FRET studies on a series of BODIPY-dye-labeled switchable resorcin[4]arene cavitands

Article abstract of DOI:10.1002/chem.201001625

A series of borondipyrromethane (BODIPY)-dye-labeled resorcin[4]arene cavitands 1-4 with different lengths of oligo(phenylene-ethynylene) spacers between the dyes and the macrocyclic rim has been synthesized. Their switching behavior from the "vase" to "k

Full text of DOI:10.1002/chem.201001625

DOI: 10.1002/chem.201001625
FRET Studies on a Series of BODIPY-Dye-Labeled Switchable
Resorcin[4]arene Cavitands
Igor Pochorovski, Benjamin Breiten, W. Bernd Schweizer, and FranÅois Diederich*[a]
Abstract: A series of borondipyrro-
methane (BODIPY)-dye-labeled resor-
cin[4]arene cavitands 1–4 with different
lengths of oligo(phenylene–ethynylene)
spacers between the dyes and the mac-
rocyclic rim has been synthesized.
Their switching behavior from the
“vase” to “kite” conformations in bulk
solution was examined by both varia-
ble-temperature (VT) NMR and fluo-
rescence spectroscopy. Both VT-NMR
and VT fluorescence resonance energy
transfer (FRET) experiments showed
that cavitands 1–4 undergo vase-to-kite
switching at low temperatures. Acid-
triggered switching to the kite confor-
mation was observed by fluorescence
spectroscopy. Quantitative evaluation
of the FRET data led to the determi-
nation of the Fçrster radius R0 =37 ꢀ
for the BODIPY-dye FRET pair and
an average cavitand opening angle a=
168 in the vase conformation.
G
ACHTUNGTRENNUNG
R
ACHTUNGTRENNUNG
Keywords: cavitands
· conforma-
tion analysis · FRET · molecular
devices · molecular switches
Introduction
ently bridged resorcin[4]arene cavitands.[7–10] Based on these
methods, donor–acceptor borondipyrromethane (BODIPY)-
dye[11]-substituted cavitand 1 was prepared, allowing investi-
gations on the mechanism of the vase–kite switching process
through fluorescence resonance energy transfer (FRET)
studies (Figure 1).[9,12,13] These investigations exploited the
fact that the energy-transfer process between the donor and
the acceptor dye is strongly dependent on the distance be-
tween the two chromophores. Hence, the transition to the
kite conformation upon addition of trifluoroacetic acid
(TFA) was clearly demonstrated by FRET measurements,
as the donor intensity strongly increased and the acceptor
intensity almost disappeared, due to the increased distance
between the two dyes. However, an unexpectedly low
FRET efficiency was observed in the contracted state; be-
cause the dyes were assumed to be in close proximity to one
another (based on models derived from X-ray structures of
Among various classes of receptor molecules, the quinoxa-
line-bridged resorcin[4]arene cavitands, which were first in-
troduced by Cram and co-workers in 1982, are particularly
fascinating because of their ability to undergo a triggered
conformational transition from a contracted “vase” state to
an expanded “kite” state.[1] To parlay such dynamic behavior
into advanced materials that serve as molecular grippers,
switches, or receptors, fundamental studies on these cavitand
systems are essential.[2] Three types of stimuli have been
shown to induce the vase-to-kite transition in the quinoxa-
line-bridged cavitands: changes in temperature,[1,3,4] pH,[5]
and ZnII ion concentration.[6] At ambient temperature, neu-
tral pH, or in the absence of ZnII ions, the closed vase geom-
etry is preferred, whereas lowering the temperature, acidifi-
cation, or addition of ZnII ions induces the transition to the
open kite conformation.
quinoxaline-bridged resorcin[4]arene cavitands),
a high
Growing interest in the functionalization of the cavitand
system for various applications[2] led to the development of
synthetic methods for the preparation of partially and differ-
FRET efficiency was expected. This surprising result was at-
tributed to either the dynamic behavior of the cavitand or
an unfavorable orientation of the transition dipole moments
of the dyes.[9,13] A separate investigation on dipyrene- and
dianthracene-substituted cavitands strengthened the hypoth-
esis that a large conformational flexibility is inherent to
these cavitand systems.[14] Both cavitands were shown to
form excimers in the vase conformation by means of fluo-
rescence spectroscopy. Opening of these cavitands to the
kite state was induced by acidification, presumably impart-
ing a large distance between the fluorophore moieties. Con-
[a] I. Pochorovski, B. Breiten, Dr. W. B. Schweizer, Prof. Dr. F. Diederich
Laboratorium fꢁr Organische Chemie
ETH Zꢁrich, Hçnggerberg, HCI
8093 Zꢁrich (Switzerland)
Fax : (+41)44-632-1109
E-mail: diederich@org.chem.ethz.ch
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201001625.
