Synthesis, electronic and photophysical properties of a bisacridinium-Zn(II) porphyrin conjugate

The synthesis of a novel bisacridinium-Zn(II) porphyrin is reported and its properties investigated via electrochemical, photophysical and computational studies. Cyclic voltammetry studies revealed a two-electron oxidation of the Zn(II) porphyrin and the simultaneous one electron reductions of the two acridiniums. Using absorption, emission and ultrafast transient absorption spectroscopies, the near total fluorescence quenching observed following excitation of either the acridinium or Zn(II) porphyrin units was assigned to ultrafast electron transfer (<=0.3 ps) leading to a reduced acridinium and an oxidized porphyrin unit in the bisacridinium-Zn(II) porphyrin conjugate. In addition, computational studies were found to complement experimental results, with calculations revealing two near degenerate HOMOs for the porphyrin.