Fuqun Zhao

Detailed investigation on a negative photochromic spiropyran

Abstract The negative photochromic properties of a spiropyran are investigated in various solvents and in solutions of different acidity. The results indicate that the polarity of the solvent has a prominent effect on λ max of the coloured merocyanine form (MC), whereas its effects on λ max of the closed form (SP) and on the coloration rates after visible bleaching are very weak. From the effect of acid concentration on the coloration rates the p K a of the cis intermediate Y in the coloration process is determined to be about 1.1 lower than that of the protonated merocyanine (MCH + ). The structures and configurations of MC, SP, MCH + and Y are assigned via their 1 H NMR spectra.

Novel chelation of photochromic spironaphthoxazines to divalent metal ions

Abstract The chelation properties of two photochromic spironaphthoxazine derivatives to divalent metal ions were studied in acetone. Two types of chelate can be observed in the absorption spectrum: an unstable chelate which is formed in the presence of Ni(NO3)2 or Co(NO3)2 on UV irradiation and may revert to the corresponding colourless form in the dark or by bleaching with visible light; the decolouration rate is decreased significantly compared with the metal-ion-free solution; a stable chelate with intense fluorescence emission, which cannot be bleached by visible light. From the influence of the structure of the spiro- oxazines and the nature and concentration of the metal ions and their counteranions on chelate formation, the structures of the two chelates and the mechanisms of the photoreaction and thermal reaction are discussed.

Complexation of phosphorus (III) with a novel tetrapyrrolic phthalocyanine-like macrocyclic compound

Abstract This contribution reports a detailed study of the complex formed by a novel phthalocyanine-like compound (2,9,16,23-tetraisopropoxy tetrabenzotriazacorrole) with phosphorus(III). The structure of this new tetrapyrrolic macrocycle (H[TBC(O i Pr) 4 P(OH)]) was identified by elemental analysis, conventional spectral measurements (FAB-MS, UV-Vis, IR, 1 H NMR, 13 C NMR, and 31 P NMR), as well as its chemical reactivities. The Q band in the electronic transition spectra of the complex lies at a wavelength of around 660 nm, which is slightly shorter than in the mother phthalocyanine. The ϵ of the Q band is approximately one half of the value of the sharp Soret band which exists at 450 nm. The unusual electronic transition spectra are interpreted as the molecular symmetry of the novel complex being reduced to C 1 or lower two-fold symmetry. Three chemically different species formed by protonation or/and deprotonation of the compound with acid and base were characterised and identified. In addition, the previously reported phosphorus(III) phthalocyanine [PcP III ] + is proposed to be H[TBCP(OH)] when compared with H[TBC(O i Pr) 4 P(OH)] in detail.

Study on phosphorus(III) complex of tetrabenzotriazacorrole : A novel phthalocyanine-like photosensitizer

Abstract The photosensitizing properties of a novel phthalocyanine analogue—hydrogen hydroxy-phosphorus(III)-2,9,16,23-tetraisopropxy tetrabenzotriazacorrole (H[TBC(O1Pr)4P(OH)] has been studied. Using diphenyl-isobenzofuran as chemical quencher, the photogeneration of singlet oxygen by H[TBC(O1Pr)4P(OH)] was identified together with its quantitative analysis. It is found that H[TBC(O1Pr)4P(OH)] is a more efficient single oxygen photosensitizer (θΔ =0.44, in N,N-dimethylformamide) than empty phthalocyanine H2Pc(O1Pr)4, and can be comparable to zinc phthalocyanine ZnPc(O1Pr)4. H[TBC(O1Pr)4P(OH)] can also effectively photo-generate the superoxide anion as shown by spin-trapping measurements. From the interpretation of the free energy changes ΔG ∗ in excited state electron transfer reactions, it is concluded that the superoxide anion is formed by electron transfer from the lowest excited singlet state (not the lowest excited triplet state) of H[TBC(O1Pr)4P(OH)] to oxygen. The results from confirm the presence of both Type I (radical) mechanism and Type II (single oxygen) mechanism in the H[TBC(O1Pr)4(OH)] photosensitized system.

