Monophotonic Ionization of 7-Azaindole, Indole, and Their Derivatives and the Role of Overlapping Excited States

7-Azaindole undergoes monophotonic ionization just as its counterpart, indole. This result suggests that 7-azaindole is qualitatively more similar to indole than has previously been recognized. The appearance of the solvated electron for zwitterionic and anionic 7-azatryptophan and for 7-azaindole in water and methanol is complete within 1 ps, which indicates that the fluorescent state whose lifetime is \u3elo0 ps cannot be the source of the electron. The origin of the electron is related to the presence of closely spaced or overlapping excited states in 7-azaindole, which is another similarity that this chromophore bears with respect to indole. The fluorescence quantum yield of 7-azaindole is shown to be excitation wavelength dependent. The excitation-wavelength dependence and the temperaturedependence of the fluorescence quantum yield of 7-azaindole are explored and related to the production of the solvated electron. The implications of these observations for the use of 7-azatryptophan as an alternative to tryptophan as a probe of protein structure and dynamics are discussed