“Naked” Iron-5,10,15-triphenylcorrole on Cu(111): Observation of Chirality on a Surface and Manipulation of Multiple Conformational States by STM

Abstract

A new member of the metalloporphyrinoid class, the one-carbon short corrole, has been developed in the past decade to a very accessible and easily tunable compound with many potential applications in material science and catalysis. Other than for the structurally related iron porphyrins, all attempts to prepare and study the "naked" iron triphenylcorrole molecule (FeTPC) in bulk have failed. Here, we demonstrate stabilization of FeTPC as adsorbates on a surface. Local investigations by means of scanning tunneling microscopy reveal that along with the adsorption of FeTPC in a saddle conformation, surface induced chirality is the result. Using scanning tunneling microscopy as a local manipulation tool, individual molecules can be controllably switched between different orientations and conformations. Even conformations which are unfavorable during the adsorption process are feasible. The presented experiments demonstrate that metalated corroles are a highly interesting class of metalloporphyrinoids for local investigations but, in comparison with the well established class of porphyrins, add an additional degree of experimental freedom via chirality.

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].…”

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.…”

“…Vapour deposition of the iron triphenylcorrole derivatives (Cl)FeTPC, (NO)FeTPC and (O)(FeTPC) 2 onto Cu (1 1 1) led in all cases to the loss of the axial ligand and thus to adsorbates of FeTPC, even though the Cu (1 1 1) substrate was held at 25 K during deposition and measurement. Isolated FeTPC molecules on Cu (1 1 1) were studied by STM and conformational manipulation was conducted with the STM tip [170]. Corrole dimers were studied by Miao et al on HOPG [441], Au(1 1 1) and mica [442] after preparation by dropcasting under ambient conditions.…”