The direct application of laser flash photolysis to cotton fabric dyed with a phthalocyanine dye

Flash photolysis studies of sulphonated aluminium(III) phthalocyanine contained in cotton fabric show that the dye has essentially the same spectral behaviour as when dissolved in water, but the lifetime of excited states is longer. Following excitation of the Soret band, the triplet-triplet absorption of the dye has a lifetime of 770±60 μ s in an oxygen-free fabric, with inefficient quenching by oxygen observed only if the fibres are water-saturated. S₁S₀fluorescence from the dye is detected only when the sample contains oxygen and the decay has two components; in the absence of oxygen T₂T₁ emission occurs as well. Prolonged exposure to the 354nm exciting laser causes the build-up of a red substance in the fabric, which is believed to be the product of one-electron oxidation of the phthalocyanine. Electron acceptors and donors such as methyl viologen and hydroquinone have a limited quenching effect on the excited states of the dye. The observed behaviour of the dye is discussed in terms of the restricted diffusion of molecules within the cotton fibres and of the enhanced lifetimes of the excited states.     

II—Evidence for the Formation of Singlet Oxygen by Phototendering Vat Dyes

The reaction of tetraphenylcyclopentadienone (TPC) with singlet oxygen has been used as a probe for the photochemical formation of singlet oxygen by phototendering vat dyes. The dyes C.I. Vat Yellow 1, 2 and 26 and C.I. Vat Orange 9 sensitised the oxidation of TPC in phenol-methylene chloride solution by the action of visible light. In each case the sole photo-oxidation product was cis-dibenzoylstilbene, indicating the intermediacy of singlet oxygen. Similar results were obtained when the dyes were applied to cotton fabric, although the relative efficiencies of the dyes as sensitisers differed from those observed in solution. The singlet-oxygen-sensitising efficiencies of the dyes on cotton parralleled their relative phototendering activities towards cellulose, providing evidence in favour of the singlet-oxygen theory of phototendering. Quenching studies of the dye-sensitised oxidation of TPC confirmed that the reaction proceeded by a singlet-oxygen mechanism rather than a radical process.     

Synthesis and physicochemical behaviour of aluminium trikis and tetrakis (diaquaplatinum) octacarboxyphthalocynine

The combination of chemotherapy and photodynamic therapy was investigated by the synthesis and characterisation of phthalocyanine conjugates with Pt complexes. The complexes synthesized are: hydroxoaluminum trikis(diaquaplatinum) octacarboxyphthalocyanine (OHAlOCPc(Pt)₃) and hydroxoaluminum tetrakis(diaquaplatinum) octacarboxyphthalocyanine (OHAlOCPc(Pt)₄). The platinated phthalocyanine complexes gave long triplet lifetimes of 577 and 526 μs for OHAlOCPc(Pt)₃ and OHAlOCPc(Pt)₄, respectively. The triplet quantum yields were found to be 0.45 for OHAlOCPc(Pt)₃ and 0.57 OHAlOCPc(Pt)₄ while the singlet oxygen quantum yields were found to be 0.38 and 0.48, respectively.     

金属酞菁激发态与氧的相互作用

比较了几种金属酞菁光敏产生单重态氧和超氧负离子的能力,结果表明它们产生~1O_2的能力与中心金属的电子结构有关,取决于三重态寿命和量子产率。顺序如下:Zn>Ga>Cu>H_2>Al>Co。产生O_2~-的能力不仅与三重态寿命和量子产率有关,也与激发能和氧化还原电位有关。其顺序如下:Ga>Al>Cu>Zn。还研究了酪氨酸与镓酞菁激发态相互作用,酪氨酸猝灭镓酞菁荧光。在除氧条件光激发下,酪氨酸猝灭镓酞菁的激发三重态发生电子转移,检测到GaTSPc~-在560nm处的瞬态吸收,在氧的存在下进一步反应生成O_i~-。     

Photostability of a range of azobenzene dyes and their benzothiazolyl analogues in the presence of air

Irradiation of a range of azobenzene dyes and their benzothiazolyl analogues with visible light in the presence of air has been shown to give rise to the conversion of a triplet oxygen to the singlet state. As proof of the presence of a singlet oxygen, its reaction with tetraphenylcyclopentadienone was studied. The formation of the oxidation product cis-α,α'-dibenzoylstilbene by a singlet oxygen has been confirmed by chemical ionisation mass spectrometry, both in ethyl benzoate solution and on polyester fabric. Inhibition of photodegradation of the dyes by a singlet oxygen quencher (DABCO) has also been demonstrated.     

