Anthracene-resorcin[4]arene-based capsules: Synthesis and photoswitchable features

Article abstract of DOI:10.1039/c1ob06030a

Herein we present the synthesis and the photochemical behavior of several new hemicarcerands containing anthracene units as photoactive species. By means of NMR investigations of compounds 9 and 11 the dimerization mode was revealed as a 9,10-9′,10′-dimer

Full text of DOI:10.1039/c1ob06030a

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Organic &
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PAPER
Anthracene-resorcin[4]arene-based capsules: Synthesis and photoswitchable
features†
Sebastian Bringmann,a Ralf Brodbeck,b Ramona Hartmann,a Christian Scha¨ferc and Jochen Mattay*a
Received 27th June 2011, Accepted 5th August 2011
DOI: 10.1039/c1ob06030a
Herein we present the synthesis and the photochemical behavior of several new hemicarcerands
containing anthracene units as photoactive species. By means of NMR investigations of compounds 9
and 11 the dimerization mode was revealed as a 9,10-9¢,10¢-dimerization, classically known from
anthracene. Nevertheless only compound 11 could be converted to the opened form upon irradiation
with 300 nm. Reopening of compounds 9 and 10 could not be achieved so far either by heating or by
irradiation.
heating the sample to 60 ◦C. Based on this work two dimeric
Introduction
capsules consisting of two resorcinarenes and two anthracene
Supramolecular chemistry is a highly fascinating research field,
units were synthesized and their properties as switchable molecular
containers were examined.5f Both molecules can be closed upon
irradiation with UV light as expected. However the reopening
of the capsules could not be achieved either by heating or by
irradiation. The photochemical behavior of anthracene depends
in a decisive manner on the type as well as the positions of
substituents on the anthracene core.6,7 Therefore and to reduce
the sterical demand on the photoactive positions 9 and 10 we
decided to switch from the 9,10-functionalized anthracenes to their
1,5-derivatized homologues as building blocks for photochromic
hemicarcerands.
which was recognized publicly in 1987 by awarding the Nobel prize
to Pederson, Lehn and Cram.1 Calixarenes as a class of organic
macromolecules are interesting and versatile representatives of
this area. They are distinguished by their vase shaped cavity,
straightforward accessibility and by the broad range of possible
chemical functionalizations.2 In addition they exhibit a strong
tendency to coordinate charged as well as neutral guests e.g. small
molecules. Resorcinarenes are one subtype of the calixarenes and
are build up from the name-giving resorcinol.3 They are extensively
described in the literature in the form of their oxygen-bridged
derivatives, the cavitands, to form a variety of supramolecular
assemblies.4 For many years we have undertaken research on
the more flexible oxygen-methylated analogues.5 Thereby we have
also focused on the attachment of the resorcinarene scaffold to
photochromic units like anthracene. Anthracene is well known to
undergo a [4 + 4] cycloaddition with itself upon UV irradiation.6
The back reaction can be conducted by irradiation with light of
another wavelength or by thermal treatment of the sample. In
2004 Scha¨fer et al. published the attachment of two anthracenes
on 1,3-alternate positions of the resorcinarene and utilized the
photochromic behavior of the anthracene units to modulate the
accessibility of the cavity.5a–e The authors demonstrated that upon
irradiation the intramolecular dimeric form of the anthracenes
was formed and they could revert the cycloaddition by means of
Results and discussion
Synthesis and characterization
Recently we reported the synthesis of several 1,5-functionalized
anthracenes by means of Kumada coupling starting from 1,5-
dichloroanthracene (two of them, 1 and 2, are shown in Scheme
1).8
aBielefeld University, Department of Chemistry, Organic Chemistry I,
Universita¨tsstraße 25, 33615, Bielefeld, Germany. E-mail: mattay@uni-
bielefeld.de; Fax: +49-[0]521-106-6146
bIm langen Felde 2, 32756, Detmold, Germany. E-mail: ralfbrodbeck@
aol.co.uk
cUniversita` di Bologna, Dipartimento di Chimica “G. Ciamician”, Via F.
Selmi 2, 40126, Bologna, Italy. E-mail: cschaefer77@googlemail.com
† Electronic supplementary information (ESI) available: 1H-NMR spectra
and ESI-MS spectra of compounds 8, 9, 10 and 11; Optimized cartesian
coordinates of all mentioned structures; Structure of 9 and 11. See DOI:
10.1039/c1ob06030a
Scheme 1 Anthracene building blocks for the synthesis of supramolecular
systems.8
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Scheme 2 Synthesis of the two-fold hydroxy-resorcinarene 8 (R = iso-butyl): (a) NEt3, p-toluoyl chloride, CH3CN, 26%; (b) NBS, acetone, 75%; (c)
KOH, MeOH, H2O, 74%; (d) NaH, MeI, DMF, 75%; (e) n-BuLi, B(OMe)3, THF, H2O2 (30% in H2O), NaOH, H2O, 41%.
