Tetra-2,3-pyrazinoporphyrazines with externally appended pyridine rings. 18. Physicochemical properties and photochemical behavior of new uncharged water soluble low-symmetry macrocycles [Pd(OAc)2 3 (PtCl2 )LM] (M = MgII(H2 O), ZNII, PdII)

The synthesis and physicochemical characterization of a new class of low-symmetry water soluble heteropentanuclear porphyrazine complexes are described. The investigated compounds, represented as [{Pd(OAc)2}3(PtCl2)LM] · xH2O where L = tetrakis-2,3-[5,6-di(2-pyridyl)pyrazino]porphyrazinato dianion, M = MgII(H2O), ZnII or PdII and x = 3-8, were prepared under mild experimental conditions from the previously described heterobimetallic compounds [(PtCl2)LM]. Peripheral binding of one PtCl2 and three Pd(OAc)2 units in the new series of compounds occurs at the vicinal pyridine N atoms of each dipyridinopyrazine fragment via a "py-py" coordination. The newly synthesized porphyrazines were characterized by IR measurements in the solid state and UV-visible absorption spectroscopy in the polar nonaqueous solvents pyridine, dimethyl sulfoxide (DMSO) and dimethylformamide (DMF) as well as in water, the enhanced solubility in this medium being due to the presence of the external Pd(OAc)2 moieties. Data on the photosensitizing activity of the compounds for the generation of singlet oxygen, 1O2, were also obtained in DMF and should be of interest to researchers in the area of photodynamic therapy. © 2017 World Scientific Publishing Company.