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FULL PAPER
Figure 1. The synthesis of the target cavitands 1–4.
trary to expectations, however, excimer formation did not
cease under these conditions. The surprising observations in
both studies suggested a high degree of flexibility of the cav-
itand system.
In light of these results, we decided to investigate the cav-
itand dynamics in greater detail. Because the Fçrster radius
of the BODIPY-dye pair for a fixed orientation in the cavi-
Results and Discussion
Synthesis of cavitands 1–4: Two different synthetic routes
were employed for the preparation of the target cavitands
1–4 (Figure 1). Relying on the reported procedure for cavi-
tand 1, cavitands 1–3 were prepared by Sonogashira cross-
coupling of the donor dyes 5–7 and acceptor dyes 8–10 with
a common cavitand intermediate, diiodocavitand 11.[9,14] The
smallest cavitand 4 was prepared from bridging tetrol
12[7,8,10] with flap-attached BODIPY dyes 13 and 14.
tand system was unknown, we prepared
a series of
BODIPY-dye-labeled resorcin[4]arene cavitands 1–4, which
incorporate oligo(phenylene–ethynylene) spacers of varying
lengths (Figure 1). This series enabled us to correlate the
FRET efficiency with the absolute distances between the
donor and acceptor dyes and thus to determine the Fçrster
radius and the average solution-state opening angle of the
cavitand system.
To access diiodocavitand 11, iodoimide 15[9] was treated
with tetrol 12[10] in a nucleophilic substitution reaction to
afford the desired product, as well as partially bridged cavi-
tand 16 as a side product (Scheme 1). Crystals of both prod-
Scheme 1. Synthesis of diiodocavitand 11. a) K2CO3, Me2SO, 358C, 48 h; 38% (11).
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F. Diederich et al.
ucts were grown from a single acetone/CH2Cl2 solution con-
taining a mixture of both compounds (Figure 2).[15]
To prepare the oligo(phenylene–ethynylene)-conjugated
BODIPY arms for cavitands 1–3, the short donor-dye arm
7[9] was treated with phenylacetylenes 17 and 18 (Scheme 2)
to give 19[9] and 20, respectively.[16] Subsequent alkyne de-
protection afforded the two elongated donor-dye arms, 5[9]
and 6, respectively. In a similar sequence of reactions, elon-
gated acceptor-dye derivatives 8[9] and 9 were obtained from
the short acceptor BODIPY dye 10[9] after deprotection of
21[9] and 22, respectively (Scheme 3).
Following the procedure for the formation of 23,[9,13]
donor arms 6 and 7 were each coupled to diiodocavitand 11
to yield 24 and 25, respectively (Scheme 4). Compared to
the purification of 23 and 24, purification of 25 was tedious
due to its poor solubility in CHCl3; however, recycling gel
permeation chromatography (GPC) afforded clean samples
of all three monosubstituted cavitands. In the next step, the
acceptor arms 8–10 were affixed to the monosubstituted cav-
itands 23–25, affording target cavitands 1–3, which were also
purified using recycling GPC.
In the smallest cavitand 4, the BODIPY dyes are directly
affixed to the phenyl linker, thereby necessitating a separate
synthesis of quinoxaline-substituted BODIPY arms. Toward
this goal, alcohol 26[17] was oxidized with pyridinium chloro-
chromate (PCC) and the resulting aldehyde 27 was treated
with 3-ethyl-2,4-dimethyl-1H-pyrrole in a three-step se-
quence, yielding BODIPY dye 28 (Scheme 5). Dye 29 was
obtained in a similar fashion by reaction of aldehyde 27
with pyrrole 30.[11b] Crystals of 28 were obtained by evapora-
tion from CH2Cl2 (the X-ray structure of 28 is shown in Fig-
ure 2SI in the Supporting Information).
