Synthesis and evaluation of novel fluorinated hematoporphyrin ether derivatives for photodynamic therapy.

A photosensitizer with high phototoxicity, suitable amphipathy and low dark toxicity could play a pivotal role in photodynamic therapy (PDT). In this study, a facile and versatile approach was adopted to synthesize a series of novel fluorinated hematoporphyrin ether derivatives (I1-I5 and II1-II4), and the photodynamic activities of these compounds were studied. Compared to hematoporphyrin monomethyl ether (HMME), all PSs showed preferable photodynamic activity against A549 lung tumor cells. The longest visible absorption wavelength of these compounds was approximately 622 nm. Among them, II3 revealed the highest singlet oxygen yield (0.0957 min-1), the strongest phototoxicity (IC50 = 1.24 µM), the lowest dark toxicity in vitro, and exhibited excellent anti-tumor effects in vivo. So compound II3 could act as new drug candidate for photodynamic therapy.

Iron-catalyzed ortho trifluoromethylation of anilines via picolinamide assisted photoinduced C-H functionalization.

A convenient, oxidant-free protocol was developed for the ortho trifluoromethylation of aniline via picolinamide assisted Fe-promoted C-H functionalization under ultraviolet irradiation. In this transformation acetone essentially acted as both a solvent to dissolve reactants and a low-cost radical initiator to efficiently generate a CF3 radical from Langlois' reagent. A broad substrate scope was tolerated and picolinamide bearing strong electron withdrawing groups also could be transformed into the corresponding products with acceptable yields. Furthermore, the value of this method has been highlighted via the efficient synthesis of the nonsteroidal anti-inflammatory drug floctafenine.

Assessment of the atmospheric loss processes initiated by OH radicals and sunlight, and the radiative efficiency for a series of hydrofluoroolefins, CF3(CF2)x=1,3,5CHCH2.

Hydrofluoroolefins (HFOs) of the type CF3(CF2)x≥0CHCH2, are currently being suggested as substitutes of some hydrofluorocarbons (HFCs). In this work, an assessment of the atmospheric removal of CF3(CF2)x=1,3,5CHCH2, initiated by reaction with hydroxyl (OH) radicals and UV solar radiation is addressed. For that purpose, the rate coefficients for the OH + CF3(CF2)x=1,3,5CHCH2 reaction, kOH(T = 263-358 K), were determined by the pulsed laser photolysis-laser induced fluorescence technique. A slightly negative temperature dependence of kOH was observed, obtaining Ea/R (in K) values of -124 ± 15, -128 ± 6 and -160 ± 10, for CF3CF2CHCH2, CF3(CF2)3CHCH2 and CF3(CF2)5CHCH2, respectively. The estimated atmospheric lifetimes are around 8 days, considering that HFOs are well-mixed in the troposphere. Furthermore, an evaluation of the long-wave and short-wave absorption process of these HFOs have been carried out by determining the UV (191-367 nm) and IR (4000-500 cm(-1)) absorption cross sections at 298 K. Based on the obtained UV absorption cross sections, no photolysis of CF3(CF2)x=1,3,5CHCH2 is expected in the troposphere (λ > 290 nm). These species strongly absorb IR radiation in the atmospheric IR window. Despite the strong absorption in the IR region, the lifetime corrected radiative efficiencies are low (0.033 W m(-2) ppb(-1) for CF3(CF2)3CHCH2 and 0.039 Wm(-2) ppb(-1) for CF3(CF2)5CHCH2). Calculation of GWPs for these species has been performed as a function of the horizon time, providing values higher than unity for a short-period term, decreasing dramatically for longer periods. Therefore, it is concluded that emissions of these species do not affect the radiative forcing of climate, making them suitable replacements of large-GWP HFCs.

Difluoro-C4'-oxidized abasic site for efficient amine modification in biological systems.

An oligodeoxynucleotide (ODN) containing a 2',2'-difluorinated analogue of a C4'-oxidized abasic site (C4'-OAS) was designed for the amine modification of biomolecules that interact with nucleic acids. In contrast to the parent C4'-OAS, which yielded amine-modified products accompanied by DNA strand scission, the ODN containing the difluoro C4'-OAS efficiently yielded products carrying ODNs. The amine modification proceeded without additional reagents being required and might be applicable to reactions in biological systems.

Accelerated and efficient photochemistry from higher excited electronic states in fulgide molecules.

The photoinduced electrocyclic ring-opening of a fluorinated indolylfulgide is investigated by stationary and ultrafast spectroscopy in the UV/vis spectral range. Photoreactions, initiated by optical excitation into the S(1) (570 nm) and S(N) (340 nm) absorption band of the closed isomer, lead to considerable differences in reaction dynamics and quantum yields. Transient absorption studies point to different reaction pathways depending on the specific excitation wavelength: excitation into the S(1) state leads to the known reaction behavior with a picosecond decay to the ground state and a small quantum yield of 7% for the photoproduct. The S(N) state shows an unexpected long lifetime of 0.5 ps. The photoreaction starting from the S(N) state leads to a large extent directly to the product ground state and back to the educt ground state. This results in an increased reaction quantum yield of 28%. In contradiction to Kasha's rule, the S(1) state is only populated with an efficiency of 38%. The observed behavior strongly differs from the expected picture with fast relaxation into the S(1) state and a subsequent ring-opening reaction starting from the lowest excited electronic state. Quantum chemical calculations confirm and complement the experimental findings allowing a sound molecular interpretation to be obtained.

Synthesis and microwave assisted polymerization of fluorinated 2-phenyl-2-oxazolines: the fastest 2-oxazoline monomer to date.