The molecules 1 and 2 are perfectly suited for the linkage to a
resorcinarene via nucleophilic substitution, owing to their benzylic
bromide functions. In addition Fages et al. reported that 1,5-
functionalized anthracenes show a similar photochromic behavior
like anthracene itself,7 i.e. [4 + 4] cycloaddition via positions 9 and
10. Therefore the anthracenes 1 and 2 seem to be ideally suited for
the synthesis of a photochromic, reversible hemicarcerand.
For the two-fold 1,3-functionalization of resorcinarene 3 a
procedure that had already been reported before was applied
(Scheme 2).9
The distal derivatization was realized by the introduction of
four ester functions in a yield of 26%. Owing to the sterical
demand of these groups the following bromination with NBS
only took place on the two positions between the free hydroxy-
functions and led to the dibrominated resorcinarene 5 in 75%. The
esters were cleaved under basic conditions and the corresponding
resorcinarene 6 was obtained with 74% yield. The methylation
of the hydroxy-functions was performed under standard reaction
conditions with methyl iodide and sodium hydride in DMF (75%).
The subsequent formation of a boronic ester with oxidative work-
up to yield the needed building block 8 for the hemicarcerand
synthesis (41%) was adopted from Irwin et al.10 However the
reaction conditions were slightly modified, in particular the
reaction times for the lithiation and the following quenching
with trimethyl borate were extended (see experimental section).
Though the synthesis of the corresponding cavitand was already
described in 2000,10 surprisingly compound 8 was not reported
before.
The reactions between resorcinarene building block 8 and
anthracenes 1 and 2 were performed in DMF with caesium
carbonate as base to yield the dimeric capsules 9 and 11 as well as
the trimeric capsule 10 (Scheme 3).
The capsules are directly obtained in one step instead of two
consecutive reaction steps which is an advantage compared to our
previous work whereby one tedious purification step via HPLC
can be avoided. As normal for these kind of reactions the yields
of the isolated products are rather low, since the formation of
oligomer or polymer byproducts is inevitable. The reaction of the
resorcinarene 8 with anthracene 2 afforded capsule 11 with the
highest yield of 14%. Compounds 9 and 10 could only be isolated
in yields of 4% and 2%, respectively. Compounds 9–11 have not
been reported in the literature so far. In addition, 10 is, to the best
of our knowledge, the first example of a photoreactive trimeric
capsule based on calixarene units.
All compounds were characterized by means of NMR and
high resolution mass spectrometry. Especially the NMR spectra
in CDCl3 reveal that the symmetry of the resorcinarene core
unit is maintained not only in both dimers 9 and 11 but also
in trimer 10. Thus in all three cases the aromatic protons of the
resorcinarene part can be assigned to three signals in the 1H NMR
spectrum exactly like for the starting macrocycle 8. In addition the
anthracene units in compounds 9 and 10 only show four distinctive
aromatic signals. In the case of 11 two more signals are expected
and observed in toluene-d8 due to the protons of the additional
phenyl rings. This indicates furthermore that the anthracenes are
fixed symmetrically to each other.
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Scheme 3 Schematic depiction of the dimer and trimer capsule formation starting from diol 8 and anthracenes 1 and 2, respectively. Blue bowl =
dihydroxyresorcinarene 8, reaction conditions: Cs2CO3, DMF, 9: 4%, 10: 2%, 11: 14%.
Photochemistry
decrease of the anthracene bands as well, however a complete
disappearance could not be observed. This behavior is expected
since the photochemical reaction between two anthracenes in
one capsule still leaves one anthracene subunit unreacted. An
intermolecular dimerization and thus a linkage of two trimers
via the “free” anthracene can be excluded owing to the low sample
concentration of ca. 10-4 M.
A thermal reversion of the cycloaddition could not be detected
in all three cases even though the dimerized samples were heated
over several hours at 100–120 ◦C. Higher temperatures e.g. 160 ◦C
led to decomposition of the compounds.
The absorption spectra of compounds 9–11 in degassed toluene
solution are shown in Fig. 1.
All compounds show the typical anthracene pattern of absorp-
tion bands between 300 and 425 nm. 9 and 10 display very similar
absorption spectra owing to the same anthracene unit. In contrast
anthracene bands of 11 are broader and shifted by ca. 20 nm to
longer wavelengths, due to the extension of the aromatic system.
Anthracene dimerization occurs in all three cases upon irradiation
with 350 nm light indicated by a decrease of the anthracene signals.
