Mercedes Alonso Giner - Invited speaker

Creating functional nanoscale devices using single molecules as active electronic components is the ultimate goal of the field of molecular electronics. Besides their potential to meet the growing demand for miniaturization of electronics, molecular electronics opens up the possibility of de-vices with novel, unforeseen functionalities beyond silicon-based technologies. Through a bot-tom-up quantum chemistry approach, we have shown that expanded porphyrins represent a unique platform to develop a novel type of molecular switches for different nanoelectronic ap-plications taking advantage of their conformational flexibility.[1] These macrocycles are flexible enough to switch between different π-conjugation topologies (Möbius, Hückel and twisted-Hückel) encoding distinct electronic properties and aromaticity.

In the first part of my talk, I will focus on two challenging applications: conductance switch-ing[2] and bithermoelectric devices.[3] In this regard, the electron transport properties were care-fully investigated with the non-equilibrium Green´s function formalism in combination with DFT. Our findings reveal that the negative relationship between conductance and molecular aromaticity or polarizability does not hold for most of the configurations of the molecular junc-tions, so we devise new selection rules to predict the occurrence of quantum interference around the Fermi level for Hückel and Möbius -systems.[4] Thus, a simple counting rule was derived based on the number of atoms of the resulting polyenes upon deleting the contact positions. Overall, I will show how the concept of aromaticity and molecular topology can be exploited to fine-tune the quantum interference effects in charge transport through single-molecule junctions.

Despite these intriguing properties, such Hückel-Möbius interconversions in expanded porphy-rins represent a complicated test for most of wavefunction methods, localized orbital coupled cluster theory and DFT functionals. Many of the errors can be connected to the variable degree of static correlation as a function of the topology as well as the delocalization error. According-ly, in the second part, I will focus on the performance of a variety of quantum chemistry ap-proaches for describing the energetic profiles of topology interconversions across a wide range of macrocycles.[5]

13 Dec 2021

Event (Conference)

TitleInternational symposium on “Chemical Concepts from Theory and Computation”
Abbrev. TitlePacifichem2020
Period12/12/2119/12/21
Web address (URL)
CityHONOLULU
CountryUnited States

ID: 54443440