Structure determination of photoproducts of anthracenes with (Arylmethoxymethyl) sidechains

Article abstract of DOI:10.1002/ejoc.200700140

Irradiation of 9-(arylmethoxymethyl)anthracenes 3 leads either to a cyclomer and cyclodimer mixture (3a→4a,5a), to selectively formed dimers (3b→5b), or a selectively formed cyclomer (3c→4c). The [4π+4π]cyclodimerization is under the conditions used a reg

Full text of DOI:10.1002/ejoc.200700140

FULL PAPER
DOI: 10.1002/ejoc.200700140
Structure Determination of Photoproducts of Anthracenes with
(Arylmethoxymethyl) Sidechains
Silvia Dobis,[a] Dieter Schollmeyer,[a] Chunmei Gao,[b] Derong Cao,[b,c] and
Herbert Meier*[a,c]
Keywords: Cyclization / Cyclodimerization / Photochemistry / Regioselectivity / Rotamers
Irradiation of 9-(arylmethoxymethyl)anthracenes
3
leads
in an antiperiplanar position related to the CC bonds gener-
ated in the dimerization. In solutions, however, the structures
consist of three rotamers the equilibration of which was
studied by temperature-dependent NMR spectra.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2007)
either to a cyclomer and cyclodimer mixture (3aǞ4a,5a), to
selectively formed dimers (3bǞ5b), or a selectively formed
cyclomer (3cǞ4c). The [4π+4π]cyclodimerization is under
the conditions used a regioselective head-to-tail process. In
the crystals of the dimers 5a,b, the sidechains are attached
Introduction
Results and Discussion
9-(Chloromethyl)anthracene (1) reacts with the benzyl
alcohols 2a–c and KOH under phase-transfer conditions to
give the anthracene derivatives 3a–c (Scheme 1). These
compounds contain two independent chromophores sepa-
rated by a CH2–O–CH2 chain. The anthracene moiety has
Molecular switches and memories attract a lot of atten-
tion in organic chemistry and materials science.[1–15] Some
time ago we found a seco-cyclo isomerism which is based
on the reversible intramolecular [4π+4π]photocycloaddition
of benzene rings to anthracene.[16] The utility of such a sys-
tem depends strongly on clean switching processes in both
directions. The photochemistry of anthracenes, however,
contains several reaction types. The [4π+4π]photodimeriza-
tion of two anthracene molecules was already discovered –
without structural interpretation – by Fritzsche in the 19th
century.[17] Bulky sidechains in 9-position lead to a remark-
able valence isomerization (disrotatory [4π] electrocyclic re-
action) to “Dewar anthracenes”.[18–20] Apart from the intra-
molecular [4π+4π]cycloaddition of anthracene and benzene
moieties mentioned above, we found in concentrated solu-
tions of 9,10-disubstituted anthracenes the corresponding
intermolecular process.[21] Moreover, anthracenes with spe-
cial substituents exhibit several further photoreac-
tions.[22–27]
The switching process discussed here, is typical for an-
thracenes which have in 9-position a phenylmethoxymethyl
sidechain with an electron-rich benzene ring.[16] We describe
in this paper such compounds which bear methoxyphenyl
and dimethoxyphenyl groups.
[a] Institut für Organische Chemie der Johannes Gutenberg-Uni-
versität,
Duesbergweg 10–14, 55099 Mainz, Germany
Fax: +49-6131-39-25396
E-mail: hmeier@mail.uni-mainz.de
[b] LCLC, Guangzhou Institute of Chemistry, Chinese Academy
of Sciences,
Guangzhou 510650, China
[c] South China University of Technology,
Guangzhou 510640, China
Scheme 1. Preparation and photoreactivity of 9-[(arylmethoxy)-
methyl]anthracenes (3).
