TY  - JOUR
A1  - Heinrich, Benjamin W.
A1  - Ehlert, Christopher
A1  - Hatter, Nino
A1  - Braun, Lukas
A1  - Lotze, Christian
A1  - Saalfrank, Peter
A1  - Franke, Katharina J.
T1  - Control of oxidation and spin state in a single-molecule junction
JF  - ACS nano
N2  - The oxidation and spin state of a metal-organic molecule determine its chemical reactivity and magnetic properties. Here, we demonstrate the reversible control of the oxidation and spin state in a single Fe porphyrin molecule in the force field of the tip of a scanning electron tunneling microscope. Within the regimes of half-integer and integer spin state, we can further track the evolution of the magnetocrystalline anisotropy. Our experimental results are corroborated by density functional theory and wave function theory. This combined analysis allows us to draw a complete picture of the molecular states over a large range of intramolecular deformations.
KW  - porphyrin
KW  - oxidation state
KW  - spin state
KW  - scanning tunneling microscopy
KW  - scanning tunneling spectroscopy
KW  - density functional theory
Y1  - 2018
U6  - https://doi.org/10.1021/acsnano.8b00312
SN  - 1936-0851
SN  - 1936-086X
VL  - 12
IS  - 4
SP  - 3172
EP  - 3177
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Ehlert, Christopher
A1  - Gühr, Markus
A1  - Saalfrank, Peter
T1  - An efficient first principles method for molecular pump-probe NEXAFS spectra
BT  - application to thymine and azobenzene
JF  - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr
N2  - Pump-probe near edge X-ray absorption fine structure (PP-NEXAFS) spectra of molecules offer insight into valence-excited states, even if optically dark. In PP-NEXAFS spectroscopy, the molecule is "pumped" by UV or visible light enforcing a valence excitation, followed by an X-ray "probe" exciting core electrons into (now) partially empty valence orbitals. Calculations of PP-NEXAFS have so far been done by costly, correlated wavefunction methods which are not easily applicable to medium-sized or large molecules. Here we propose an efficient, first principles method based on density functional theory in combination with the transition potential and Delta SCF methodology (TP-DFT/Delta SCF) to compute molecular ground state and PP-NEXAFS spectra. We apply the method to n ->pi* pump/O-K-edge NEXAFS probe spectroscopy of thymine (for which both experimental and other theoretical data exist) and to n -> pi* or pi -> pi* pump/N-K-edge NEXAFS probe spectroscopies of trans-and cis-azobenzene. Published by AIP Publishing.
Y1  - 2018
U6  - https://doi.org/10.1063/1.5050488
SN  - 0021-9606
SN  - 1089-7690
VL  - 149
IS  - 14
PB  - American Institute of Physics
CY  - Melville
ER  -