Nanosecond Time-Resolved Emission Spectroscopy: Spectral Shifts due to Solvent-Excited Solute Relaxation

Abstract

Nanosecond time‐resolved emission spectral techniques have been applied to the problem of the origin and nature of the well‐known temperature‐dependent spectral shifts characteristic of the aminophthalimides in alcohol solvents. It is demonstrated that the temperature‐dependent spectral shifts are in fact due to time‐dependent spectral shifts. At least two relaxation times characterize this phenomenon. One relaxation time is observed to be subnanosecond in character and may be associated with the exciplex that presumably is present in the system. The other relaxation time is presumably associated with the nonspecific dipolar reorientation although it has distinctly different characteristics from the solvent dielectric relaxation time. Wavelength‐dependent fluorescence decay that can be explained by the time dependence of the emission spectrum is also observed.