From an extensive study of dyeings on wool using natural dye plants indigenous to the Highlands of Scotland, a selection representing some of the brighter colours obtained have been examined colorimetrically, and the fastnesses to washing and light recorded. The original colours and the colour changes during light fading have been recorded in Munsell and CIELAB (1976) colour coordinates. The fastnesses of these dyeings have been compared with the corresponding results previously reported for the more widely used natural dyes that formerly were traded internationally. The colours and colour changes are briefly discussed in terms of biosynthetic pathways, and related to the colours of yarns used in Scottish tartans of the past and present.

Abstract— The photochemistry of several 4‐hydroxy‐ and 4‐methoxybenzothiazoles has been investigated by laser flash photolysis. In aqueous solutions of pH3–12, the 4‐hydroxybenzothiazole chromophore undergoes monophotonic photoionization to afford e‐aq with quantum yields on the order of 0.06; no evidence for triplet species was obtained. The spectra and stability of the resultant free radicals were determined using pulse radiolysis. In contrast, triplet transients with life‐times on the order of 8 mUs are readily observable upon irradiation of the 4‐methoxybenzothiazole analog. Triplet sensitization experiments with the water‐soluble carotenoid crocetin were employed to obtain the triplet extinction coefficients and subsequently the triplet quantum yields. The significance of these differences in photochemical behavior is discussed in relationship to the photochemistry and photobiology of the epidermal melanin pigment pheomelanin.

Abstract— Nanosecond laser flash photolysis and pulse radiolysis have been used to generate and characterise the triplet state, and semioxidised and semireduced radicals of haematoporphyrin, and three 0‐acyl compounds derived from it (the monoacetate, the diacetate and the disuccinate).After 347 nm irradiation in water containing 2% Triton X‐100, haematoporphyrin forms the triplet state (φT= 0.92) and photoionises monophotonically (φI= 0.03). For the O‐acyl derivatives, φT approaches unity and photoionisation is reduced. In acetone the triplet yield of all four compounds are close to unity. The difference and corrected spectra for the triplet species are presented and decay rates (k1˜104s‐1) and oxygen quenching constants (kQ˜1.5times109M‐1s‐1) for the triplet state have been measured. The difference and corrected spectra for the semi‐reduced species in methanol and semi‐oxidised species in aqueous Triton X‐100 are presented.The photophysical characteristics in fluid solution of haematoporphyrin and its 0‐acyl derivatives are rather similar to those previously recorded for other photosensitising porphyrins.

Nanosecond laser flash photolysis and pulse radiolysis have been used to characterise the excited states and radicals of meso-tetraphenylporphyrin tetrasulphonic acid as the tetrasodium salt (Na4TPPS) and of meso-tetra-N-methylpyridylporphyrin as the tetra-p-toluenesulphonate (TMPyrP). After 347 nm irradiation, aqueous Na4TPPS forms triplet states (ϕT= 0.76) and photoionises monophotonically (ΦI= 0.029), while TMPyrP forms only triplets (ΦT= 0.92) and does not photoionise. The difference and corrected spectra of the triplet states and the semi-oxidised and semi-reduced radicals of these molecules have been obtained.

Chemischer InformationsdienstVolume 12, Issue 3 Preparative Organic Chemistry ChemInform Abstract: PHOTOCHEMISTRY OF 4-HYDROXYBENZOTHIAZOLE: A MODEL FOR PHEOMELANIN PHOTODEGRADATION M. R. CHEDEKEL, M. R. CHEDEKELSearch for more papers by this authorE. J. LAND, E. J. LANDSearch for more papers by this authorR. S. SINCLAIR, R. S. SINCLAIRSearch for more papers by this authorD. TAIT, D. TAITSearch for more papers by this authorT. G. TRUSCOTT, T. G. TRUSCOTTSearch for more papers by this author M. R. CHEDEKEL, M. R. CHEDEKELSearch for more papers by this authorE. J. LAND, E. J. LANDSearch for more papers by this authorR. S. SINCLAIR, R. S. SINCLAIRSearch for more papers by this authorD. TAIT, D. TAITSearch for more papers by this authorT. G. TRUSCOTT, T. G. TRUSCOTTSearch for more papers by this author First published: January 20, 1981 https://doi.org/10.1002/chin.198103116Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume12, Issue3January 20, 1981 RelatedInformation

