TY  - JOUR
  - Eisenberger, H.,Nickel*, B.,Ruth, A. A.,Alsoufi, W.,Grellmann, K. H.,Novo, M.
  - 1991
  - December
  - Journal of Physical Chemistry
  - Keto-Enol Tautomerization of 2-(2'-Hydroxyphenyl)Benzoxazole and 2-(2'-Hydroxy-4'-Methylphenyl)Benzoxazole in the Triplet-State - Hydrogen Tunneling and Isotope Effects .2. Dual Phosphorescence Kinetics
  - Validated
  - ()
  - 95
  - 25
  - 10509
  - 10518
  - In the metastable triplet state of 2-(2'-hydroxyphenyl)benzoxazole (HBO) and its deuteriooxy analogue (DBO), the keto tautomer (K) and the enol tautomer (E) have about the same energy, and a dual phosphorescence, 3K* --> 1K and 'E* --> 1E, can be observed. From the initial time dependence of the dual phosphorescence from DBO the effective rate constant theta-1 almost-equal-to k(KE) + k(EK) of the keto-enol equilibration 3K* half arrow right over half arrow left 3E* has been determined. 3E* of DBO is almost exclusively populated from 3K*. In the dual phosphorescence from DBO the relative intensity of the keto band is smaller than in the dual phosphorescence from HBO; this is attributed to a small isotope effect on the keto-enol equilibrium in the triplet state. In the metastable triplet state of 2-(2'-hydroxy-4'-methylphenyl)benzoxazole (m-MeHBO) and its deuteriooxy analogue (m-MeDBO) the keto-enol equilibrium is strongly shifted to the side of the enol. No keto phosphorescence from m-MeHBO is observed. Due to the slower keto-enol equilibration in m-MeDBO, an initial keto phosphorescence from m-MeDBO can be observed. The values of theta-1 obtained from the time dependence of the phosphorescence of DBO and m-MeDBO agree reasonably well with the values obtained from transient-absorption experiments. The rate constants for the nonradiative decays of 3K* and 3E* to the electronic ground state are strongly decreased by deuteration.In the metastable triplet state of 2-(2'-hydroxyphenyl)benzoxazole (HBO) and its deuteriooxy analogue (DBO), the keto tautomer (K) and the enol tautomer (E) have about the same energy, and a dual phosphorescence, 3K* --> 1K and 'E* --> 1E, can be observed. From the initial time dependence of the dual phosphorescence from DBO the effective rate constant theta-1 almost-equal-to k(KE) + k(EK) of the keto-enol equilibration 3K* half arrow right over half arrow left 3E* has been determined. 3E* of DBO is almost exclusively populated from 3K*. In the dual phosphorescence from DBO the relative intensity of the keto band is smaller than in the dual phosphorescence from HBO; this is attributed to a small isotope effect on the keto-enol equilibrium in the triplet state. In the metastable triplet state of 2-(2'-hydroxy-4'-methylphenyl)benzoxazole (m-MeHBO) and its deuteriooxy analogue (m-MeDBO) the keto-enol equilibrium is strongly shifted to the side of the enol. No keto phosphorescence from m-MeHBO is observed. Due to the slower keto-enol equilibration in m-MeDBO, an initial keto phosphorescence from m-MeDBO can be observed. The values of theta-1 obtained from the time dependence of the phosphorescence of DBO and m-MeDBO agree reasonably well with the values obtained from transient-absorption experiments. The rate constants for the nonradiative decays of 3K* and 3E* to the electronic ground state are strongly decreased by deuteration.
  - 0022-36540022-3654
  - ://A1991GU91100044 ://A1991GU91100044
DA  - 1991/12
ER  - 

@article{V67924350,
   = {Eisenberger,  H. and Nickel*,  B. and Ruth,  A. A. and Alsoufi,  W. and Grellmann,  K. H. and Novo,  M. },
   = {1991},
   = {December},
   = {Journal of Physical Chemistry},
   = {Keto-Enol Tautomerization of 2-(2'-Hydroxyphenyl)Benzoxazole and 2-(2'-Hydroxy-4'-Methylphenyl)Benzoxazole in the Triplet-State - Hydrogen Tunneling and Isotope Effects .2. Dual Phosphorescence Kinetics},
   = {Validated},
   = {()},
   = {95},
   = {25},
  pages = {10509--10518},
   = {{In the metastable triplet state of 2-(2'-hydroxyphenyl)benzoxazole (HBO) and its deuteriooxy analogue (DBO), the keto tautomer (K) and the enol tautomer (E) have about the same energy, and a dual phosphorescence, 3K* --> 1K and 'E* --> 1E, can be observed. From the initial time dependence of the dual phosphorescence from DBO the effective rate constant theta-1 almost-equal-to k(KE) + k(EK) of the keto-enol equilibration 3K* half arrow right over half arrow left 3E* has been determined. 3E* of DBO is almost exclusively populated from 3K*. In the dual phosphorescence from DBO the relative intensity of the keto band is smaller than in the dual phosphorescence from HBO; this is attributed to a small isotope effect on the keto-enol equilibrium in the triplet state. In the metastable triplet state of 2-(2'-hydroxy-4'-methylphenyl)benzoxazole (m-MeHBO) and its deuteriooxy analogue (m-MeDBO) the keto-enol equilibrium is strongly shifted to the side of the enol. No keto phosphorescence from m-MeHBO is observed. Due to the slower keto-enol equilibration in m-MeDBO, an initial keto phosphorescence from m-MeDBO can be observed. The values of theta-1 obtained from the time dependence of the phosphorescence of DBO and m-MeDBO agree reasonably well with the values obtained from transient-absorption experiments. The rate constants for the nonradiative decays of 3K* and 3E* to the electronic ground state are strongly decreased by deuteration.In the metastable triplet state of 2-(2'-hydroxyphenyl)benzoxazole (HBO) and its deuteriooxy analogue (DBO), the keto tautomer (K) and the enol tautomer (E) have about the same energy, and a dual phosphorescence, 3K* --> 1K and 'E* --> 1E, can be observed. From the initial time dependence of the dual phosphorescence from DBO the effective rate constant theta-1 almost-equal-to k(KE) + k(EK) of the keto-enol equilibration 3K* half arrow right over half arrow left 3E* has been determined. 3E* of DBO is almost exclusively populated from 3K*. In the dual phosphorescence from DBO the relative intensity of the keto band is smaller than in the dual phosphorescence from HBO; this is attributed to a small isotope effect on the keto-enol equilibrium in the triplet state. In the metastable triplet state of 2-(2'-hydroxy-4'-methylphenyl)benzoxazole (m-MeHBO) and its deuteriooxy analogue (m-MeDBO) the keto-enol equilibrium is strongly shifted to the side of the enol. No keto phosphorescence from m-MeHBO is observed. Due to the slower keto-enol equilibration in m-MeDBO, an initial keto phosphorescence from m-MeDBO can be observed. The values of theta-1 obtained from the time dependence of the phosphorescence of DBO and m-MeDBO agree reasonably well with the values obtained from transient-absorption experiments. The rate constants for the nonradiative decays of 3K* and 3E* to the electronic ground state are strongly decreased by deuteration.}},
  issn = {0022-36540022-3654},
   = {://A1991GU91100044 ://A1991GU91100044},
  source = {IRIS}
}