Fotoquímica de ß-Carbolinas en soluciones orgánicas diluidas = Photochemistry of ß-carbolines in diluted organic solutions

Institución otorgante:

Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales

Fecha:

1996

Tipo de documento: 

info:eu-repo/semantics/doctoralThesis
 

Formato:

application/pdf

Idioma:

spa

Temas:

SS-CARBOLINAS - FOTOQUIMICA DE SS-CARBOLINAS - SS-CARBOLINAS-TETRACLORURO DE CARBONO - EQUILIBRIO ACIDO-BASE DE SS-CARBOLINAS - ESPECTROS ELECTRONICOS DE SS-CARBOLINAS - SS-CARBOLINES - SS-CARBOLINES-PHOTOCHEMISTRY - SS-CARBOLINES-CARBON-TETRACHLORIDE - SS-CARBOLINES-ACID-BASE EQUILIBRIUM - SS-CARBOLINES-ELECTRONIC SPECTRA

Descripción:

In this work the photochemical behavior of full aromatic b-carbolines (nor-harmane, harmane, harmine and harmol) and two 3,4-dihydro b-carbolines (harmaline and harmalol) was studied. For the first time the UV absorption, emission and excitation spectra in organic solutions were described as well as on solid supports (silica gel, paper) and on powdered sample. The K of the complexation equilibrium between the full aromatic b-carbolines with alcohols forming a 1:2 adducts were measured and the pKa and pKa* in acetonitrile were determined by means of electronic absorption and fluorescence spectroscopy. Considering that these compounds are markedly fluorescent their behavior in the presence of CCl4 and other halomethanes (CH2Cl2, CHCl3, CH2BrCH2Br, CHBr3 and CBr4) which act as quenchers using either EtOH, iso-PrOH or MeCN as solvents was studied. We concluded that this quenching is dynamic and may take place through the formation of an exciplex followed by an electron transfer from the excited b-carboline to the halogenated compound starting the photochemical reaction. When a solution of either of these alkaloids (10-3 M) was irradiated in the presence of CCl4 in a protic organic solvent, the main product obtained, with more than 98% yield, was the hydrochloride. Besides, the gc-MS analysis showed traces of carboalcoxy and chloro-derivatives.%The feasibility of an exciton or a photon single electron transfer mechanism is discussed and parameters such as DGote, Ksv, kq, DG‡, DG‡(0), l, and E0ox were calculated using the Rehm-Weller, Marcus and Stern-Volmer models.%The quantum yield of photobleaching in different solvents was determined relative to the disappearance of harmane in EtOH-CCl4, which in turn was determined using potassium ferrioxalate as actinometer.

Identificador:

https://hdl.handle.net/20.500.12110/tesis_n2831_Biondic