To condense the BODIPY-dye moiety with the quinoxa-
line flap of the cavitand, nitroarenes 28 and 29 were reduced
to the corresponding aniline derivatives, 31 and 32, respec-
tively, using hydrazine and Pd/C[18] (Scheme 5). Aniline-dye
derivatives 31 and 32 were then each condensed with anhy-
dride 33[8,19] to afford dye arms 13 and 14, respectively
(Scheme 6). Crystals of both 13 and 14 were obtained by
Figure 2. Molecular structures of diiodocavitand 11 (top) and partially
bridged cavitand 16 (bottom) in the crystal measured at 123 K. Solvent
molecules, n-hexyl chains, and hydrogen atoms are omitted for clarity in
both cases. Thermal ellipsoids are shown at the 20% probability level for
11 and at the 50% probability level for 16.
slow evaporation from CH2Cl2. The X-ray structure of 13 is
shown in the Supporting Information (Figure 3SI), the one
Scheme 2. Synthesis of donor-dye arms 5 and 6. a) [Pd
96% (5), 77% (6). THF=tetrahydrofuran.
G
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Cavitands
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Scheme 3. Synthesis of acceptor-dye arms 8 and 9. a) [Pd
30 min; 79% (8), 86% (9).
N
Scheme 4. Synthesis of target cavitands 1–3. a) [Pd
ACHTUTNGRENGU(N PPh3)4], CuI, iPr2NEt, THF, 238C, 2–5 d; 26% (23), 24% (24), 22% (25). b) [PdACHUTGNTRENN(NGU PPh3)4], CuI,
iPr2NEt, THF/CHCl3, 358C, 2–5 d; 30% (1), 39% (2), 45% (3).
Scheme 5. Synthesis of BODIPY dyes 31 and 32. a) PCC, CH2Cl2, 238C, 1 h; 89% (27). b) 1) TFA, CH2Cl2, 238C, 3 h. 2) DDQ, toluene, 238C, 1 h, then
NEt3, BF3·Et2O, 75 8C, 40 min; 70% (28), 69% (29). c) N2H4·H2O, Pd/C, THF/EtOH, 708C, 1–32 h; 92% (31), 51% (32). PCC=pyridinium chlorochro-
mate, TFA=trifluoroacetic acid, DDQ=2,3-dichloro-5,6-dicyano-p-benzoquinone.
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F. Diederich et al.
BODIPY and pyrazinedione planes. Upon introduction of
13 and 14 into cavitand 4, such alignment should ensure a
parallel arrangement of the two BODIPY dyes, leading to
electronic decoupling of the BODIPY moiety from the
phenyl linker and an optimum transition dipole orientation
for FRET.
In the final assembly of cavitand 4, BODIPY dyes 13 and
14 were attached to tetrol 12 using standard conditions
(K2CO3, Me2SO)[7] (Scheme 7). Donor-dye-substituted cavi-
tand 34 was obtained under these conditions in only 6%
yield. MALDI (matrix-assisted laser-desorption-ionization)
mass spectra of crude product mixtures from this reaction
suggest that the low yield can be attributed to polymeri-
zation of the product, in which the free phenolic hydroxy
groups of a given molecule of 34 attack the quinoxaline
moiety in other molecules 34. Gratifyingly, the subsequent
bridging reaction with dye arm 14 was substantially higher
yielding and afforded cavitand 4 in 66% yield.
Figure 3. Molecular structure of BODIPY-dye arm 14 in the crystal mea-
sured at 123 K. A disordered CH2Cl2 molecule is omitted for clarity.
Thermal ellipsoids are shown at the 50% probability level.
of 14 is depicted in Figure 3. The dimethylphenyl rings in
the two structures are nearly orthogonal to both the
Temperature-triggered switch-
ing of cavitands 1–4 monitored
1
by H and 19F NMR spectrosco-
py: The vase-to-kite transitions
for cavitands 1–4 were conve-
AHCTUNGTERGnNNUN iently monitored by variable-
temperature (VT) 1H NMR
spectroscopy (see Figures 5SI–
8SI in the Supporting Informa-
tion).[9] Above 330 K, the meth-
AHCTUNGTERGiNNUN ne protons in the octol bowl
appear around 5.5 to 5.6 ppm,
which is indicative of the vase
conformation.
