This document summarizes research applying density functional theory to scanning tunneling microscopy. It studies osmium complexes deposited on a gold surface, comparing the electronic structures of [Os(bpy)2(P0P)Cl]+ and [Os(bpy)2(P2P)Cl]+. DFT calculations reveal that the LUMO and HOMO energies differ, with the P2P complex having deeper lying orbitals. STM images also show differences in the apparent heights, consistent with the DFT results.

1. Application of Density
Functional Theory to Scanning
Tunneling Microscopy
Noel O’Boyle
Han Vos
Dublin City University
National Centre for Sensor Research

2. In situ Scanning Tunneling
Microscopy
Reference
Counter
Bias voltage
STM tip
Osmium (II/III) complex
Gold Surface

3. +
+
N N
N N
II
II Os
Os N N
N N
Cl N
Cl N
N
N
[Os(bpy)2(P0P)Cl]+ [Os(bpy)2(P2P)Cl]+

4. DFT (B3LYP/LanL2DZ)
[Os(bpy)2(P0P)Cl]+ [Os(bpy)2(P2P)Cl]+

7. Os P0P/P2P
Cl bpy
-3 -3
-4 -4
-5 -5
LUMO LUMO
-6
Energy (eV)
-6
-7 -7
HOMO HOMO
-8 -8
-9 -9
-10
0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0
[Os(bpy)2(P0P)Cl]+
P0P P2P
[Os(bpy)2(P2P)Cl]+

8. Os P0P
Cl bpy
-3
-4 -7
-5 -8
LUMO
-6 -9
Energy (eV)
LUMO
-7 -10
HOMO HOMO
-8 -11
-9 -12
-10 -13
0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0
Os II
OsIII

11. Au Au
Os
Os
-2 -2
-2 -3 -3
-3 -4 -4
-4 -5 -5
LUMO LUMO LUMO
-5
Energy (eV)
HOMO -6 HOMO -6
-6 -7 -7
HOMO
-7 -8 -8
-8 -9 -9
-9 -10 -10
-10 -11

12. Acknowledgements:
SUSANA network Prof. Jens Ulstrup
Prof. Han Vos Dr. Tim Albrecht