Ground and excited state acidity constants of indole derivatives

CHED 1407

Nahid Shabestary, nshabes@siue.edu, Danielle N. Reed, dareed@siue.edu, and Amanda L. Hustedt, ahusted@siue.edu. Department of Chemistry, Southern Illinois University Edwardsville, Box 1652, Edwardsville, IL 62026-1652
Excited state proton transfer is a phenomenon first noted by Weber when he observed that varying the pH of certain solutions correlated to a change in fluorescence but not to a corresponding change in absorption. This difference in fluorescence is attributed to a change in acidity or basicity in the excited state relative to ground state due to the change in electron density. In this research, the effect of substitution of certain electron donating and electron withdrawing groups on the acidity constant of indole derivatives is studied. The excited state acidity constant (pK*) is determined by fluorometric titration and the ground state acidity constant (pK) is calculated by the use of Förster cycle principle.