Cooling
the
sample to below 230 K resulted
in a diagnostic shift of these
Scheme 6. Synthesis of dye arms 13 and 14. a) THF, 408C, 30 min, then (COCl)2, pyridine, 508C, 16 h; 98%
(13), 99% (14).
Scheme 7. Synthesis of cavitand 4. a) K2CO3, Me2SO, 238C, 4 h; 6% (34), 66% (4).
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Cavitands
FULL PAPER
methine protons to about 3.7 ppm, consistent with the prev-
alence of the kite geometry.
We were initially puzzled by a difference observed in the
19F NMR spectra (376 MHz) at 298 K of cavitands 1–3 and
of cavitand 4 (Figure 4). For cavitands 1–3, a quartet at
fluorine atoms distinct from one another.[11b,20] The barrier
for the interconversion between syn and anti conformations
for the free acceptor dye is relatively low (19F NMR spectra
of simple acceptor BODIPY-dye derivatives include only
one signal, and the X-ray crystal structure of BODIPY-dye
arm 14 shows it in an anti conformation, Figure 3). When
the acceptor-dye arm is incorporated into cavitand 4, howev-
er, close spatial interactions between the donor and acceptor
dyes apparently lock the acceptor dye into a syn conforma-
tion. Furthermore, unlike in the extended cavitands 1–3, ro-
tation of the BODIPY moieties in cavitand 4 is likely to be
more restricted due to methyl groups at both the BODIPY
core and the phenyl unit. To test this hypothesis, we per-
formed VT 19F NMR experiments[21] on cavitand 4, hoping
to observe coalescence of the two acceptor dye signals at
lower temperatures when the kite geometry puts the donor
and acceptor dyes at a greater distance. Indeed, as illustrat-
ed in Figure 5, two signals are observed for the BF2 unit of
the acceptor dye in cavitand 4 at 333 K, but only a single
broad peak at about ꢀ135 ppm is apparent upon cooling the
sample to 213 K. In the kite conformation at lower tempera-
tures, the acceptor dye is no longer locked in an arch-
shaped conformation and rapid syn–anti fluctuation in the
BODIPY dye renders the two fluorine atoms equivalent on
the NMR timescale.
Room-temperature UV/Vis and fluorescence spectroscopy:
The UV/Vis spectra of cavitands 1–4 exhibit three main ab-
Figure 4. 19F NMR spectra (282 MHz) of cavitands 1–4 in CDCl3 at
298 K.
ꢀ145 ppm corresponds to the BF2 unit of the donor dye and
another quartet at ꢀ135 ppm arises from the BF2 unit of the
acceptor; the quartet splitting pattern of both signals results
1
from JBF coupling. The 19F NMR spectrum of cavitand 4
also exhibits a quartet at ꢀ145 ppm for the BF2 unit of the
donor dye. For the BF2 unit of the acceptor dye, however,
two sets of overlapping doublets of quartets are observed.
The presence of the two signals and their splitting pattern
suggest that the two fluorine atoms in the acceptor
BODIPY dye are not equivalent; thus, each fluorine atom
couples not only to the neighboring boron atom (1JBF), but
also to the other fluorine atom (2JFF). To explain the non-
equivalence of these fluorine atoms, closer examination of
the acceptor BODIPY-dye conformation in cavitand 4 was
necessary.
In literature reports on similar BODIPY dyes, the pyrrole
wings are canted in the same direction (syn) to form an
arch-shaped structure, a conformation that renders the two
Figure 5. 19F NMR spectra (282 MHz) of cavitand 4 in CD2Cl2 at different
temperatures (213, 273, 333 K). Exponential apodization of 8.00 Hz along
t1 was used for spectrum processing.
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F. Diederich et al.
sorption bands corresponding to the oligo(phenylene–ethy-
nylene) spacers (l=300–350 nm), the donor-dye moieties
a certain average opening angle and are not aligned parallel.
Greater distances separate the dyes on cavitands with
longer arms, correlating to decreased FRET and an in-
creased ratio of donor/acceptor emission intensity.
