FIGURE 5.

Emission wavelength-dependent anisotropy of DASPMI. In response to high-membrane-potential conditions, electrons are withdrawn from the electron-rich aniline moiety, leading to a less polar DASPMI structure. Consequently, an increase in rigidity of the single bonds (i.e., double bond-like character) neighboring the olefinic double bond leads to an increase in anisotropy. The dependence of anisotropy on emission wavelength indicates the gradual change in molecular configuration and hence the transition in dipole moment from the initially excited Franck-Condon level.