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mmol, 76%) as yellow solid, which was used for the next step
without further purification. 1H NMR (400 MHz, CDCl3): δ
(ppm) 9.01 (s, 1H), 8.54 (s, 1H), 8.04 (d, J = 8.6 Hz, 2H), 7.63
(d, J = 6.8 Hz, 2H), 7.43 (dd, J = 6.8, 8.6 Hz, 2H), 5.16 (s, 4H).
Synthesis of 1,8-Bis[(pyridin-1-ium-1-yl)methyl]anthra-
cene dibromide. A mixture of 1,8-bis(bromomethyl)anthra-
cene (919 mg, 2.52 mmol) and pyridine (4 mL) was stirred at
r.t. for 4 hr. MeOH was added to give a homogenous solution,
which was then added dropwise into Et2O. The yellow solid
precipitated was collected by centrifugation and dissolved into
MeOH again. The solution was filtered through a Teflon mem-
brane (pore size 0.45 ¯m) and subjected to vapour diffusion
recrystallization using MeOH with Et2O. The obtained solid
was washed with Et2O and dried under vacuum to give yellow
solid of 1,8-bis[(pyridin-1-ium-1-yl)methyl]anthracene dibro-
mide (914 mg, 1.75 mml, 69%). 1H NMR (400 MHz, CD3OD):
δ (ppm) 9.07 (d, J = 6.0 Hz, 4H), 8.84 (s, 1H), 8.70 (s, 1H),
8.64 (t, J = 7.7 Hz, 2H), 8.29 (d, J = 8.6 Hz, 2H), 8.12 (dd,
J = 6.8, 7.7 Hz, 4H), 7.63 (dd, J = 6.8, 8.6 Hz, 2H), 7.50 (d,
J = 6.8 Hz, 2H), 6.63 (s, 4H).
Figure 1. Thermal solid-state reaction.
and of 1,8-bis[(pyridin-1-ium-1-yl)methyl]anthracene dibro-
mide (52.0 mg, 0.100 mmol) in H2O (1 mL). After 1 hr with
stirring, dropwise addition of the mixture into Et2O afforded a
precipitate, which was collected by centrifugation and washed
with Et2O. The brown solid obtained was reprecipitated from
MeOH solution into Et2O twice and vacuum-dried to give 3
(49.0 mg, 0.075 mmol) as milky brown solid. Vapour diffusion
recrystallization from MeOH-H2O solution with acetone under
dark conditions was repeated twice to form red crystals along
with dark brown powder, the former of which were picked up
by using tweezers (27.4 mg, 0.042 mmol, 42%). 1H NMR spec-
trum (400 MHz, D2O): δ (ppm) 8.69 (d, J = 5.8 Hz, 4H), 8.48
(t, J = 7.6 Hz, 2H), 8.10 (s, 1H), 7.94 (t, J = 7.1 Hz, 4H), 7.72
(d, J = 8.6 Hz, 2H), 7.56 (s, 1H), 7.32 (m, 2H), 7.21 (m, 4H),
7.15 (t, J = 7.7 Hz, 2H), 7.02 (d, J = 6.7 Hz, 2H), 6.04 (s, 4H).
13C NMR spectrum (D2O, 100 MHz): δ (ppm) 183.3, 182.6,
177.5, 146.1, 144.1, 141.0, 133.7, 131.6, 131.5, 131.0, 130.7,
129.7, 129.7, 128.3, 128.2, 127.5, 126.8, 125.4, 125.3, 114.9,
61.6. NMR spectra are shown in Figures S5-S8 in Supporting
Information.
General Procedure for Thermal Solid-State Reaction.
Crystals of 1 or 3 were heated on a glass plate under N2 flow by
using an aluminium block bath (Figure 1). The spectroscopic
data for product 2 are shown by Figures 4, 5, and S9-S12. TG-
DTA showed that the decomposition of 2 started at 313 °C
without melting. The spectroscopic data for product 4 are
shown by Figures S14 and S17-S21. ESI MS: Found 499.1181
(C32H18O6+H), 521.0999 (C32H18O6+Na); Calc 499.1176
(C32H18O6+H), 521.1001 (C32H18O6+Na). Mp. 350 °C (dec.).
