Distinguishing and quantifying the torquoselectivity in competitive ring-opening reactions using the stress tensor and QTAIM

Abstract

Currently the theories to explain and predict the classification of the electronic reorganization due to the torquoselectivity of a ring-opening reaction cannot accommodate the directional character of the reaction pathway; the torquoselectivity is a type of stereoselectivity and therefore is dependent on the pathway. Therefore, in this investigation we introduced new measures from quantum theory of atoms in molecules and the stress tensor to clearly distinguish and quantify the transition states of the inward (TSIC) and outward (TSOC) conrotations of competitive ring-opening reactions of 3-(trifluoromethyl)cyclobut-1-ene and 1-cyano-1-methylcyclobutene. We find the metallicity ξ(r ) of the ring-opening bond does not occur exactly at the transition state in agreement with transition state theory. The vector-based stress tensor response β was used to distinguish the effect of the CN, CH , and CF groups on the TSIC and TSOC paths that was consistent with the ellipticity ε, the total local energy density H(r ) and the stress tensor stiffness S . We determine the directional properties of the TSIC and TSOC ring-opening reactions by constructing a stress tensor UσTS space with trajectories TσTS (s) with length l in real space, longer l correlated with the lowest density functional theory-evaluated total energy barrier and hence will be more thermodynamically favored. © 2016 Wiley Periodicals, Inc.

Next‐generation QTAIM for scoring molecular wires in E‐fields for molecular electronic devices

“…The QTAIM eigenvector trajectories T( s ) are constructed from the set of shifts dr ( s ), associated with steps s , where the parameter s is a sequence number of a given BCP in 3‐D Cartesian space as an ordered set of vectors dr ’ ( s ) in the eigenvector projection U‐space. Earlier, for a series of competitive ring‐opening reactions, some of the current authors found a BCP that moves further relative to the { e 1σ , e 2σ , e 3σ } framework at the transition state of that BCP , that is, with a longer l signifying the attainment of a lower transition state energy barrier than a BCP trajectory T σ ( s ) with a shorter l . The real‐space lengths l ( s ) of the stress tensor T( s ) and QTAIM T( s ) are calculated as the sum: …”

A vector‐based representation of the chemical bond for predicting competitive and noncompetitive torquoselectivity of thermal ring‐opening reactions

“…Some of the current authors also demonstrated that the ξ( r b ) is inversely related to “nearsightedness” of the first‐order density matrix and is suitable for closed‐shell systems . Recently, the use of the metallicity ξ( r b ) was demonstrated for the ring‐opening BCP . The ξ( r b ), therefore, relates to the reaction electronic flux (REF, J [ξ]) that corresponds to a chemical process along the IRC(ξ) and is defined to be J (ξ) = −d μ /dξ .…”

“…Recent studies have shown new interpretations to treat this bottleneck in electrocyclic reactions using frameworks ranging from the electron localization function (ELF), electronic structure principles, to stress tensor and QTAIM . Of these formalisms, only the stress tensor and QTAIM allowed the identification and quantification of the reaction coordinate through directional parameters, although the later was limited to use with reactions with very similar nuclear skeletons.…”

“…The larger yield (65%) for the TSIC experiment product indicated that it is preferred over the smaller yield of (35%) for the TSOC product. The recent investigation by some of the current authors successfully demonstrated a new method to distinguish the torquoselectivity along the reaction coordinate of a pair of competitive reactions without the use of orbital information or symmetry . There are, however, disadvantages of this recent QTAIM and stress tensor analysis.…”

Next generation QTAIM for the design of quinone-based switches

“…Recently developed "next-generation" QTAIM (quantum theory of atoms in molecules) 9 has provided a set of tools to study the bond structure of molecular systems [4][5][6][7] , which can be used to improve our understanding of molecular switches. A recent investigation by some of the current authors 8 focussed on 3-imino-6methylenecyclohexa-1,4-diene-1,4-diamine that we referred to as the quinone switch, with F substituted in two locations (UP or DOWN) for the ring hydrogens and with and without a coordinated Fe atom above the ring, see Scheme 1.…”