Utilize este identificador para referenciar este registo: http://hdl.handle.net/10400.1/6555
Título: Surface photochemistry: diffuse reflectance studies of thioketones included into p-tert-butylcalix[6 and 8]arenes
Autor: Ferreira, Luís F. Vieira
Machado, I. Ferreira
Oliveira, A. S.
Silva, José P. da
Krawczyk, A.
Sikorski, M.
Palavras-chave: Surface photochemistry
SuThioketones
Calixarenes
Inclusion complexes
Diffuse reflectance
Room temperature phosphorescence
STime resolved luminescence
Laser flash photolysis
Photodegradation products
Data: 2007
Editora: Elsevier
Resumo: This paper presents time resolved laser induced luminescence (LIL) and diffuse reflectance laser flash-photolysis (DRLFP) studies of solid powdered samples of xanthione (XT) and 4H-1-benzopyran-4-thione (BPT). These thioketones form inclusion complexes with ptert-butylcalix[6]arene (CLX[6]) and p-tert-butylcalix[8]arene (CLX[8]). Room temperature air equilibrated LIL studies for XT/CLX[8] inclusion complex have shown the existence of both fluorescence and delayed fluorescence emission S-2 -> S-0 emissions in the nanosecond and microsecond time ranges, respectively) peaking at ca. 460 nm while phosphorescence peaks at about 670 nm with a half life of about 4 mu s. For the BPT/CLX[8] inclusion complex, the emissions now peak at ca. 450 and 630 nm, respectively. When these two thioketones are included into the CLX[6] nanocavities similar luminescence spectra were detected. The phosphorescence spectra in all cases present a clear vibrational structure characteristic of non-polar environments, in accordance with the non-polar character of the calixarene's cavities. Diffuse reflectance transient absorption spectra revealed in all cases the presence of the triplet state of the thioketones and also of longer lived species. The use of chromatographic methods (GC-MS) allowed us to identify the formation of xanthone, chromone and hydroxy-thio ketones following laser irradiation at 355 or 337 nm. (c) 2006 Elsevier B.V. All rights reserved.
Peer review: yes
URI: http://hdl.handle.net/10400.1/6555
DOI: https://dx.doi.org/10.1016/j.molstruc.2006.04.049
ISSN: 0022-2860
Aparece nas colecções:FCT2-Artigos (em revistas ou actas indexadas)



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