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Doctoral Thesis
DOI
10.11606/T.46.1976.tde-29042014-100000
Document
Author
Full name
Maria Eunice Ribeiro Marcondes
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 1976
Supervisor
Title in Portuguese
Mecanismo de supressão da fluorescência de antraceno e derivados por N,N-dimetilanilina, trifenilfosfina e tris-(pentafluorofenil)-fosfina
Keywords in Portuguese
Antraceno e derivados
Compostos aromáticos
Exciplex
Físico-química
Fluorescência
Fotoquímica
Supressão
Abstract in Portuguese
Foram medidas as constantes de velocidade, Kq, para a supressão da fluorescência de antraceno e dez dos seus derivados (substituídos nas posições 9- ou 9,10-) por N,N-dimetilanilina, trifenilfosfina e tris-(pentafluorofenil)-fosfina. Para os dois primeiros supressores, Kq foi relacionada com os potenciais de redução e energias singlete dos antracenos, de acordo com os tratamentos de Weller, Evans e Hammond. A supressão dos antracenos deficientes de eletrons é mais eficiente que a dos derivados ricos em eletrons e ocorre por transferência de carga para ambos os supressores. A supressão dos antracenos ricos em eletrons ocorre por um processo que parece depender da natureza do supressor e do solvente. Embora a transferência de carga possa ser um fator contribuinte na formação desses exciplexes, outras interações, como a ressonância de excitação, podem ser ainda mais importantes. Para supressão por tris-(pentafluorofenil)-fosfina, kq foi relacionada com os potenciais de oxidação e as energias singlete dos antracenos e foram desenvolvidos os mesmos tratamentos. Foi verificado que ocorre uma inversão na direção da transferência de carga e os antracenos ricos em eletrons são mais eficientemente suprimidos. Excetuando-se antraceno e seus derivados metílicos, que mostram um comportamento característico, a supressao dos demais antracenos parece ocorrer por um único mecanismo, onde as interações de transferência de carga são predominantes. Emissões dos exciplexes, deslocadas para o vermelho, só foram observadas com dimetilanilina como supressor. A supressão dos antracenos pelas fosfinas parece envolver a formação de exciplexes não emissivos.
Title in English
Fluorescence quenching of antracene and derivatives by N,N dimethylanyline, triphenylphosphine and tris-(pentafluorophenyl)-phosphine
Keywords in English
Antracene and derivatives
Aromatic compoundsPhotochemistry
Exciplex
Fluorescence
Physico-chemical
Singlets
Abstract in English
N,N-Dimethylaniline, triphenylphosphine and tris-(pentafluorophenyl)-phosphine were employed as quenchers of the fluorescence of anthracene and ten of its derivatives substituted in the 9- or 9,10-positions. The quenching rate constants, kq, for the first two quenchers were correlated with reduction potentials and singlet excitation energies of the anthracenes according to the treatments of Weller, Evans and Hammond. The singlets of the electron-poor anthracenes were quenched more efficiently than those of electron-rich anthracenes by both of quenchers in a process which is found to occur by a charge-transfer mechanism. Singlets of the electron-rich anthracenes are quenched in processes wich appear to depend on the nature of the quencher and the solvent. Although charge-transfer is probably a contributing factor in this case, other interactions such as excitation resonance may be of greater importance. The rate constants for the quenching by tris-(pentafluorophenyl)-phosphine were correlated with oxidation potentials and singlet excitation energies of the anthracenes using the three treatments mentioned above. An inversion in the direction of charge transfer was noted, with the electron-rich anthracenes being quenched more efficiently than the-electron-poor ones. Although antharacene and its methyl derivatives exhibited unique behavior, both electron-rich and electron-poor anthracenes appear to be quenched by the same mechanism, with charge transfer being the most important interaction. Red-shifted exciplex emissions were observed only with N,N-dimethylaniline as quencher. The quenching by the phosphines is thought to occur via the formation of non-emissive exciplexes.
 
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Publishing Date
2014-04-30
 
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