ligands ideally suited for studies of optical, electronic, and magnetic coupling between the redox centers. 7−11 It was also shown that introduction of aromatic rings such as benzene, naphthalene, anthracene, thiophene, or other bridges such as carboranes for instance in the polyynediyl spacer increases the chemical stability of the oxidized species and allows a fine-tuning of the coupling between the metal centers.…”