טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentLavy Tali
SubjectPhotochemical Reactions of Inclusion Compounds in the
Solid State
DepartmentDepartment of Chemistry
Supervisor Professor Emeritus Menahem Kaftory
Full Thesis textFull thesis text - English Version


Abstract

An inclusion compound is composed of an inert host molecule and reactive guest molecules. Usually the reaction occurs in a cavity formed by the host molecule. 
This work is divided into two separated projects. The first deals with [4] photodimeriztion of pyridon derivatives and the other deals with unimolecular photoyclization of N,N-α-oxoamids. These two projects shall be referred to henceforth as "unimolecular" and "bimolecular" projects.


            The goal of the first project was to find and study systems in which the reactions are associated with a decrease in the guest volume. The questions that arise are: What happens when the volume of the product is smaller than that of the reactant molecule?

            Will the unit cell collapse and the crystal be destroyed? Will molecules from the surrounding penetrate the crystal and occupy generated voids so that the crystalline nature is maintained?
What is the influence of hydrogen bonds on the freedom of  movement of potentially reacting molecules?

We have found two inclusion compounds, each of them consist of 1,1,6,6-tetraphenyl-2,4-hexadiyne-1,6-diol as a host molecule and 6-methyl-2-1H-pyridone or or 2-(1H)- pyridone as photosensitive guest molecule. In these inclusion compounds, the  photodimerization of the guest was associated with significant, extremely unexpected rotation, without destruction of its crystal nature. Due to the dimerization, the volume of the product decreased in respect to the reactant’s volume, and consequently,

            channels were formed. These channels were occupied by water molecules that  penetrate the crystal from the surroundings, only at the very end stage of the conversion, in order to stabilize it. A mechanism for the manner in which the water molecules penetrate the crystal was proposed.

 

            The goal of the second project was to study the influence of the reactant’s surrounding on the course of the reaction in the case of unimolecular reactions. Inclusion compounds in which the guest molecule are N,N-alpha-oxoamids were examined. I have found that by changing the host molecule, different surrounding environments can be achieved, which can alter the course of the reaction.