(lmax =529 nm), and the acceptor-dye moieties (lmax
=
619 nm) (Figure 6, top). As the number of phenylene–ethy-
nylene moieties in the spacers increases from 4 to 1, stron-
ger absorption bands in the corresponding part of the UV/
Vis spectra are observed.
Acid-triggered switching monitored by fluorescence spec-
troscopy: Figure 9SI (in the Supporting Information) illus-
trates the fluorescence titration curves for cavitands 1–4.
The opening to the kite form upon protonation is accompa-
nied in each case by an increase in the ratio of donor/accept-
or emission intensity. Although these data are internally
consistent, and in line with previous results,[9,13] acid-mediat-
ed degradation of the BODIPY dyes (see Figures 11SI–13SI
in the Supporting Information) precludes a quantitative
evaluation of these data.[22] Because changes in temperature
can also induce the vase-to-kite transition, we turned to this
non-destructive and fully reversible switching method for
quantitative fluorescence studies.
Temperature-triggered switching of cavitands 1–4 monitored
by fluorescence spectroscopy: The temperature-dependent
fluorescence spectra of cavitands 1–4 were measured in
CHCl3 at temperatures ranging from 218 to 298 K (Fig-
ure 10SI in the Supporting Information). The vase-to-kite
transitions in all four cavitands are indicated by increases in
the ratios between donor and acceptor emission intensities
upon lowering the temperature. Figure 7 summarizes these
Figure 6. Top: UV/Vis spectra of cavitands 1–4 in CHCl3 at 298 K.
Bottom: Fluorescence spectra of cavitands 1–4 in CHCl3 at 298 K (c=
0.5ꢃ10ꢀ7 m, lexc =490 nm) with graph showing the ratios in the donor/ac-
ceptor (d/a) dye emission intensity for cavitands 1–4.
Figure 7. Donor/acceptor dye emission intensities for cavitands 1–4 at dif-
ferent temperatures (c=0.5ꢃ10ꢀ7 m, lexc =490 nm).
The fluorescence spectra of cavitands 1–4 are presented in
Figure 6 (bottom); they were recorded in CHCl3 at 298 K
with an excitation wavelength of lexc =490 nm, at which only
results, showing the ratios of donor/acceptor intensities for
cavitands 1–4, plotted against temperature. Stronger temper-
the donor dye is excited. The emission maxima at lem
=
ature dependence is correlated to larger phenylene–ethy
ene spacer size: the dependence of FRET on temperature is
amplified in cavitands with longer arms.
ACHTUNGTRENNUNGnyl-
542 nm correspond to the donor and those at lem =630 nm
to the acceptor-dye moieties. A notable conclusion can be
drawn from the fluorescence spectra: the ratio of donor/ac-
ceptor emission increases with increasing cavitand size. This
suggests that the two arms of the cavitands are separated by
ACHTUNGTRENNUNG
Determination of the average opening angle a and the Fçr-
ster radius R0 of cavitands 1–3 in the vase conformation:
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Cavitands
FULL PAPER
The intriguing observation that relative FRET efficiencies of
the cavitands in the vase form decrease with increasing
phenylene–ethynylene spacer size (Figure 6, bottom) sug-
gests that there is a certain, non-zero average opening angle
in the cavitands when they are in the vase conformation.
Derivation of this opening angle (a; for definition see
Figure 8) and of the Fçrster radius (R0)[23] for the donor–ac-
ceptor BODIPY-dye pair from fluorescence data will be
presented herein. If we assume that the average opening
angle a is constant for the four cavitands 1–4 at a certain
temperature, then the distance between the donor and ac-
ceptor BODIPY dyes (R) may be expressed as a function of
a and the number of phenylethynyl moieties (n) in the
spacer units. The top panel in Figure 8 shows a cavitand that
is open with an arbitrary average angle a.
tions (2) and (3), R can be written as a function of the open-
ing angle a and the number of spacer units n [Equation (4)].
