Journal of Porphyrins and Phthalocyanines

The present review is focused on the relationship between oligomeric and heme properties of HbGp, emphasizing the characteristics that can be generalized to other hemoproteins. This study represents the state-of-the-art with respect to the approaches for investigating giant extracellular hemoglobins as well as the correlation between oligomeric assembly alterations and their consequent changes in the first coordination sphere. A wide introduction focused on the properties of this hemoglobin is developed. Indeed, this hemoprotein is considered an interesting prototype of blood substitute and biosensor due to its peculiar properties, such as resistance to autoxidation and oligomeric stability. Previous studies by our group employing UV-vis, EPR and CD spectroscopies have been revised in a complete approach, in agreement with recent and relevant data from the literature. In fact, a consistent and inter-related spectroscopic study is described propitiating a wide assignment of "fingerprint" peaks found in the techniques evaluated in this paper. This review furnishes physicochemical information regarding the identification of ferric heme species of hemoproteins and metallic complexes through their spectroscopic bands. This effort at the attribution of UV-vis, EPR and CD peaks is not restricted to HbGp, and includes a comparative analysis of several hemoproteins involving relevant implications regarding several types of iron-porphyrin systems.

To determine if the dihedral angle between the phenyl group and the porphyrin ring in the meso-phenyl porphyrin (H₂TPP) could be adjusted by selective substitution of the naphthyl group for phenyl groups, novel dyads with a free-base porphyrin donor and anthraquinone acceptor linked by a rigid azo bond were synthesized and their spectral properties were investigated in detail. The Soret absorption band of dyads with meso-naphthyl groups in porphyrin shows 5–7 nm red shift as compared to the corresponding raw materials due to the introduction of the anthraquinone moiety. Fluorescence from the porphyrin moiety was found to be intensely quenched with the addition of anthraquinone moiety in the dyads; the highest quenching rate was observed to be 95% in the dyad prepared by meso-tetranaphthyl porphyrin. This indicates that the efficiency of the intramolecular photoinduced electron transfer in porphyrin-anthraquinone dyads could be changed by substituting the meso-phenyl group in porphyrin for the meso-naphthyl group.

The reactions of unsymmetrical porphyrins (1 and 2) with Ni(OAc)₂·4H₂O in boiling DMF produce porphyrin complexes (3 and 4). From the reactions of free porphyrin ligands 1 and 2 with hexachlorocyclotriphosphazatriene, N₃P₃Cl₆, the new free porphyrino-phosphazene derivatives (5 and 6) are obtained. On the other hand, the reactions of N₃P₃Cl₆ with porphyrin complexes (3 and 4) afford the new porphyrino-phosphazene complexes (7 and 8). In the literature there are a few examples of the porphyrino-phosphazene architectures. The structural investigations of all the compounds have been made by elemental analyses, MS, FTIR, ¹H NMR, ³¹P NMR and UV-visible techniques. The cyclic voltammograms (CVs) are examined in acetonitrile (MeCN) containing 0.1 M tetrabutylammonium-tetrafluoroborate (TBATFB) to investigate the surface attachment properties at the glassy carbon electrode (GCE) and the influence of the presence of metal cations in the porphyrin ring.

Cobalt tetra(para-chlorophenyl)porphyrin (CoTCPP) and zinc tetraphenyl porphyrin (ZnTPP) were linked on the side chains of the copolymer of 4-vinylpyridine (4VP) and styrene (St), P(4VP-co-St), via axial coordination reactions, respectively, and the metalloporphyrin-functionalized macromolecules, CoTCPP-P(4VP-co-St) and ZnTPP-P(4VP-co-St), were prepared. Their chemical structures were characterized by FTIR and ¹H NMR. The spectral properties of the two macromolecular axial coordination complexes were mainly studied, and their photophysical behavior were discussed in depth. The experimental results show that the metalloporphyrin-functionalized macromolecules, CoTCPP-P(4VP-co-St) and ZnTPP-P(4VP-co-St), can be prepared favorably through axial coordination reaction with the side pyridine groups of the copolymer P(4VP-co-St) as ligands. The two complexes have characteristic spectra similar to that of the small molecular metalloporphyrins, CoTCPP and ZnTPP, respectively. At the same time, they also display the characteristic spectroscopic property of axial coordination complexes: the electronic adsorption spectra of CoTCPP-P(4VP-co-St) and ZnTPP-P(4VP-co-St) red-shifted obviously as compared to that of CoTCPP and ZnTPP, and the fluorescence emission of ZnTPP-P(4VP-co-St) blue-shifted apparently with respect to that of ZnTPP. For CoTCPP-P(4VP-co-St) and ZnTPP-P(4VP-co-St), some polymer effects were found: (1) the bonding degree of the small molecular metalloporphyrin, CoTCPP or ZnTPP, on the side chains of the copolymer P(4VP-co-St) has a limit value because of the steric hindrance and there is a bonding degree difference between the actual value and the theoretical value; (2) for ZnTPP-P(4VP-co-St), slight energy transfer between adjacent ZnTPP units on an identical macromolecule occurs, leading to slight static quench of the fluorescence emission as the bonding density of ZnTPP units on the side chains of the copolymer P(4VP-co-St) reaches a certain value.

