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Papers by Osvaldo Rodriguez
Photochemistry and Photobiology, 1978
Abstract— The ternary chemiluminescent system consisting of tetramethyl-dioxetane (TMD), 9,10-dib... more Abstract— The ternary chemiluminescent system consisting of tetramethyl-dioxetane (TMD), 9,10-dibromoanthracene (DBA) and rubrene (Ru) has been investigated in benzene solution and in polystyrene matrices. DBA has been found to mediate the energy transfer between excited triplet acetone (3K), generated from TMD, and rubrene resulting in the enhancement of the Ru emission and reduction in the DBA emission. A detailed kinetic analysis confirms that ca. 50% of the enhanced chemilumines-cence involves triplet-singlet (TS) energy transfer from 3K to DBA, followed by singlet-singlet (SS) energy transfer from DBA to Ru, the remainder ca. 50% being due to reabsorption of DBA fluorescence by rubrene. It is concluded that the TS energy transfer is of the resonance type, occurring with a rate of kTSK.DBA= (1.4 ± 0.4) ± 109M-1s-1 and an efficiency of øTSK.DBA= 0.3 ± 0.1. As expected, the SS energy transfer is also of the resonance type, taking place at comparable rates in benzene solution and in polystyrene matrices, is. kSSDBARU= 1.5 ± 1010 M-1 and (2.2 ± 0.2) ± 1010M-1s-1, respectively.
Photochemistry and Photobiology, 1977
Abstract. –In acidified acetonitrile, ergostatetraenone (E) efficiently quenches the tetramethyl-... more Abstract. –In acidified acetonitrile, ergostatetraenone (E) efficiently quenches the tetramethyl-1,2-dioxetane (TMD) chemiluminescence at 410 nm, with the appearance of a new chemiluminescence at ca. 530 nm due to ergostatetraenone fluorescence. Control experiments exclude energization by triplet acetone and the trivial process (emission and reabsorption), establishing singlet-singlet energy transfer between excited singlet acetone (A) and ground state ergostatetraenone as major pathway. From the kinetics the rate constant for singlet-singlet energy transfer (KssA,1,) was estimated to be ca. 101 2S-1. The chemiluminescence yield (φCL) for the TMD/ergostatetraenone system was determined to be ca. 12 × 10-8. The fluorescence efficiency of ergostatetraenone (φ) in acidified acetonitrile is a function of acid concentration, ranging between 0.06-0.82. The efficiency of singlet acetone production (α) was found to be 500-fold lower than in neutral medium due to a competing acid-catalysed, dark decomposition of TMD. A 60-fold light enhancement has been established for this binary chemiluminescent system.
Journal of Organic Chemistry, 1978
- Skeletal rearrangement of the molecular ion with loss of S, SH, and 25 does not become appare... more 19) Skeletal rearrangement of the molecular ion with loss of S, SH, and 25 does not become apparent even in allyl alkyl disulfides 4,7, 11, and 15 in contrast with previous reports." (20) Instability of the [RSSH]+. fragment (I) upon electron impact cannot account for the low intensities observed as shown by comparison of 2-propyl ethyl disulfide (5) and 2-butyl 2-propyl disulfide in which peaks d e 108 [(CH&CH-SSH]+. show 1 and 57 % relative intensities, respectively. (21) This inability to decompose by a pathway other than bond disconnection might explain the high relative abundance of m/e 80 [CH&SH]+. in the spectra of methyl alkyl disulfides studied. (22) These disulfides contain the allyl moiety in which the availability of rr protons may be spurred by their being sandwiched between the sulfur atom and the vinyl group. (23) H. E. Wijers, H. Boelens, A. van der Gen, and L. Brandsma, Recl. rrav. Chim. Pays-Bas, 88, 519 (1969). (24) R. D. Baechler, J. P. Hummel. and K. Mislow, J. Am. Chem. SOC., 95, 4442 (1973): R. D. Baechler. S. K. Dalev. and K. McGlynn, Tetrahedron Lett., 105 (1978). (25) One referee pointed out that the comparison of R'SSH/M+ intensity ratios of compound 2 with that of 5 seems in opposition to this argument. This fact may be explained, however, by assuming that 1,4-H transfer (y-hydrogen migration) is less favored than 1,3-H transfer (@hydrogen migration). Therefore, the presence of only one 6 H plus six y H in 2 should impart a decreased tendency toward H migration in this compound as compared to the six /? H in 5. A similar situation is found for compounds 4 and 7. . (34) Rathke's labeling procedure allows for a maximum of 75% deuteration of ethyl isobutyrate (see ref 35)
Vivíamos en Estiria, en un castillo. No es que nuestra fortuna fuera principesca, pero en aquel r... more Vivíamos en Estiria, en un castillo. No es que nuestra fortuna fuera principesca, pero en aquel rincón del mundo era suficiente una pequeña renta anual para poder llevar una vida de gran señor. En cambio, en nuestro país y con nuestros recursos sólo habríamos podido llevar una existencia acomodada. Mi padre es inglés y yo, naturalmente, tengo un apellido inglés, pero nunca he visto Inglaterra.