The cycloaddition of capsule 9 is completed within 5 min where
capsule 11 needs to be irradiated for 20 min before no further
changes in the spectrum can be observed. Trimer 10 shows a
After irradiation of the macrocycles 9 and 10 with 300 nm
light the cycloaddition could also not be reversed. Instead of the
recovery of the anthracene bands the absorption curves are just
Fig. 1 UV/Vis spectra of compounds 9 (a), 10 (b) and 11 (c) in toluene and 11 in chloroform (d), c = ca. 1 ¥ 10-4 mol L-1.
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lifted over the complete spectrum. This points to a decomposition
of the compounds.
singlets in the open form (for details see experimental part). New
signals can be observed for the aromatic resorcinarene protons as
well (Fig. 2, open: 3 signals, closed 5 signals). However, the signals
that can be assigned to the anthracene part indicate a symmetrical
arrangement of this photochromic unit in the dimerized form.
The two doublets at 6.89 ppm and 6.91 ppm and the triplet at 6.73
ppm suggest that the anthracenes dimerized via positions 9 and
10. Other possible cycloadditions like the 9,10–1¢,4¢-dimerization
would give rise to quite a different signal pattern.7 As expected the
photochemical reaction results in the disappearance of the signal
of the directly involved protons at 8.37 ppm, due to the loss of
aromaticity on the central anthracene ring in the cycloaddition.
Instead these protons are shifted to higher field to give a singlet
at 5.04 ppm. Summarizing the results obtained from the NMR
spectrum of the closed form, dimerization of both anthracene
units seems to occur between positions 9 and 10.
The process of the cycloaddition of 11 could be investigated
by means of NMR spectroscopy as well. The 1H NMR spectrum
of 11 in toluene before and after 25 min irradiation with 350 nm
is shown in Fig. 3. The signal at 8.28 ppm which is ascribed to
the anthracene protons in position 9 and 10 vanishes completely
after irradiation with 350 nm. Instead a new singlet at 4.58 ppm
appears for these protons indicating a symmetrical dimerization.
This interpretation is supported by the signals in the aromatic
area. The protons of the aromatic part of the resorcinarene can be
assigned to three singlets just as before irradiation. In addition,
the aromatic anthracene protons only show three signals and prove
Compound 11 differs decisively from this behavior. Irradiation
of the dimerized compound in toluene with 300 nm light leads
to an increase of the anthracene bands to more than 60% of the
starting intensity already after 1 min, indicating a reopening of
the closed form. It is most likely that a complete reopening is
not possible due to degradation processes with energy-rich 300
nm light which occurs upon further irradiation. This only leads
to an increase of the absorption curve between 300 and 330 nm
indicating decomposition of 11.
An essential difference of the switching behavior occurs upon
changing the solvent from toluene to chloroform. Dimerization
can be conducted in chloroform just as in toluene by means of
irradiation with 350 nm light indicated by the decreasing an-
thracene bands in the absorption spectrum (Fig. 1d). Remarkably,
the cyclized form of 11 in chloroform cannot be reopened neither
by heating nor by irradiation.
NMR experiments
Due to the high reactivity of 9 towards UV light the corresponding
closed form of the capsule could be isolated and examined via
NMR spectroscopy. A comparison of the 1H NMR spectra of the
open and the closed form points to a change in the symmetry of
the resorcinarene units during the dimerization. Thus the methoxy
functions display four singlets in the closed form instead of two
Fig. 2 NMR spectra of the open (blue) and closed form (red) of 9 in CDCl3. The blue coloured circle in the upper spectrum represents the corresponding
aromatic anthracene protons. In the closed form the protons at position 9 and 10 are shifted to a new signal at higher field (red rectangle).
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Fig. 3 NMR spectra of dimer 11 in toluene-d8 before (top) and after 25 min irradiation with 350 nm light (bottom). In the upper spectrum two aromatic
signals of the anthracenes are covered by the toluene-d8 signal. Upon irradiation the signal for the protons at position 9 and 10 (blue circle) is shifted to
higher field (red rectangle).
the 9,10–9¢,10¢ cycloaddition. In case of a different cyclization e.g.
between positions 9,10 and 1¢,4¢ the spectrum would give rise to
a more complex signal pattern. Much smaller signals mainly in
the aromatic area, point to a reaction competitive to the 9,10–
9¢,10¢ dimerization. However, due to the low intensity they cannot
be assigned so far. In comparison to the 9,10–9¢,10¢ dimerization
such a side reaction seems to be much less significant.
In principle dimerization in CDCl3 shows the same behavior
upon irradiation as in toluene-d8. However, a complete analysis of
the NMR spectrum is complicated due to the fact that a chlorina-
tion of 11 by irradiation in chloroform took place as well. By means
of ESI mass spectrometry the capsule mass plus one chlorine
atom could be detected after 20 min irradiation in chloroform.