Synthesis of 1,8-Bis[(pyridin-1-ium-1-yl)methyl]anthra-
cene anthracene-1,8-dicarboxylate (1). There are two pre-
paration ways as follows.
a) Anthracene-1,8-dicarboxylic acid (51.9 mg, 0.194 mmol)
and 1,8-bis[(pyridin-1-ium-1-yl)methyl]anthracene dibromide
(100 mg, 0.191 mmol) was stirred with Ag2O (50.4 mg, 0.217
mmol) in MeOH (30 mL) at r.t. overnight. The mixture was
centrifuged, and the supernatant was vacuum-dried and dis-
solved again into MeOH/H2O (2/1 v/v, 3 mL). The solution
was filtered through a Teflon membrane (pore size 0.45 ¯m)
and subjected to vapour diffusion recrystallization with acetone
under dark conditions to form yellow needle-like crystals,
which were washed with acetone and vacuum-dried to afford
1 (65 mg) containing 4.5 wt% (evaluated by TGA) of MeOH/
H2O, thus, in 51% yield.
b) An aqueous solution (40%) of tetrabutylammonium
hydroxide (360 mg, 0.555 mmol) was added to anthracene-1,8-
dicarboxylic acid (74.7 mg, 0.281 mmol) in MeOH (1 mL). To
the mixture stirred for 10 min was added 1,8-bis[(pyridin-1-
ium-1-yl)methyl]anthracene dibromide (145 mg, 0.277 mmol).
After 2 hr with stirring at r.t., the mixture was added dropwise
to Et2O to give a milky brown precipitate, which was collected
by centrifugation and vacuum-died. The obtained crude prod-
uct of 1 (166 mg, 0.264 mmol) was purified by vapour diffusion
3. Results and Discussion
Preparation of 1,8-Bis[(pyridin-1-ium-1-yl)methyl]-
anthracene anthracene-1,8-dicarboxylate (1). The anionic
component, anthracene-1,8-dicarboxylic acid, was prepared by
the reported procedure6 and transformed to the cationic com-
ponent, 1,8-bis[(pyridin-1-ium-1-yl)methyl]anthracene dibro-
mide (Scheme 1). They were combined to give 1 by the counter
anion exchange of the benzylpyridinium salt from bromide to
carboxylate, mediated by silver(I) oxide or tetrabutylammo-
nium hydroxide. The former reagent works to precipitate AgBr,
and the pyridinium carboxylate is isolated from the super-
natant. The latter reagent converts the carboxylic acid to the
tetrabutylammonium carboxylate, which is subjected to ion-
exchange with the pyridinium bromide. The pyridinium car-
boxylate is separated from the tetrabutylammonium bromide by
reprecipitation into Et2O. The ionic combination compound, 1,
was prepared in this manner and purified by vapour diffusion
recrystallization under dark conditions.
1
recrystallization as mentioned above. H NMR spectrum (400
MHz, CD3OD): δ (ppm) 9.94 (s, 1H), 9.15 (s, 1H), 9.01 (d, J =
5.6 Hz, 4H), 8.68 (s, 1H), 8.37 (t, J = 7.8 Hz, 2H), 8.28 (s, 1H),
8.14 (d, J = 8.7 Hz, 2H), 7.87 (m, 6H), 7.65 (dd, J = 6.8, 1.0
Hz, 2H), 7.48 (dd, J = 6.9, 8.7 Hz, 4H), 7.41 (dd, J = 6.8, 8.5
Hz, 2H), 7.08 (d, J = 6.9 Hz, 2H), 6.85 (s, 4H). 13C NMR spec-
trum (100 MHz, CD3OD): δ (ppm) 177.6, 146.6, 146.3, 140.9,
133.4, 133.0, 132.2, 131.4, 130.6, 130.1, 130.0, 129.6, 129.2,
128.1, 127.7, 126.4, 126.0, 125.8, 125.6, 118.6, 63.4. NMR
spectra are shown in Figures S1-S4 in Supporting Information.
Synthesis of 1,8-Bis[(pyridin-1-ium-1-yl)methyl]anthra-
cene anthraquinone-1,8-dicarboxylate (3). To an aqueous
solution (0.5 mL) of anthraquinone-1,8-dicarboxylic acid (29.5
mg, 0.100 mmol) were successively added solutions of tetra-
butylammonium hydroxide in H2O (40%, 130 mg, 0.200 mmol)
Crystal Structure of 1.7 Pale yellow needle-like crystals of
1 were obtained by the vapour diffusion method from a MeOH-
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