Laser flash photolysis using 347 nm excitation and pulse radiolysis have been used to study the transient species produced from solutions of a series of eight hydrazone compounds synthesised from substituted (R1,R2) 1,3-diones coupled to substituted (Ar) aromatic amines. Three classes of transient behaviour were found in hexane solution. Compound (8) gave a very short-lived transient (t½ca. 45 ns, λmax. 510 nm) which was identified as a triplet species. The other three compounds from unsymmetrical dione derivatives gave short-lived transients (t½ca. 50–100 µs) in the spectral region 440–460 nm and long-lived transients (t½ca. 0.5–2.0 s) occurring at ca. 425 nm, whereas the four symmetrical derivatives (R1= R2) gave only the short-lived transients in the region 450–470 nm. The lifetimes of the longer-lived transients were shown to be dependent on solvent polarity and added acid. It is proposed that the longer-lived transients are associated with isomerism about the CN bond, induced by photoexcitation into the singlet excited state. Rate constants for quenching of various triplet species by three of the hydrazones were determined and shown to correlate with the triplet energy of the compounds being quenched. Assuming quenching occurred by electronic energy transfer the triplet energies of the hydrazones were estimated to lie in the range 150–190 kJ mol–1. The photochemical breakdown products arising from extensive u.v. irradiation have been examined by chromatographic and spectroscopic techniques. It was shown that the compounds are relatively stable to irradiation above 330 nm.

Laser flash photolysis and pulse radiolysis have been used to obtain triplet–triplet spectra, extinction coefficients, quantum yields of formation, rates of decay and quenching by oxygen of the triplet states of seven porphyrin esters (mesoporphrin, deuteroporphyrin, photoprotoporphyrin isomers, coproporphyrins I and II and uroporphyrin I). Results on protoporphyrin, reported elsewhere, are included for comparison.

Bilirubin (BR) which is known to bind strongly to human serum albumin (HSA) (1,2,3) and to lipids, lipoproteins and cell membranes (4,5) can be considered, in the body to be distributed according to the equilibrium: % MathType!MTEF!2!1!+- % feaagCart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOqaiaadk % facqGHsislcaWGibGaam4uaiaadgeacqWImhYGcaWGcbGaamOuaiaa % cIcacaWGMbGaamOCaiaadwgacaWGLbGaaiykaiablYCidkaadkeaca % WGsbGaeyOeI0IaamiDaiaadMgacaWGZbGaam4CaiaadwhacaWGLbaa % aa!4DDF! $$ BR - HSA \rightleftharpoons BR(free) \rightleftharpoons BR - tissue $$ The high BR level in infants suffering from neonatal jaundice exposes them to the risk of kernicterus in which irreversible tissue damage results from the uptake of BR by brain cells (6). Although phototherapy, in recent years, has proved extremely effective in the reduction of BR levels in jaundiced infants, the precise mechanism for this process is still not fully understood and has provoked much photochemical study (7). One interpretation postulates self sensitised photooxidation (8) and another proposes photoisomerisation (9,10) of BR.

The radicals derived from three 1,4-disubstituted anthraquinones containing NH2, NHMe and OH substituent groups have been studied in methanol solution using the technique of pulse radiolysis. Absorption spectra and rates of formation of semiquinone radical species (DH· and D–.), formed respectively under acidic and alkaline conditions, have been recorded. Aggregation of the ground state dye must be assumed to obtain positive extinction coefficients for the radical formed under alkaline conditions.

The radical cations and anions of a number of carotenoid pigments have been generated and their absorptions characterised using pulse radiolysis techniques. For all the radical ions studied there is a broad absorption peak at longer wavelengths than the first absorption band of the parent molecule. The wavelength maxima of the absorption bands are linearly dependent on the number of conjugated double bonds. For most polyenes the radical anion absorbs at a slightly shorter wavelength than the radical cation derived from the same parent molecule, although the differences in energy of excitation are quite small (∼10 kJ mol–1). The radical ion absorptions are shifted hypsochromically on moving from hexane to methanol solutions. Theoretical calculations (by Huckel and PPP methods) are in broad agreement with the experimental findings.