The effect of three amino acid protoporphyrin IX (PPIX) derivatives evaluated as sensitizers in photodynamic therapy — disodium N,N-dialanyl protoporphyrinate (PP(Ala)₂Na₂), diarginine protoporphyrinate (PPArg₂) and diarginine N,N-dialanyl protoporphyrinate (PP(Ala)₂Arg₂) – non-irradiated and pre-irradiated with UV-A, on respiratory burst of non-stimulated and opsonized zymosan stimulated neutrophils was studied. A potential synergistic effect of diazepam (7-chloro-1-methyl-5-phenyl-1,3-dihydro-2H-1,4-benzodiazepin-2-one) was also examined. PP(Ala)₂Na₂ showed strong pro-oxidant effect towards non-stimulated neutrophils, while PPArg₂ and PP(Ala)₂Arg₂ revealed no significant effect. In the case of stimulated neutrophils all studied porphyrins showed antioxidant effect, although for PP(Ala)₂Na₂ this effect was significantly weaker than that of PPArg₂ and PP(Ala)₂Arg₂. After pre-irradiation with UV-A (λ = 365 nm, fluence 2.0 J.cm^-2, fluence rate 6.7 mW.cm^-2) the antioxidant activity of all studied sensitizers towards non-stimulated granulocytes did not change significantly when compared to effects of non-irradiated porphyrins, while in the case of stimulated cells, only PPArg₂ caused significant decrease of respiratory burst. Non-irradiated diazepam showed significant antioxidant effect and enhanced antioxidant effect of all studied porphyrins towards stimulated neutrophils, while after UV-A pre-irradiation it revealed no significant antioxidant effect on non-stimulated and stimulated neutrophils, both alone and in combination with porphyrin sensitizers.

This work reports the use of metallo tetra-amino phthalocyanines (MTAPc, M = Co and Mn) polymer thin films on gold and glassy carbon electrode surfaces for the detection and monitoring of hydrogen peroxide (H₂O₂). The polymer-modified electrodes were characterized using electrochemical and microscopic-based methods. Atomic force microscopy (AFM) was used to study the bare and polymer-modified ITO surfaces. The electrocatalytic reduction of H₂O₂ with glassy carbon polymer-modified electrodes gave higher current densities compared to their gold counterparts. The electroanalytical properties of H₂O₂ were obtained using a real-time calibration curve of the amperometric determination in pH 7.4 aqueous solution. The limits of detection (LoD) of the polymer-modified electrodes towards electroreduction of H₂O₂ were of the order of 10^–7 M, with high sensitivity ranging from 6.0–15.4 mA.mM^-1.cm^-2.

A novel porphyrin-dextran coated Fe₃O₄ nanoparticle (5) was designed and synthesized. The structure of 5 was confirmed by IR, UV-vis and inductively coupled plasma atomic emission spectrometry, and dynamic laser scattering (DLS); magnetic property was measured by a vibrating sample magnetometer (VSM). The interaction between compound 5 and human serum albumin (HSA) was investigated through UV-vis absorbance spectra and fluorospectrophotometer, compared with the 5-(4-aminophenyl)-10,15,20-tris-(4-sulfonatophenyl)porphyrin, trisodium salt (3). The results showed compound 5 containing porphyrin moiety and 3 could interact with HSA. The quenching constant (K_sv) was 4.739 × 10⁵ M^-1 for 3, and 2.846 × 10⁵ M^-1 for 5; the apparent affinity binding constant (K_A) was 8.562 × 10³ M^-1 for 3, and 4.978 × 10⁴ M^-1 for 5.

This study is focused on the final stage of the formation mechanism of chloroboron subphthalocyanine from boron trichloride and phthalonitrile, in the context of recent work on the earlier stages of this reaction. The results of extensive quantum-chemical energetic, structural, and charge-distribution computations show that a catalytic effect of boron trichloride is most probably essential to explain the fact that molecular chlorine is liberated in the formation of chloroboron subphthalocyanine (reaction 2). This process turns out to be closely concerted (reactions 2a and 2b).

Lipophilic substituted zinc(II) phthalocyanines: 2,3,9,10,16,17,23,24-octakis[(N,N-dimethylaminoethylsulfanyl)]phthalocyaninatozinc(II) (S1) and tetrakis(N,N-dibutylaminoethoxy)phthalocyaninatozinc(II) (3) were incorporated into soybean L-α-phosphatidylcholine (SPC) liposomes of 100 nm diameter. Liposomes were characterized by static light scattering (SLS), transmission electronic microscopy (TEM), and differential scanning calorimetry. The fluorescence quantum yield and singlet molecular oxygen production of 3 are Φ_F = 0.15 and Φ_Δ = 0.24, respectively, whereas the same photophysical parameters for S1 are Φ_F = 0.13 and Φ_Δ = 0.51. Higher values of Φ_F and Φ_Δ are obtained in organic solvent for both dyes. Synthesis of compound 3 has also been reported.

Iron(III) tetraphenylporphyrin chloride, Fe(TPP)Cl, efficiently catalyzed the insertion of carbenes derived from methyl 2-phenyldiazoacetates into O-H bonds of aliphatic and aromatic alcohols, with yields generally above 80%. Although the analogous N-H insertions are rapid at room temperature, the O-H insertion reactions are slower and required heating in refluxing methylene chloride for about 8 hours using 1.0 mol.% catalyst. Fe(TPP)Cl was also found to be effective for tandem N-H insertion/cyclization reactions when 1,2-diamines and 1,2-alcoholamines were treated with diazo reagents to give piperazinones and morpholinones and related analogs such as quinoxalinones and benzoxazin-2-ones. This approach provides a new one-pot route for synthesizing these classes of heterocyclic compounds.