• A computational investigation of the photochemical oxaziridine and amide conversion process of open-chain conjugated nitrone with electron-withdrawing trifluoromethyl group on nitrogen

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      https://www.ias.ac.in/article/fulltext/jcsc/127/10/1757-1768

    • Keywords

       

      CASSCF; 𝑁-substituted nitrone; oxaziridine; conical intersection; singlet excited state.

    • Abstract

       

      This computational study investigates the photo-excitation process and subsequent photoproduct formation steps through non-radiative deactivation channels in open-chain conjugated N-substituted nitrone systems (model compounds of corresponding retinylnitrones) having electron-withdrawing groups on nitrogen. Calculations mostly based on CASSCF/6-31G* and CASMP2/6-31G* level of theories on a representative system with N-trifluoromethyl substituent have predicted initial photo-excitation to a planar singlet state. This photochemical path is subsequently followed by a barrierless non-radiative channel towards the lowest-energy conical intersection (CI) geometry having a terminal CNO kink, and situated at 30 kcal/mol below the planar excited state. Following the direction of its gradient difference (GD) vectors, an oxaziridine-type species (RC−O = 1.38 Å, RN−O = 1.53 Å, < CNO= 55.8°) appears at 3–6 kcal mol−1 below the ground state nitrone system through a transition state (along its reverse direction of minimum-energy path), situated on the reaction pathway. This species with an elongated N-O bond seems to be heading towards an amide geometry. On the other hand, in the opposite GD vector direction a proper oxaziridine geometry has been obtained with a much shorter N-O bond distance (RN−O = 1.42 Å).

    • Author Affiliations

       

      Praveen Saini1 Anjan Chattopadhyay1

      1. Department of Chemistry, Birla Institute of Technology and Science (BITS), Pilani K K Birla Goa Campus, Goa, 403 726, India
    • Dates

       
  • Journal of Chemical Sciences | News

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