Xanthene

About: Xanthene is a research topic. Over the lifetime, 2132 publications have been published within this topic receiving 34803 citations. The topic is also known as: Xanthene & dibenzo[a,e]pyran.

Photobleaching of xanthene dyes in a poly(vinyl alcohol) matrix

Abstract: Photobleaching of three different xanthene dyes namely, Erythrosin B (ERB), Eosin Y (EOY) and Rose Bengal (ROB) in Poly(Vinyl Alcohol) (PVA) matrix has been studied. Quantum yield values of photobleaching using an argon-ion laser (514.5 nm) were determined in presence of an electron donor (TriEthAnolamine, TEA) and/or Cr(VI). Evaluated quantum yield values suggest that erythrosin B undergoes faster photobleaching than eosin Y or rose bengal in presence of TEA. Presence of Cr(VI) in addition to TEA drastically decreases the quantum yield. Possible reaction pathways of photobleaching are discussed.

Fluorescent water base ink for ink-jet recording

Abstract: A fluorescent water base ink for ink-jet recording contains a fluorescent dye having a xanthene skeleton, and a glycol. In the fluorescent dye, the difference in hydrophilic index log P is not less than 2.6 between a substituent bonded to C-9 carbon atom of the xanthene skeleton and other portion of the fluorescent dye than the substituent bonded to the C-9 carbon atom. The glycol has a distance between hydroxyl groups substantially equivalent to or longer than an interatomic distance between atoms directly bonded to C-3 and C-6 carbon atoms of the xanthene skeleton of the fluorescent dye, respectively. It is assumed that the glycol is coordinated with the xanthene skeleton in a bridge form to increase the fluorescence intensity by increasing the electron density of the xanthene skeleton. The ink having high fluorescence intensity and in which the fluorescence intensity is not lowered in a time-dependent manner is provided.

Cobalt(II)–Salen Complexes for Photocatalytic Hydrogen Production in Noble Metal-Free Molecular Systems

Abstract: Developing cost-effective hydrogen-production systems is always appealing in order to satisfy the future energy request. Here, two Co(II)–salen complexes 1 and 2 were firstly introduced into homogeneous photocatalytic hydrogen-evolution systems. Based on these two cobalt complexes, we developed noble-metal-free hydrogen production systems using xanthene dyes [such as Disodium salts of Eosin Y (EY2−), Rose Bengal (RB2−) and Fluorescein (Fl2−)] as photosensitizers and trimethylamine (TEA) as sacrificial donor. Complex 1 presented the best catalytic performance for hydrogen production with a TON of 319 based on catalyst within 9 h irradiation, which is superior to other cobalt complexes in noble-metal-free systems. UV–Vis spectra studies demonstrate that EY2− suffered quick decomposition, especially under the presence of complex 1, which should be responsible for hydrogen-production deactivation. The thermodynamically favorable photo-induced electron transfer from 3*EY2− to complex 1 was supported by investigations involving fluorescence quenching and cyclic voltammetry studies. However, the immediate color change (within seconds) as the hydrogen production systems exposed under the irradiation indicates that EY2− firstly suffered dehalogenation which functions as the real active dyes.

Microwave-assisted clean synthesis of xanthenes and chromenes in [bmim][PF6] and their antioxidant studies

Abstract: An efficient one-pot synthesis of xanthene and chromene derivatives by three-component reactions of aryl aldehydes, cyclic 1,3-diketones, and 2-naphthol/4-hydroxy coumarin catalyzed by ionic liquid (IL) [bmim][PF6] under microwave irradiation is described. The present scheme provides several advantages such as short reaction time, mild reaction conditions, good yields, convenient operation, and reuse of IL. In vitro antioxidant activity was evaluated for the synthesized compounds by DPPH method. Compounds 6a, 6h, 6c, 6b, 4k, and 4a showed the highest antioxidant potency.