Abstract
The structures and photophysical properties of single molecule MEH-PPV (2-methoxy-5-(2�-ethylhexyloxy)-p-phenylenevinylene) and CN-PPV (2,5,2�,5�-tetrahexyloxy-7,8�-dicyano-pphenylenevinylene)nanoparticles are investigated with electronic structure theory and high resolution fluorescence experiments. It is shown that electron withdrawing substitutients, such as CN, on the vinyl group of the PPV polymer backbone cause substantial change in the π electronic structure which subsequently decreases the interchain distance. Not only does CN-PPV have a smaller interchain separation compared to MEH-PPV, but also an increased binding energy and more efficient charge transport (carrier mobility) due to larger electronic coupling (charge transfer integrals). These changes help explain the enhanced luminescence quantum yield, photo-stability, and lifetime for CN-PPV versus MEH-PPV observed in experimental high resolution fluorescence imaging of individual single molecule nanoparticles.
