The relationship between photographic activity and structure of masked pyrazolone colour couplers

Abstract Nine masked pyrazolone colour couplers were synthesised and their photographic activities (A) determined by the Elvegard γ-t equation: γ = A logt + B where A is the slope of the line. The superdelocalisabilities S re and electron densities Q r at the coupling position of the colour couplers were calculated using Huckel molecular orbital theory. From a plot of In A against S re , a linear relationship was observed, viz. InA = 31.84S re -33.16 (n = 9 and r = 0.95).