Therefore some unforeseen radical processes obviously took place.
These side reactions could be a possible explanation for the non-
reversible switching behavior in chloroform in contrast to toluene.
Owing to this chloroform is not a suitable solvent for this kind
of investigation. Higher masses due to an intermolecular reaction
could not be observed either in chloroform or toluene.
available for potential guest molecules we examined one confor-
mation isomer of 11 with KS-DFT calculations. We focused on 11
since this is the only compound that shows the desired reversible
switching behavior. The DFT-calculations were conducted for the
derivative of 11 wherein the iso-butyl groups are exchanged against
methyl functions.
Because of 11’s comparatively large number of atoms we chose
as theoretical method the BP8611a,11b local density functional
in combination with the Stuttgart-Dresden pseudo potentials
and associated double zeta quality basis set,12 SDD, without
polarization functions (thereby reducing significantly the num-
ber of used basis functions). Although neglecting polarization
functions is normally not advisable we checked that missing
polarization functions have no effect on the structurally important
phenyl–arene dihedral angles (by comparing the BP86-D/SDD
and RIMP2/def2-TZVP equilibrium structures of the model
compound a-phenylnaphthalene) and no significant effect on
internuclear distances (carbon–carbon internuclear distances are
underestimated at maximum by 1.5 pm with respect to the
RIMP2/def2-TZVP optimized structure; we expect no larger
errors for internuclear distances in the resorcinarene unit of 11).
Overall, the BP86/SDD method seems to be accurate enough for
the purpose of estimating structural parameters of 11.
Theoretical calculations
At the moment no crystallographic structure information is
available for compounds 9–11. To get at least some insight into
the overall molecular shape and especially into the dimensions
A priori it was unclear if there are attractive non-bonding
interactions between 11’s anthracene units and maybe even
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between the phenylene rings bonded to the anthracene units.
Therefore we re-optimized the obtained BP86/SDD stationary
point using the BP86-D/SDD method (the BP86/SDD method
in combination with Grimme’s empirical vdW-correction13a,13b
for KS-DFT). Unfortunately, a (numerical) normal coordinate
analysis for this BP86-D/SDD stationary point is computationally
very expansive (as the used ORCA programme14 has no analytical
second derivatives implemented) and was therefore omitted.
Additionally, also the normal mode analysis of the BP86/SDD
stationary point turned out to be impossible because of an
internal error of the used Gaussian03 programme15 (toomany ECP
integrals in the programme part for calculation of the Hessian).
Nevertheless, we are optimistic that both structures shown in Fig.
4 are local minima on their respective potential energy surfaces as
we observed no negative eigenvalues of the approximate Hessians
obtained during the structure optimization.
guest between the anthracene subunits. The structure obtained
from the dispersion-corrected BP86 calculation should be nearly
identical to pure 11’s equilibrium structure in the gas phase or
solid state.
If the attractive interaction between the anthracene units is not
disturbed by a guest or a solvent the precoordination between
the anthracenes may lead to a preferred dimerization between
positions 9 and 10. This could be an explanation for the fact
that dimerization of capsule 11 mainly leads to a symmetri-
cal dimer as proven by NMR-experiments shown in the last
section.
Optimized cartesian coordinates of all mentioned structures are
given in the ESI.†
Conclusions
In conclusion, we present the synthesis of three new macrocyclic
capsules based on resorcinarene units and anthracene linkers.
All three compounds dimerize upon irradiation with 350 nm
but only capsule 11 can be reopened by means of exposure to
300 nm light in toluene to more than 60%. Investigation of the
dimerization behavior in NMR indicates that both compounds,
9 and 11, dimerize “classically” via positions 9 and 10 as known
from anthracene itself.
This is the first example in the literature where the shape of
an anthracene-calixarene-based capsule like 11 can be switched
reversibly by irradiation at different wavelengths. In addition, the
closed form is stable at room temperature and even at elevated
temperatures since a thermal back reaction was never observed.
Our future objective is to improve the efficiency of the reopening
and to investigate the effects of dimerization on the coordination
of smaller molecules. Since the shape of the inner cavity of 11
can be controlled by light a number of interesting applications,
e.g. light-driven reactions or host–guest interactions inside the
supramolecular system, are thinkable.
Fig. 4 Stick representations of the obtained (a) BP86/SDD (no dis-
persion correction) and (b) BP86-D/SDD (with dispersion correction)
stationary point, respectively.