R ¼ 2d þ a
ð1Þ
ð2Þ
ð3Þ
ð4Þ
d ¼ c sin ðaÞ
c ¼ nb þ e
R ¼ 2½ðnb þ eÞsinðaÞꢁ þ a ¼ 2e sinðaÞ þ a þ 2b sinðaÞ n
ꢀ
The parameter for the O O distance, that is a=9.6 ꢀ,
was extracted from the X-ray crystal structure of diiodocavi-
tand 11 (Figure 8, bottom). The arm length for n=0, that is,
e=14.2 ꢀ, was obtained from the X-ray crystal structures of
BODIPY-dye arms 13 and 14. The length of a single phenyl-
ethynyl moiety in the spacers was assumed to be b=6.8 ꢀ,
in agreement with X-ray data on 1,4-bis(phenylethynyl)ben-
zene.[24]
ꢀ
The B B distance between the boron atoms in the two
dyes (R) can be expressed by Equation (1). Using Equa-
Equation (5) enumerates the relationship between the
measured FRET efficiency E and the distance R between
the BODIPY dyes, with R0 being the Fçrster radius. The
Fçrster radius is assumed to be constant for the cavitands 1–
3 at a given temperature. For cavitand 4, R0 is assumed to
be distinct from 1–3, owing to the restricted rotation of the
dye moieties in 4, resulting in a different orientation factor.
The FRET efficiency E can be calculated from the measured
emission intensities of the donor in the presence of the ac-
ceptor (IDA, Figure 6, bottom) and in the absence of the ac-
ceptor (ID) [Equation (6)]. For the reference ID value, the
emission intensity of donor-dye arm 20 was used (c=0.5ꢃ
10ꢀ7 m, lexc =490 nm, ID =35ꢃ105).
1
E ¼
ꢀ ꢁ
6
ð5Þ
R
1 þ
R0
IDA
ID
ð6Þ
E ¼ 1 ꢀ
Equation (5) can be rewritten as Equation (7), which ena-
bles the calculation of R/R0 values from FRET efficiencies.
When the expression for R from Equation (4) is substituted
into Equation (7), we obtain an expression for R/R0 that is a
linear function of n [Equation (8)].
rffiffiffiffiffiffiffiffiffiffiffiffi
6
1
E
R
R0
ð7Þ
ð8Þ
ꢀ 1 ¼
rffiffiffiffiffiffiffiffiffiffiffiffi
6
1
R
R0
2e sinðaÞ þ a 2b sinðaÞ
ꢀ 1 ¼
¼
þ
n ¼ p þ qn
E
R0
R0
|fflfflfflfflfflfflfflfflffl{zfflfflfflfflfflfflfflfflffl} |fflfflfflfflffl{zfflfflfflfflffl}
p
q
Figure 8. Top: Arbitrary cavitand with oligo(phenylene–ethynylene)
Thus, the plot of R/R0 versus n can be subjected to a
linear fit, from which the slope (q) and a y intercept (p) can
be easily obtained. From q and p, the Fçrster radius R0 and
the opening angle a can be calculated. Figure 9 shows such
plot of R/R0 versus the number of spacer units, n, at 298 K.
ꢀ
spacers at a certain average opening angle a. The B B distance between
the boron atoms in the two BODIPY dyes, R, can be derived from the
parameters a, b, and e. Bottom: X-ray crystal structures, from which the
parameters e and a were extracted. Parameter b was obtained from X-
ray data on 1,4-bis(phenylethynyl)benzene.[24]
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F. Diederich et al.
data was possible and provided new insights into the confor-
mations of these cavitands in solution. Together with the dis-
tance parameters obtained from X-ray crystal structures, the
quantitative FRET data obtained from the cavitand series
enabled determination of the Fçrster radius for the
BODIPY-dye FRET pair (R0 =37 ꢀ) and the average cavi-
tand opening angle in the vase conformation (a=168). In
contrast to the small opening angle apparent in X-ray crystal
structures,[2] such as of vase-cavitand 11, our studies show
that the average opening angle in solution is, in fact, consid-
erably larger. Further time-resolved FRET studies on these
cavitand systems are planned to examine their conforma-
tional flexibility in solution.
Experimental Section
Figure 9. R/R0 against the number of phenylethynyl units n in the spacer
at 298 K.