Photochemistry and Photobiology, 1978
Abstract— The ternary chemiluminescent system consisting of tetramethyl-dioxetane (TMD), 9,10-dib... more Abstract— The ternary chemiluminescent system consisting of tetramethyl-dioxetane (TMD), 9,10-dibromoanthracene (DBA) and rubrene (Ru) has been investigated in benzene solution and in polystyrene matrices. DBA has been found to mediate the energy transfer between excited triplet acetone (3K), generated from TMD, and rubrene resulting in the enhancement of the Ru emission and reduction in the DBA emission. A detailed kinetic analysis confirms that ca. 50% of the enhanced chemilumines-cence involves triplet-singlet (TS) energy transfer from 3K to DBA, followed by singlet-singlet (SS) energy transfer from DBA to Ru, the remainder ca. 50% being due to reabsorption of DBA fluorescence by rubrene. It is concluded that the TS energy transfer is of the resonance type, occurring with a rate of kTSK.DBA= (1.4 ± 0.4) ± 109M-1s-1 and an efficiency of øTSK.DBA= 0.3 ± 0.1. As expected, the SS energy transfer is also of the resonance type, taking place at comparable rates in benzene solution and in polystyrene matrices, is. kSSDBARU= 1.5 ± 1010 M-1 and (2.2 ± 0.2) ± 1010M-1s-1, respectively.
Photochemistry and Photobiology, 1977
Abstract. –In acidified acetonitrile, ergostatetraenone (E) efficiently quenches the tetramethyl-... more Abstract. –In acidified acetonitrile, ergostatetraenone (E) efficiently quenches the tetramethyl-1,2-dioxetane (TMD) chemiluminescence at 410 nm, with the appearance of a new chemiluminescence at ca. 530 nm due to ergostatetraenone fluorescence. Control experiments exclude energization by triplet acetone and the trivial process (emission and reabsorption), establishing singlet-singlet energy transfer between excited singlet acetone (A) and ground state ergostatetraenone as major pathway. From the kinetics the rate constant for singlet-singlet energy transfer (KssA,1,) was estimated to be ca. 101 2S-1. The chemiluminescence yield (φCL) for the TMD/ergostatetraenone system was determined to be ca. 12 × 10-8. The fluorescence efficiency of ergostatetraenone (φ) in acidified acetonitrile is a function of acid concentration, ranging between 0.06-0.82. The efficiency of singlet acetone production (α) was found to be 500-fold lower than in neutral medium due to a competing acid-catalysed, dark decomposition of TMD. A 60-fold light enhancement has been established for this binary chemiluminescent system.
Journal of Organic Chemistry, 1978
- Skeletal rearrangement of the molecular ion with loss of S, SH, and 25 does not become appare... more 19) Skeletal rearrangement of the molecular ion with loss of S, SH, and 25 does not become apparent even in allyl alkyl disulfides 4,7, 11, and 15 in contrast with previous reports." (20) Instability of the [RSSH]+. fragment (I) upon electron impact cannot account for the low intensities observed as shown by comparison of 2-propyl ethyl disulfide (5) and 2-butyl 2-propyl disulfide in which peaks d e 108 [(CH&CH-SSH]+. show 1 and 57 % relative intensities, respectively. (21) This inability to decompose by a pathway other than bond disconnection might explain the high relative abundance of m/e 80 [CH&SH]+. in the spectra of methyl alkyl disulfides studied. (22) These disulfides contain the allyl moiety in which the availability of rr protons may be spurred by their being sandwiched between the sulfur atom and the vinyl group. (23) H. E. Wijers, H. Boelens, A. van der Gen, and L. Brandsma, Recl. rrav. Chim. Pays-Bas, 88, 519 (1969). (24) R. D. Baechler, J. P. Hummel. and K. Mislow, J. Am. Chem. SOC., 95, 4442 (1973): R. D. Baechler. S. K. Dalev. and K. McGlynn, Tetrahedron Lett., 105 (1978). (25) One referee pointed out that the comparison of R'SSH/M+ intensity ratios of compound 2 with that of 5 seems in opposition to this argument. This fact may be explained, however, by assuming that 1,4-H transfer (y-hydrogen migration) is less favored than 1,3-H transfer (@hydrogen migration). Therefore, the presence of only one 6 H plus six y H in 2 should impart a decreased tendency toward H migration in this compound as compared to the six /? H in 5. A similar situation is found for compounds 4 and 7. . (34) Rathke's labeling procedure allows for a maximum of 75% deuteration of ethyl isobutyrate (see ref 35)
Vivíamos en Estiria, en un castillo. No es que nuestra fortuna fuera principesca, pero en aquel r... more Vivíamos en Estiria, en un castillo. No es que nuestra fortuna fuera principesca, pero en aquel rincón del mundo era suficiente una pequeña renta anual para poder llevar una vida de gran señor. En cambio, en nuestro país y con nuestros recursos sólo habríamos podido llevar una existencia acomodada. Mi padre es inglés y yo, naturalmente, tengo un apellido inglés, pero nunca he visto Inglaterra.