Experimental section
General remarks
Fig. 4 shows stick representations of the obtained stationary
points: on the left hand side without dispersion correction and on
the right hand side with dispersion correction. In the conformation
isomer obtained from the dispersion corrected BP86-D calculation
the parallel oriented anthracene units are roughly at right angle
with the phenyl ring planes of the resorcinarene while in the BP86
conformation isomer this dihedral angle is only approx. 45 degrees.
The whole molecule is of roughly cylindrical shape with a length
All commercially available compounds were purchased from
Acros, Alfa Aesar or Sigma-Aldrich and were used without further
purification. Dibromoresorcinarene 7 needed for the synthesis of
8 was synthesized according to literature.9 Solvents were dried
according to standard procedures. Column chromatography was
performed with silica gel (0.040–0.063 mm, Macherey–Nagel). All
HPLC separations were conducted on a Kontron Instruments
system using an UV/VIS detector (observing at 280 nm and
365 nm) and a silica gel column from Machery–Nagel.
˚
of approximately 25.14 A. Without the dispersion correction the
distance between the two planes containing the anthracene carbon
˚
nuclei is approximately 6.43 A and with dispersion correction it
NMR spectra were recorded on a 500 MHz NMR spectrometer
(Bruker, DRX500). Spectra were referenced to solvent peaks
(CDCl3 = 7.24 ppm (1H), 77.0 ppm (13C), DMSO-d6 = 2.49 ppm
(1H), 39.52 ppm (13C), CD2Cl2 = 53.80 ppm (13C), toluene-d8 =
7.09 ppm (1H), acetone-d6 = 29.84 ppm). HRMS spectra were
performed using a Fourier Transform Ion Cyclotron Resonance
(FT-ICR) mass spectrometer Bruker APEX III. Irradiations at
350 nm and 300 nm were carried out in a rayonet reactor.
Absorption spectra were recorded with a Perkin-Elmer Lambda
40 spectrometer.
˚
shrinks to approximately 3.14 A. Taking the carbon atom’s van
der Waals radius of 1.70 A into account the space between the
anthracene units available for a guest has a diameter of roughly
4.73 A in the structure without dispersion correction while in the
structure with dispersion correction no space at all is available.
In the BP86 calculation without dispersion correction there are
no attractive but (Pauli) repulsive forces between the anthracene
subunits. Therefore this theoretical conformation isomer will be
more or less similar to the structure of 11 containing a not too large
˚
˚
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rccc-5,17-Dihydroxy-4,6,10,12,16,18,22,24-octa-O-methyl-
2,8,14,20-tetra(iso-butyl)-resorcin[4]arene (8)
a) dimer 9: 8.0 mg (3.8 mmol, 4%), b) trimer 10: 6.0 mg (1.9 mmol,
2%).
Before the reaction was started rccc-5,17-Dibromo-4,6,10,12,
16,18,22,24-octa-O-methyl-2,8,14,20-tetra(iso-butyl)-resorcin-
[4]arene (7, 500 mg, 0.509 mmol, 1eq) was transferred into a flame
dried flask and treated with dry THF (5 mL). The solvent was
removed in vacuum and the residue was dried in vacuum for 45 min
at 80 ◦C. This procedure was performed three times. The remaining
solid (489 mg, 0.497 mmol, 1 eq) was dissolved in 30 mL dry
THF, cooled to -78 ◦C (acetone, dry ice bath) and treated with n-
butyllithium (1.27 mL, 2.04 mmol, 1.6 M in hexane, 4.1 eq). After 2
h stirring at this temperature freshly distilled trimethyl borate (0.29
mL, 2.5 mmol, 5.0 eq) was added, the cooling bath was removed
and the mixture was stirred over night at room temperature. 6.0
mL of a 1 : 1 mixture of aqueous hydrogen peroxide (30%) and
sodium hydroxide solution (3 M) were added under ice cooling
on the next day. After the ice bath was removed the solution was
stirred over night at room temperature (formation of a colourless
solid). Afterwards aqueous sodium bisulfite solution (50 mL, 1
M) was carefully (!) added at 0 ◦C. The reaction mixture was
extracted with ethyl acetate (3 ¥ 40 mL), the combined organic
phases washed with aqueous sodium bisulfite solution (2 ¥ 40 mL,
1 M), saturated aqueous sodium hydrogen carbonate solution (1 ¥
40 mL), brine (1 ¥ 40 mL) and dried over magnesium sulfate. After
evaporation of the solvent the raw product was purified by column
chromatography on silica gel (cyclohexane/ethyl acetate 7 : 3; raw
product was dissolved in ethylacetate and adsorbed onto silica gel;
Rf 0.10). Yield: 173 mg (0.202 mmol, 40%; corrected yield because
a small amount of ethyl acetate could not be removed in vacuum);
mp = 224 ◦C; dH (CDCl3, [ppm]) = 0.89 (d, 3J = 6.5 Hz, 24H, iso-
butyl CH3), 1.45–1.54 (m, 4H, iso-butyl CH), 1.65–1.70 (m, 8H,
iso-butyl CH2), 3.54 (s, 12H, OCH3), 3.66 (s, 12H, OCH3), 4.62 (t,
3J = 7.6 Hz, 4H, Ar-CH-Ar), 5.26 (s, 2H, OH), 6.27 (s, 2H, ArH),
6.34 (s, 2H, ArH), 6.68 (s, 2H, ArH); dC (acetone-d6, [ppm]) =
22.75, 22.78, 25.81, 33.55, 44.63, 55.83, 60.30, 96.40, 116.65,
125.66, 126.59, 133.42, 141.46, 143.64, 155.76; HRMS (ESI): m/z
calc. for [C52H72O10 + Na]+: 879.50177; found: 879.50045.
