Fluorescence quenching of pyrene monomer and excimer by CH3I |
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| Institution: | 1. Centro de Quı́mica-Fı́sica Molecular, Instituto Superior Técnico, Complexo I Av. Rovisco Pais, 1, 1049-001 Lisboa, Portugal;2. Faculdade de Farmácia da U.L., Av. das Forças Armadas, 1600 Lisboa, Portugal;1. Jagiellonian University, Faculty of Chemistry, Ingardena 3, 30-060 Kraków, Poland;2. Jerzy Haber Institute of Catalysis and Surface Chemistry, PAS, Niezapominajek 8, 30-239 Kraków, Poland;1. Gerencia Química, Centro Atómico Constituyentes, Comisión Nacional de Energía Atómica, Av. Gral Paz 1499 (B1650KNA) San Martín, Buenos Aires, Argentina;2. Departamento de Química Inorgánica, Analítica y Química Física and INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón II, C1428EHA Buenos Aires, Argentina;3. Instituto de Nanosistemas, Universidad Nacional de General San Martín, 25 de Mayo y Francia (1650) San Martín, Buenos Aires, Argentina |
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| Abstract: | The fluorescence quenching rate constants of pyrene monomer and excimer by CH3I were obtained at several temperatures in methylcyclohexane. Both quenching processes are kinetically controlled, allowing insight on the mechanism of quenching. The rate constants have both temperature-independent and temperature-dependent components. The temperature-independent component for both monomer and excimer fluorescence is consistent with quenching due to enhanced intersystem crossing to a lower energy triplet state. The monomer temperature-dependent component comes from the enhancement of the intersystem crossing to a higher energy triplet state. The thermally activated excimer quenching is associated with the excimer dissociation step to give a pyrene in a second triplet state plus a ground state pyrene molecule. |
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