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9-(Arylmethoxymethyl)anthracene Photochemistry
FULL PAPER
a typical absorption between 300 and 410 nm. Irradiation
In principle, the rotamers of 5b, shown in Scheme 2,
into this absorption of 3a in diluted solution in oxygen-free should give the NMR signals listed in Table 1, when the
benzene yields a mixture of cyclomer 4a and cyclodimer 5a. rotations depicted in Scheme 1 are slow in terms of the
The same procedure selectively transforms 3b into 5b and NMR time scale.
3c into 4c.[28] Obviously, small differences of the electronic
effects in the benzene ring control the competition between
the intramolecular and the intermolecular [4π+4π]cycload-
dition. The ratio 4a/5a of about 1:1 is typical of 0.5–1.0 m
solutions of 3a in benzene. Enhanced concentrations
(2.85 m) of 3a yield 82% dimer 5a and only traces of 4a.
The selective dimerization 3bǞ5b can not effectively be in-
fluenced by changing the concentration. Due to the high
aggregation tendency of 3b, cyclomer 4b is found only in
traces, when the concentration is lowered to about 0.1 m.
On the other hand, 3c does not form a dimer of type 5 –
even not in a saturated solution in benzene.
The structure determination of 4a,c is based on one- and
two-dimensional 1H and 13C NMR measurements. The
1
products 5a,b pose much more problems. Their H-NMR
spectroscopic data show at room temperature (25 °C) a
double set of signals. Our original idea, that a mixture of
head-to-head and head-to-tail cyclodimers[24–27] was gener-
ated, had to be dismissed, since the two signal sets coalesce
reversibly to one set at high temperatures (Ն 90 °C). Conse-
quently, stereoisomers must be present in the product mix-
ture. Since the heptacyclic scaffold of 5a,b is completely ri-
gid, different rotamers of the sidechains have to be consid-
Scheme 2. Rotamers of 5 (formula without condensed benzene
rings).
ered. Table 1 summarizes the staggered conformers con-
sisting of two pairs of enantiomers having C1 and C2 sym-
1
Many temperature-dependent H and 13C NMR spectra
of 5b were recorded. Signals of methylene groups having
diastereotopic geminal protons (AB spin patterns) could
not be found in the temperature range between –40 and
+90 °C. Therefore we assume that a fast AB exchange pro-
cess in the α- and β-CH2 groups takes place. The number
of singlet signals depends strongly on the temperature of
the 1H-NMR measurement (Figure 1 and Table 2). At
90 °C, sharp singlets exist for the α- and β-CH2 groups and
for the two different methoxy groups, and a broad coal-
metry, respectively, and two further diastereomers with C2h
and Ci symmetry, respectively.
1
Table 1. H-NMR signals expected for different conformers of 5b.
Conformation
5b (C2h
5b (C1)/(C1Ј)
5b (C2)/(C2Ј)
5b (Ci)
Bridgehead CH
α-CH2
β-CH2 OCH3
)
1s
2s
1s
1s
1s
1s
2s
4s
2s
1s
2AB
1AB
1AB
2AB
1AB
1AB
1
Figure 1. Temperature-dependent H-NMR spectra (in the range 5.5 Ͻ δ Ͻ 3.0) of 5b measured at 400 MHz in CDCl2–CDCl2.
Eur. J. Org. Chem. 2007, 2964–2969
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2965

S. Dobis, D. Schollmeyer, C. Gao, D. Cao, H. Meier
FULL PAPER
escence signal can be found for the bridgehead protons. the CC single bonds formed in the photocyclodimerization.
Cooling to 25 °C causes doubling of all signals (Table 2). The important structural features of the attachment of the
At 18 °C a further splitting of the signals starts and at sidechains in 5a,b are listed in Table 3. Crystal structure 5b
–20 °C all signals are doubled again – except for the high- contains two independent molecules (A) and (B) which are
field resonance at δ = 3.544.[29] Six singlets for the methoxy located at different special positions (A: 0.5, 0.5, 0; B: 0, 0,
groups can be seen at –20 °C. Consequently three conform- 0.5) of the unit cell. The molecular geometry of the two
ers exist in the range of slow exchange (Scheme 2), namely molecules is identical.
