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.

Photocurrents in the ZnO and TiO2 Photoelectrochemical Cells Sensitized by Xanthene Dyes and Tetraphenylporphines. Effect of Substitution on the Electron Injection Processes

Abstract: The photocurrents in zinc oxide and titanium dioxide electrodes sensitized by anionic xanthene dyes (Eosine Y, Phloxine B, Erythrosine, and Rose Bengal) and metal tetraphenylporphines were studied in aqueous solutions. The quantum efficiencies of the photocurrents sensitized by anionic xanthene dyes were unaffected by substitution of the dye with various halogen atoms, while those sensitized by the tetraphenylporphines were affected by changing the central metal. It is concluded from these results that the electron injection from the excited xanthene dyes to the semiconductor electrodes is a process so rapid (<<0.1 ns) that no internal quenching processes can compete with it, while that from the tetraphynelporphines is relatively slow competing with the internal deactivation processes. It is also concluded that the electron back transfer from the semiconductor conduction band to the oxdized dye decreases the sensitization efficiency.

Synthesis and conjugate additions of 2,3,4,9-tetrahydro-1h-xanthene-1,9-diones

Abstract: An efficient two step procedure for the synthesis of 2,3,4,9-tetrahydro-1H-xanthene-1,9-diones is described. A study of their conjugate additions has shown them to be efficient Michael acceptors. Reaction of 2,3,4,9-tetrahydro-1H-xanthene-1,9-dione with tris(methylthio)methyllithium, followed by mercury(II) catalysed methanolysis, gave methyl 1-hydroxy-9-oxo-3,4,4a,9-tetrahydro-2H-xanthene-4a-carboxylate, the nucleus of the secalonic acids and other natural products

Precise Control of Thermal and Redox Properties of Organic Hole-Transport Materials

Abstract: We report design principles of the thermal and redox properties of synthetically accessible spiro-based hole transport materials (HTMs) and show the relevance of these findings to high-performance perovskite solar cells (PSCs). The chemical modification of an asymmetric spiro[fluorene-9,9'-xanthene] core is amenable to selective placement of redox active triphenylamine (TPA) units. We therefore leveraged computational techniques to investigate five HTMs bearing TPA groups judiciously positioned about this asymmetric spiro core. It was determined that TPA groups positioned about the conjugated fluorene moiety increase the free energy change for hole-extraction from the perovskite layer, while TPAs about the xanthene unit govern the Tg values. The synergistic effects of these characteristics resulted in an HTM characterized by both a low reduction potential (≈0.7 V vs. NHE) and a high Tg value (>125 °C) to yield a device power conversion efficiency (PCE) of 20.8 % in a PSC.

Radical reactivity of aza[60]fullerene: preparation of monoadducts and limitations.

Abstract: Six aza[60]fullerene monoadducts were synthesized by the thermal reaction between the azafullerene radical C59N• and 9-alkyl-substituted fluorenes, 9,10-dihydroanthracene, or xanthene. Unlike fluorenes, dihydroanthracene, and xanthene, the structurally related substituted diphenylmethanes, ethylbenzene, cumene, 1,2-diphenylethane, 5,6,11,12-tetrahydrodibenzo[a,e]cyclooctene, 10,11-dihydro-5H-dibenzo[a,d]cycloheptene, 9-methylanthracene, and 9-benzylanthracene do not lead to the isolation of azafullerene monoadducts. Moreover, 1,2-dichlorobenzene, the most commonly utilized solvent for azafullerene reactions, reacts slowly with the azafullerenyl radical C59N• affording the corresponding aza[60]fullerene monoadduct.