Photoexcited triplet-state dynamics of novel porphyrinoids: octaethylcorrphycene and octaethylhemiporphycene. Time-resolved electron paramagnetic resonance study

The photoexcited triplet state of the two new porphyrin isomers, octaethylh emiporphycene (OEHPC) and octaethylcorrphycene (OECPC), embedded in isotrop ic (toluene) and an anisotropic liquid crystal matrices was studied by time -resolved electron paramagnetic resonance (EPR) spectroscopy in the tempera ture range of 150-300 K. The magnetic, kinetic and orientation parameters w ere determined and interpreted in terms of structure, symmetry and dynamic. Analysis of the results suggests that at T greater than or equal to 250 K, the orientation and packing of the chromophores result from a discrete sol id-like jumps mechanism, which is more efficient for OECPC. This difference is rationalized in terms of differences in the symmetry of the two chromop hores. (C) 1999 Elsevier Science B.V. All rights reserved.