5b(C2h) and the equilibrated species 5b(Cs) and 5b(C2hЈ).
Both molecules 5a,b have a center of inversion, so that
The sidechains having antiperiplanar position of the ORЈ the arrangement of the two sidechains is equivalent. The
groups (present twice in 5b(C2h) and a single time in the antiperiplanar conformation is characterized by torsion
equilibrated 5b(Cs) conformer) are restricted in their rota- angles between 178.5 and 179.9°. The relatively small non-
tion.[30] This interpretation is based on the proximity of bonding distances between O16 and the hydrogen atoms
ORЈ to two benzene ring hydrogen atoms. Although a com- H3, H13 and H9, respectively, indicate the difficulty of the
plete assignment of the signals, shown in Figure 1 and rotation of the sidechains (see Table 1, Scheme 1, Figures 2
Table 2, to the three conformers was not possible, a con- and 3). The two graphics also demonstrate the steric inter-
former ratio 5b(C2h):5b(Cs):5b(C2hЈ) = 1:2:1 can be evalu- action of the hydrogen atoms on C15 (α-CH2) and C17 (β-
ated.
CH2) with those on C3 and C13. Interestingly, the splitting
of the H-NMR signals is larger for the β-CH2 group than
1
for the α-CH2 group.
Table 2. Selected 1H-NMR signals of 5b (δ values measured at dif-
ferent temperatures in C2D2Cl4, related to δ (CHCl2–CDCl2) =
5.995 ppm).
The photodimerization of 9-substituted anthracenes nor-
mally leads to head-to-tail regioisomers; however, some
head-to-head dimers were reported as well.[23–27] Certainly
head-to-head regioselectivity is due to the reaction in con-
strained media or due to the topochemical control in the
solid state, but the structures of those head-to-head dimers,
which were postulated in solution, should be scrutinized in
the light of the results obtained here for the existence of
different rotamers. We suspect that particularly many di-
mers with long and/or bulky sidechains may give at room
temperature a double set of NMR signals for pure head-to-
tail structures.
Temperature Bridgehead
α-CH2
(s)
β-CH2
(s)
OCH3
(s)
[°C]
CH (s)
–10
3.512
4.680
4.700
4.766
4.802
5.011
5.019
4.481
4.493
4.515
4.538
3.838
3.850
3.851
3.861
3.897
3.931
3.894
3.894
3.930
3.990
3.952
4.019
+25
+90
3.544
4.735
4.823
5.051
4.538
4.569
To the best of our knowledge, only one discussion of rot-
amers in the structure elucidation of anthracene dimers has
been published.[31] Crystal structure analyses reveal two dif-
ferent rotamers as separable photodimers of 9-(2-hydroxy-
2-propyl)anthracene. Since an antiperiplanar arrangement
of the OH group can be excluded, both stereoisomers give
4.30 (br.)
5.002
4.613
Head-to-head regioisomers could not be detected under
the reaction conditions used – even not in the 1H-NMR
spectra of the crude reaction mixtures. The substituents in
9-position of 3a,b are probably too bulky to permit the for-
mation of head-to-head dimers.
1
almost identical H-NMR spectra with the same singlet for
the bridgehead protons. On the contrary we observe for the
rotamers of our compounds 5a,b fairly different H-NMR
1
signals, but only one crystal structure.
The arrangement of the sidechains of 5a,b in the crystal-
line state is shown in Figures 2 and 3. The ORЈ groups are
Both reaction types, 3Ǟ4 and 3Ǟ5, are thermally as
in both cases in an antiperiplanar arrangement related to well as photochemically reversible. The system 3c i 4c is
Figure 2. Crystal structure of dimer 5a (atom numbering not in accord with nomenclature rules).
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9-(Arylmethoxymethyl)anthracene Photochemistry
FULL PAPER
Figure 3. Crystal structure of dimer 5b. Upper part: Unit cell which contains two molecules 5b (A,B) in slightly different positions which
are separated by two molecules CHCl3. Lower part: Platon plot of 5b (A). (atom numbering not in accord with nomenclature rules).
