Relationship between solid state charge transfer behavior and molecular structure in a series of 1-(p-substituted phenylazo)-2-naphthols

Charge transfer properties of a series of substituted arylazonapthols are shown to correlate with the Hammett's substituent constant σ. For both contact charge exchange of the dyes to metal and field assisted, photostimulated charge transfer from the dyes into nonpolar fluids, the amount of charge transferred is found to increase with increasing σ. However, the efficiency of charge transfer into fluids does not change with σ. In addition the energies of the highest filled and lowest unoccupied molecular levels are shown (by measurement of the oxidation and reduction potentials) to decrease as σ increases. The correlations establish a relationship between charge exchange phenomena and the energy levels of the dyes.