Tetra-2,3-pyrazinoporphyrazines with Externally Appended Pyridine Rings. 10. A Water-Soluble Bimetallic (ZnII/PtII) Porphyrazine Hexacation as Potential Plurimodal Agent for Cancer Therapy: Exploring the Behavior as Ligand of Telomeric DNA G-Quadruplex Structures

Tetra-2,3-pyrazinoporphyrazines with Peripherally Appended Pyridine Rings. 19. Pentanuclear Octa(2-pyridyl)tetrapyrazinoporphyrazines Carrying Externally Carboranthiolate Groups: Physicochemical Properties and Potentialities as Anticancer Drugs

New pentanuclear porphyrazine complexes of formula [{Pd(CBT)₂}₄LM]· xH₂O (L = tetrakis-2,3-[5,6-di(2-pyridyl)pyrazino]porphyrazinato anion, CBT = m-carborane-1-thiolate, and M = Mg^II(H₂O), Zn^II, Pd^II) were prepared in good yield as dark green hydrated amorphous solids by reaction of the respective pentanuclear species [(PdCl₂)₄LM] with m-carboran-1-thiol in CH₃CN. Physicochemical characterization of the new species was carried out by elemental and thermogravimetric analysis along with IR and ¹H/¹³C NMR measurements. UV-vis spectral characterization performed in DMSO, DMF, and pyridine solution provided information about the stability of the new homo/heteropentanuclear species and their tendency to undergo detachment of the peripheral Pd(CBT)₂ groups. The data from NMR, UV-vis, and electrochemical experiments indicate that external coordination of the Pd(CBT)₂ units to the mononuclear [LM] species affects only slightly the π electron distribution within the internal macrocyclic choromophore. The Pd(CBT)₂ units are released in pyridine solution and in the case of the Zn^II complex [{Pd(CBT)₂}₄LZn] give rise to a finely crystalline light-yellow solid identified by single-crystal X-ray work as the trans isomer of the bispyridine adduct [py₂(CBT)₂Pd]. The new pentanuclear macrocyclic complexes behave in DMF solution as active photosensitizers for singlet oxygen production, ¹O₂, the cytotoxic agent in anticancer photodynamic therapy, and have larger quantum yield values (Φ_Δ = 0.6-0.7) than those found on average for the related tetrapyrazinoporphyrazine analogs (Φ_Δ = 0.4-0.6). The presence of the CBT groups in the currently investigated complexes opens up the possibility for their use in boron neutron capture therapy, leading potentially to new bimodal anticancer curative drugs.

Photodynamic properties of aza-analogues of phthalocyanines

Spectral and photophysical properties and in vitro photodynamic activity of aza-analogues of phthalocyanines are summarized.

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(H2O), 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)[Formula: see text]}[Formula: see text](PtCl[Formula: see text]LM] •xH[Formula: see text]O where L [Formula: see text] tetrakis-2,3-[5,6-di(2-pyridyl)pyrazino]porphyrazinato dianion, M [Formula: see text] Mg[Formula: see text](H[Formula: see text]O), Zn[Formula: see text] or Pd[Formula: see text] and [Formula: see text] 3–8, were prepared under mild experimental conditions from the previously described heterobimetallic compounds [(PtCl[Formula: see text]LM]. Peripheral binding of one PtCl[Formula: see text]and three Pd(OAc)[Formula: see text]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)[Formula: see text] moieties. Data on the photosensitizing activity of the compounds for the generation of singlet oxygen, [Formula: see text]O[Formula: see text] were also obtained in DMF and should be of interest to researchers in the area of photodynamic therapy.

Exploring the activity of a polyazine bridged Ru(ii)–Pt(ii) supramolecule in F98 rat malignant glioma cells

[(Ph₂phen)₂Ru(dpp)PtCl₂]Cl₂exhibits multiple light-dependent cytotoxicity pathways that preferentially target DNA, offering promise for the development of novel photodynamic therapy agents.

Fluorescent cyclodextrin carriers for a water soluble ZnII pyrazinoporphyrazine octacation with photosensitizer potential

Novel, negatively charged, fluorescent cyclodextrin oligomers form highly stable complexes with a water soluble, octacationic porphyrazine photosensitizer in dimeric form.

