Time-resolved fluorescence studies of porphycene isolated in low-temperature gas matrices

Picosecond time-resolved fluorescence (TRF) was used to study excited state deactivation processes of porphycene and 2,7,12,17-tetra-t-butylporphycene incorporated in solid argon and nitrogen matrices, and in liquid solutions. For the matrix-isolated samples, excitation of both molecules into the Soret band, located about 11 000 cm−1 above the lowest excited singlet state, results in major spectral evolution of the TRF band on the time scale of 100 ps. No such evolution is detected in the case of low energy excitation (Q bands) as well as for high energy excitation in solution. These experimental facts indicate that heat transport from the cage to the bulk in the case of low temperature matrices consumes about 100 ps, and, consequently, the local transient ‘temperature’ can be much higher than the bulk temperature.