Yi Wang

Publications (2)12.85 Total impact

• Article: Fluorescence enhancement by symmetry breaking in a twisted triphenylene derivative.

  Jack W Levell, Arvydas Ruseckas, John B Henry, Yi Wang, Andrew D Stretton, Andrew R Mount, Trent H Galow, Ifor D W Samuel
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  ABSTRACT: 1,4,5,8,9,12-hexamethyltriphenylene (HMTP) shows a high photoluminescence quantum yield (PLQY) of 31% in the solid state, making it of interest for luminescence applications. The detailed photophysical properties of HMTP have been investigated by using time-resolved and steady-state luminescence, PLQY, and molar absorption coefficient measurements. An enhancement of the transition dipole moment for fluorescence and absorption was demonstrated compared to the case of unsubstituted triphenylene, which resulted in a 20-fold increase in the radiative decay rate. This is attributed to a breaking of triphenylene symmetry as a result of the necessarily twisted structure induced by steric crowding. In addition, it was shown that HMTP shows similar photoluminescence energies in solution, powder, and film, indicating a reduced propensity for intermolecular π-stacking compared to the case of triphenylene, as a result of this twisted structure. This work also develops a method for calculating the photoluminescence quantum yield of powders by using a calibrated photodiode in combination with an uncalibrated CCD spectrometer.
  The Journal of Physical Chemistry A 12/2010; 114(51):13291-5. · 2.95 Impact Factor
• Article: 1,4,5,8,9,12-Hexamethyltriphenylene. A molecule with a flipping twist.

  Yi Wang, Andrew D Stretton, Mark C McConnell, Peter A Wood, Simon Parsons, John B Henry, Andrew R Mount, Trent H Galow
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  ABSTRACT: The synthesis and characterization of 1,4,5,8,9,12-hexamethyltriphenylene (5) is described. In the solid state, X-ray crystallographic studies reveal that compound 5 presents a highly distorted C2 geometry with a 53 degrees end-to-end twist. In solution, variable-temperature 1H NMR studies and molecular modeling present a story of rapid dynamic conformational interconversions between two C2 enantiomers (with a low activation barrier) and a slower C2-D3 interconversion (with a relatively high barrier)--the first time clear evidence of conformational interchange for these hindered triphenylenes has been provided. Further studies have established that 5 is a fluorescent stable blue emitter, and that the compound undergoes an irreversible one-electron electrochemical oxidation. Calculations have predicted this to be a radical cation of C2 geometry with 60 degrees end-to-end twist.
  Journal of the American Chemical Society 11/2007; 129(43):13193-200. · 9.91 Impact Factor