Dimer 9.
l
max(toluene)/nm 283 (e/dm3 mol-1 cm-1 4600), 292sh
(3500), 316 (1100), 334 (2000), 349 (3500), 366 (4900) and 387
(3400); dH (CDCl3, [ppm]) = 0.95 (dd, 3J = 12.8 Hz, 6.3 Hz,
48H, iso-butyl CH3), 1.54–1.64 (m, 16H, iso-butyl CH2), 1.91–
1.99 (m, 8H, iso-butyl CH), 3.21 (s, 24H, OCH3), 4.02 (s, 24H,
3
OCH3), 4.74 (dd, J = 9.5 Hz, 5.0 Hz, 8H, Ar-CH-Ar), 4.97 (s,
8H, anthracene-CH2), 6.15 (s, 4H, ArH), 6.64 (s, 4H, ArH), 6.97
3
3
(dd, J = 8.1 Hz, 6.8 Hz, 4H, anthracene-ArH), 7.02 (d, J =
5.5 Hz, 4 H, anthracene-ArH), 7.09 (s, 4H, ArH), 7.50 (d,3J =
8.5 Hz, 4H, anthracene-ArH), 8.37 (s, 4H, anthracene-ArH); dC
(CDCl3, [ppm]) = 22.20, 23.72, 25.80, 26.90, 33.58, 44.29, 56.13,
60.48, 72.75, 95.47, 120.59, 123.13, 123.88, 126.66, 127.15, 128.61,
129.13, 129.32, 131.22, 131.81, 132.94, 145.49, 150.98, 155.10.
HRMS (ESI): m/z calc. for [C136H164O20 + Na2]2+: 1081.58002;
found: 1081.58112.
Trimer 10.
l
max(toluene)/nm 286 (e/dm3 mol-1 cm-1 15600),
292sh (11700), 317 (3100), 332 (6100), 349 (12100), 366 (18700)
and 386 (13700); dH (CDCl3, [ppm]) = 0.90 (d, 3J = 5.8 Hz, 36H, iso-
butyl CH3), 0.95 (d, 3J = 5.9 Hz, 36H, iso-butyl CH3), 1.20–1.32 (m,
12H, iso-butyl), 1.50–1.53 (m, 12H, iso-butyl), 1.84–1.92 (m, 12H,
iso-butyl), 3.11 (s, 36H, OCH3), 3.92 (s, 36H, OCH3), 4.73 (dd, 3J =
8.9 Hz, 5.4 Hz, 12H, Ar-CH-Ar), 5.20 (s, 12H, anthracene-CH2),
3
6.30 (s, 6H, ArH), 6.54 (s, 6H, ArH), 6.91 (dd, J = 8.3 Hz, 6.9
3
Hz, 6H, anthracene-ArH), 7.07 (s, 6H, ArH), 7.16 (d, J = 6.7
Hz, 6H, anthracene-ArH), 7.55 (d, 3J = 8.5 Hz, 6H, anthracene-
ArH), 8.56 (s, 6H, anthracene-ArH). dC (CDCl3, [ppm]) = 22.41,
23.49, 25.74, 26.90, 33.03, 44.73, 56.08, 60.22, 72.92, 95.43, 120.44,
123.30, 124.32, 125.87, 126.92, 128.34, 129.11, 129.56, 131.68,
131.97, 133.30. 145.38, 150.70, 155.02.
HRMS (ESI): m/z calc. for [C204H246O30 + Na]+: 3198.76162;
found: 3198.78411.
