“…Rate constants, k q , for energy transfer were obtained from the least-squares slopes, and those for hydrogen abstraction, k r , were determined from the intercepts of the least-squares plots and [RH] at each pressure. The pressure dependence values of k r obtained in toluene, methanol, and n -hexane are in good agreement with those of our previous work . The values for k q in toluene, methanol, and acetonitrile at 25 °C and in n -hexane at 15, 25, and 35 °C are listed in Tables and , respectively, together with those of solvent viscosity. − 1 Plots of k obs against the concentration of naphthalene, [N], in toluene at 25 °C.…”
Section: Resultssupporting
confidence: 86%
“…All data were analyzed by using a NEC microcomputer interfaced to the digitizers. Details about the associated high-pressure techniques have been described elsewhere. , …”
The rate constants, k
q, for the exothermic
energy transfer from the triplet states of benzophenone
(3BZP*)
and triphenylene (3TPh*) to naphthalene (N), and also
from the singlet sate of triphenylene (1TPh*)
to
benzophenone (BZP), were measured in polar and nonpolar solvents as a
function of pressure at 25 °C. For
all the systems of the donor−acceptor pairs, the plots of
k
q against 1/η showed downward curvature.
For
3BZP*/N in acetonitrile, methanol, and
n-hexane, the plots of ln k
q against
ln η were linear with the slopes
larger than −1, while for 3BZP*/N in toluene and for
1TPh*/BZP in n-hexane they showed downward
curvature.
However, the plots of 1/k
q against η were
linear with positive intercepts for all the systems examined. It
was
also found that the plot of 1/k
q against
η/T, in which k
q was measured for
3BZP*/N as a function of temperature
and pressure in n-hexane, is linear. These results were
interpreted by the energy transfer mechanism via the
formation of an encounter complex between the donor and acceptor
molecules, and it was concluded that the
exothermic energy transfer examined in the present study is not fully
diffusion-controlled but competes with
a diffusion process that is expressed by a modified Debye equation.
The bimolecular rate constants for the
energy transfer, k
bim
(=k
diff
k
et/k
-
diff),
were in the range of (1−10) × 1010
M-1 s-1 depending
on solvent. The
pressure dependence of k
et is discussed from the
experimental fact that k
bim is independent of
solvent viscosity
changed by varying pressure and temperature in all the systems
examined.
“…Rate constants, k q , for energy transfer were obtained from the least-squares slopes, and those for hydrogen abstraction, k r , were determined from the intercepts of the least-squares plots and [RH] at each pressure. The pressure dependence values of k r obtained in toluene, methanol, and n -hexane are in good agreement with those of our previous work . The values for k q in toluene, methanol, and acetonitrile at 25 °C and in n -hexane at 15, 25, and 35 °C are listed in Tables and , respectively, together with those of solvent viscosity. − 1 Plots of k obs against the concentration of naphthalene, [N], in toluene at 25 °C.…”
Section: Resultssupporting
confidence: 86%
“…All data were analyzed by using a NEC microcomputer interfaced to the digitizers. Details about the associated high-pressure techniques have been described elsewhere. , …”
The rate constants, k
q, for the exothermic
energy transfer from the triplet states of benzophenone
(3BZP*)
and triphenylene (3TPh*) to naphthalene (N), and also
from the singlet sate of triphenylene (1TPh*)
to
benzophenone (BZP), were measured in polar and nonpolar solvents as a
function of pressure at 25 °C. For
all the systems of the donor−acceptor pairs, the plots of
k
q against 1/η showed downward curvature.
For
3BZP*/N in acetonitrile, methanol, and
n-hexane, the plots of ln k
q against
ln η were linear with the slopes
larger than −1, while for 3BZP*/N in toluene and for
1TPh*/BZP in n-hexane they showed downward
curvature.
However, the plots of 1/k
q against η were
linear with positive intercepts for all the systems examined. It
was
also found that the plot of 1/k
q against
η/T, in which k
q was measured for
3BZP*/N as a function of temperature
and pressure in n-hexane, is linear. These results were
interpreted by the energy transfer mechanism via the
formation of an encounter complex between the donor and acceptor
molecules, and it was concluded that the
exothermic energy transfer examined in the present study is not fully
diffusion-controlled but competes with
a diffusion process that is expressed by a modified Debye equation.
