Dr. Erwin Buncel, Emeritus  
           
Physical Organic Chemistry

Current projects in our lab are multifarious in nature, and come under the following headings:
 

   
 Materials Science...                     
 

 

 

 

 

   

A collaborative research program with Xerox Research Centre of Canada has led to the development of organic materials for application as photo-activated molecular switches.  These switches have the potential of becoming the basis for the next generation of 3-D optical data devices that will replace existing CD-ROM and silicon-based technologies.  Reading and writing of data in these systems is performed by photochromic molecules where the reversible switching process is based on photochemically induced interconversion between two states having different absorption spectra.   A related project focuses on light harvesting dendrimers and star polymers.  

 1

 
 Environmental Chemistry...             
   

   

In a collaborative program with Prof. Gary vanLoon we are investigating the mechanisms of abiotic degradation and soil/water interactions of pesticides and other hydrophobic organic compounds.  A number of the pesticides such as fenitrothion (1), are organo-phosphorus ester derivatives and their degradation (via nucleophilic substitution at P) can be studied by UV/VIS spectro-photometric techniques, leading to structure-activity relationships.  Herbicides such as trifluralin (2) and benefin are electron-deficient nitroaromatic derivatives which undergo degradation through SNAr mechanisms.  The dehalogenation of chlorinated hydrocarbons as mediated by cyclodextrins is also investigated.  

 1

 
 Metal Ion-Biomolecule Interactions...                   
   

   

Metal ions play vital roles in important biochemical processes involving biomolecules such as proteins, enzymes, nucleic acids, etc.  In our research the binding of metal ions to heteroatomic centres of biomolecules has been utilized as a probe of metal ion effects in living systems. Isotopic hydrogen/deuterium/ tritium exchange in imidazoles, histidines, thiazoles and purine derivatives, is mediated by metal ions such as Pt(II), Co(III) and Cr(III).   The studies are also informative on the mechanism of drug action, e.g. cis-platin analogues as anti-cancer agents.

   
 Nitro Aromatic Electrophiles and Super-Electrophiles...         
   

   
Electron deficient nitroaromatic base interactions: Various possible interactions between nitroaromatic electrophiles, super-electrophiles and normal or ambident nucleophiles have been explored in our labs via mechanistic and synthetic studies. The studies pertain to organic conductors and provide insight as biochemical-biophysical probes. 

 

   
   
   

   
This topic is concerned with stable and/or transient carbanionic species/organometallic reagents. Experimental approaches include synthesis of novel organometallics, multinuclear NMR and hydrogen isotope exchange. Studies are extended to other group 14 anions (Si, Ge, Sn, Pb); electronic effects - inductive, field, resonance - along the series are contrasted.

   C,   Si,  Ge.......               

 Bioorganic Chemistry...                       
       

Cyclodextrin based enzyme models: This project concerns the design of artificial catalytic enzyme model systems based on cyclodextrin. It involves synthesis of modified cyclodextrins as well as kinetic studies and molecular mechanics calculations on potential cyclodextrin enzyme model systems. Complexation by CD's of aromatics and halogenated hydrocarbons is also investigated as part of remediation studies.  Complexation work by CD's is supple-
mented by computational studies.

 1