The Role of Anthraquinonoid Dyes in the Catalytic Fading'of Dye Mixtures– Substituent–dependent Triplet Yield of Diaminoanthraquinones

Taking various diaminoanthraquinones as model compounds for commercial anthraquinonoid dyes it was found that the ability of initiating catalytic fading via singlet oxygen mechanism is closely related to the quantum yield of triplet formation in these dyes. The quantum yields of triplet formation show a marked difference between the various diaminoanthraquinones. Whereas 1, 4– and 1, 2–diaminoanthraquinones have very small quantum yields, the 1, 5– and 1, 8–derivatives pass into the triplet state with a fairly high efficiency. From this it was concluded that catalytic fading occuring via singlet oxygen mechanism must be expected in dye mixtures consisting of 1, 5– or 1, 8–diamino substituted anthraquinonoid dyes and easily oxidizable azo–compounds.     

Lightfastness and spectroscopic properties of basic triphenylmethane dyes: Effect of the substrate

The lightfastness of five basic triphenylmethane dyes in cotton and acrylic fibres is compared with their primary photochemical behaviour on flash photolysis in appropriate model solvents. The low lightfastness of the dyes in cotton is paralleled by the observation of strong transient absorption in propan-2-ol whereas their higher lightfastness in acrylic fibre is paralleled by a lack of transient absorption in acetonitrile. The transient species is attributed to the triphenylmethane radical formed by electron transfer. Further, the relative importance of photoreduction and triplet sensitisation in dye fading is also examined using benzhydrol as a hydrogen-atom donor and benzophenone as a triplet sensitiser.     

On the curing of fatty acids with singlet oxygen

A review on the transformation of triplet oxygen to singlet oxygen via sensitising agents commonly found in fatty oils is presented. The Wigner spin conservation rule restricts the direct reaction of triplet oxygen with organic molecules possessing singlet multiplicities. Sensitisers present in fatty oils are energetically and mechanistically capable of changing oxygen from its triplet state to its singlet state. Lowering the oxygen multiplicity overcomes the spin restriction, thus allowing for the oxidative curing of fatty acids commonly used in alkyd resins.     

Evidence for the Participation of Singlet Oxygen in the Vat–dye Photosensitized Degradation of Cellulose

A study has been made of the vat–dye photosensitized degradation of cellulose. Whilst the part played by the dyes in direct hydrogen abstraction from a cellulose substrate cannot be overlooked, it is apparent that the role played by singlet oxygen is important. The ability of a dye to produce singlet oxygen has been studied by measuring the amount of tetraphenylcyclopentadienone the dye can photo–oxidize. It would appear that the singlet oxygen is initially formed in its high energy g state by energy transfer from the triplet state of the dye to ground state molecular oxygen. Luminescence spectroscopy has been employed in order to gain information about the excited state energies of the dye molecules, and an electron spin resonance study of the dyes in rigid media has been carried out in order to obtain information about the triplet state.     

Synthesis and Application of Some New Reactive Chlorohydrin Dyes

Azo and phthalocyanine dyes carrying the chlorohydrin group, as the precursor of the reactive epoxy group, were prepared using new catalyzed reactions. The reactive group is attached to the coupling component in some cases and to the diazonium component in other cases. A phthalocyanine dye carrying two reactive groups was also synthesized. The dyeing of cotton, wool and multifibre fabrics was studied, under different dyeing conditions. Various techniques of dyeing and printing were used. Exhaustion and padding methods were investigated for dyeing, and direct, reserve and discharge methods for printing. One–stage and two–stage procedures were employed for both printing and dyeing. It was found that the chlorohydrin reactive dyes prepared in the present work could be applied by nearly all known methods of dyeing and printing on cotton, wool, viscose rayon, nylon and acrylic fibres. The dyeings obtained had satisfactory fastness properties and showed fairly good dye fixation on the substrate.     