Investigation of a novel triazatetrabenzcorrole photosensitizer

A novel phthalocyanine-like photosensitizer, oxophosphorus(V) tetrasulfotriaza-tetrabenzcorrole (POTBCS4), has been synthesized. Its structure and absorption spectrum are unique. POTBCS4 has an axial P=O group and peripheral sulfo groups. The fluorescence emission spectra, fluorescence quantum yield and quantum yield of singlet oxygen generation have been studied. The uptake and the photodynamic activities against HeLa cells were measured. The results indicated that POTBCS4 was a potential photosensitizer for photodynamic therapy (PDT).

Photokinetic study of a novel phenylfulgide: effects of solvents on its photochromic reaction

Abstract A photokinetic method was used to study the photochromic reaction of a novel fulgide, (E) -2-isopropylidene-3[1-3,4-dimethoxy-phenyl)ethylidene]-3-isopropylidene succinic anhydride. It was found that the photochromic reaction depends on the solvent polarity. The apparent ring-closure rate decreased with increasing solvent polarity, while the rate of E to Z isomerization increased. It was supposed that there were two kinds of conformation in the excited states. Increasing the solvent polarity favoured thr twisted conformation, which accelerated the E to Z photo isomerization, inhibiting the electrocyclilc reaction.

Degradation of rhodamine 6G in the peroxyoxalate chemiluminescent reaction

Abstract The degradation process of rhodamine 6G in the peroxyoxalate chemiluminescent system was monitored for the first time. A preferential degradation of rhodamine 6G dimers was suggested and identified spectroscopically. The influence of light irradiation or H 2 O 2 oxidation on dye degradation was insignificant according to our observations. The possible cause of rhodamine 6G degradation in the peroxyoxalate chemiluminescent system was discussed.

A further study on the degradation mechanism of rhodamine 6G in the peroxyoxalate chemiluminescent reaction

Abstract In previous work, we have demonstrated that the degradation of rhodamine 6G (R6G) in the peroxyoxalate chemiluminescent reaction may be related to the formation of an intermediate and that the oxidation effect of H 2 O 2 is insignificant. In this paper, the effect of 9,10-diphenylanthracene (DPA) on the degradation of R6G has been examined. The experimental results show that, as the concentration of DPA is increased, the degradation rate of R6G decreases. This can be interpreted in terms of the competitive interaction of DPA and R6G molecules with the intermediate. It was also found that N 2 bubbling of the reaction mixture leads to a decrease in the degradation rate of R6G. On the basis of these experimental results, a mechanism for R6G degradation in the peroxyoxalate chemiluminescent system, involving a reaction intermediate and dissolved oxygen, is suggested.

Rewritable volume holographic optical storage on PMMA film of diarylethene

In this paper, diarylethene derivative, 1,2-bis(2-methyl-5-N,N-dimethylaminophenyl)-thien-3-yl) perfluorocyclopentene (BMDTP) was synthesized. And the PMMA film of 10μm thickness of BMDTP was fabricated by spin-coating method. The maximal UV-Visible absorption of amorphous PMMA film is 634nm. And the reflective index modulation(Δn) is 2.14×10-3 between the open- and close-rings form. On the PMMA film, ten gratings of hologram are recorded in one volume by angle multiplexing. Therefore, the diarylethene is a promising material for rewritable volume holographic optical storage.

Influence of peptide bond on photosensitized oxidation of tryptophan, tyrosine and histidine dipeptides

IN photodynamic therapy, the damage of protein results from the photooxidation of one ormore of only five amino acid residues (tryptophanyl, tyrosyl, histidyl, methionyl and cys-teinyl). These five amino acids are also readily photooxidized in their monomeric states. How-ever, the reaction kinetics and mechanisms of free amino acids and bound amino acid residuesin proteins are somewhat different. For example, Tassin found that the incorporation of tryp-tophan into a peptide linkage dramatically altered its susceptibility to photooxidation as well as