Estudo da reatividade do estado excitado triplete de 1,4-diaza-9-fluorenonas frente a doadores de hidrogênio e de elétron

• Autor(a) principal: Takaizumi,Andreza A. C.
• Data de Publicação: 2009
• Outros Autores: Santos,Frances R. dos, Silva,Mônica T. da, Netto-Ferreira,José Carlos
• Tipo de documento: Artigo
• Idioma: por
• Título da fonte: Química Nova (Online)
• Texto Completo: http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0100-40422009000700022
• topic: fluorenones; laser flash photolysis; triplet excited state

The effect of the introduction of nitrogen atoms upon the triplet excited state reactivity of 1,4-diaza-9-fluorenone (1) and 1,4-diaza-9-benz[b]fluorenone (2), in acetonitrile, was investigated employing the nanosecond laser flash photolysis technique. The intersystem crossing quantum yield (Φces) for 1 and 2 was determined using 9-fluorenone as a secondary standard (Φces= 0.48, in acetonitrile) and for both diazafluorenones a value of Φces= 0.28 was found. Quenching rate constants ranged from 8.17x10(4) L mol-1 s-1 (2-propanol) to 1.02x10(10) L mol-1 s-1 (DABCO) for 1,4-diaza-9-fluorenone and from 6.95x10(5) L mol-1 s-1 (2-propanol) to 5.94x10(9) L mol-1 s-1 (DABCO) for 1,4-diaza-9-benz[b]fluorenone, depending if the quenching process involves energy, hydrogen or electron transfer. A comparison between quenching rate constants for both diazaflurenones and the parent compound, i.e. 9-fluorenone, a ketone with lowest triple state of ππ* configuration, lead to the conclusion that the reactive triplet excited state for 1,4-diaza-9-fluorenone and 1,4-diaza-9-benz[b]fluorenone has ππ* configuration.