(R 1 -R 2 ) homolytic cleavage 3( R 1 R 2 ) ISC 1( R 1 R 2 )
description
Transcript of (R 1 -R 2 ) homolytic cleavage 3( R 1 R 2 ) ISC 1( R 1 R 2 )
(R1-R2) homolytic cleavage 3(R1R2) ISC 1(R1R2)• • • •
recombinations
disproportionations
“Cage” Reactions Involving Radical Pairs
Model System
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The States of a Spin Correlated Radical Pair
vector model of electron spin
3(R1R2)• • • •
1(R1R2)
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ISC in Triplet Radical Pairs 3
Spin Rephasing Mechanism for ISC
T0 S
spin clock(top-down view, projection in the xy-plane)
J < a
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Spin-orbit coupling, g rate, kTS
Typical organic radical, g ~ 0.000-0.001Earth’s H ~ 1G 3 X 103 HzLab H ~ 100,000G 3 X 108 HzHyperfine coupling, aTypical organic radical, a ~ 10-100G 3 X 107 - 3 X 108 Hz
kTS ~ (3 X 106)(gH ±Ms a1 )
T0 S
Timescales for ISC in Radical Pairs
2 mechanisms: Spin Rephasing (g) and Spin Flipping (a)
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kTS ~ (3 X 106)(gH ±Ms a1 )
T0 S
Power of Spin in Product Distribution
Spin RephasingNo nuclear spin flip involved Spin Flipping
Sort magnetic nuclei from nonmagnetic nuclei!then kTS
+1/2 > kTS-1/2
Sort nuclear spin states! Polarized (non-Boltzmann) product distribution!
Ms = 0
Ms = ± 1/2 , a1 is positive
a >>>H
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