The synthesis of novel,visible-wavelength,oxidizable polymerization sensitizers based on the 8-halogeno-5,12-dihydroquinoxalino[2,3-b]quinoxaline skeleton

Novel dyes, based on the 8-halogeno-5,12-dihydroquinoxalino[2,3-b]quinoxaline skeleton, were synthesized and characterized using ¹H NMR spectroscopy and chemical ionization mass spectroscopy. Their electrochemical and spectral properties, such as absorption and emission spectra, quantum yield of fluorescence and quantum yield of singlet oxygen generation, were also measured. These dyes were used as oxidizable sensitizers for diphenyliodonium and N-alkoxypyridinium salts. Photoredox pairs, consisting of dyes and pyridinium or iodonium salts, were found to be effective visible-wavelength initiators of free radical or cationic polymerization, respectively. The ability of each dye to act as a photoinitiator strongly depended upon its chemical structure. The heavy atoms present in the chemical structure could lead to excited triplet states within the dye, thereby facilitating electron transfer from these states.     

Dyeing of natural fibres from perfluoro-polyether reverse micelles in supercritical carbon dioxide

The dyeing of natural fibres from a reverse-micellar system in supercritical carbon dioxide has been investigated using ammonium carboxylate perfluoropolyether as surfactant. Protein fibres such as silk and wool were satisfactorily dyed in deep shades with conventional acid dyes without special pretreatment. Exhaustion was excellent. It was however found that on these fibres the performance of acid dyes was strongly influenced by temperature and carbon dioxide density. Conventional reactive dyes in this system were adsorbed on cotton, even in the absence of dyeing auxiliaries, but the fixation of the dye was not satisfactory. Compared with supercritical dyeing methods reported previously, it was found in this study that the temperature and pressure required were significantly lower.     

Mechanism of the photofading of dye: Contribution of singlet oxygen to the photofading of aminoanthraquinone dyes

The contribution of singlet oxygen (¹Δ_gO₂) to the photofading of some animoanthraquinone dyes in solution is examined. The rates of the photofading are accelerated in the presence of sensitizers of singlet oxygen, e.g. Rose Bengal or Methylene Blue. The rates are retarded by adding effective singlet oxygen quenchers, such as DABCO or nickel dimethyldithiocarbamate (NMC). Additional evidence for the intermediacy of singlet oxygen is obtained by examining the effect of deuterium solvent, the effect of chemical sources of singlet oxygen, and the competitive photo-oxygenation with the dyes and NMC.     

The synthesis,fluorescence behaviour and singlet oxygen studies of new water-soluble cationic gallium(III) phthalocyanines

The preparation of cationic water-soluble gallium phthalocyanine derivatives are described for the first time. Peripheral and non-peripheral 3-hydroxypyridine tetrasubstituted gallium(III)phthalocyanines (5a, 6a) and their quaternarized derivatives (5b and 6b) have been synthesized and characterized by elemental analysis, IR, ¹H NMR spectroscopy, electronic spectroscopy and mass spectra. The quaternarized compounds (5b and 6b) are soluble in water and not aggregated (in water and in organic solvents) within a wide concentration range. General trends are described for singlet oxygen quantum yields, fluorescence quantum yields and fluorescence lifetimes of these compounds. These complexes showed better singlet oxygen quantum yields in water than the related quarternarized porphyrazine complexes.     