Tetra-2,3-pyrazinoporphyrazines with externally appended pyridine rings 14: UV-visible spectral and electrochemical behavior of homo/heterobinuclear neutral and hexacationic macrocycles

Detailed UV-visible, electrochemical and spectroelectrochemical studies were carried out in DMSO on two known series of homo/heterobimetallic pyrazinoporphyrazine compounds, i.e.[( M′Cl 2) LM ] and [( PtCl 2)( CH 3)6 LM ]( I )6, where L = tetrakis-2,3-[5,6-di(2-pyridyl)pyrazino]porphyrazinato anion, M = Zn II , Mg II ( H 2 O ) or Pd II and M′ = Pd II or Pt II . The [( M′Cl 2) LM ] compounds, as obtained from the mononuclear species [LM], undergo only subtle UV-visible spectral changes and exhibit practically unchanged half wave potentials for reduction; thus, peripheral coordination to the [LM] macrocycles of a single PdCl 2 or PtCl 2 unit at one of the external dipyridinopyrazine fragments only minimally disturbs the σ/π electronic distribution within the entire porphyrazine unit. In contrast, quaternization by CH 3 I of the six unligated pyridine N atoms of the species [( PtCl 2) LM ] leading to formation of the hexacations [( PtCl 2)( CH 3)6 LM ]6+ results in a significant bathochromic shift (5–15 nm) of the Q-band positions, thus suggesting an enhanced electron-withdrawing effect determined by an incremented displacement of the σ/π electronic system towards the periphery of the macrocycle. Accordingly, there is a facilitated thermodynamic uptake of electrons upon going from [( PtCl 2)( CH 3)6 LM ]6+ to [( PtCl 2)( CH 3)6 LM ] n (n = 5+ → 2+). Noteworthy, the UV-visible spectra of the salt-like species [( PtCl 2)( CH 3)6 LM ]( I )6 in water at c = 5 × 10-5 M ) indicate the presence of a monomer-dimer equilibrium, persistent even at very low concentrations (ca. 5 × 10-7 M).

Pyrazinoporphyrazines with externally appended pyridine rings. 13. Structure, UV-visible spectral features, and noncovalent interaction with DNA of a positively charged binuclear (Zn(II)/Pt(II)) macrocycle with multimodal anticancer potentialities

We investigated with spectroscopic techniques the noncovalent interaction of a bimetallic water-soluble (Zn(II)/Pt(II)) porphyrazine hexacation, [(PtCl(2))(CH(3))(6)LZn](6+), and its octacationic analogue [(CH(3))(8)LZn](8+), lacking the cis-platin-like functionality, with a 21-mer double strand (ds) 5'-d[GGG(TTAGGG)(3)]-3'/3'-d[CCC(AATCCC)(3)]-5', as model for B-DNA. Both hexacation and octacation tend to aggregate in water. The structure as well as the ground and excited-state electronic properties of the Zn(II)/Pt(II) hexacation [(PtCl(2))(CH(3))(6)LZn](6+) in water solution were investigated using density functional theory (DFT) and time-dependent DFT (TDDFT) methods. TDDFT calculations of the lowest excited states of [(PtCl(2))(CH(3))(6)LZn](6+) in water provided an accurate description of the Q-band spectral region. In particular, the calculated optical spectra were in agreement with the experimental ones, obtained in the presence of micelles favoring complete disruption of the aggregates. The model for dsDNA binding that emerges from the analysis of UV-vis absorption and time-resolved fluorescence data shows the presence of complexes of 1 dsDNA molecule with 1, 2, and 4 macrocycles. Comparing the results for the hexacation [(PtCl(2))(CH(3))(6)LZn](6+) with those for the [(CH(3))(8)LZn](8+)octacation, we observed a higher degree of monomerization for the [(PtCl(2))(CH(3))(6)LZn](6+) derivative.

