Photochemical & Photobiological Sciences
Paper
reasonable to expect that decay of the cis-phenallylmethylene
intermediate in Scheme 1 would give similar amounts of cc-
and tc-DPB. The ϕct→cc value is not known in cyclohexane, but
if we use the quantum yield ratio in ethanol as a guide and
assume ϕct→tc ≈ ϕct→cc then the yield of tc-DPDd2 would be too
small to detect in our experiment.
ed. H. Dürr and H. Bouas-Laurent, Elsevier, Amsterdam,
1990, pp. 64–164.
7 D. H. Waldeck, Photoisomerization Dynamics of Stilbenes,
Chem. Rev., 1991, 91, 415–436.
8 L. R. Eastman Jr., B. M. Zarnegar, J. M. Butler and
D. G. Whitten, Unusual Case of Selectivity in a Photochemical
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1
1
Conclusions
9 W. A. Yee, S. J. Hug and D. S. Kliger, Direct and Sensitized
Photoisomerization of 1,4-Diphenylbutadienes, J. Am.
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We showed that the BP process does not play a significant role
in the photochemistry of ct-DPB. Assuming that the decays of
the phenallylmethylene intermediates in Scheme 1 give cis and
1
0 J. Saltiel, T. S. R. Krishna, S. Laohhasurayotin, Y. Ren,
K. Phipps, W. A. Yee and P. H. Davis, Medium Effects on
the Direct Cis-Trans Photoisomerization of 1,4-Diphenyl-
1
trans double bonds with equal probability, the fraction of ct-
DPB* that avoid torsional relaxation by undergoing radiation-
less decay directly to the ct-DPB ground state can be estimated
from ϕic = 1–2ϕct→tt, where ϕic is the quantum yield of internal
conversion. Values of ϕic range from a low of ∼0.65 in benzene
1
2
,3-butadiene in Solution, J. Phys. Chem. A, 2011, 115,
120–2129.
11 J. Saltiel and C. E. Redwood, Photochemistry of the 1,4-
Diphenyl-1,3-butadienes in Ethanol. Trapping Conical
Intersections, J. Phys. Chem. A, 2016, 120, 2832–2840.
1
0,11
to a high of 0.88 in saturated hydrocarbon solvents.
1
Similarly large ϕic values were estimated for tt-DPB* where
12 J.
Saltiel, T. S. R. Krishna and R. J. Clark,
1
10
decay via an unreactive 2 A
g
state was implicated. An unreac-
Photoisomerization of cis,cis-1,4-Diphenyl-1,3-butadiene in
the Solid State: The Bicycle-Pedal Mechanism, J. Phys.
Chem. A, 2006, 110, 1694–1697.
1
1
tive 2 A-like state may also be involved in the decay of ct-
DPB*.
1
1
1
3 J. Saltiel, T. S. R. Krishna, S. Laohhasurayotin, K. Fort and
R. J. Clark, Photoisomerization of cis,cis- to trans,trans-1,4-
Diaryl-1,3-butadienes in the Solid State: The Bicycle-Pedal
Mechanism, J. Phys. Chem. A, 2008, 112, 199–209.
4 J. Saltiel, T. S. R. Krishna, A. M. Turek and R. J. Clark,
Photoisomerization of cis,cis-1,4-Diphenyl-1,3-butadiene in
Glassy Media at 77 K: The Bicycle-Pedal Mechanism,
J. Chem. Soc., Chem. Commun., 2006, 1506–1508.
Conflicts of interest
There are no conflicts to declare.
Acknowledgements
5 J. Saltiel, M. A. Bremer, S. Laohhasurayotin and
T. S. R. Krishna, Photoisomerization of cis,cis- and cis,trans-
This research was supported by the National Science
Foundation, most recently by Grant No. CHE-1361962, and by
the Florida State University.
1
,4-Di-o-tolyl-1,3-butadiene in Glassy Media at 77 K: One
Bond Twist and Bicycle-Pedal, Angew. Chem., Int. Ed., 2008,
7, 1237–1240.
4
1
6 A. Warshel, Bicycle-Pedal Model for the First Step in the
Vision Process, Nature, 1976, 260, 679–683.
Notes and references
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