Homo/Heteropentanuclear Porphyrazine MgII, ZnII, and PdIIMacrocycles with Externally Pending PdCl2and Pd(CBT)2Units: 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 = MgII(H2O), ZnII, PdII) and [{Pd(CBT)2}4Py8PzM]·xH2O (M = MgII(H2O), ZnII 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 = MgII(H2O), ZnII) and the mono-PdII 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.