Journal of Porphyrins and Phthalocyanines

The interaction modes and nuclease activity against RNA of methylpyridiniumyl/phenyl-hydroxamic acid porphyrin adducts have been investigated. These compounds are derived from the tetracationic meso-tetrakis(N-methyl-4-pyridiniumyl)porphyrin (H2TMPyP-4) by replacing one or two pyridinium rings with a phenyl group. This group is bearing an aliphatic chain of three carbon atoms in the para position to a hydroxamic acid. A different interaction mode is observed depending on the number of charges and hydroxamic acid function. The nuclease activity of the porphyrin adducts against RNA has been demonstrated. Also the effect of the presence of various lanthanide ions on the porphyrin nuclease activity has been tested.

Synthesis of pyropheophorbide-a-paclitaxel (PPa-PTX) conjugate was performed in high yield with the aim of searching for an optimal agent for cancer treatment. After synthesis, the conjugate was confirmed to be linked through an ester bond at the 2′ position of the paclitaxel moiety using multi-nuclear magnetic resonance spectroscopy. Phototoxicity of PPa and PPa-PTX conjugate, as well as PTX, was evaluated with three human cancer cell lines (HeLa, CaSki and TC-1). The new conjugate at 0.01–0.06 μM displayed 20–40% higher phototoxicity in HeLa and CaSki cell lines than free PPa and PTX. Furthermore, cellular uptake of these bio-molecules was examined by confocal laser scanning microscopy. Although PPa-PTX showed a delayed uptake compared to PPa, it penetrated completely into cells within 24 h incubation.

Synthesis and measurements of third order nonlinear optical (NLO) coefficients of water soluble zinc octacarboxy phthalocyanine (ZnOCPc) are reported here using different laser pulse durations. Nonlinear absorption and refraction behaviour in the nanosecond (ns), picosecond (ps) and femtosecond (fs) time domains were studied in detail. Three-photon absorption was the prevalent mechanism with femtosecond laser excitation whereas strong reverse saturable absorption due to dominant two-photon absorption (TPA) was observed with picosecond and nanosecond excitations. We have evaluated the sign and magnitude of the third order nonlinearity in fs, ps, and ns regimes. We observed large off-resonant second order hyperpolarizability (γ) with ultrafast nonlinear optical response in the femtosecond domain using degenerate four wave mixing (DFWM) technique. We also report the optical limiting characteristics and figure of merit (FOM) of ZnOCPc for optical switching.

This report focuses on the conjugation of a chemotherapeutic drug and photodynamic therapy (PDT) agent with the intention of obtaining an optimal anticancer agent for use in combination cancer treatment. We have used pyropheophorbide-a (PPa) as a PDT agent, which was linked with ethylenediamine using carbodimide/N-hydroxysuccinicimide coupling reagents to obtain a resulting reactive amine group. Next, the free amine-bearing PPa and potassium tetrachloroplatinate (K₂PtCl₄) were reacted in aqueous solution to obtain PPa-cisplatin complex. Subsequently, the PPa-based platinum complex was characterized through several methods including NMR spectroscopy, mass spectrometer and UV absorption spectroscopy and its in vitro cytotoxicity and cellular uptake were evaluated on the TC-1 cancer cell line. The results indicated that the conjugate has a greater cytotoxic effect in the dark than cisplatin, even though its phototoxic effect was slightly lower than that of free photosensitizer; in addition, the cellular uptake of complex at 0.125 and 0.25 μM was higher than that of free photosensitizer.

Highly efficient aerobic epoxidation of olefins catalyzed by cationic meso-tetrakis-(1-methyl-4-pyridyl) (TM4PyP) metalloporphyrins immobilized into montmorillonite (MT) interlayer was achieved. The heterogeneous catalysts were characterized by diffuse reflectance UV spectra, infrared, X-ray diffraction, nitrogen adsorption isotherm and scanning electron microscopy. Manganese porphyrin (MnTM4PyP-MT) showed excellent activity and selectivity for the aerobic epoxidation of olefins under ambient conditions, in which more 90% yields of epoxides were obtained. The clay basal spacing played significant role in the catalytic efficiency and selectivity for different olefins. The catalyst could be reused consecutively five times without significant loss of activity.

The results of use of chemical kinetics receptions, approaches and methods for the study of porphyrins and their metal complexes reactivity are discussed on an example of oxidation, acid-basic, and catalytic reactions of rhodium, palladium, and rhenium complexes of porphyrin in liquid solutions. The peculiarity of the porphyrin reaction rates is analyzed in a brief context of general provisions of the chemical kinetics. The opportunity to use the quasistationarity principle at the definition of the kinetic equation of the reactions with participation of metal porphyrins is shown. The transition from the process kinetic description to consideration of its mechanism is explored.

We present here the simple procedure for synthesizing elongated fibers like porphyrin aggregates. Usually whenever the aggregation in dye molecules takes place the emission always tends to quench. In this work we explore and discuss the unusual enhanced emission property of these aggregates. The nanofibers of porphyrin were characterized with the help of atomic force microscopy and UV-vis spectroscopy whereas photoluminescence spectroscopy was used to check their emission property.

The opto-electronic characteristics of porphyrin-fullerene bulk heterojunction photovoltaic cells of different active layer thicknesses were studied. In order to achieve different active layer thicknesses, the photovoltaic cells were prepared by spin coating the active layer of each cell at a different spin speed. To determine the active layer thickness, average of absorption coefficients of the materials constituting the active layer was used along with the optical density. Active layer thicknesses were also measured by using surface profilometer. Atomic force microscope surface scans revealed that there was no considerable change in active layer surface roughness from 1000 to 1500 rpm. However, a decrease in average grain size with increasing spin speed was observed. Current density as a function of voltage curves at different active layer thicknesses were recorded in dark and under a simulated solar spectrum AM 1.5G (100 mW.cm^-2). Incident photon-to-current conversion efficiency spectra at different active layer thicknesses were also determined. The solar cell having active layer thickness of 68 nm (spin coated at 1200 rpm) showed optimum results. The power conversion efficiency of the photovoltaic cell at this thickness was 0.24%.

New series of iron, ruthenium, and osmium octabutoxynaphthalocyanines were synthesized by inserting corresponding metals into the metal-free octabutoxynaphthalocyanine. Although preparation of axial ligand-free iron octabutoxynaphthalocyanines was reported before, we could not reproduce the synthesis by following the reported method. We attributed the failure to the instability of the iron octabutoxynaphthalocyanines. Bis-ligation increased the stability of the iron complex but only sufficiently for characterization. The application of iron complexes will be limited by their instability. However, ruthenium and osmium formed stable complexes with this macrocycle ring but with significantly lower reaction yields. These new complexes were characterized by NMR, UV-vis, and mass spectrometry.