Flash photolysis of azo dyes in aqueous solutions of biacetyl

Irradiation by microsecond flash of aqueous aerobic solutions of biacetyl (2, 3-butanedione) and a number of different azo dyes resulted in oxidative fading of the dyes. The fading kinetics of all tautomeric dyes could only be described properly by assuming three oxidative species. The first one is believed to be singlet oxygen. Due to its short lifetime in aqueous systems, the dye fraction consumed by singlet oxygen was confined to a maximum of about 30%. Second order reaction rate constants for the second oxidator were in the range of 1.4–4.7 × 10⁸ l/(mol s). A radical mechanism is proposed, in which the adduct of oxygen and triplet biacetyl is the second oxidising species. A third oxidator formed from the second was necessary to describe adequately the fading curves of four azo dyes with slow fading rates. This oxidator could be an acylperoxy-radical. The non-tautomeric dye Cl Acid Red 37 was recycled partially after very fast fading during the first 0.5 ms.     

Mechanism of the photofading of Dye. Contribution of singlet oxygen in the catalytic fading of anthraquinone dye mixtures

The mechanism of the catalytic fading of some dyes has been investigated. The relative fading of quinophthalone in solution increases when C.I. Disperse Red 15 was added. The mechanism of catalytic fading proceeds via the singlet oxygen mechanism, since this phenomenon is suppressed by adding singlet oxygen quencher as DABCO or nickel dimethyldithiocarbamate (NMC). However, when quinophthalone mixed with C.I. Disperse Blue 14 was irradiated under the same conditions (λ > 520 nm), no catalytic fading occurred. Competitive photo-oxidation experiments for these dyes with NMC, giving evidence for intermediacy of singlet oxygen by the self-sensitised process, were carried out. The relative rate constants for reactions in solution were examined to predict the possibility of the catalytic fading in these dye mixtures.     

金属络合染料光稳定性研究进展

综述了不同金属离子对偶氮型、甲臜型和酞菁型3种染料光稳定性的影响。在染料结构中引入Co(Ⅲ)、Co(Ⅱ)、Ni(Ⅱ)、Cu(Ⅱ)等金属离子后,由于这些金属离子的最低激发态能量低于染料三重态能量,在染料结构中起到了能量吸收剂的作用,有效猝灭了染料三重态,从而使染料的光稳定性得到明显提高。     

Singlet oxygen lifetime in polymer films

Singlet oxygen lifetimes [τ(¹O₂)] in polymer matrices were calculated using the strong exponential correlation between the incremental rate constant (K_xy) of energy transfer from ¹O₂ to terminal oscillators X—Y contained in solvent molecules and the energy (E_xy) of the highest fundamental vibration of the oscillator X—Y. The lifetimes in polymers correspond very well to experimental data in the literature. They depend only on the nature and quantity of molecular oscillators in the medium but not on the state of aggregation. The computed lifetimes in common polymers vary only from 10 to 50 μs. Therefore the lifetime of ¹O₂ in singlet oxygen reactions in polymers is of secondary importance in comparison to the diffusion coefficient.     

Improvement of the light fastness of natural dyes: the action of singlet oxygen quenchers on the photofading of red carthamin

While the contribution of singlet oxygen quenchers to synthetic dyes has been investigated previously by several workers, there have been few studies pertaining to the use of singlet oxygen quenchers as a means of improving the light fastness of natural dyes. In this paper, the influence of various additives on the photofading of carthamin has been examined in cellulose acetate film. The rate of photofading of the colour was remarkably suppressed in the presence of nickel hydroxyarylsulphonates, while the addition of UV absorbers afforded little retardation in the rate of fading.     

The Photochemistry of Dyes. IV—The Role of Singlet Oxygen and Hydrogen Peroxide in Photosensitised Degradation of Polymers

The effect of sensitising dyes on the photochemical degradation of textile fibres is discussed. The degradation is dependent upon the presence of oxygen, and is accelerated by water vapour and rise in temperature. The study of simple model photochemical systems intended to simulate the dyed fibre system indicates that there are significant differences between the two systems. The sensitising effect of dyes in the textile systems seems to be due to the formation of excited singlet oxygen and hydrogen peroxide. The latter is not formed in the absence of water vapour.