STEADY-STATE AND TIME-RESOLVED FLUORESCENCE ANISOTROPY OF ONENE-5,6,11,12-TETRACARBOXY-BIS-N-HEPTADECYLIMIDE

The photophysical properties of 6,11,12-tetrahydrocoronene-5,6,11,12-t etracarboxy- bis-n-heptadecylimide (P5-17) in solution are investigate d as a function of concentration, In 2-methyltetrahydrofuran, above 2 X 10(-5) M, a new absorption band with a maximum at 688 nm is observed indicating the formation of an aggregate. Upon excitation in this abs orption band, emission from the aggregate with a maximum at 710 nm is observed, This emission coincides with that of the liquid crystalline discotic phase. The rotational dynamics of P5-17 and its aggregate are investigated using steady-state fluorescence measurements and time-re solved fluorescence anisotropy. From. the global analysis of the polar ised fluorescence decay traces, it is found that for both monomer and aggregate, the anisotropy decay can be described by a monoexponential decay law. The rotational correlation time for the monomer is linked o ver two excitation wavelengths corresponding to S-0 --> S-1 and S-0 -- > S-n transitions. For the aggregate, the excitation and emission dipo les are perpendicular and a fast fluorescence depolarization was obser ved.