Combination of Scanning Probe Microscopy and Coordination Chemistry: Structural and Electronic Study of Bis(methylbenzimidazolyl)ketone and Its Iron Complex

Here, we report the
bulk synthesis of [FeII(BMBIK)­Cl2] bearing the
redox noninnocent bis­(methylbenzimidazolyl)­ketone
(BMBIK) ligand and the synthesis of the similar complex [FeI(BMBIK)]+ on a Au(111) surface using lateral manipulation
at the atomic level. Cyclic voltammetry and scanning tunneling spectroscopy
are shown to be useful techniques to compare the coordination compound
in solution with the one on the surface. The total charge, as well
as the oxidation and spin state of [FeI(BMBIK)]+, are investigated by comparison of the shape of the lowest unoccupied
molecular orbital (LUMO), visualized by tunneling through the LUMO,
with theoretical models. The similar reduction potentials found for
the solution and surface compounds indicate that the major effect
of lowering the LUMO upon coordination of BMBIK to the iron center
is conserved on the surface. The synthesis and analysis of [FeI(BMBIK)]+ using scanning tunneling microscopy,
scanning tunneling spectroscopy, and atomic force microscopy are the
first steps toward mechanistic studies of homogeneous catalysts with
redox noninnocent ligands at the single molecule level.