“…Materials and Solutions. O -Acyl derivatives (I−V) of 1-hydroxy-2-methoxyanthraquinone were obtained by acylation of 1-hydroxy-2-methoxyanthraquinone according to ref . The toluene used as the solvent was Merck Uvasol grade.…”
Section: Methodsmentioning
confidence: 99%
“…Three types of photochromic processes are currently available to quinone derivatives. They are characterized by light-induced isomerization of the p -quinoid to the anaquinoid structure by photochemical migration of aryl, hydrogen, or acyl groups − …”
Section: Introductionmentioning
confidence: 99%
“…To account for the relationship between the reactivity of these compounds and their chemical structure, it was assumed that photochemical migration of the acetyl group occurs adiabatically . Later, the triplet state of the product (ana-quinone) was detected as a precursor of the ana-quinone ground state in the case of 1-acetoxy-2-methoxyanthraquinone (I). According to this result, a triplet adiabatic mechanism was proposed for the photochemical reaction of acyl group migration, but a detailed study of the primary processes required a better time resolution …”
Section: Introductionmentioning
confidence: 99%
“…Later, the triplet state of the product (ana-quinone) was detected as a precursor of the ana-quinone ground state in the case of 1-acetoxy-2-methoxyanthraquinone (I). According to this result, a triplet adiabatic mechanism was proposed for the photochemical reaction of acyl group migration, but a detailed study of the primary processes required a better time resolution …”
Section: Introductionmentioning
confidence: 99%
“…The influence of temperature and solvent and migrant nature on the rate constant of thermal migration of the acyl group was previously studied. , It was found that donor substituents in the migrating acyl group significantly reduce the rate constant of the thermal migration. It is reasonable to expect, therefore, that donor substituents also reduce the rate constant of the photochemical migration.…”
Nanosecond laser flash photolysis has been used to
study the primary processes in the photochromic reaction
of five O-acylic derivatives of
1-hydroxy-2-methoxyanthraquinone with methyl (I), tolyl (II), phenyl
(III),
ethoxyl (IV), and diethylamino (V) groups in the migrating acyl.
The triplet−triplet absorption spectra of
the reactive triplet states of quinones IV and V were detected, and the
rate constants of the primary
photochemical step were measured. The temperature dependence of
the rate constants of acyl migration in
the triplet states of quinones IV and V was studied, and the Arrhenius
parameters were determined. The rate
constants of thermal acyl migration and their Arrhenius parameters were
measured for compounds I−V. It
was found that migrant nature significantly influences the activation
energy of both thermal and photochemical
reactions of acyl migration. The activation energy of thermal
migration increases from 37.9 ± 0.2 kJ/mol
for compound I up to 66.5 ± 0.7 kJ/mol for compound V. The
photochemical process is characterized by
considerably lower values of the activation energy (15.9 ± 0.8 and
26.0 ± 1.7 kJ/mol for compounds IV and
V, respectively). It was confirmed in the present work that
photochemical migration of acyl groups is an
adiabatic process occurring on the triplet potential energy
surface.
“…Materials and Solutions. O -Acyl derivatives (I−V) of 1-hydroxy-2-methoxyanthraquinone were obtained by acylation of 1-hydroxy-2-methoxyanthraquinone according to ref . The toluene used as the solvent was Merck Uvasol grade.…”
Section: Methodsmentioning
confidence: 99%
“…Three types of photochromic processes are currently available to quinone derivatives. They are characterized by light-induced isomerization of the p -quinoid to the anaquinoid structure by photochemical migration of aryl, hydrogen, or acyl groups − …”
Section: Introductionmentioning
confidence: 99%
“…To account for the relationship between the reactivity of these compounds and their chemical structure, it was assumed that photochemical migration of the acetyl group occurs adiabatically . Later, the triplet state of the product (ana-quinone) was detected as a precursor of the ana-quinone ground state in the case of 1-acetoxy-2-methoxyanthraquinone (I). According to this result, a triplet adiabatic mechanism was proposed for the photochemical reaction of acyl group migration, but a detailed study of the primary processes required a better time resolution …”
Section: Introductionmentioning
confidence: 99%
“…Later, the triplet state of the product (ana-quinone) was detected as a precursor of the ana-quinone ground state in the case of 1-acetoxy-2-methoxyanthraquinone (I). According to this result, a triplet adiabatic mechanism was proposed for the photochemical reaction of acyl group migration, but a detailed study of the primary processes required a better time resolution …”
Section: Introductionmentioning
confidence: 99%
“…The influence of temperature and solvent and migrant nature on the rate constant of thermal migration of the acyl group was previously studied. , It was found that donor substituents in the migrating acyl group significantly reduce the rate constant of the thermal migration. It is reasonable to expect, therefore, that donor substituents also reduce the rate constant of the photochemical migration.…”
Nanosecond laser flash photolysis has been used to
study the primary processes in the photochromic reaction
of five O-acylic derivatives of
1-hydroxy-2-methoxyanthraquinone with methyl (I), tolyl (II), phenyl
(III),
ethoxyl (IV), and diethylamino (V) groups in the migrating acyl.
The triplet−triplet absorption spectra of
the reactive triplet states of quinones IV and V were detected, and the
rate constants of the primary
photochemical step were measured. The temperature dependence of
the rate constants of acyl migration in
the triplet states of quinones IV and V was studied, and the Arrhenius
parameters were determined. The rate
constants of thermal acyl migration and their Arrhenius parameters were
measured for compounds I−V. It
was found that migrant nature significantly influences the activation
energy of both thermal and photochemical
reactions of acyl migration. The activation energy of thermal
migration increases from 37.9 ± 0.2 kJ/mol
for compound I up to 66.5 ± 0.7 kJ/mol for compound V. The
photochemical process is characterized by
considerably lower values of the activation energy (15.9 ± 0.8 and
26.0 ± 1.7 kJ/mol for compounds IV and
V, respectively). It was confirmed in the present work that
photochemical migration of acyl groups is an
adiabatic process occurring on the triplet potential energy
surface.
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