Rob's Research Page











CNN





CNN2







Background



    I am a fourth year graduate student in
 the research group of Professor Christopher S. Foote at UCLA.  Our main
areas of research
interest within the Foote group revolve around photochemistry and singlet
oxygen, and include:









*
Studying the
reaction pathways, mechanisms of and product formation in the reaction of
singlet oxygen with various substrates.






*
The
oxidation
of guanosine derivatives, the reaction of these
derivatives with singlet oxygen, and this process' possible role in cell
mutation.






*
The continuing
study of fullerenes, including:

        
    buckyball
        * The
derivatization of this newly discovered allotrope of carbon and
classification of its reactivity profile.
    

        * The
discovery of C60's utility as a singlet oxygen sensitizer.
    

        * Detailed analyses of the photophysics of
C60,
C70 and other fullerene derivatives.











My Research Topics



   Since joining the Foote group I have taken on several
research projects:



 






*
A
project which two other Foote group members and myself recently completed
was a
photophysical examination of the changes which occur upon derivatization
of C60.  A homologous series of fullerene derivatives,
synthesized via a
tether-directed methodology (Rubin,
Y.; Qian, W. Angew. Chem. Int. Ed.
Eng.),
were analyzed using flash-photolysis as well as our previously
described singlet oxygen detection set-up.  Our results ("Triplet State
Properties and Singlet Oxygen Generation of
a Complete Series of Functionalized Fullerene Derivatives", Prat, F.;
Stackow, R.; Bernstein, R.; Qian, W.; Rubin, Y.; Foote, C. S.;
J. Phys. Chem. A, 1999, 103, 7230-7235),  clearly
showed a correlation between the degree of substitution
and the fullerene derivatives photophysical properties. Clicking on
the picture below will take you to an HTML version of the paper.











sorry








*
I am currently working on a collaboration with
the research group of J.
Fraser Stoddart which focuses on utilizing
flash-photolysis to study the molecular motion within a
special group of molecules called catenanes (a molecule comprised of
interlocked rings).  These molecules contain a tetrathiafulvalene unit
(see below) which can be easily oxidized, causing the
rings to shift with respect to one another. This motion
has been coined "circumrotation" and is pictured in the scheme below. The
motion, upon oxidation, results from the displacement of the now
positively charged TTF
unit from the cavity within the electron deficient cyclophane, leading to
the less electron-rich aromatic moiety (compared to
neutral TTF) taking up that position. By using
3C60 generated with our laser flash-photolysis
set-up, which is a good electron acceptor in its excited state, we are
able to watch this circumrotation take place.  We are in the process now
of trying to evaluate which method of data interpretation will yield the
most accurate estimate of the timescale of the rings' motion upon
oxidation. Clicking on this picture will take you to a page containing
animations of the molecular motion I am referring to.
 
 







Sorry










*
An additional photophysical characterization was
recently completed
where the subject of our examination was ring-opened fullerene
derivatives.  These novel C60
derivatives are the first to bear a sizable orifice, and offer the
ability to encapsulate atoms, and small molecules. The consequences of
this orifice's disruption in the
 fullerene core are of interest to us.  We have been shown that the
photophysical properties of these
 unique molecules are still very similar to C60, including
relatively high singlet oxygen and
triplet quantum yields (recently published, "Photophysics of Open
C60 Derivatives", Robert Stackow, Georg
Schick, Thibaut Jarrosson, Yves Rubin, and Christopher S. Foote*, Journal of
Physical Chemistry B 2000, 104 (33), 7914-7918.












Sorry









*
The photooxidation of methylphenylindene (MPI)
has been
examined previously in our group (see reaction scheme below), however,
 I hope to make use of our
flash-photolysis set-up in order to observe a transient intermediate in
the photooxidation of MPI by singlet oxygen.  This will hopefully shed
light on the reactive
intermediates involved in singlet oxygen photooxidation.
This project has required
the synthesis of several key synthetic intermediates in order to obtain
mass quantities of the final MPI product.











Sorry













Several current avenues of interest in this
project
are:

        
    
        * As
mentioned above, are any ephemeral intermediates of the oxidized product
observable by transient absorption techniques? If so, can we describe
the reactive intermediates?
    

        * Can
the solvent-dependence of the product ratio be explained by any of these
intermediates observed by transient absorption?
    

        * Is
there any effect on the product distribution by placing electron-donating
groups on the aromatic ring of the indene?
















*
Several
other very interesting flash-photolysis are currently
under investigation or soon to begin.














[
Home |
About Me
]




[
My Research |
My Résumé |
Links
]











e-mail





 














This site was last modified 8/17/00