Spectroscopic Scanning Tunneling Microscopy Studies of Single Surface-Supported Free-Base Corroles

Abstract

Corroles are versatile chemically active agents in solution. Expanding their applications toward surface-supported systems requires a fundamental knowledge of corrole–surface interactions. We employed the tip of a low-temperature scanning tunneling microscope as local probe to investigate at the single-molecule level the electronic and geometric properties of surface-supported free-base corrole molecules. To provide a suitable reference for other corrole-based systems on surfaces, we chose the archetypal 5,10,15-tris(pentafluorophenyl)corrole [H3(TpFPC)] as model system, weakly adsorbed on two surfaces with different interaction strengths. We demonstrate the nondissociative adsorption of H3(TpFPC) on pristine Au(111) and on an intermediate organic layer that provides sufficient electronic decoupling to investigate geometric and frontier orbital electronic properties of almost undisturbed H3(TpFPC) molecules at the submolecular level. We identify a deviating adsorption behavior of H3(TpFPC) compared to structurally similar porphyrins, characterized by a chiral pair of molecule–substrate configurations.

Manipulation resolves non-trivial structure of corrole monolayer on Ag(111)

“…The short molecular axis of the single corrole molecule is marked by a dashed line labeled 's'. Similar topographies have been reported by STM studies of single triphenyl-corrole molecules on Cu(111) [6,7] and tris(pentafluorophenyl)-corrole Au(111) [8]. Based on the topographies exemplified in figure 2(a), we conclude that single TpFPC molecules remain intact after being displaced by the STM tip and, furthermore, that their macrocycles are oriented roughly parallel to the substrate surface.…”

“…Interdigitation, partial overlap, or stacking of molecules can promote the formation of non-trivial (intricate) molecular arrangement within networks. Increased structural complexity of the individual molecules is believed to strongly affect the formation of intricate networks, as observed in previous studies of corrole derivatives [6][7][8]. Corroles [9,10] are emerging as highly potent agents in catalysis, photochemical sensing, molecular electronics and biomedicine [11][12][13].…”

“…Corroles [9,10] are emerging as highly potent agents in catalysis, photochemical sensing, molecular electronics and biomedicine [11][12][13]. Corrole molecules, exhibiting low symmetry (C 1 ) when adsorbed on metal substrates, facilitate non-trivial network structures, originating either from multiple conformational states [6,8] or dissociation of axial ligands [7]. In such cases, a distinct structure determination of the molecular network turns out to be complicated-even when using scanning probe imaging methods that operate at sub-molecular resolution in real space.…”

Surface chemistry of porphyrins and phthalocyanines

“…For the latter application, triphenylamine-functionalized corroles have also been tested, but performance was poor [168]. In surface science, corroles have found less attention than they certainly deserve [169][170][171][172]. In nature, the partially hydrogenated corroles, the corrines, play an important role as active centers of biomolecules; an example is the Co corrin in cobalamin (vitamin B12).…”

“…A monolayer of h-BN on the weakly interacting Cu (1 1 1) [170,172]. As an example, 5,10,15-tris (pentafluorophenyl)-corrole (3HTPFC) on Au(1 1 1) formed a well-ordered monolayer of intact molecules, onto which further 3HTPFC was deposited in order to obtain electronically decoupled molecules in the second layer for STS studies.…”