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Å3, Z =16, T = 100(2) K, absorption coefficient =V0ie.w8A0r3ticlme Omnl−in1e,
DOI: 10.1039/C6CC09261F
reflections collected = 81097, unique = 10593 [R(int) = 0.0303],
refinement by Full matrix least-squares on F2,
data/restraints/parameters = 10593/0/801, goodness-of-fit on
F2 = 1.041, final R indices [I > 2sigma(I)] R1 = 6.12%, wR2 =
17.26%; R indices (all data) R1 = 6.46%, wR2 = 17.68%, largest
diff. peak and hole = 1.5 and −0.5 e Å−3, respectively.
2: C16H14N2O4 (298.29), monoclinic, P-1, a = 7.9596(2) Å, alpha
= 107.407(2)°; b = 15.2341(4) Å, beta = 100.757(1)°; c =
16.7564(5) Å, gamma = 97.385(1)°. V = 1829.0(1) Å3, Z =4, T =
100(2) K, absorption coefficient = 4.772 mm−1, reflections
collected = 29515, unique = 6332 [R(int) = 0.0345], refinement
by Full matrix least-squares on F2, data/restraints/parameters
= 6332/0/473, goodness-of-fit on F2 = 1.026, final R indices [I >
2sigma(I)] R1 = 2.96%, wR2 = 7.36%; R indices (all data) R1 =
3.22%, wR2 = 7.48%, largest diff. peak and hole = 0.3 and −0.3
e Å−3, respectively.
Figure 2. Mechanistic aspects
hydrazides.
- photochemical reaction of
On the other hand, in the case of the oxoamide based
hydrazide 4, the formation of a triplet excited state is likely
(through direct excitation of the keto-amide).14 This triplet-
excited state can react to form the photoproduct through a
biradicaloid (3BR; Figure 2) species or through an
intramolecular charge transfer pathway. This reactive triplet
excited state of the reactant may also be accessed through
direct irradiation (as in the case of hydrazide 6). While the
mechanistic details for a specific substrate presented in our
system requires further scrutiny using photochemical and
photophysical studies, our generalized approach where an
excited state encounter complex initiates the reactivity is quite
general for the investigated photochemical transformations.
We propose that the substrates can adopt differing routes
from the encounter complex (viz., electron vs. energy transfer
pathway) depending on the oxidation and reduction potentials
as well as on the triplet energy of the hydrazide derivative.
In summary, our study utilizes the features of a hydrazide
chromophore for photoreactions with TX as the sensitizer. The
study opens up avenues for chemists to utilize visible light to
perform classical photoreactions that are useful for targeting
complex structural scaffolds. Additionally, the hydrazide
handle can be subjected to simple chemical modification,
making the approach modular. Thus the hydrazide essentially
acts as a “photo-auxiliary” enabling us to perform classical
photoreactions with visible light sensitization. This novel
strategy can enable chemists across disciplines to initiate
photochemical reactions under metal free visible light
irradiation conditions.
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Notes and references
The authors thank the National Science Foundation for
generous support for their research (CHE-1465075). Authors
thank Dr. Angel Ugrinov for solving single crystal XRD
structures, Prof. Guodong Liu for access to cyclic voltammetric
instrumentation and Anthony Clay for intellectual discussions.
Single crystal XRD: 1: C16H14N2O4 (298.29), monoclinic, P2(1)/c,
a = 32.0290(13) Å, alpha = 90.00°; b = 11.6208(5) Å, beta =
103.875(2)°; c = 16.5874(7) Å, gamma = 90.00°. V = 5993.7(4)
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4 | J. Name., 2012, 00, 1-3
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