SPECTROSCOPY OF THE TRIPLET-STATE OF PSEUDOISOCYANINE MOLECULAR AGGREGATES

We investigate the triplet state of molecular aggregates of pseudoisocyanine iodide by emission, excitation, and optically detected magnetic resonance spectroscopy. The phosphorescence seems to stem entirely from aggregated species. It is enhanced by reabsorption processes. H and J aggregates can be distinguished by their different triplet energies and zero-field resonances. The spin-lattice relaxation does not play any significant role in the triplet dynamics up to temperatures as high as 8 K. Apart from phosphorescence detection of zero-field resonances, resonances could also be found by observing the delayed fluorescence. These resonances were attributed to the monomer species which has a lifetime on the order of 1 s. © 1990 American Chemical Society.