Abstract:
Phosphorescence in the near-IR range under stationary lamp excitation was studied of three palladium and three platinum complexes of benzocondensed hydroporphyrazine phthalocyanine analogues in which molecule one or two isoindole fragments are replaced by a hydrogenated pyrrole ring, giving macrocycles of photosynthetic pigments analogues of chlorin, bacteriochlorin and isobacteriochlorin types. For the first time, the phosphorescence spectra of trans-dibenzotetrahydroporphyrazines (for both platinum and palladium) have been registered, which detection failed during long time due to the record removal of 0–0 bands from the visible area (1.67 and 1.52 $\mu$m for Pd and Pt), and also because of the small quantum yield of phosphorescence. The fluorescence of these complexes was also detected.in the near-IR range. On the basis of comparison of experimental results with own and literature data for palladium complexes of a number of tetrapyrroles is shown the approximate additivity of the influence of structural factors – hydrogenation of pyrrole rings, aza- and benzo substitution – on the energy of the lower triplet state $T_1$. The information obtained is essential for targeted creation of emitters in the near-IR range (1.0–1.7 $\mu$m).
Keywords:palladium and platinum complexes of benzohydroporphyrazines, trans- dibenzotetrahydroporphyrazine, phthalocyanine analogs, near-IR range, absorption spectrum, phosphorescence spectrum, quantum yield of phosphorescence, lower triplet state, luminescence of singlet oxygen.
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