Table 3. Selected data of the crystal structures of the dimers 5a and 5b (The numbering corresponds to Figure 2 and Figure 3 and not to
the nomenclature).
5a
5b
Molecule A
Molecule B
Bond lengths [Å]
C1–C8
C1–C15
C15–O16
1.632(2)
1.526(2)
1.420(2)
C1–C14
C1–C15
C15–O16
1.636(7)
1.514(8)
1.433(7)
1.617(9)
1.527(8)
1.433(8)
Bond angles [°]
C8–C1–C15
C1–C15–O16
104.6(1)
109.7(1)
C14–C1–C15
C1–C15–O16
104.7(4)
109.4(4)
105.2(5)
109.2(5)
Torsion angles [°]
C8–C1–C15–O16
Distances [Å]
178.5(2)
C14–C1–C15–O16
–179.2(5)
–179.9(5)
O16–H3
O16–H13
2.65
2.58
O16–H3
O16–H9
2.62
2.60
2.65
2.60
best suited for a clean and fast switching process.[32] The act under the irradiation conditions used (λ Ն 300 nm) to
change of the absorption as well as the change of the fluo- give cyclomers 4 and/or cyclodimers 5. The selectivity of the
rescence can be used to control the switching. In contrast mono- or bimolecular process is determined by the electron
to 3c, cyclomer 4c does not emit fluorescence light.
density in p-position of the benzene ring; high electron den-
sity favors the intramolecular reaction.
Conclusions
Both processes are thermally as well as photochemically
Depending on the substitution pattern on the benzene (λ = 254 nm) reversible. The quantitative process 3c i 4c is
ring, anthracenes 3 bearing 9-(benzyloxy)methyl chains, re- best suited as molecular switch.
Eur. J. Org. Chem. 2007, 2964–2969
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S. Dobis, D. Schollmeyer, C. Gao, D. Cao, H. Meier
FULL PAPER
When 150 mg (0.46 mmol) 3a were dissolved in 160 mL benzene,
the photoreaction yielded under the same conditions 123 mg (82%)
of dimer 5a and only traces of 4a.
The structure elucidations of the dimers 5a and 5b reveal
a new aspect. According to crystal structure analyses, both
dimers are [4π+4π] head-to-tail adducts. In solution, they
show temperature-dependent (+90 °C to –40 °C) NMR
spectra indicating the existence of three different rotamers.
Head-to-head dimers could not be found.
Irradiation of 3b, 3c: The irradiation of 3b (87 mg, 0.24 mmol) was
performed as described above for 3a. Yield after recrystallization
from CH2Cl2/C2H5OH (1:2): 62 mg 5b (71%), colorless crystals,
which melted at 222 °C (decomp.). The irradiation of 3c (60 mg,
0.17 mmol) afforded 60 mg (≈100%) of pure 4c, which melted at
98 °C (decomp.).[31]
Experimental Section
7-Methoxy-3-oxahexacyclo[7.6.6.25,8.01,5.010,15.016,21]tricosa-
General: The FT-IR spectra were obtained with the Perkin–Elmer
spectrometer GX. The 1H and 13C NMR spectra were recorded
with the Bruker spectrometer AMX 400. If not otherwise indicated,
CDCl3 served as solvent, and TMS was used as internal standard.
The field desorption (FD) mass spectra were obtained with a Finni-
gan MAT 95. Elemental analyses were performed in the microana-
lytical laboratory of the Institute of Organic Chemistry of the Uni-
versity of Mainz. The melting points were measured with a Stuart
Scientific SMP/3 apparatus and are uncorrected.