Dimer 11
Same procedure as for the synthesis of 9 and 10. The used
substances were: 1,5-bis(4-bromomethylphenyl)anthracene (2, 80
mg, 0.16 mmol, 1 eq), rccc-5,17-dihydroxy-4,6,10,12,16,18,22,24-
octa-O-methyl-2,8,14,20-tetra(iso-butyl)-resorcin[4]arene (8, 133
mg, 0.155 mmol, 1 eq), caesium carbonate (1.01 g, 3.10 mmol, 20
eq). The reaction and the work up should be conducted under light
exclusion! Yield: 27 mg (11 mmol, 14%); Rf 0.21 (cyclohexane/ethyl
acetate 9 : 1); lmax(toluene)/nm 283 (e/dm3 mol-1 cm-1 13500),
292sh (8400), 341sh (2700), 362 (4800), 381 (6500) and 402 (4700);
dH (CDCl3, [ppm]) = 0.96 (d, 3J = 6.4 Hz, 24H, iso-butyl CH3), 1.00
(d, 3J = 6.4 Hz, 24H, iso-butyl CH3), 1.51–1.66 (m, 16H, iso-butyl
CH2), 1.92–2.00 (m, 8H, iso-butyl CH), 3.41 (s, 24H, OCH3), 3.97
(s, 24H, OCH3), 4.75 (dd, J = 9.2 Hz, 5.6 Hz, 8H, Ar-CH-Ar),
4.83 (s, 8H, anthracene-CH2), 6.16 (s, 4H, ArH), 6.58 (s, 4H, ArH),
6.73 (dd, 3J = 8.3 Hz, 6.9 Hz, 4H, anthracene-ArH), 6.96 (d, 3J =
6.5 Hz, 4H, anthracene-ArH), 7.13 (s, 4H, ArH), 7.33 (d, J =
8.6 Hz, 4H, anthracene-ArH), 7.39–7.45 (m, 16H, anthracene-
Dimer 9 and trimer 10
1,5-Bis(bromomethyl)anthracene (1, 85 mg, 0.23 mmol,
1
eq) and rccc-5,17-dihydroxy-4,6,10,12,16,18,22,24-octa-O-
methyl-2,8,14,20-tetra(iso-butyl)-resorcin[4]arene (8, 200 mg,
0.233 mmol, 1 eq) were dissolved in 20 mL dry DMF in a flame
dried flask under argon and light exclusion. Caesium carbonate
(1.52 g, 4.67 mmol, 20 eq) was added, the solution was stirred for
1 h at room temperature and afterwards 4 d at 60 ◦C. The mixture
was filtered and the DMF was removed in vacuum. The residue
was dissolved in dichloromethane (80 mL) and water (50 mL).
After phase separation the aqueous phase was extracted with
dichloromethane (2 ¥ 50 mL). The combined organic phases were
washed with water (2 ¥ 80 mL) and brine (1 ¥ 80 mL) and dried over
magnesium sulfate. The dissolved crude product was adsorbed
onto silica gel und purified by means of column chromatography
(cyclohexane/ethyl acetate 85 : 15) and HPLC (cyclohexane/ethyl
acetate 9 : 1, Rf = a) dimer 9: 0.22, b) trimer 10: 0.25). The reaction
and the work up should be conducted under light exclusion! Yield
3
3
ArH), 8.14 (s, 4H, anthracene-ArH); dH (toluene-d8, [ppm]) = 1.11
(d,3J = 6.4 Hz, 24H, iso-butyl CH3), 1.14 (d, J = 6.3 Hz, 24H,
3
iso-butyl CH3), 1.82–1.93 (m, 16H, iso-butyl CH2), 2.24–2.32 (m,
8H, iso-butyl CH), 3.64 (s, 24H, OCH3), 3.69 (s, 24H, OCH3),
5.05 (s, 8H, anthracene-CH2), 5.20 (dd, 3J = 10.1 Hz, 4.6 Hz, 8H,
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3
Ar-CH-Ar), 6.49 (s, 4H, ArH), 6.62 (dd, J = 8.3 Hz, 6.9 Hz,
integration, automatically generated auxiliary basis set for charge
density fitting, de-activated fast multiple method and standard
convergence criteria in the SCF convergence and structure opti-
mization, resulting in a relative accuracy of the electronic energy
of 1 ¥ 10-7 a.u. The structure optimization took place under
constraint of Ci symmetry.
The BP86-D/SDD calculations were performed with the ORCA
programme14 using the “grid6, nofinalgrid” accuracy in numerical
integration, the SV/J auxiliary basis set for charge density
fitting (taken from the programme’s internal basis set database),
“scfconv7” SCF convergence criteria and standard convergence
criteria in structure optimization, resulting in a relative accuracy
of the electronic energy of 5 ¥ 10-7 a.u. No symmetry constrained
was used (not possible in the used programme version) but as
the starting structure was Ci-symmetric the obtained equilibrium
structure is also approximately Ci-symmetric.
