Journal of Porphyrins and Phthalocyanines

Aluminium phthalocyanines sulfonated to a different degree (AlPcS_n) and consisting of various isomeric species were studied by spectroscopic techniques to determine their tendencies to form dimers and aggregates. These characteristics were compared with the cell-penetrating properties of the species, using the Ehrlich ascites mouse tumor cell line, to arrive at structure-activity relationships. AlPcS_n preparations consisting of the least number of isomeric species exhibited the highest tendency to form dimers and aggregates, whereas the more complex preparations, consisting of many isomeric products, showed more consistent monomeric features in aqueous environments. Uptake in cells was shown to correlate well with the overall hydrophobicity of the preparation and inversely with its degree of aggregation in the extracellular environment. Among the purified, single isomeric AlPcS_n the amphiphilic disulfonated AlPcS_2a, enriched in positional isomers featuring sulfonate groups on adjacent phthalic subunits, showed the best membrane-penetrating properties. Even higher cell uptake was observed for the AlPcS_2mix reflecting a combination of optimal lipophilicity and a low degree of aggregation. Similarly, in the case of AlPcS₄, the pure isomeric compound showed less cell uptake than the mixed isomeric preparation of similar hydrophobicity, reflecting the higher degree of aggregation invoked by its symmetrical structure. Our data indicate that mixed sulfonated phthalocyanine preparations may exert higher photodynamic efficacy in biological applications as compared to the pure isomeric constituents.

A series of water-soluble viologen-linked zinc porphyrins with different methylene chain lengths (n = 3−6) between porphyrin and viologen, ZnP(C_nV)₄, were synthesized and characterized. The intra- molecular electron transfer rate constants from the porphyrin moiety of ZnP(C_nV)₄ to viologen were measured by using fluorescence lifetime and laser flash photolysis. Both the photoexcited singlet state and the triplet state of the porphyrin were quenched by the bonded viologen. These compounds were applied to photoinduced hydrogen evolution in the system containing nicotinamide-adenine dinucleotide phosphate (reduced form NADPH), ZnP(C_nV)₄ and hydrogenase under steady-state irradiation.

A stepwise synthesis method was used to encapsulate tetrachloro-tetramethyl porphyrin in NaCoX molecular sieve supercages. Characterization of the encapsulated porphyrin was carried out by UV-vis and IR Spectroscopy, DTA, SEM and EPR. A comparison was made of the activities of tetrachloro-tetramethyl porphyrin, its Co(II) complex, NaCoX molecular sieve and the encapsulated porphyrin as catalysts in the oxidation reactions of styrene and p-cresol. The stability and catalytic capability of the metalloporphyrin were increased after combination of the porphyrin with the molecular sieve. In addition, this new type of catalyst, tetrachloro-tetramethyl porphyrin encapsulated in NaCoX molecular sieve supercages, not only possesses the advantages of both the porphyrin and the molecular sieve, but also makes up for their respective deficiencies. In this study, another method called sealing–melting was also used to encapsulate the Zn(II) complex of meso-tetraphenyl-tetrabenzoporphyrin into NaY molecular sieve supercages. The catalytic capabilities of the free Zn(II) complex of meso-tetraphenyl-tetrabenzoporphyrin, the Zn(II) complex encapsulated in NaY molecular sieve supercages and the NaY molecular sieve itself in the oxidation of styrene by hydrogen peroxide were also studied. The experimental results again confirmed that both the stability and catalytic capability of the metalloporphyrin encapsulated in molecular sieve supercages are increased.

Three types of amphiphilic water-soluble fluorinated zinc phthalocyanines are characterized. They have absorption bands at long wavelength, which cause greater penetration depth of a tissue. The uptake and photodynamic activity of the phthalocyanines against HeLa cells were measured, showing that the phthalocyanines exhibited higher photodynamic activities than zinc tetrasulfonated phthalocyanine.

Monomeric and polymeric iron phthalocyanine compounds were synthesized and their dielectric properties were measured in the frequency range from 100 Hz to 10 MHz between 25 and 200 °C. The dielectric constant and dielectric loss showed strong frequency and temperature dependences. Interestingly, large dielectric constants were observed around 100 °C for both monomers and polymers. A dielectric constant as high as 5000 at 110 Hz was observed for the iron phthalocyanine polymer. The origin of the large dielectric constant in metallophthalocyanines is discussed.

Perylene derivative films doped with metal ion were deposited on indium tin oxide (ITO)-coated glass electrodes by electrodeposition from solutions of N, N″-4-hydroxyphenyl-3,4,9,10-perylenetetracarboxylic-diimide (hph-PTC) and CaCl₂, PbCl₂, ZnCl₂ or CoBr₂ as a supporting electrolyte in N, N-dimethylformamide (DMF). The p-n junction diodes consisting of a p-type phthalocyanine (Pc) sublimed film and an n-type hph-PTC electrodeposited film doped with metal ion exhibited Zener-type breakdown and photocurrent enhancement. The device with a p-n junction consisting of a Pc sublimed film and an hph-PTC electrodeposited film doped with Ca²⁺ showed the largest amplification of photocurrent. This result suggests that the dopant ion in hph-PTC is an important factor in the preparation of p-n junction diodes.

