The Torsion Path Of Retinal Molecule And Ring Opening Reactions From QTAIM And Stress Tensor

This dissertation is introduc a new approach to analysis the physical and chemical properties of torsion pathways and ring opening reactions base on the QTAIM and the stress tensor.These datas are performed with Gaussian 09 package and the topological analysis for total electronic charge density distribution ?(r)of molecules is carried out with AIMALL.The main contents contain five relatively independent chapters.In chapter 1,we briefly recapitulate the basic concepts of QTAIM,in order to provide the reader with a general understanding of QTAIM.In chapter 2,a QTAIM investigation of the torsion in both the clockwise and counter-clockwise directions about the ? bonds of the retinal protonated Schiff base chromophore in the lowest electronically excited state provided a detailed description of the changing bonding topology that was sensitive to both the torsion and the direction of torsion.Analysis of the separate torsion calculations demonstrated a clear order of preferred bonding torsion in terms of principles of maximizing bonding.Unusual behavior of the bond ellipticity in the S1 state was found for the two less favorable bonds for torsion and explained in terms of the presence of weak bonding interactions.In chapter 3 and chapter 4,the realization of technologically relevant functional systems from idealized photochromic compounds remains elusive due to the double requirement that such switches must possess both highly efficient photo-isomerization reactivity and extremely low fatigue over a large number of switching cycles.Nowadays,improvements of the switching properties in complex diarylethene structures are mainly attained on a "trial and error" basis through chemical substitutions aimed at tuning the chemical properties of the core of the diarylethene.Therefore,we present new guiding principles to analyze the first excited state reactivity of diarylethenes based on the Quantum Theory of Atoms in Molecules(QTAIM)including the stress tensor.This approach straightforwardly provides consistent theoretical justification to partner the already successful symmetric substitution patterns obtained from experiments.The guiding principles provided by QTAIM and stress tensor suggest more complex asymmetric patterns should be included for the systematic design of new technologically relevant functional compounds.The stress tensor trajectory T??(s)analysis is also used to characterize the photochromism reaction as reusable and the fatigue reaction as irreversible.In chapter 5,a conclusion and future research work on the basic of this thesis are provided in this part.