Picosecond fluorescence dynamics of auramine with a long aliphatic chain

The acyl derivative of auramine with dodecyl carbon chain has solvent dependent absorption and emission spectra. The Lippert-Mataga plot shows two trends, a small slope in alcohols and a significant one in polar aprotic solvents. The change of dipole moment between ground and excited-state in aprotic solvent is 12 D, indicating an intramolecular charge-transfer process. Decay components of 5 and 600 ps appear in aprotic polar solvents. In protic polar solvents, the fast component, ranging from 9 ps in ethanol up to 53 ps in n-octanol, is correlated with the Debye dielectric relaxation time of the n-alcohols.