Jiří Mosinger

Photophysical properties of metal complexes of meso-tetrakis(4-sulphonatophenyl)porphyrin

Abstract Laser kinetic spectroscopy was used to determine the photophysical parameters (fluorescence and triplet-triplet (T-T) spectra, lifetimes of the triplet and singlet states, bimolecular constant for oxygen quenching, fluorescence quantum yield and quantum yield of formation of the triplet state) of the water-soluble complexes of Ag(II), Cd(II), Co(II), Cu(II), Mg(II), Ni(II), Pd(II), Pt(II) and Zn(II) with the tetrasodium salt of meso-tetrakis(4-sulphonatophenyl)porphyrin (H 2 TPPS 4 ). The complexes of metals with d 0 and d 10 electron configurations (Cd(II), Mg(II) and Zn(II)) are characterized by high triplet quantum yields and strong fluorescence in the red spectral region and are thus more efficient photosensitizers than the ligand alone.

CYCLODEXTRINS IN ANALYTICAL CHEMISTRY

Cyclodextrins play an important role in all major areas of modern instrumental analysis. Most of the interest in cyclodextrins results from their ability to form inclusion (host-guest) complexes with a variety of molecules and ions in aqueous solutions. Complexation by cyclodextrins can alter some of the physical and chemical properties of guest molecules, such as solubility, chemical reactivity and the spectroscopic and electrochemical properties, and many of these effects can be utilized in a variety of chemical analytical techniques. This review summarizes the use of cyclodextrins in major areas of analytical chemistry such as chromatography, electrophoresis, spectroscopy, electrochemistry and as analytical sensors.

Bactericidal nanofabrics based on photoproduction of singlet oxygen

We present novel photofunctional nanofabrics that produce singlet oxygen on irradiation and have a bactericidal effect.

Quantum yields of singlet oxygen of metal complexes of meso-tetrakis(sulphonatophenyl) porphine

Abstract The iodide method and the method of bleaching of p -nitroso- N , N ′-dimethylaniline (RNO) were used to measure the quantum yields of singlet oxygen from the tetrasodium salt of meso-tetrakis(4-sulphonatophenyl) porphine (H2TPPS4) and its water-soluble metal complexes with divalent metals, Ag(II)TPPS4, Cd(II)TPPS4, Co(II)TPPS4, Cu(II)TPPS4, Mg(II)TPPS4, Ni(II)TPPS4, Pd(II)TPPS4, Pt(II)TPPS4 and Zn(II)TPPS4. Complexes of metals that have completely full or completely empty d-orbitals (Cd(II), Mg(II) and Zn(II)) are characterized by high quantum yields of singlet oxygen and are more efficient photosensitizers than the ligand alone. Comparison of the quantum yields of 1 O 2 obtained by the two methods confirmed the assumption that the iodide method yields identical values to the standard method of bleaching of RNO. However, the sensitivity of the iodide method is ten times higher.

Fluorescent polyurethane nanofabrics: a source of singlet oxygen and oxygen sensing.

Polyurethane (PUR) nanofabrics based on nanofibers of average diameters in the range of 250-110 nm with different meso-tetraphenylporphyrin (TPP) loading (0.01-5 wt %) were prepared by an electrospinning process. The oxygen quenching of excited states and singlet oxygen-sensitized delayed fluorescence (SODF) of TPP were studied at different oxygen pressures. We found that TPP in PUR matrix is present in monomeric state, and it is easily accessed by oxygen. Analysis of the kinetics of the TPP triplet, singlet oxygen, and SODF indicates that repopulation of TPP fluorescent state includes reaction of singlet oxygen with TPP triplets. The integrated SODF achieved more than 20% of the prompt fluorescence for nanofabric loaded with 5 wt % TPP. The dependence of SODF intensity on the TPP concentration in nanofibers is nearly quadratic.

Photophysical Properties and Photoinduced Electron Transfer Within Host–Guest Complexes of 5,10,15,20‐Tetrakis(4‐N‐methylpyridyl)porphyrin with Water‐soluble Calixarenes and Cyclodextrins¶

Abstract We report the formation of host–guest complexes between water-soluble calix[n]arene-p-tetrasulfonates (n = 4, 6, 8) or 2-hydroxypropyl-cyclodextrins (α-, β-, γ-) and the tetratosylate salt of 5,10,15,20-tetrakis(4-N-methylpyridyl)porphyrin (TMPyP). The binding constants ranging between 102 and 105 M−1 were calculated from the absorption and fluorescence changes. Calix[4]arene-p-tetrasulfonate has a high binding affinity and forms with TMPyP a 1:1 complex, whereas other calixarenes bind two molecules of TMPyP. Electrostatic attraction is the dominating binding mode. Binding to calixarenes leads to a considerable decrease of the quantum yields of the triplet and excited singlet states and to shortening of the singlet and triplet lifetimes of TMPyP. The quenching mechanism is attributed to electron transfer between calixarene phenolates and excited TMPyP. Photoinduced electron transfer within a novel supramolecular complex calixarene/TMPyP (electron donor)/methyl viologen (electron acceptor) has been proven by absorption and fluorescence measurements. Electrostatic attraction between the cationic donor and cationic acceptor, on the one hand, and the anionic host, on the other, overcomes the electrostatic repulsion forces. In contrast, the interaction of cyclodextrin with TMPyP is hydrophobic in nature and only slightly influences the photophysical properties of TMPyP. The different behavior of TMPyP bound to either of the hosts has been assigned to the specific effects of the dominant binding modes, viz. the electrostatic attraction for calixarenes and the hydrophobic interactions for inclusion complexes with cyclodextrins.