6,10,12,14,16,18,20,22-octaene (4a): IR (KBr): ν = 1597, 1490,
˜
1
1467, 1454, 1268, 1165, 1135, 1108, 1037, 780, 694 cm–1. H NMR
(CDCl3): δ = 2.75 (s, 3 H, OCH3), 3.18 (m, 1 H, 8-H), 3.69/3.83
(AB, 2J = –8.9 Hz, 2 H, 4-H), 4.03 (d, 3J = 10.7 Hz, 1 H, 9-H),
4.11 (d, 4J = 2.2 Hz, 1 H, 6-H), 4.49 (“s”, 2 H, 2-H), 5.70 (m, 2 H,
22-H, 23-H), 6.78–7.36 (m, 8 H, aromat. H) ppm. 13C NMR
(C6D6): δ = 47.0 (C-8), 54.1, 54.8, 54.9 (C-5, C-9, OCH3), 64.4 (C-
1), 72.1 (C-2), 80.5 (C-4), 103.9 (C-6), 122.7, 123.1, 124.2, 124.7,
124.8, 125.4, 127.4 (aromat. CH, signals partly superimposed),
132.9, 141.3 (C-22, C-23), 143.8, 144.6, 146.0, 146.2 (aromat. Cq),
160.6 (CqO) ppm. FD MS: m/z (%) = 329 (100) [M + H+].
C23H20O2 (328.4): calcd. C 84.12, H 6.14; found C 84.52, H 6.04.
The preparation of the 9-[(benzyloxy)methyl]anthracenes 3a–c was
accomplished according to a procedure given in the literature.[33]
9-{[(3-Methoxybenzyl)oxy]methyl}anthracene (3a): Yellowish solid,
yield 1310 mg (80%) from 1130 mg (5.0 mmol) 1 and 760 mg
(5.5 mmol) 2a; m.p. 101 °C. H NMR (CDCl3): δ = 3.77 (s, 3 H,
To the spectroscopic characterization of 4c see reference.[33] The
quantitative process 3c Ǟ 4c can be quantitatively reversed
(4cǞ3c) by heating to 110 °C or by irradiation with λ = 254 nm.
1
OCH3), 4.69 (s, 2 H, β-CH2), 5.48 (s, 2 H, α-CH2), 6.86 (m, 1 H,
phenyl H), 6.97 (m, 2 H, phenyl H), 7.28 (m, 1 H, phenyl H), 7.39–
7.54 (m, 4 H, anthracene H), 7.99 (m, 2 H, anthracene H), 8.31 (m,
2 H, anthracene H), 8.45 (s, 1 H, 10-H) ppm. 13C NMR (CDCl3): δ
= 55.2 (OCH3), 64.0 (α-CH2), 72.3 (β-CH2), 113.0, 113.8, 120.3,
124.4, 124.4, 124.9, 126.1, 128.4, 129.0 (aromat. CH), 129.4, 131.1,
131.5 (Cq, anthracene), 140.1, 159.8 (Cq, benzene) ppm. FD MS:
m/z (%) = 328 (100) [M+·]. C23H20O2 (328.4): calcd. C 84.12, H
6.14; found C 83.97, H 6.08.
5,11-Bis{[(3-methoxybenzyl)oxy]methyl}-5,6,11,12-tetrahydro-5,12-
[1Ј,2Ј]:6,11[1ЈЈ,2ЈЈ]dibenzenodibenzo[a,e]cyclooctene (5a): IR (KBr):
1
ν = 1597, 1454, 1268, 1164, 1108, 1036, 780, 694 cm–1. H NMR
˜
(CDCl3, 25 °C): δ = 3.53, 4.72 (2 br. s, 2 H, bridgehead H), 3.79,
3.84 (2 s, 6 H, OCH3), 4.46 (br. s, 4 H, α-CH2), 4.73 (br. s, 2 H, β-
CH2), 4.97 (br. s, 2 H, β-CH2), 6.75–7.40 (m, 24 H, aromat. H)
ppm. 13C NMR (CDCl3, 25 °C): δ = 55.2 (OCH3), 71.1 (br.), 73.6,
73.9, 75.0 (CH2), 112.9, 113.4, 113.7, 120.0, 120.5, 123.6, 124.0,
124.9, 125.3, 125.5, 127.4, 128.0, 129.5, 129.6 (aromat. CH, signals
partly superimposed), 139.8, 142.9, 144.9, 159.8 (br., aromat. Cq,
partly superimposed) ppm. Due to the exchange mechanism of rot-
amers, some signals are very broad; the signals of the bridgehead
carbon atoms can not be found at all. FD MS: m/z (%) = 657 (1)
[M + H+], 329 (100) [M + 2 H+]. C46H40O4 (656.8): calcd. C 84.12,
H 6.14; found C 84.15, H 6.11.
