Research Topics

Sulfur-bridged Conjugated Oligomers

Bridging conjugate oligomers such as oligothiophenes with sulfur groups gives rise to interesting new photophysical and photochemical behavior. The oxidation state of the bridging sulfur can be varied (sulfide, sulfoxide and sulfone), resulting in changes in the electronic interactions in these species. Symmetrically substituted bridged oligomers possess remarkable properties including enhanced emission quantum yield relative to species without the sulfur bridge. These properties are anticipated to be useful for new emitters in organic light emitting devices (OLEDs) as well as in organic photovoltaic devices (OPVs).

     

Sulfur-bridged anthracenes have unusual photochemical behavior.  The sulfoxide bridged species photochemically eliminate SO to give dianthryl, while the sulfone bridged species forms a rare episulfone species. Exploitation of this new photochemistry in photopatterned emissive films and OLEDs are being explored.

 

Electrocatalysts for Reduction of Carbon Dioxide

Efficient reduction of carbon dioxide to fuels such as carbon monoxide or methane is being explored as a method to combat the debilitating effects of rising atmospheric CO2 levels. One approach is the use of electrocatalysts which bind and activate CO2, followed by electrochemical reduction. Ultimately, it is desirable that the energy required to drive this process is obtained from solar energy, however at present the development of new electrocatalysts presents an important challenge. We have developed a new family of metal electrocatalysts based on Group 10 metals and are exploring their application in the reduction of CO2 to CO.

 

Metal Complex and Lewis Acid-Base Pair Functionalized Conjugated Oligomers

Pendant functional groups attached to conjugated oligomers such as oligothiophenes can be used to control the photophysical properties of these species. We are using pendant metal complexes to alter the photophysical properties of terthiophene oligomers in different solvents. Folding and unfolding of such complexes has been demonstrated in solution and the solid state.

Pendant Lewis acid and base groups on adjacent rings in a conjugated oligothiophene can interact to form an unreactive Lewis acid-base adduct, or under certain circumstances remain free, with both acid and base component available to react. We have developed such “flexible” Lewis acid-base systems, and have shown that the photophysical properties of the system depend on whether the acid-base pair are “closed” (adduct) or “open” (free). Temperature and solvent may be used to control which state the flexible Lewis pair is in. Applications in sensing and catalysis are being explored.

   

 

Photophysics of Metal Complexes

Cyclometallated Ir complexes are of interest as emitters in OLEDs, as catalysts in photoredox catalysis, and in bioimaging. The photophysics of such Ir complexes with pendant conjugated groups such as pyrene are being explored, targeting extremely long lifetime emitters which take advantage of the long triplet lifetime of the pyrenyl group.

Photochromic metal complexes containing the dithienylethane group are being explored. Direct excitation of the metal group leads to triplet state photochemical ring opening and closing of the DTE group, allowing photoactivity of closely linked DTE groups.


Other areas of interest...

Photophysics of photoredox catalysts, Materials for singlet fission and triplet fusion, Photochromic materials, Nanomaterials for methane oxidation catalysis.