I. Vanderschuerenrprijs 2020: Qualitative Insights into the Transport Properties of Molecular Electronic Devices: A quantum Chemical approach'

Project Details

Description

The research presented throughout this dissertation is situated in the field of single-molecule electronics, the study of the electrical transport through single molecules connected in a circuit. Single-molecule electronics can be considered as the ultimate step in the downsizing of electronic components and thus carries great technological potential. However, chemical understanding of the transport properties of molecules is still rather limited, providing an impetus for theoretical and experimental chemists alike to investigate the phenomena associated with electric transport through molecules and the influence of the structure of these molecules on them, in order to provide new insights that could help in the design of efficient molecular wires, switches, rectifiers, etc.

By starting from the so-called Source-and-Sink Potential model at Hückel, i.e. tight- binding, level of theory, an expression for the transmission probability of electrons through a molecule can be obtained which can be cast in a graph-theoretical form. Through manipulation of the resulting expression, we obtained clear structure-property relationships for the electric transport through molecules which can be connected to "old" chemical concepts, central to the
field of theoretical chemistry since the dawn of quantum mechanics.
With the help of the derived structure-property relationships, the occurrence of quantum interference – leading to an extremely low current when a small voltage is applied – can be predicted based on an inspection of the structure of the molecule. Additionally, several guiding principles can be formulated for tuning the conductivity of molecules, either through geometrical changes, through changes in the aromaticity patterns or through substitution. With all of these tools at hand, we considered a wide range of applications throughout this thesis. We explored the switching properties of a number of light-, redox- and heat sensitive molecules, among which expanded porphyrins. Additionally, we considered a wide range of molecular wires and all the different ways to make them more/less conducting. Furthermore, the pathways through conjugated molecules taken by the current have also been studied and a strategy was
devised to "seal off" part of the molecule for this current. Finally, we contributed to the further development of the Source-and-Sink Potential
(SSP) formalism, by developing a computer code capable of visualizing the path the current takes through the molecule in real space at higher levels of theory (Hartree-Fock and Density Functional Theory). This new visualization tool offers further insight in the transport properties of the considered molecules.
The results of this thesis will hopefully guide experimentalists in their quest for the design of optimal functional electronic components at the single-molecule level and bring the long-standing dream of molecular-scale circuitry one step closer to reality.
AcronymVOPPU95
StatusActive
Effective start/end date1/10/2030/09/23

Flemish discipline codes

  • Molecular and organic electronics

Keywords

  • molecular electronic devices