9-{[(2,3-Dimethoxylbenzyl)oxy]methyl}anthracene (3b): Yellowish
solid, yield 1380 mg (77%) from 1130 mg (5.0 mmol) 1 and 925 mg
1
(5.5 mmol) 2b; m.p. 111 °C. H NMR (CDCl3): δ = 3.79 (s, 3 H,
OCH3), 3.86 (s, 3 H, OCH3), 4.83 (s, 2 H, β-CH2), 5.53 (s, 2 H, α-
CH2), 6.88 (m, 1 H, phenyl H), 7.06 (m, 2 H, phenyl H), 7.43–7.54
(m, 4 H, anthracene H), 8.00 (m, 2 H, anthracene H), 8.35 (m, 2
H, anthracene H), 8.45 (s, 1 H, 10-H) ppm. 13C NMR (CDCl3): δ =
55.8, 61.1 (OCH3), 64.5 (α-CH2), 67.4 (β-CH2), 112.1, 121.7, 124.0,
124.5, 124.9, 126.1, 128.3, 128.9 (aromat. CH), 128.8, 131.1, 131.5,
132.2 (aromat. Cq), 147.4, 152.7 (aromat. CqO) ppm. FD MS: m/z
(%) = 358 (100) [M+·]. C24H22O3 (358.4): calcd. C 80.42, H 6.19;
found C 80.39, H 6.27.
5,11-Bis{[(2,3-dimethoxybenzyl)oxy]methyl}-5,6,11,12-tetrahydro-
5,12[1Ј,2Ј]:6,11[1ЈЈ,2ЈЈ]dibenzenodibenzo[a,e]cyclooctene (5b): IR
(KBr): ν = 1588, 1477, 1454, 1431, 1351, 1276, 1233, 1135, 1099,
˜
1077, 1059, 1023, 1009, 777, 751, 693 cm–1. 1H NMR (CDCl3,
25 °C): δ = 3.55, 4.73 (2 s, 2 H, bridgehead H), 3.88, 3.92, 3.99 (3
s, 12 H, OCH3), 4.55 (br. s, 4 H, α-CH2), 4.83 (br. s, 2 H, β-CH2),
5.05 (s, 2 H, β-CH2), 6.73–7.35 (m, 22 H, aromat. H) ppm. 13C
NMR (CDCl3, 25 °C): δ = 55.8, 61.1 (OCH3), 57.1, 60.0 (CH,
bridgehead), 67.7, 68.5 (β-CH2), 71.3, 75.3 (α-CH2), 111.9, 121.3,
121.9, 123.7, 124.2, 125.2, 125.5, 127.3, 128.0 (aromat. CH, some
signals superimposed), 132.1, 143.0, 145.0, 147.1, 152.6 (aromat.
Cq) ppm. Some signals are broad, some signals look like doublets.
FD MS: m/z (%) = 717 (5) [M + H+], 359 (100) [M + 2 H+].
C48H44O6 (716.9): calcd. C 80.42, H 6.19; found C 80.59, H 6.16.
