Next generation QTAIM for the design of quinone-based switches

The National Natural Science Foundation of China is acknowledged, project approval number: 21673071. The One Hundred Talents Foundation of Hunan Province is also gratefully acknowledged for the support of S.J. and S.R.K. The Royal Society is thanked by S.J., S.R.K, T.X, T.v.M and H.F. for support through an International Exchanges grant. We thank EaStCHEM for computational support via the EaStCHEM Research Computing Facility.Investigation of the hydrogen transfer tautomerization process yielded metallic hydrogen bonds in the benzoquinone-like core of the switch. Bond-path framework sets B and Bσ, comprising a three-stranded, non-minimal 3-D bond, which included the familiar QTAIM bond-path and two additional paths defining the least and most preferred directions of electron density motion, were used with QTAIM and the stress-tensor respectively. The B and Bσ were visualized and uncovered the destabilizing effects on the hydrogen bond of the presence of an Fe atom. The lengths of B and Bσ quantified this effect and the dependence on the position of a fluorine substituent.PostprintPostprintPeer reviewe

Quinone-based switches for candidate building blocks of molecular junctions with QTAIM and the stress tensor

The National Natural Science Foundation of China is acknowledged, project approval number: 21673071. The One Hundred Talents Foundation of Hunan Province and the aid program for the Science and Technology Innovative Research Team in Higher Educational Institutions of Hunan Province are gratefully acknowledged for the support of S.J. and S.R.K. The Royal Society is thanked by S.J., S.R.K, T.X, T.v.M and H.F. for support through an International Exchanges grant.The current work investigates candidate building blocks based on molecular junctions from hydrogen transfer tautomerization in the benzoquinone-like core of an azophenine molecule with QTAIM and the recently introduced stress tensor trajectory analysis. We find that in particular the stress tensor trajectories are well suited to describe the mechanism of the switching process. The effects of an Fe-dopant atom coordinated to the quinone ring, as well as F and Cl substitution of different ring-hydrogens, are investigated and the new QTAIM and stress tensor analysis is used to draw conclusions on the effectiveness of such molecules as molecular switches in nano-sized electronic circuits. We find that the coordinated Fe-dopant greatly improves the switching properties, both in terms of the tautomerisation barrier that has to be crossed in the switching process and the expected conductance behavior, while the effects of hydrogen substitution are more subtle. The absence of the Fe-dopant atom led to impaired functioning of the switch ‘OFF’ mechanism as well coinciding with the formation of closed-shell H–––H bond critical points that indicated a strained or electron deficient environment.  Our analysis demonstrates promise for future use in design of molecular electronic devices.PostprintPeer reviewe