Polystyrene Nanofiber Materials Modified with an Externally Bound Porphyrin Photosensitizer

Polystyrene ion-exchange nanofiber materials with large surface areas and adsorption capacities were prepared by electrospinning followed by the sulfonation and adsorption of a cationic 5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrin (TMPyP) photosensitizer on the nanofiber surfaces. The morphology, structure, and photophysical properties of these nanofiber materials were characterized by microscopic methods and steady-state and time-resolved fluorescence and absorption spectroscopies. The externally bound TMPyP can be excited by visible light to form triplet states and singlet oxygen O2((1)Δg) and singlet oxygen-sensitized delayed fluorescence (SODF). The photophysical properties of the nanofibers were strongly dependent on the amount of bound TMPyP molecules and their organization on the nanofiber surfaces. The nanofibers demonstrated photooxidative activity toward inorganic and organic molecules and antibacterial activity against E. coli due to the sensitized formation of O2((1)Δg) that is an effective oxidation/cytotoxic agent. The nanofiber materials also adsorbed heavy metal cations (Pb(2+)) and removed them from the water environment.

Antibacterial nanofiber materials activated by light

Electrospun polymeric nanofiber materials doped with 5,10,15,20-tetraphenylporphyrin (TPP) photosensitizer were prepared from four different polymers and were characterized with microscopic methods, steady-state, and time-resolved fluorescence and absorption spectroscopy. The polymers used included polyurethane Larithane™ (PUR), polystyrene (PS), polycaprolactone (PCL), and polyamide 6 (PA6). The antibacterial activity of all nanofiber materials against E. coli was activated by visible light and it was dependent on oxygen permeability/diffusion coefficients and the diameter of the polymeric nanofibers. This activity is based on oxidation ability of singlet oxygen O₂(¹Δ(g)) that is generated upon irradiation. All tested nanofiber materials exhibited prolonged antibacterial properties, even in the dark after long-duration irradiation. The post-irradiation effect was explained by the photogeneration of H₂O₂, which provided the material with long-lasting antibacterial properties.

Porphyrin-layered double hydroxide/polymer composites as novel ecological photoactive surfaces

Nanocontainer and nanofiller aspects of layered double hydroxides (LDH) were combined to prepare porphyrin-LDH/polymer composites for photoactive coatings. The suggested properties are derived from cytotoxicity of singlet oxygen, O2(1Δg), produced by interaction of molecular oxygen with excited porphyrin molecules located within the interlayer space of ZnRAl and MgRAl LDH. Porphyrins, Pd(II)-5,10,15,20-tetrakis(4-carboxyphenyl) porphyrin (PdTPPC) and 5,10,15,20-tetrakis(4-sulfonatophenyl) porphyrin (TPPS) photoproducing O2(1Δg), were successfully intercalated into LDH hosts using the co-precipitation procedure and then used as fillers in two eco-friendly polymers, namely polyurethane (PU) and poly(butylene succinate) (PBS). Porphyrin-LDH/polymer composites were prepared either by the solvent cast/cross-linking technique or melt-compounding with different porphyrin-LDH filler loadings (up to 1.3 wt%). Both X-ray diffraction and transmission electron microscopy measurements indicate a good dispersion of porphyrin-LDH fillers into the polymer matrices and that the porphyrin molecules remain intercalated within LDH layers. The polymers do not block the diffusion of oxygen and the triplet states of the intercalated porphyrins in the composite films have enough long lifetimes to produce O2(1Δg) upon irradiation by visible light. The present composites allow the elaboration of photoactive surfaces with a precise control of the O2(1Δg) concentration depending on porphyrin-LDH filler loadings.

In vitro toxicity testing of supramolecular sensitizers for photodynamic therapy.

We report the phototoxicity of meso-tetrakis(4-sulphonatophenyl)porphine (TPPS4) and zinc metallocomplex (ZnTPPS4) sensitizers in the presence or absence of 2-hydroxypropyl-beta-cyclodextrin (HP-beta-CD) on G361human melanoma cells. Morphological changes in cell cultures have been evaluated using inversion fluorescent microscope and image analysis. Viability of cells was determined by means of molecular probes for fluorescence microscopy (LIVE/DEAD kit- double staining with Calcein AM and Ethidium Homodimer). The quantitative changes of cell viability in relation to sensitizers concentrations and irradiation doses were proved by fluorometric measurement with fluoroscan Ascent. We found that the most effective sensitizer is ZnTPPS4 bound to HP-beta-CD, since the IC50 value was 12.5 g/ml at the dose of light radiation of 10 J/cm2.