The transient photoinduced transmission of quinquethiophene-S,S-dioxide in solution is reported. Stimulated emission is observed in the viscous solvent, but quenched in polar and nonpolar low viscosity solvents. The lifetime of the photoexcited state changes of more than one order of magnitude depending on the solvent properties, pointing out conformational effects. Low-energy coherent transient is observed and assigned to real time conformational dynamics.