Showing papers on "Xanthene published in 1980"

Time-resolved fluorescence depolarization studies of rotational relaxation in viscous media

Abstract: Rotational relaxation times (τroi) were measured for xanthene dyes in several n-alcohols, ethylene glycol and glycerol by following the fluorescence depolarization using a single photon counting technique. Additional studies were made of the fluidity of the hydrocarbon micellar interior using pyrene derivatives as fluorescent probes. While the correlation between τroi and viscosity for the smaller n-alcohols is good, as anticipated by the models of Stokes—Einstein—Debye and later Perrin, a saturation in this correlation is observed in more viscous systems in accordance with recent molecular dynamics calculations. The influence of molecular structure on both viscosity and rotational relaxation times is also discussed. Pyrene, 1-pyrene suphonic acid and 1-pyrene butyeric acid exhibit rapid reorientation τroi ⪖ 10−9 s, in glycerol and micellar systems.

Long‐range triplet‐singlet energy transfer from enzyme generated triplet acetone to xanthene dyes

Abstract: — Enzyme-generated and protected acetone transfers its energy to xanthene dyes by a nontrivial process. The relative populations of the S1 state are indicative of the operation of a heavy atom effect, being 1:15:100 for fluorescein, eosine and Rose Bengal. On the other hand Stern-Volmer constants and kET0 values are similar for the three dyes and are remarkably higher than for collisional processes. It is tentatively suggested that at least for eosine and Rose Bengal, a triplet-triplet cxciton transfer may occur to populate an upper triplet state of the dye followed by heavy-atom enhanced intersystem crossing to the S1 state.

Novel xanthene compounds and photographic products and processes employing the same

Abstract: In one embodiment, the present invention is concerned with novel xanthene compounds of the formula ##STR1## wherein R' is alkyl; Y is an electron-withdrawing group and A is an anion. In another embodiment, the present invention is concerned with photographic products and processes employing these xanthene compounds.

3,6-Di(alkyl/phenyl)amino-9-carboxamidophenyl-xanthenes

Abstract: In one embodiment, the present invention is concerned with novel xanthene compounds of the formula ##STR1## wherein each R 1 the same or different is hydrogen or alkyl, each R 2 the same or different is alkyl or phenyl, R 3 is phenyl or alkyl, Y is an electron-withdrawing group and A is an anion. In another embodiment, the present invention is concerned with photographic products and processes employing these xanthene compounds.

3,6-Di(N-indolinyl)-9-sulfonamidophenyl-xanthenes

Abstract: In one embodiment, the present invention is concerned with novel xanthene compounds of the formula ##STR1## wherein X is ##STR2## wherein R' is alkyl; Y is an electron-withdrawing group and A is an anion. In another embodiment, the present invention is concerned with photographic products and processes employing these xanthene compounds.

Sulfo-substituted-3,6-di(N-indolinyl)-9-sulfonamidophenyl-xanthenes

Abstract: In one embodiment, the present invention is concerned with novel xanthene compounds of the formula ##STR1## wherein X is ##STR2## wherein R' is alkyl, Y is an electron-withdrawing group and n is 0 or 1. In another embodiment, the present invention is concerned with photographic products and processes employing these xanthene compounds.

Novel epoxy resin and production thereof

Abstract: PURPOSE:To obtain title epoxy resin having excellent heat resistance and useful as paint, etc., by reacting specified xanthene cpd. with epihalohydrin in the presence of an alkaline cpd. CONSTITUTION:A xanthene cpd. of formula I (wherein R1, R2 are H, 1-5C alkyl) such as 3, 6-dihydroxy-9, 9-dimethylxanthene is reacted with epihalohydrin of formula II (wherein R3 is H, CH3; X is halogen) such as epichlorohydrin or beta-methylepibromohydrin in an amt. of from 0.6-10mol per one hydroxyl gp. of the xanthene cpd. in the presence of an alkaline cpd. such as sodium hydroxide, sodium silicate at a temp. of from 20-120 deg.C to produce epoxy resin of formula III (wherein n>=0).

Xanthene dyes and photographic products and processes utilising them

Abstract: Novel dyes have the formula or the formula wherein each R 1 is the same or different and is alkyl; each R 2 is the same or different and is an electron-withdrawing group having a positive sigma value grater than 0.6; X is wherein R 3 is alkyl; Y is an electron-withdrawing group preferably having a positive sigma value greater than 0.6, n is 0 or 1 and A is an anion. They may be included in photographic products and used in photographic processes.

Cidnp study of quenching processes of excited xanthene dyes by aromatic amines

Abstract: Strong proton nuclear polarization is produced by the quenching of excited triplet state Rose Bengal molecules by aromatic amines. In secondary amines significant polarization (but no permanent chemical change) is observed in the ring ortho and para protons and in the N-alkyl α methylene (or methyl) protons. In this case the operation of a highly reversible hydrogen atom transfer quenching mechanism is indicated. Tertiary aromatic amines give polarized unstable intermediates for which the perpendicular aromatic ring structure is suggested.