9-{[(3,5-Dimethoxybenzyl)oxy]methyl}anthracene (3c): Yellowish so-
lid, yield 1470 mg (82%) from 1130 mg (5.0 mmol) 1 and 925 mg
(5.5 mmol) 2c; m.p. 100 °C, spectroscopic characterization.[14]
Irradiation of 9-{[(3-Methoxybenzyl)oxy]methyl}anthracene (3a): A
solution of 40.0 mg (0.12 mmol) 3a in 160 mL of dry, degassed ben-
zene was irradiated with a Hanovia 450-W medium-pressure mer-
cury lamp equipped with a Duran glas filter. A slow Ar stream was
purged through the solution. After 1 h the solvent was reduced, so
that dimer 5a, which has a low solubility, precipitated. Recrystalli-
zation from CH2Cl2/C2H5OH (1:2) yielded 21.0 mg (53%) of color-
less, crystalline 5a which melted at 213 °C. The remaining benzene
solution contained the better soluble cyclomer 4a. Further concen-
tration gave 16.5 mg (41%) yellowish 4a which melted at 206 °C.
(The melting processes of 4a and 5a show clean decompositions to
3a.)
Crystal Structure Analysis of 5a and 5b: The measurement was done
on an Enraf–Nonius CAD-4-diffractometer with the software Col-
lect V5 (Enraf–Nonius B. V., 1989, Delft, The Netherlands). The
structures were solved with SIR 92[34] and refined by full-matrix
least-squares technique on F2 with SHELXL-97.[35] Details of the
X-ray crystal structure analysis are listed in Table 4.
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9-(Arylmethoxymethyl)anthracene Photochemistry
FULL PAPER
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[7] D. D. Nolte, Mind at Light Speed: A New Kind of Intelligence,
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Table 4. Details of X-ray crystal structure analysis of the dimers 5a
and 5b.
5a
5b
[8] Molecular Switches (Ed.: B. L. Feringa, Wiley-VCH,
Weinheim, 2001.
Formula
Mr
Habit
Crystal size [mm]
Space group
Cell constants:
a [Å]
b [Å]
c [Å]
α [°]
β [°]
C46H40O4
656.78
block
0.04ϫ0.35ϫ0.55 0.1ϫ0.1ϫ0.2
P21/c
C48H44O6·2CHCl3
955.57
block
[9] S. O. Kasap, Optoelectronic and Photonics: Principles and Prac-
tices, Prentice-Hall, Upper Saddle River, 2001.
[10] M. Irie, Chem. Rev. 2000, 100, 1683–1890.
[11] Organic Photochromic and Thermochromic Compounds (Eds.:
J. C. Crano, R. J. Guglielmetti), Plenum Press/Kluwer Aca-
demic, New York, 1999.
[12] Photo-Reactive Materials for Ultrahigh Density Optical Mem-
ory (Ed.: M. Irie) Elsevier, Amsterdam, 1994.
[13] Applied Photochromic Polymer Systems (Ed.: C. B. McArdle),
Blackie, Glasgow, 1992.
[14] Photochromism: Molecules and Systems (Eds.: H. Dürr, H.
Bouas-Laurent) Elsevier, Amsterdam, 2003.
[15] Organic Photochromes (Ed.: A. V. El’tsov), Consultants Bu-
reau, New York, 2003.
[16] D. Cao, S. Dobis, H. Meier, Tetrahedron Lett. 2002, 43, 6853–
6855.
¯
P1
12.284(3)
17.215(2)
8.208(2)
90
92.64(1)
90
1733.8(5)
2
1.258
Cu-Kα
0.62
10.589(2)
14.276(3)
16.416(5)
92.93(2)
90.61(2)
111.54(2)
2304(1)
2
1.377
Cu-Kα
3.801
992
–80
γ [°]
V (Å3)
Z
Dx (Mgm–3)
Radiation
µ [mm–1]
F (000)
696
25
70
[17] For details see H. D. Roth, Angew. Chem. 1989, 101, 1220–
1234; Angew. Chem. Int. Ed. Engl. 1989, 28, 1193–1207.
[18] H. Guesten, M. Mintas, L. Klasinc, J. Am. Chem. Soc. 1980,
102, 7936–7937.