Materials and general methods: All chemicals were purchased as reagent
grade and used without further purification. All solvents for fluorescence
spectroscopy were HPLC grade. All reactions were performed in stan-
dard glassware under an inert atmosphere of Ar. When stated, solvents
were degassed by bubbling Ar through the solution for 30 min. Flash
chromatography (FC) was performed using SiO2-60 (230–400 mesh
ASTM, 0.040–0.063 mm; Fluka) or SiO2-F60 (0.040–0.063 mm, 60 ꢀ, Sili-
cycle). Melting points were measured on a Bꢁchi B-540 melting-point ap-
paratus in open capillaries and are uncorrected. The melting points of
the deeply colored BODIPY derivatives could not be accurately deter-
mined. Preparative recycling gel permeation chromatography (GPC) was
run on a Japan Analytical Industries LC-9101 preparative recycling
HPLC apparatus using HPLC-grade CHCl3 as the mobile phase and
The linear fit of the plot shows a good correlation (R2 =
0.996), with a slope of q=0.104 and a y intercept of p=
0.477. From the slope and y intercept of this line, values for
the Fçrster radius and the average opening angle can be cal-
culated: R0 =37 ꢀ and a=168. The value for a is in good
agreement with the opening angle range of 0–298 deter-
mined by sum-frequency vibrational spectroscopy.[25] Thus,
the average distances between the dye moieties in vase-
shaped cavitands 1–3 at 298 K in CHCl3 range between 21 ꢀ
for cavitand 3 and 29 ꢀ for cavitand 1.
The determined solution-state opening angle is much
higher than that in the solid state, observed in the crystal
structures of diiodocavitand 5 (Figure 2, top). Indeed, in the
solid state, the cavitand walls are directed inwards, resulting
in a small, negative opening angle of ꢀ28. Thus, FRET in-
vestigations have provided important insights about the
vase-type conformation of our cavitands in bulk solution.
Jaigel-2H as the stationary phase with a flow of 5 mLminꢀ1 1H NMR,
.
13C NMR, and 19F NMR spectra were recorded on a Bruker DRX 400 or
Bruker AV 400 spectrometer at 298 K. Residual solvent peak was used as
an internal reference. Infrared spectra (IR) were recorded on a Varian
800 FT-IR spectrometer. The spectra were measured neat. Selected ab-
sorption bands are reported in wavenumbers (cmꢀ1). Mass spectrometry
was performed by the MS-service at ETH Zꢁrich. High-resolution elec-
tron impact mass spectra were measured on a Waters Micromass Auto-
Spec Ultima spectrometer. High-resolution matrix-assisted laser-desorp-
tion-ionization mass spectra were measured on a Varion Ionspec Ultima
MALDI-FTICR mass spectrometer with 3-hydroxypyridine-2-carboxylic
acid (3-HPA) as matrix or on Bruker Daltonics Ultraflex II MALDI-
TOF mass spectrometer with (2-[(2E)-3-(4-tert-butylphenyl)-2-methyl-
prop-2-enyliden]malononitrile) (DCTB) as matrix. High-resolution elec-
tro-spray-ionization mass spectra were measured on a Bruker Daltonics
maXis spectrometer. Isotope peaks with the highest relative abundance
are reported. UV/Vis spectroscopy was carried out with a Varian Cary
500 Scan spectrophotometer. Fluorescence spectroscopy was carried out
with an Instruments S. A. Fluorolog-3 spectrofluorimeter. Both UV/Vis
and fluorescence experiments were carried out in standard 3.5 mL quartz
cells (4 optical windows for UV/Vis, 2 optical windows for fluorescence)
with 10 mm path length.
Conclusion
A series of BODIPY-dye-labeled resorcin[4]arene cavitands
with different lengths of oligo(phenylene–ethynylene)
spacers (1–4) was synthesized. In addition to full characteri-
zation of the new cavitands (including UV/Vis and fluores-
cence spectroscopic characterization), X-ray crystal struc-
tures of important synthetic intermediates were obtained.
These data provided essential molecular distance parameters
that were later used to deduce quantitative information
about the vase conformation of the cavitands in bulk solu-
tion. Upon obtaining the desired target cavitands, their
vase-to-kite switching behavior was observed by both NMR
and fluorescence spectroscopy; acid-triggered switching was
monitored by fluorescence spectroscopy, and both VT-NMR
and VT-FRET experiments confirmed temperature-triggered
switching of all four cavitands. Because a series of cavitands
could be prepared, a quantitative evaluation of the FRET
X-ray analysis: All measurements were performed on a Bruker-Nonius
Kappa-CCD diffractometer with graphite monochromator and MoKa ra-
diation, l=0.7107 ꢀ. The structures were solved by direct methods (SIR-
97)[26] and refined by full-matrix least-squares analysis (SHELXL-97).[27]
All non-hydrogen atoms were refined with anisotropic ADPs. Hydrogen
positions were calculated and included in the structure factor calculation.