Cobalt phthalocyanine (Na_2.8CoPc) organic molecular ferromagnets with a Curie temperature higher than room temperature were synthesized. By means of EXAFS spectroscopy the nearest coordinational environment of the Co ion was examined in both Na_2.8CoPc and pristine β-CoPc as well as in standard substances containing metallic cobalt. The nearest coordinational environment of the Co ion in ferromagnetic Na_2.8CoPc is shown to remain virtually invariable as compared with that in pristine β-CoPc. This environment is conditioned by the nitric and carbonic coordination spheres of the phthalocyanine and differs essentially from the nearest coordinational environment of Co in metallic cobalt. The results of EXAFS studies serve as direct structural evidence that the nature of the ferromagnetism in Na_2.8CoPc is conditioned by the organic matrix, namely by (CoPc)²⁻ and (CoPc)³⁻ anions with unpaired π-electrons in the 7e_g doubly degenerate MO of the conjugated phthalocyanine macro-ring.

The UV-vis and variable-temperature X-band EPR spectral studies (298–77 K) on π-cation of zinc(II) tetraphenylporphyrin (ZnTPP) have revealed for the first time a labile electronic ground state. The electronic structure changes from ²A_2u to ²A_1u as the temperature is lowered from 298 to 150 K. Axial ligands and σ-donor solvents show a significant effect on the spectral data. The lability in the ground state electronic configuration is attributed to the flexibility of the porphyrin moiety in changing from a ‘ruffled’ to a lower symmetry.

The mechanism of the dioxygen interaction with and reduction reaction at iron α,β,γ,δ-tetra(4-pyridyl) porphyrin (FeTPyP) deposited on carbon and silver supporting electrodes was investigated with cyclic voltammetry and FTIR, UV-vis and resonance Raman spectroscopies. Results indicate a strong influence of the ligand upon the reduction electrocatalysis. Spectroelectrochemical results support a two-electron pathway resulting most probably in hydrogen peroxide as the primary reduction product.

Acylimidorhenium and molybdenum porphyrin complexes were prepared by reaction of the corresponding nitridometalloporphyrins with substituted acetic anhydrides and their spectral and electrochemical properties were determined. Analysis of the electronic spectral changes with time and initial reactant concentration confirmed that the acylimido formation reaction was first-order in each reactant and second-order overall. Second-order rate constants for formation of the chloroacetic anhydride complex increased in the order Mn<Cr<Re<Mo. In contrast with the previously reported reactivity of acylimidomanganese and chromium porphyrin complexes, the rhenium and molybdenum derivatives were unreactive towards triphenylphosphine, strained olefins and silyl ethylene ethers.

Phthalocyaninato(2–)iridate(I) is oxidized by air in acetone to form acetonato(C)chlorophthalocyaninato(2–)iridate(III) in the presence of chloride. The anion is isolated as its 2,4,6-triphenylpyrylium salt, (TPPy)[Ir(aC)(Cl)Pc²⁻]. Its monohydrate crystallizes in the monoclinic space group P1n1 (#7). The cell parameters are a = 12.452(3) Å, b = 12.339(3) Å, c = 15.352(4) Å, β = 100.75(2) °, Z = 2. Hexa-coordinated Ir is located slightly out of the centre (ct) of the Pc core (d(Ir-ct) = 0.02 Å) and directed towards the acetonato C atom. It coordinates four isoindole N atoms (N_iso) together with a Cl atom and a C-bonded acetonate in a mutual trans position. The average Ir–N_iso distance is 1.966 Å;, the Ir–Cl distance is 2.501(5) Å; and the Ir–C distance is 2.11(2) Å.

The μ-Oxo stacks of tin(IV) porphyrins rearrange to staircase-type and lateral aggregates upon replacement of the oxygen ligands by chloride ions. The lateral aggregation of tin(IV) 2,18-dipropionate porphyrins in hydrochloric acid at pH 0–0.5 is favoured by 8,13-ethyl groups instead of the natural 8,13-vinyl groups of protoporphyrin IX and is impeded by hydrogen atoms at these positions. Replacement of axial chloride counterions to the tin(IV) central ions by cyanate counterions at pH 4.5 leads to similar aggregates if the cyanate ions are connected by hydrogen bonding to acetic or lactic acid. In this case, aggregation is not necessarily impeded by hydrogen atoms at positions 8 and 13. D- and L-lactic acid enforce chiral assemblies of the tin(IV) deuteroporphyrin 1a with mirror image CD (circular dichroism) spectra (θ ≈ 8 × 10⁵deg cm²dmol⁻¹), whereas the gluconoyl hydrazide-substituted tin(IV) deuteroporphyrin 1d does not form aggregates at all.