Tetra-2,3-pyrazinoporphyrazines with externally appended pyridine rings. 12. New heteropentanuclear complexes carrying four exocyclic cis-platin-like functionalities as potential bimodal (PDT/cis-platin) anticancer agents

Heteropentanuclear porphyrazines having the formula [(PtCl2)4LM] where L = tetrakis-2,3-[5,6-di(2-pyridyl)pyrazino]porphyrazinato dianion and M = Zn(II), Mg(II)(H2O), Pd(II), Cu(II) or Co(II) were characterized by elemental analyses, IR-UV-visible spectroscopy and electrochemistry and the data compared to new and previously published results for the corresponding homopentanuclear compound [(PtCl2)4LPt]. This latter species has four external N2(py)PtCl2 coordination sites which closely resemble cis-platin, (NH3)2PtCl2, the potent chemotherapeutic anticancer drug, and is able to act as a photosensitizer for the generation of (1)O2, the cytotoxic agent in photodynamic therapy (PDT). UV-visible spectra and half wave potentials for reduction of [(PtCl2)4LM], [(PtCl2)4LPt], the parallel series of mononuclear [LM] compounds and the pentanuclear [(PdCl2)4LM] compounds were examined in the nonaqueous solvents dimethyl sulfoxide, pyridine, and dimethylformamide. The complete set of available data indicate that external coordination of the PtCl2 and PdCl2 units significantly increases the level of the electron-deficiency of the entire molecular framework despite the fact that these groups are far away from the central porphyrazine π-ring system and have coordination sites nearly orthogonal to the plane of the macrocycle. The pentanuclear species [(M'Cl2)4LM] (M' = Pt(II), Pd(II)) undergo multiple one-electron transfers and exhibit an easier reducibility as compared to related electrode reactions of the parent compounds [LM] having the same central metal. Aggregation phenomena and reducibility of the porphyrazines to their monoanionic form (prevalently in DMF) are observed for some of the examined compounds and were analyzed and accurately taken into account. Quantum yields of (1)O2 (ΦΔ), of interest in PDT, were measured for [(PtCl2)4LM] with M = Zn(II), Mg(II)(H2O), or Pd(II) and the related macrocycles [(PdCl2)4LM] and [LM] in dimethylformamide (DMF) and/or DMF preacidified with HCl (DMF/HCl, [HCl]: 1-2 × 10(-4) M). Excellent ΦΔ values (0.5-0.6) which qualify the compounds as potent photosensitizers in PDT were obtained for the pentanuclear species having Zn(II) or Pd(II) as central metal ions. The [(PtCl2)4LZn] and [(PtCl2)4LPd] complexes are of special interest as potential bimodal anticancer agents because of the incorporated four cis-platin-like functionalities.

Tetra-2,3-pyrazinoporphyrazines with externally appended pyridine rings: 11 Photoactivity of a new Pt(II) pentanuclear macrocycle bearing four cisplatin-like functionalities and its related monoplatinated species

The pentanuclear PtII porphyrazine compound [(PtCl2)4LPt] (L = tetrakis-2,3-[5,6-di(2-pyridyl)pyrazino]porphyrazinato dianion), the mononuclear species [LPt] and the octacation [L′Pt]8+ (neutralized by I- ions; L′ = L octaquaternized at the pyridine N atoms) were synthesized and characterized by IR/UV-visible spectral measurements. 1H and 13C NMR spectral data on [(PtCl2)4 LPt] indicate that the four PtCl2 units are coordinated at the pyridine N atoms of the peripheral dipyridinopyrazine fragments ("py–py" coordination) and the largely prevalent conformational arrangement of the entire macrocycle, established to have the external N2(py)PtCl2 coordination sites all oriented on the same side with respect to the plane of the central porphyrazine framework, closely recalls that which was previously defined for the related PdII analog [(PdCl2)4LPd] . The currently investigated triad of PtII macrocycles, like the related PdII species, behave as photosensitizers for the generation of singlet oxygen, the cytotoxic agent active in photodynamic therapy (PDT). A bimodal anticancer potentiality is expressed by the pentaplatinated compound, [(PtCl2)4LPt] , which represents an unprecedented example of a multifunctional drug due to the presence of four contiguous cisplatin-like functionalities.