Homo/Heteropentanuclear Porphyrazine MgII, ZnII, and PdII Macrocycles with Externally Pending PdCl2 and Pd(CBT)2 Units: Synthesis, Physicochemical Characterization, and Photoactivity Studies

Recent work has been developed on two new classes of neutral porphyrazine complexes of formulas [(PdCl₂)₄Py₈PzM]·xH₂O (Py₈Pz = octakis(2-pyridyl)porphyrazinato anion; M = Mg^II(H₂O), Zn^II, Pd^II) and [{Pd(CBT)₂}₄Py₈PzM]·xH₂O (M = Mg^II(H₂O), Zn^II; CBT = m-carborane-1-thiolate anion). Characterization of all the species has been conducted by IR and UV-visible spectral measurements in a systematic comparison with the corresponding already known mononuclear species [Py₈PzM] (M = Mg^II(H₂O), Zn^II) and the mono-Pd^II analogue isolated and presented here for the first time. Comparison includes also the two parent classes of pentanuclear tetrapyrazinoporphyrazines having the more extended π-electron delocalized macrocyclic core Py₈TPyzPz. The reported new classes of pentanuclear complexes behave as active photosensitizers in photodynamic therapy (PDT), and due to the high boron content of the CBT derivatives, perspectives for them are open of application in the field of bimodal PDT/BNCT (boron neutron capture therapy) anticancer treatments.

Exocyclically metallated tetrapyridinoporphyrazine as a potential photosensitizer for photodynamic therapy

Synthesis and biological evaluations of a potential dual chemotherapeutic photosensitizer for photodynamic therapy based on the first exocyclically platinated tetrapyridinoporphyrazine.

Zinc(II) complexes of tetrakis-(6,7-quinoxalino)porphyrazine bearing externally appended 2-pyridyl rings: Synthesis, UV-visible spectral behavior and photoactivity for singlet oxygen generation

The synthesis and physicochemical properties of the Zn II complexes, [ Py 8 QxPzZn ]( Py 8 QxPz = tetra -2,3-[6,7-di(2-pyridyl)quinoxalino]porphyrazinato dianion), the corresponding octacation [(2- Mepy )8 QxPzZn ]8+ (neutralized by I - ions), and the heteropentanuclear complex [( PdCl 2)4 Py 8 QxPzZn ] are presented and discussed. According to their UV-visible spectral data in non aqueous solvents ( CHCl 3, pyridine, dimethyl sulfoxide, dimethylformamide), the species exhibit intense absorptions in the Q-band region at 750–770 nm, in line with parallel spectral data observed for the free base [ Py 8 QxPzH 2], also reported, and the previously investigated Mg II complex [ Py 8 QxPzMg ( H 2 O )]. The observed Q-band position for this series of "quinoxalinoporphyrazine" macrocycles is about 100 nm to the red with respect to the position of the same absorption for the series of the already reported "pyrazinoporphyrazine" analogs. The spectral effects induced by the peripherally appended methyl-pyridinium groups in the octacation [(2- Mepy )8 QxPzZn ]8+ or by exocyclic coordination in the complex [( PdCl 2)4 Py 8 QxPzZn ] are also considered. Of the investigated Zn II complexes, [ Py 8 QxPzZn ] and the related octacation [(2- Mepy )8 QxPzZn ]8+ are active in dimethylformamide solution as singlet oxygen photosensitizers, which is of interest for applications in the photodynamic therapy (PDT) of cancer.