Synthesis and Properties of Porphyrazine Containing Dendrimeric Supramolecules

Abstract

The polyphenylene dendrons, characterized by their shape-persistent structure, and out-of-plane twisted phenyl components, have been successfully attached to various functions.1-2 We were recently able to develop convenient methods for the synthesis of porphyrazines containing both flexible (linear) and more rigid (dendritic) groups. The synthesis of this type of completely aromatic dendrimers is unique in that it is based on the [2+4] Diels-Alder cycloaddition of the tetraphenylcyclopentadienone to an ethynyl diketone compound, followed by the elimination of carbon monoxide. And phenylene groups can be connected each to supramolecule by intramolecular cyclodehydrogenation3, which have a planar structure, and strong electron donating effect. The most representative property of a porphyrazine is the polymeric behavior being caused on the aggregation of compounds. The reason of these aggregates is the π-stacking of planar structure of porphyrazines which have groups of strong electron-accepting ability and aromatic heterocycles. It has been found that such stacking can lead to efficient nonradioactive energy relaxtion, thereby reducing their triplet-state population and, consequently, significantly decreasing their photosensitizing efficiency. The degree of aggregation can be changed by concentration, solvents, adding base, and temperature. Tetrapyrazinoporphyrazinato metal (M = Cu, Mg) complexes were prepared by 2,3-dicyano-5-polyphenylpyrazines with one equivalent of cuprous chloride in o-dichlorobenzene in the presence of hexaammonium heptamolybdate tetrahydrate as catalyst, or magnesium in n-butanol. The synthesized tetrapyrazinoporphyrazine metal complexes were characterized by UV-visible spectroscopy, MALDI-TOF-Ms (matrix-assisted laser desorption ionization time-of-flight mass) spectroscopy, elemental analysis and 1H NMR spectroscopy.