The Luminescence of Pd and Pt Benzohydroporphyrazines in the Near-IR Range

Abstract

The phosphorescence of three new palladium and three platinum complexes of benzo-fused hydroporphyrazines—analogues of phthalocyanine, in which molecule one or two isoindole fragments are replaced by a hydrogenated pyrrole ring which gives macrocycles of the type of chlorin, bacteriochlorin, and isobacteriochlorin—analogues of photosynthetic pigments, is studied in the near-IR range under stationary lamp excitation. The phosphorescence spectra of the complexes of trans-dibenzotetrahydroporphyrazines are recorded for the first time (for both platinum and palladium) which could not be found for a long time because of the unprecedented remoteness of the 0–0 bands from the visible region (1.67, 1.52 µm for Pd, Pt) as well as because of the low quantum yield of phosphorescence. The fluorescence of these complexes in the near-IR range is found as well. The approximate additivity of the action of the structural factors—hydrogenation of the pyrrole rings, aza-substitution, and benzo-substitution—on the energy of the lowest triplet state T1 is shown based on the comparison of the experimental results with the own and published data for palladium complexes of the tetrapyrrole series. The obtained information is substantial for the targeted creation of emitters in the near-IR range (1.0–1.7 µm).