Photophysical properties of tri-tert-butylpyridinotribenzotetraazaporphinatozinc (ZnPcPy) complexes, a self-assembled dimer ((ZnPcPy)2) and a monomer (ZnPcPy-Py) in a non-polar solvent and with pyridine, respectively, have been studied. The lowest excited singlet (S1) state is investigated by the combined use of electronic absorption, magnetic circular dichroism and fluorescence spectroscopy and the S1 properties are analyzed by configuration interaction calculations including exciton interactions between ZnPcPy constituents. The lowest excited triplet state is investigated by time-resolved electron paramagnetic resonance (TREPR). TREPR spectra of (ZnPcPy)2 exhibit a dramatic temperature dependence at 10-220 K, in contrast to a negligible change for ZnPcPy-Py. The spectral changes are reasonably attributed to triplet energy transfer between two ZnPcPy constituents, and are well reproduced using energy transfer rates, k = 3 x 108 s-1 (100 K), 7 x 108 s-1 (140 K), and 2 x 109 s-1 (180 K), respectively. The activation energy of the energy transfer process is evaluated as 2.7 x 102 cm-1 from the Arrhenius plot. This study demonstrates the utility of TREPR for investigating energy transfer processes among these macrocycles.
|Number of pages||5|
|Journal||Journal of the Chemical Society, Dalton Transactions|
|Publication status||Published - 2002|
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