3
4H, anthracene-ArH), 6.68 (s, 4H, ArH), 7.48 (d, J = 8.0 Hz,
8H, anthracene-ArH), 7.52 (s, 4H, ArH), 7.56 (d, 3J = 8.0 Hz, 8H,
anthracene-ArH), 8.28 (s, 4H, ArH), two signals of the anthracene
moiety are covered by the residual proton signals of toluene-d8. dC
(CDCl3, [ppm]) = 11.09, 14.09, 22.38, 23.08, 23.32, 23.60, 25.76,
30.10, 33.38, 41.95, 44.34, 56.11, 60.54, 65.31, 74.13, 95.25, 120.46,
124.01, 124.37, 126.11, 126.91, 127.50, 127.83, 128.54, 128.84,
129.96, 131.28, 131.93, 137.29, 138.51, 139.84, 145.54, 150.73,
154.97.
HRMS (ESI): m/z calc. for [C160H180O20
+
(NH4)2]2+:
1228.68722; found: 1228.68891.
Irradiation of 9, 10 and 11
Solutions of 9, 10 and 11 (c = ca. 1 ¥ 10-4 mol L-1) in toluene
were filled into a quartz glass cuvette and degassed for 15 min
by bubbling argon through the solution via cannula. The sealed
sample was placed in a 350 nm photoreactor and irradiated.
The closed forms were subsequently irradiated in a 300 nm
photoreactor.
Acknowledgements
Support by the Deutsche Forschungsgemeinschaft (SFB 613) is
gratefully acknowledged.
For NMR investigation of the dimerization process, dimer 11
was dissolved in chloroform (c = 5.2 ¥ 10-4 mol L-1) and toluene (c =
6.2 ¥ 10-4 mol L-1), respectively. The solutions were degassed for 15
min as described above with argon and irradiated in a sealed quartz
glass cuvette (for the chloroform solution) or directly in a NMR
tube (for the toluene solution). The process of the dimerization
was checked by means of 1H NMR measurements.
Notes and references
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Closed form of 9 in chloroform
dH (CDCl3, [ppm]) = 0.93 (t, 3J = 5.7 Hz, 48H, iso-butyl CH3),
1.43–1.49 (m, 8H, iso-butyl CH2) 1.57–1.65 (m, 8H, iso-butyl
CH2), 1.87–2.00 (m, 8H, iso-butyl CH), 3.21 (s, 12H, OCH3),
3.48 (s, 12H, OCH3), 3.94 (s, 12H, OCH3), 4.01 (s, 12H, OCH3),
4.62–4.71 (m, 16H, Ar-CH-Ar, anthracene-CH2), 5.04 (s, 4H,
anthracene dimer-9,10-H), 5.90 (s, 2H, ArH), 6.03 (s, 2H, ArH),
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6.53 (s, 2H, ArH), 6.64 (s, 2H, ArH), 6.73 (t, J = 7.5 Hz, 4H,
3
anthracene dimer-ArH), 6.89 (d, J = 7.4 Hz, 4H, anthracene
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3
dimer-ArH), 6.91 (d, J = 7.7 Hz, 4H, anthracene dimer-ArH),
7.03 (s, 4H, ArH).
Closed form of 11 in toluene
dH (CDCl3, [ppm]) = 1.11 (dd, J = 12.1 Hz, 6.1 Hz, 48H, iso-
3
butyl CH3), 1.80–1.91 (m, 16H, iso-butyl CH2), 2.23–2.32 (m, 8H,
iso-butyl CH), 3.55–3.63 (m, 24H, OCH3), 3.65–3.72 (m, 24H,
OCH3), 4.58 (s, 4H, anthracene dimer-9,10-H), 4.79 (d, 2J = 10.2
Hz, 4H, anthracene-CH2), 4.86 (d, 2J = 10.1 Hz, 4H, anthracene-
CH2), 5.15–5.24 (m, 8H, Ar-CH-Ar), 6.49 (s, 4H, ArH), 6.66 (t,
3J = 7.5 Hz, 4H, anthracene dimer-ArH), 6.73 (s, 4H, ArH), 6.77
(d, 3J = 7.6 Hz, 4H, anthracene dimer-ArH), 6.83 (d,3J = 7.6 Hz,
4H, anthracene dimer-ArH), 7.25 (d,3J = 7.9 Hz, 8H, anthracene
3
dimer-ArH), 7.46 (d, J = 7.7 Hz, 8H, anthracene dimer-ArH),
7.52 (s, 4H, ArH).
Closed form of 11 in chloroform
Owing to the complexity of the obtained spectrum a precise
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Computational details
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programme15 using the “ultrafinegrid” accuracy in numerical
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The Royal Society of Chemistry 2011
Org. Biomol. Chem., 2011, 9, 7491–7499 | 7499
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