Triplet Excited States and Singlet Oxygen Production by Analogs of Red Wine Pyranoanthocyanins

Autor(es)

Silva, Gustavo Thalmer M. ^[1] ; Thomas, Suma S. ^{[2, 3]} ; Silva, Cassio Pacheco ^[1] ; Schlothauer, Jan C. ^[4] ; Baptista, Mauricio S. ^[4] ; Freitas, Adilson A. ^[5] ; Bohne, Cornelia ^{[2, 3]} ; Quina, Frank H. ^[1]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Inst Quim, Dept Fundamental Chem, Sao Paulo - Brazil

^[2] Univ Victoria, Dept Chem, Victoria, BC - Canada

^[3] Univ Victoria, Ctr Adv Mat & Related Technol CAMTEC, Victoria, BC - Canada

^[4] Univ Sao Paulo, Inst Quim, Dept Biochem, Sao Paulo - Brazil

^[5] Univ Lisbon, Inst Super Tecn, Ctr Quim Estrutural, Lisbon - Portugal

• Tipo de documento: Artigo Científico
• Fonte: Photochemistry and Photobiology; v. 95, n. 1, p. 176-182, JAN 2019.
• Citações Web of Science: 2

Resumo

During the maturation of red wines, the anthocyanins of grapes are transformed into pyranoanthocyanins, which possess a pyranoflavylium cation as their basic chromophore. Photophysical properties of the singlet and triplet excited states of a series of synthetic pyranoflavylium cations were determined at room temperature in acetonitrile solution acidified with 0.10 mol dm(-3) trifluoroacetic acid (TFA, to inhibit competitive excited state proton transfer) and at 77 K in a rigid TFA-acidified isopropanol glass. In solution, the triplet states of these pyranoflavylium cations are efficiently quenched by molecular oxygen, resulting in sensitized formation of singlet oxygen, as confirmed by direct detection of the triplet-state decay by laser flash photolysis and of singlet oxygen monomol emission in the near infrared. The strong visible light absorption, the relatively small singlet-triplet energy differences, the excited state redox potentials and the reasonably long lifetimes of pyranoflavylium triplet states in the absence of molecular oxygen suggest that they might be useful as triplet sensitizers and/or as cationic redox initiators in polar aprotic solvents like acetonitrile. (AU)

• Processo FAPESP: 16/13433-0 - Espectroscopia do desbalanço redox induzidos por radiação UVA e visível em fibroblastos XPC e em melanócitos
• Beneficiário: Jan Caspar Schlothauer
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado
• Processo FAPESP: 13/07937-8 - Redoxoma
• Beneficiário: Ohara Augusto
• Modalidade de apoio: Auxílio à Pesquisa - Centros de Pesquisa, Inovação e Difusão - CEPIDs