The living cationic ring-opening polymerization of 2-oxazolines with fluorinated aromatic substituents was found to be strongly accelerated by o-fluoro substituents.

Formation of hydrogen fluoride by gamma and beta sterilisation in medical devices containing perfluoroheptane.

Infusion of hexadecafluoroheptane, a liquid perfluorocarbon released from repaired Althane dialysers was found to be the most probable reason for the deaths of 53 dialysis patients reported in the year 2001. This study focuses on toxic decomposition products generated due to gamma and beta sterilisation of hexadecafluoroheptane. The responsible dialysers were sterilised with a maximum dose of 45 kGy gamma irradiation. We investigated the influence of both 20-500 kGy gamma and beta irradiation on perfluoroheptane. Analysis of the irradiated samples verified the decomposition of perfluoroheptane in dependence on the dose of irradiation. Beta irradiation resulted in a higher degree of decomposition than the same dose of gamma irradiation. As decomposition products, hydrogen fluoride, CO2, and one saturated fluorinated hydrocarbon which could not be analysed exactly were identified. Even at 20 kGy gamma irradiation hydrogen fluoride was detectable. Our results provide evidence that hydrogen fluoride is generated as a highly toxic decomposition product when perfluoroheptane is sterilised with gamma irradiation as it was applied on the affected dialysers. There is no evidence of other toxic degradation products especially perfluoroisobutylene. Therefore, hydrogen fluoride or the dissociated fluoride ions might act as a toxic agent when medical devices containing liquid perfluorocarbons are sterilised by irradiation.

Investigation of a new approach to decompose two potent greenhouse gases: photoreduction of SF(6) and SF(5)CF(3) in the presence of acetone.

In this paper, we addressed the utilization of photochemical method as an innovative technology for the destruction and removal of two potent greenhouse gases, SF(6) and SF(5)CF(3). The destruction and removal efficiency (DRE) of the process was determined as a function of excitation wavelength, irradiation time, initial ratio of acetone to SF(5)X (X represented F or CF(3)), initial SF(5)X concentration, additive oxygen and water vapor concentration. A complete removal was achieved by a radiation period of 55min and 120min for SF(6)-CH(3)COCH(3) system and SF(5)CF(3)-CH(3)COCH(3) system respectively under 184.9nm irradiation. Extra addition of water vapor can enhance DRE by approximately 6% points in both systems. Further studies with GC/MS and FT-IR proved that no hazardous products such as S(2)F(10), SO(2)F(2), SOF(2), SOF(4) were generated in this process.

Optical image processing using the photoinduced anisotropy of pyrrylfulgide.

A synthesized photochromic compound-pyrrylfulgide--is prepared as a thin film doped in a polymethylmethacrylate (PMMA) matrix. Under irradiation by UV light, the film converts from the bleached state into a colored state that has a maximum absorption at 635 nm and is thermally stable at room temperature. When the colored state is irradiated by a linearly polarized 650 nm laser, the film returns to the bleached state; photoinduced anisotropy is produced during this process. Application of optical image processing methods using the photoinduced anisotropy of the pyrrylfulgide/PMMA film is described. Examples in non-Fourier optical image processing, such as contrast reversal and image subtraction and summation, as well as in Fourier optical image processing, such as low-pass filtering and edge enhancement, are presented.

VUV photon induced fluorescence study of SF5CF3.

The interaction of SF(5)CF(3) with vacuum-UV radiation has been investigated by photon induced fluorescence spectroscopy. Total fluorescence yield and dispersed fluorescence spectra of SF(5)CF(3) were recorded in the 200-1000 nm fluorescence window. In all cases, the fluorescence spectra resemble those of CF(3)X (X = H, F, Cl, and Br) molecules. At photon energies below 20 eV, the emission is attributed to the excited CF(3) and CF(2) fragments. The threshold for the CF(3) emission is 10.2 +/- 0.2 eV, giving an upper limit estimate for the SF(5)-CF(3) bond dissociation energy of 3.9 +/- 0.3 eV. The excitation functions of the CF(3) and CF(2) emissions were measured in the photon energy range 13.6-27.0 eV. The resonant structures observed in SF(5)CF(3) are attributed to electronic transitions from valence to Rydberg orbitals, following similar assignments in CF(3)X molecules. The photoabsorption spectrum of SF(5)CF(3) shows features at the same energies, indicating a strong contribution from Rydberg excitations.

Radiation damage of fluorinated organic compounds measured by parallel electron energy loss spectroscopy.

The sensitivity of fluorinated organic compounds to radiation damage in the electron microscope was measured by electron energy loss spectroscopy (EELS). Five classes of molecules were investigated with fluorine atoms situated on: (1) an aliphatic chain, (2) an aromatic ring, (3) a trifluoromethyl group on an aromatic ring, (4) a trifluoromethyl group on a heterocyclic ring, and (5) a trifluoromethyl group next to a carbonyl group. The damage dose for fluorine loss was found to depend strongly on the position of the fluorine atoms and on specimen temperature. For poly-substituted fluorine on an aliphatic chain, approximately half of the fluorine was retained at doses in excess of 10(7) e/nm2. At room temperature molecules containing trifluoromethyl groups on aromatic or heterocyclic rings were much more sensitive to fluorine loss than compounds having fluorine substituted directly on the rings. This behavior is consistent with the relatively low chemical stability of the trifluoromethyl group in these structures. The rapid loss of fluorine at low electron doses (approximately 10(4) e/nm2) in the trifluoromethyl aromatic compounds was reduced several orders of magnitude by cooling the specimen to liquid-nitrogen temperatures. An understanding of how specific types of fluorinated compounds suffer damage under the electron beam will be important in their potential application as biochemical or pharmacological probes.