Published evidence relating the rate of fading of a colorant to its physical state in the substrate, and to the photochemical layer effect, is discussed, and a new theoretical Model of light fading is proposed. In this the rate of oxygen diffusion from the atmosphere is considered, first in traversing the polymeric substrate, and then in entering an embedded colorant particle, under illumination. Expressions are derived which show that the rate of fading should vary with I/a 2 (a = radius of particle), for large particles. As the particles become smaller, the rate tends towards a 1/a dependence, and eventually, with very small particles, it is independent of their size. Recently reported rates of fading of pigments of measured particle size gave results in agreement with the present treatment; the smallest particles thus considered are of the same order of magnitude as those of high light fastness direct dyes in cellulose, as observed by electron microscopy. Thus the model may be applicable to at least some water‐soluble dyes as well as pigments.

J. Lafferty, E. J. Land and T. G. Truscott, J. Chem. Soc., Chem. Commun., 1976, 70 DOI: 10.1039/C39760000070

The triplet—triplet absorption spectra, quantum efficiencies of intersystem crossing, triplet extinction coefficients, and triplet energy levels of 1,6-diphenyl-1,3,5-hexatriene, and 1,8-diphenyl-1,3,5,7-octatetraene, in ethanol and benzene have been obtained. The quantum efficiencies of intersystems crossing are found to be less than 0.03 for both molecules in both solvents, indicating that the excited singlet is efficiently deactivated by internal conversion and flourescence emission. The triplet—triplet absorption spectra and the triplet energy level of 1,6-diphenyl-1,3,5,hexatriene are compared with previous results in other solvent systems.

Chemischer InformationsdienstVolume 7, Issue 40 Article ChemInform Abstract: TRIPLET EXCITED STATES OF 1,4-DISUBSTITUTED ANTHRAQUINONES- POSSIBLE EVIDENCE FOR ASSOCIATION OF QUINONES IN SOLUTION EDWARD J. LAND, EDWARD J. LANDSearch for more papers by this authorEOGHAN MCALPINE, EOGHAN MCALPINESearch for more papers by this authorROY S. SINCLAIR, ROY S. SINCLAIRSearch for more papers by this authorT. GEORGE TRUSCOTT, T. GEORGE TRUSCOTTSearch for more papers by this author EDWARD J. LAND, EDWARD J. LANDSearch for more papers by this authorEOGHAN MCALPINE, EOGHAN MCALPINESearch for more papers by this authorROY S. SINCLAIR, ROY S. SINCLAIRSearch for more papers by this authorT. GEORGE TRUSCOTT, T. GEORGE TRUSCOTTSearch for more papers by this author First published: October 5, 1976 https://doi.org/10.1002/chin.197640065Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume7, Issue40October 5, 1976 RelatedInformation

The visible spectra of a series of 1,4‐disubstituted aminoanthraquinone dyes dissolved in different solvents and polymer substrates have been measured. The position of the absorption maximum has been correlated with a weighted mean ionization potential of the substituent groups. Solvent shifts were found to be small but the dependence on polarity and hydrogen‐bonding ability was shown to act in opposite directions.A detailed examination of the characteristic double‐peak structure of the visible‐absorption band has shown that the splitting is due to vibrational effects. The variation in the absorbance ratio of the two peaks with substituent and solvent has been explained in terms of the relative disposition of the ground‐ and excited‐state potential‐ energy curves. The effect of concentration on the double‐peak ratio has been re‐examined and found to be negligible.

Eight non–ionic (disperse) dyes adsorbed in films of cellulose acetates, nylon and poly(ethylene terephthalate) (PET) have been faded by visible and near–ultraviolet radiation at temperatures in the range 15 to 100°C, and in atmospheres of relative humidities (r. h.) from zero to saturation. Fading is accelerated by rise in temperature, and, at r. h. above 5%, by rise in r. h. Activation energies of fading (Ef) (r. h. > 5%) range between about 3 and 18 kcal/mole, and depend on the nature of the substrate rather than on the structure of the dye. Values rise with increasing crystallinity of the polymer structure, except for PET which gives anomalously low values. The extent of dye–fibre interaction is at a minimum with PET and the rate–controlling step is a purely photochemical one. With the other substrates, the rate of fading is controlled by the dye–substrate interaction. The accelerating action of atmospheric humidity over normal ranges is partly due to its influence on the dye–substrate bonding and partly to its effect in swelling the substrate and thus increasing the diffusion coefficient of oxygen.