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

Mixed Chiral and Achiral Character in Substituted Ethane: A Next Generation QTAIM Perspective

We use the newly introduced spanning stress tensor trajectory $U_{\sigma}$-space construction within next generation quantum theory of atoms in molecules (NG-QTAIM) for a chirality investigation of singly and doubly substituted ethane with halogen substituents: F, Cl, Br. A lack of achiral character in $U_{\sigma}$-space was discovered for singly substituted ethane. The resultant axial bond critical point (BCP) sliding responded more strongly to the increase in atomic number of the substituted halogen than the chirality. The presence of the very light F atom was found responsible for a very high degree of achiral character of the doubly substituted ethane.Comment: arXiv admin note: substantial text overlap with arXiv:2203.0975

The destabilization of hydrogen bonds in an external E-field for improved switch performance

The National Natural Science Foundation of China is acknowledged, project approval number: 21673071. The One Hundred Talents Foundation 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. We thank EaStCHEM for computational support via the EaStCHEM Research Computing Facility.The effect of an electric field on a recently proposed molecular switch based on a quinone analogue was investigated using next‐generation quantum theory of atoms in molecules (QTAIM) methodology. The reversal of a homogenous external electric field was demonstrated to improve the “OFF” functioning of the switch. This was achieved by destabilization of the H atom participating in the tautomerization process along the hydrogen bond that defines the switch. The “ON” functioning of the switch, from the position of the tautomerization barrier, is also improved by the reversal of the homogenous external electric field: this result was previously inaccessible. The “ON” and “OFF” functioning of the switch was visualized in terms of the response of the most preferred directions of motion of the electronic charge density to the applied external field. All measures from QTAIM and the stress tensor provide consistent results for the factors affecting the “ON” and “OFF” switch performance. Our analysis therefore demonstrates use for future design of molecular electronic devices.PostprintPostprintPeer reviewe

The cis-effect explained using next generation QTAIM

The National Natural Science Foundation of China is gratefully 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. H.F. and T.v.M. gratefully acknowledge computational support via the EaStCHEM Research Computing Facility.We used next-generation QTAIM (NG-QTAIM) to explain the cis-effect for two families of molecules: C2X2 (X = H, F, Cl) and N2X2 (X = H, F, Cl). We explained why the cis-effect is the exception rather than the rule. This was undertaken by tracking the motion of the bond critical point (BCP) of the stress tensor trajectories Tσ(s) used to sample the Uσ-space cis- and trans-characteristics. The Tσ(s) were constructed by subjecting the C1-C2 BCP and N1-N2 BCP to torsions ± θ and summing all possible Tσ(s) from the bonding environment. During this process, care was taken to fully account for multi-reference effects. We associated bond-bending and bond-twisting components of the Tσ(s) with cis- and trans-characteristics, respectively, based on the relative ease of motion of the electronic charge density ρ(rb). Qualitative agreement is found with existing experimental data and predictions are made where experimental data is not available.Publisher PDFPeer reviewe

Influence of an electric field on the topological stability of the neutral lithium dimer

The Hunan Natural Science Foundation of China project gratefully acknowledged approval number: 2022JJ30029. The One Hundred Talents Foundation of Hunan Province is also gratefully acknowledged for the support of S.J. and S.R.K.In this investigation, we seek to understand the role of non-nuclear attractors (NNAs) of the neutral Li2 dimer subjected to an electric (± E ) field that is directed parallel ( ±E x ) and perpendicular ( ±E y ) to the bond-path. The ±E x -fields and ±E y -fields are separately applied to the Li2 molecular graph until the bond ruptures. The next generation quantum theory of atoms in molecules (NG-QTAIM) interpretation of bonding was constructed with the stress tensor σ ( r ) eigenvectors on the Hessian of ρ( r ) molecular graph. The asymmetry induced by both the ±E y -field and ±E x -field was detected in terms of the rotation of the orthogonal triad of stress tensor σ ( r ) eigenvectors { e 1σ , e 2σ , e 3σ } relative to the Cartesian coordinate frame. The orthogonal triad of Hessian of ρ( r ) eigenvectors { e 1 , e 2 , e 3 } however, were only able to detect rotation induced by the high degree of asymmetry present for bent bond-paths induced by the ±E y -fields. Larger movement of the NNAs along the bond-path correlated with greater bond critical point (BCP) bond metallicity ξ( r b). The effect of applying the ±E x -field was compared with unpublished results on neutral Li2 subject to a stretching distortion. The lack of NNA motion along the bond-path for the stretching distortion correlated with a lower degree of bond metallicity ξ( r b). The stress tensor σ ( r ) eigenvectors have a unique ability to detect rotation relative to the Cartesian coordinate frame for high bond-path symmetry occurring for the bond-stretching distortion and application of the ±E x -field. Suggestions for future work are provided.PostprintPostprintPeer reviewe

Chirality reversal with the carrier-envelope phase : A next generation QTAIM interpretation

Funding: The Hunan Natural Science Foundation of China project gratefully acknowledged approval number: 2022JJ30029. The One Hundred Talents Foundation of Hunan Province is also gratefully acknowledged for the support of S.J. and S.R.K. MJP thanks the EPSRC for funding through grants EP/T021675 and EP/V006746.Simulated circularly-polarized 10 femtosecond laser pulses that induce a mixture of excited states are applied to ethane. Additionally, the carrier-envelope phase (CEP) angle ϕ, that quantifies the relationship between the time-varying direction of electric (E)-field and the amplitude envelope was used to manipulate the mechanical and chiral properties of ethane using Next Generation Quantum Theory of Atoms in Molecules (NG-QTAIM). The chirality assignments were reversed from S to R as the CEP angle ϕ was increased from ϕ = 0.0° to ϕ = 180°. A one-to-one mapping between the CEP angle ϕ and NGQTAIM trajectories was discovered.Peer reviewe

Halogen and hydrogen bonding in halogenabenzene/NH3 complexes compared using next-generation QTAIM

This research was funded by the National Natural Science Foundation of China grant number: 21673071. The One Hundred Talents Foundation of Hunan Province is also gratefully acknowledged for their 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.Next-generation quantum theory of atoms in molecules (QTAIM) was used to investigate the competition between hydrogen bonding and halogen bonding for the recently proposed (Y = Br, I, At)/halogenabenzene/NH3 complex. Differences between using the SR-ZORA Hamiltonian and effective core potentials (ECPs) to account for relativistic effects with increased atomic mass demonstrated that next-generation QTAIM is a much more responsive tool than conventional QTAIM. Subtle details of the competition between halogen bonding and hydrogen bonding were observed, indicating a mixed chemical character shown in the 3-D paths constructed from the bond-path framework set B. In addition, the use of SR-ZORA reduced or entirely removed spurious features of B on the site of the halogen atoms.Publisher PDFPeer reviewe