Origin of the Electron Transport Properties of Aromatic and Antiaromatic Single Molecule Circuits

• Published in: Chemphyschem Vol. 22; no. 9; pp. 864 - 869
• Main Authors: Arasu, Narendra P., Vázquez, Héctor
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 05.05.2021
• Subjects: Aromaticity; Circuit design; density functional calculations; Dopes; Electron transport; Electronic spectra; electronic structure; Interference; molecular electronics; Molecular orbitals; Resistance; Transport properties; electron transport; density functional calculations; molecular electronics; electronic structure; aromaticity
• ISSN: 1439-4235; 1439-7641
• DOI: 10.1002/cphc.202100010

Antiaromatic molecules have been predicted to exhibit increased electron transport properties when placed between two nanoelectrodes compared to their aromatic analogues. While some studies have demonstrated this relationship, others have found no substantial increase. We use atomistic simulations to establish a general relationship between the electronic spectra of aromatic, antiaromatic, and quinoidal molecules and illustrate its implications for electron transport. We compare the electronic properties of a series of aromatic‐antiaromatic counterparts and show that antiaromaticity effectively p‐dopes the aromatic electronic spectra. As a consequence, the conducting properties of aromatic‐antiaromatic analogues are closely related. For similar attachment points to the electrodes, an interference feature is expected in the HOMO‐LUMO gap of one whenever it is absent in the other one. We demonstrate how the relative conductance of aromatic‐antiaromatic pairs can be tuned and even reversed through the choice of chemical linker groups. Our work provides a general picture relating connectivity, (anti)aromaticity, and quantum interference and establishes new design rules for single molecule circuits. Antiaromaticity is shown to be double p‐doping of the electronic structure of the aromatic analogue using DFT and NEGF calculations, whereby the HOMO of the aromatic species is fully depleted. The spectra of quinones resemble those of the antiaromatic counterpart plus carbonyl‐localized states. These general relationships have important consequences for electron transport, quantum interference and molecular design rules.