Showing papers on "Xanthene published in 1968"

Fluoran derivatives and preparation thereof

Abstract: COMPOUND OF THE FORMULA 3-(O=),3''-R'',6''-R-SPIRO(PHTHALAN-1,9''-XANTHENE) WHEREIN R IS ALICYCLIC AMINO, MORPHOLINO OR PIPERIDINO, AND R'' IS HYDROGEN, CHLORINE OR LOWER ALKYL ARE DISCLOSED. THESE COMPOUNDS MAY BE INCORPORATED WITHIN COLOR COATING COMPOSITIONS.

Comparision of Photosensitizing Ability of Dyes in Oxidation of Histidine

Abstract: Various dyes were tested in order to compare photosensitizing ability based on relative quantum yield for photosensitized oxidation of histidine. Each dye belongs to such a class as thiazine, xanthene, acridine, thiazole, phenylmethane, monoazo, azine, oxazine, porphylline and flavin. The heterocyclic structure was essential to the development of photosensitizing ability, but this ability was remarkably influenced by introduction of substituents on aromatic rings. Fluorescence was not always accompanied with photosensitization.Except for fluoresceine, each dye had a common feature as to pH dependence of photosensitized oxidation of histidine, and this reaction was dependent on electrical charge of imidazole group of histidine. Each dye also showed a common behaviour on Line-weaver-Burk’s plots. Using various dyes, the photosensitized oxidation of histidine was compared with that of tryptophan, and it was found that the ratio of raction rates of both amino acids was varied with the kinds of dye. For exampl...

Studies on Triplet-Singlet Energy Transfer in the System Benzophenone—Xanthene Dye

Abstract: The transfer of electronic energy from triplet donors benzophenones to different xanthene dyes as acceptors is studied in rigid glassy solution. The acceptors are excited to their fluorescing states and the delayed emission of both donors and acceptors is measured with a calibrated phosphoroscope. Increasing halogenisation of the dyes enhances the rate of this “forbidden” triplet-singlet transfer.

Study of the structure of associates of xanthene and triphenyl-methane dyes from their vibrational and electronic spectra

Abstract: In p reced ing papers it was shown that dye molecules a re associa ted in solut ions by hydrogen bonds, the product ion of which is revea led in their in f ra red spect r a [1, 2]. The change in the i r e lec t ron ic spect ra , observed on aggregat ion of the dyes, is due, however, to an in tens i f ica t ion of the in te rac t ion between their molecu les in the excited s tate [3]. The magnitude of this in te rac t ion should depend on the mutual a r r a n g e ment of the dye molecules in the associa te [4]. At the same t ime, the p rob lem of the s t ruc tu re of the a s so c ia tes has been insuff ic ient ly d i scussed in the l i t e r a ture; moreover , the authors of those papers which have been published have not taken into account the poss ib i l i ty that the dye molecules are l inked by hydrogen bonds (see, for example, [5]). In the p r e se n t work, we analyzed a la rge amount of exper imenta l ma te r i a l on the cha rac t e r i s t i c fea tures of the assoc ia t ion of molecules of dyes of thexanthene and t r ipheny lmethane s e r i e s to de te rmine the s t ruc tu r e s of the i r assoc ia tes and i ts influence on the v ibra t ional and e lec t ron ic absorpt ion spectra . It is na tura l to begin the study of the s t ruc tu re of the assoc ia tes by es tab l i sh ing the acceptor of the p ro ton of the N----H group of the dye molecules taking par t in hydrogen bond format ion. The degree of a s soc ia tion of rhodamine 6G in b inary mix tures of polar and nonpolar solvents depends to a marked extent on the na ture of the anion [6]. This means that the species combining in the assoc ia tes a re not dye cat ions, but ion pa i r s . Study of the v ibra t iona l spec t ra of rhodamine 6G containing var ious anions has shown that the re la t ive shift and re la t ive in tens i ty of the band, which is a t t r ibuted to the eombinedN----H v ibra t ions with respec t to the band which is a t t r ibuted to f ree N---H v ibra t ions , also depend to a marked extent on the na ture of the anion [7]. This conf i rms the conclusion that the assoc ia t ion of the dyes involves the in te rac t ion of their ion pa i r s and indicates the active role of the anion in the fo r mat ion of dye assoc ia tes . The marked dependence of the in f r a red absorpt ion band on the na ture of the anion suggests that the par t of proton acceptor in the f o r m a t i o n of a hydrogen bond between the ion pa i r s may be played by the anion, which is l inked chiefly by e lec t ro s ta t ic forces to another cation according to the scheme