Reversible Achiral-to-Chiral Switching of Single Mn–Phthalocyanine Molecules by Thermal Hydrogenation and Inelastic Electron Tunneling Dehydrogenation

Abstract

Induction of chirality in planar adsorbates by hydrogenation of phthalocyanine molecules on a gold surface is demonstrated. This process merely lowers the molecular symmetry from 4- to 2-fold, but also breaks the mirror symmetry of the entire adsorbate complex (molecule and surface), thus rendering it chiral without any realignment at the surface. Repositioning of single molecules by manipulation with the scanning tunneling microscope (STM) causes interconversion of enantiomers. Dehydrogenation of the adsorbate by means of inelastic electron tunneling restores the mirror symmetry of the adsorbate complex. STM as well as density functional theory (DFT) calculations show that chirality is actually imprinted into the electronic molecular system by the surface, i.e., the lowest unoccupied orbital is devoid of mirror symmetry.

Hydrogen capture by porphyrins at the TiO2(110) surface

“…In fact, upon hydrogen exposure, first layer MnPc molecules on Au(111) have been shown to dissociate and link two hydrogen atoms at opposite meso sites. 7 This reaction path might be enhanced at the TiO 2 (110) surface, as observed for the porphyrin case, thus explaining the excess of pyrrolic nitrogen reported also for metalated species like FePc 12 and ZnPc. 14…”

“…5 Hydrogen itself can be exploited to modify the local molecular conductance by selective cleavage of one pyrrolic NH bond in 2H-P, 6 as well as tuning the chirality by selective adsorption in MnPc. 7 In order to generalize these functionalities, one must take into account the nature of the substrate, which is demonstrated to affect the gas reactivity of the MP contact layer. 3c The interface of titania with MPs and MPcs attracts large interest because of its dual purpose applications in photocatalysis and solar cells.…”

Structures and electronic properties of functional molecules on metal substrates: From single molecule to self‐assemblies

“…78 Therefore, the spin states and the Kondo resonance of MPc molecules can be manipulated by dosing small molecules such as hydrogen. 109,110 In Figure 3a it shows a high-resolution STM image of an individual MnPc, and the corresponding atomic configuration and the STM simulation. There is a bright protrusion at the center of the MnPc molecule, which originates from the 3d orbital of Mn 2+ ions.…”

Self-Assembly and Magnetic Order of Bi-Molecular 2D Spin Lattices of M(II,III) Phthalocyanines on Au(111)

“…Remarkably, the magnetic properties of these singlelayer spin systems are generally accessible by spectro-microscopy correlation, combining element sensitive X-ray photoelectron spectroscopy (XPS) and magnetic moment sensitive X-ray magnetic circular dichroism (XMCD) with local probe microscopy such as scanning tunneling microscopy (STM). The latter technique also identifies the presence or absence of magnetic states in spin-dependent tunneling experiments or from local density of states (DOS) measurements, revealing the Kondo shielding of magnetic moments, as well as the presence or absence of chemical ligands modifying the spin-bearing ions [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26].…”