T [K]
θmax [°]
71
Number of reflections
Measured reflections
Indepependent reflections 3265
Observed reflections
|F|/σ(F) Ͼ 4.0
Rσ
3506
9070
8700
[19] B. Jahn, H. Dreeskamp, Ber. Bunsen-Ges. Phys. Chem. 1984,
88, 42–47.
[20] See also K. Angermund, K. H. Claus, R. Goddard, C. Krüger,
Angew. Chem. 1985, 97, 241–252; Angew. Chem. Int. Ed. Engl.
1985, 24, 237–248.
2500
0.048
226
0.1557
0.0560
1.071
0.19
5142
0.0624
559
0.3061
0.0883
1.054
0.65
Parameters
wR (F2, all reflections)
R, F Ͼ 4σ(F)
S
[21] D. Cao, H. Meier, Angew. Chem. 2001, 113, 193–195; Angew.
Chem. Int. Ed. 2001, 40, 186–188.
[22] For more recent review articles on the photochemistry of an-
thracenes see ref.[23–27]
.
Max. ∆ρ (eÅ–3)
Min. ∆ρ (eÅ–3)
[23] H. Bouas-Laurent, A. Castellan, J.-P. Desvergne, R. Lapouy-
ade, Chem. Soc. Rev. 2001, 30, 248–263.
–0.24
–0.72
[24] H. Bouas-Laurent, A. Castellan, J.-P. Desvergne, R. Lapouy-
ade, Chem. Soc. Rev. 2000, 29, 43–55.
[25] H. D. Becker, Chem. Rev. 1993, 93, 145–172.
[26] H. D. Becker in Advances in Photochemistry (Eds.: D. H. Vol-
man, G. S. Hammond, K. Gollnik), vol. 15, p. 139–227, John
Wiley & Sons, New York 1990.
CCDC-634267 -634268 (for 5a and 5b, respectively) contain the
supplementary crystallographic data for this paper. These data can
be obtained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
[27] H. Bouas-Laurent, J.-P. Desvergne, ref.[14], chapter 14, p. 561–
630, Elsevier, Amsterdam, 1990.
[28] The 1H-NMR spectrum of the raw reaction product 5b con-
tains a trace of 4b.
Acknowledgments
[29] Allusively the splitting of this signal can be seen in a resolution-
enhanced output of the FID (free induction decay).
[30] The coalescence temperatures of the signals permit a rough
estimation of the activation barrier of the restricted rotation:
∆G϶ = 66Ϯ5 kJmol–1.
[31] H.-D. Becker, V. Langer, J. Org. Chem. 1993, 58, 4703–4708.
[32] The reverse photochemical reaction 5Ǟ3 is not sufficiently
straightforward for an optical switch.
We are grateful to the Deutsche Forschungsgemeinschaft, the
Fonds der Chemischen Industrie and the National Natural Science
Foundation of China (20272059, 20572111) for financial support.
We thank Prof. Henri Bouas-Laurent (University of Bordeaux) for
many valuable discussions.
[1] Selected books and review articles.[2–15]
.
[33] D. Cao, S. Dobis, D. Schollmeyer, H. Meier, Tetrahedron 2003,
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59, 5323–5327.
3193.
[34] A. Altomare, G. Cascarano, C. Guagliardi, M. C. Burla, G.
Polidori, M. Camalli, J. Appl. Crystallogr. 1994, 27, 435.
[35] G. M. Sheldrick, SHELXL-97: Program for crystal structure
refinement; University of Göttingen, Germany.
Received: February 16, 2007
[3] F. M. Raymo, M. Tomasulo, Chem. Soc. Rev. 2005, 24, 327–
336.
[4] F. M. Raymo, M. Tomasulo, J. Phys. Chem. A 2005, 109, 7343–
7352.
[5] V. I. Minkin, Chem. Rev. 2004, 104, 2751–2776.
Published Online: May 3, 2007
Eur. J. Org. Chem. 2007, 2964–2969
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
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