The bimolecular rate constants for the
energy transfer, k
bim
(=k
diff
k
et/k
-
diff),
were in the range of (1−10) × 1010
M-1 s-1 depending
on solvent. The
pressure dependence of k
et is discussed from the
experimental fact that k
bim is independent of
solvent viscosity
changed by varying pressure and temperature in all the systems
examined.
“…Further information on the possibility of TTET from 3 BP* to R f I, was obtained by conducting DFT calculations at the B3LYP/6‐311G(d) level using the polarizable continuum model in its integral equation formalism to simulate the CH 3 OH environment . These calculations revealed that the triplet of the benzophenone lies above the singlet state by 74 kcal mol −1 , in close agreement with the experimental value of 70 kcal mol −1 , while the singlet‐triplet gap in C 8 F 17 I is larger and equates to 90 kcal mol −1 .…”
Iodoperfluooralkylation of terminal alkenesa nd alkynes is effectively photo-promoted by benzophenone 2 (BP) or the photoreducible copper(II) complex 1.I np articular,B Pa t1mol%i n methanol upon3 65 nm irradiationw ith al ow-pressure mercury lamp (type TLC = thin layer chromatography, 6W)r esults in af ast reaction with excellent reactiony ields.C omplex 1 and BP 2 exhibited very similarr eactivity,s uggestingt hat the reactions involving 1 are likely to be governed by the benzophenone photoactivation processes,r athert han copper(I)/(II) redox processes.M echanistic investigations using transient absorption spectroscopy revealed that ad eactivation pathway of the benzophenone triplet( 3 BP*) is via its reactionw ith the methanol solvent. We propose that the generated radicals, in particular CCH 2 OH, play ak ey role in the initiation step formingR f C by reactingw ith R f I, R f C then entering ar adical chain cycle. 1 HNMR studies provided evidence that as ubstantial amount (~7% NMR yield) of the hemiacetal CH 3 OCH 2 OH is formed, i.e., the possible by-product of the reaction between CCH 2 OH and R f I. Finally,D FT calculations indicatet hat at riplet-triplete nergy transfer (TTET) process from 3 BP* to perfluorooctyl iodide (C 8 F 17 I) is unlikely or should be rather slow under the reaction conditions,c onsistent with the transient absorption studies.
“…The rate constant for the 3 BP* photoreduction in hexane is equal to 4.11 × 10 5 M −1 s −1 at 25 °C. 67 Although this is approximately half the value of the rate constant measured for the rise of the absorption at 325 nm by laser flash photolysis, 68 we assume that the rate constant for SCRP generation at 25 °C is k g = 3.2 × 10 6 s −1 because with an approximate quantum yield of unity for the photoreduction, there is good agreement with the lifetime (340 ns 54 ) of 3 BP* in SDS at room temperature. To estimate the temperature effect on k g , we have used the activation energy for the photooxidation of cyclohexane by 3 BP*, which is 7.6 kcal mol −1 .…”
Section: Kinetic Parametersmentioning
confidence: 82%
“…To estimate the temperature effect on k g , we have used the activation energy for the photooxidation of cyclohexane by 3 BP*, which is 7.6 kcal mol −1 . 67 This gives a 6-fold increase in k g when the temperature increases from 16 °C to 60 °C (Table 1).…”
Radical pairs created by the photoreduction of benzophenone (BP) in sodium dodecyl sulfate (SDS) micelles exhibit strong asymmetry in the line shapes of their time-resolved electron paramagnetic resonance (TREPR) signals. The asymmetry is strongly dependent on the temperature from 16 °C to 66 °C. Simulations of the anti-phase structure (APS) line shape of these spin correlated radical pairs (SCRPs), based on a numerical solution of the Stochastic Liouville Equation with the spin exchange interaction depending exponentially on the distance between radicals, are presented and discussed. The proposed model takes into account the diffusive motion of the radicals along with the motion of the transverse magnetization and accounts satisfactorily and self-consistently for the asymmetry of the observed TREPR signals.
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