Photochemically Induced 1,3‐Butadiene Ring‐Closure from the Topological Analysis of the Electron Localization Function Viewpoint

Abstract

The electronic rearrangement featuring the photochemically‐induced 1,3‐cis‐butadiene is discussed within a bonding evolution theory (BET) perspective based on the topological analysis of the electron localization function and Thom's catastrophe theory. The process involves the vertical singlet‐singlet excitation S0→S2, and the subsequent deactivation implying the S2/S1 and S1/S0 conical intersection regions. BET results reveal that the new CC bond is finally formed on the S0 surface, as also recently found in the photochemical addition of two ethylenes [Phys. Chem. Chem. Phys. 23, 20598, (2021)].

Uncovering Triradicaloid Structures in S1 Benzene Photochemistry**

“…ELF is a quantum tool intimately related to the electron pair concept inherent to Lewis's structures, thus allowing the reconciliation between experimental and theoretical observations. [45,50,51] Our previous results [42,43,52,53] revealed that the formation of multiple non-bonding density centers at the excited-state structure is a recurrent footprint describing photochemical reactions. This observation has also been extensively reported in ground-state pericyclic reactions; [47,[54][55][56][57][58][59][60][61] however, the nonbonding densities picture is somewhat different from the ones reported in photochemically induced reactions.…”

“…Our previous results [42,43,52,53] revealed that the formation of multiple non‐bonding density centers at the excited‐state structure is a recurrent footprint describing photochemical reactions. This observation has also been extensively reported in ground‐state pericyclic reactions; [47,54–61] however, the non‐bonding densities picture is somewhat different from the ones reported in photochemically induced reactions [55,58,59,61–63] .…”

A simple topology-based model for predicting the activation barriers of reactive processes at 0 K

“…9,13,14 Thus, insofar applications of CT in our field have been focused on providing information on the molecular mechanism or the relative reactivity of chemical species, leaving aside the energetic aspect of the discussion. Although our group has recently made some progress by revealing the intimate relationship between the unfoldings 1 and the pair-electron density symmetry in chemical reactions occurring in both grounds 15,22 and electronically excited states, 23–25 none of these works give any clue on how to correlate the unfoldings with, for instance, the activation barrier. To the best of our knowledge, the only effort in this direction was made more than two decades ago by Margalef-Roig, Miret-Artés, and Toro-Labbé.…”

Investigating the Mechanism of the Catalytic Intramolecular Aza-Wittig Reaction Involved in the Synthesis of 2-Methylbenzothiazole from the Perspective of Bonding Evolution Theory

“…14 A bit later, by combining ELFs 14 with Thom's catastrophe, 15 Krokidis and Silvi developed the Bonding Evolution Theory (BET), 16,17 which, over the years, has been demonstrated to have irrevocable robustness in unraveling the chemical bond-breaking and -forming processes in a diversity of organic synthesis mechanisms. [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] Benzothiazole is a molecule of interest. It belongs to one of the most important classes of heterocyclic compounds, and it plays a significant role in medicinal chemistry.…”