X-ray crystal structure of 11: Crystal data at 123 K for
C96H88I2N10O12·CH2Cl2·4
ACHTUNGTRENNUNG
P21/c, 1calcd =1.371 gcmꢀ3
,
20.0679(5) ꢀ, a=90.00, b=110.4544(10), g=90.008, V=10393.4(4) ꢀ3,
l=0.7107 ꢀ, m=0.065 mmꢀ1. Green-yellow cube (linear dimensions ca.
0.27ꢃ0.18ꢃ0.135 mm). Number of measured and unique reflections:
39019 and 12291, respectively (Rint =0.106). Disordered structure:
I
12598
www.chemeurj.org
ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 12590 – 12602

Cavitands
FULL PAPER
atoms and some of the n-hexyl substituents refined over two positions.
Part of an n-hexyl substituent could not be localized and was left out; no
H atoms were included. Because of poor data, only part of the non-hy-
drogen atoms refined anisotropically. Geometric restraints were placed
on n-hexyl fragments. Four acetone and one CH2Cl2, as most probable
solvent molecules, were included in refinement. Final R(F)=0.1885,
wR(F2)=0.3709 for 1095 parameters and 8619 reflections with I>2s(I)
and 2.425<q<21.9678.
123.27, 123.71, 123.91, 123.94, 125.26, 127.48, 128.27, 128.44, 128.51,
128.79, 129.13, 129.25, 129.56, 129.65, 130.63, 131.43, 131.86, 131.87,
131.95, 131.96, 132.32, 132.41, 132.50, 133.18, 133.82, 135.82, 136.26,
136.34, 136.98, 137.56, 138.19, 138.73, 139.14, 139.94, 140.84, 141.61,
151.10, 152.18, 152.37, 153.22, 154.31, 158.98, 161.61 ppm; 19F NMR
(376 MHz, CDCl3): d=ꢀ145.71 (q, J=32.0 Hz), ꢀ134.99 ppm (q, J=
33.0 Hz); IR (ATR): n˜ =2927, 2857, 2361, 2343, 1740, 1527, 1475, 1444,
1412, 1363, 1326, 1276, 1231, 1191, 1158, 1115, 1082, 1018, 978, 899, 836,
749, 709, 690, 668, 650, 626 cmꢀ1
; UV/Vis (CHCl3): lmax (e)=323
X-ray crystal structure of 13: Crystal data at 123 K for C31H30BCl2F2N5O2,
Mr =624.327, triclinic, space group P1, 1calcd =1.411 gcmꢀ3, Z=2, a=
¯
(175000), 529 (73000), 572 (24000), 620 nm (112000); HR-MALDI-MS
+
(DCTB): m/z (%): 2700.1576 (100), [M]+ (calcd for C172H148B2F4N14O12
:
11.612(4), b=11.745(4), c=12.4611(5) ꢀ, a=86.534(10), b=77.219(13),
g=62.60(2)8, V=1469.7(10) ꢀ3, m=0.273 mmꢀ1. Red plate (linear dimen-
sions ca. 0.27ꢃ0.09ꢃ0.015 mm), bad crystal quality with multiple thin
layers giving high mosaic spread. Number of measured and unique reflec-
tions: 11725 and 3986, respectively (Rint =0.105). Final R(F)=0.1787,
wR(F2)=0.3339 for 396 parameters and 3255 reflections with I>2s(I)
and 2.425<q<22.9868.
2700.1575).
Cavitand 3: [PdACHTNUTRGNEUNG(PPh3)4] (24 mg, 0.021 mmol), and CuI (4 mg, 0.02 mmol)
were added to a degassed solution of 8 (81 mg, 0.155 mmol), 25 (217 mg,
0.103 mmol), and DIPEA (0.35 mL, 2.1 mmol) in THF (5 mL) and
CHCl3 (5 mL). The mixture was stirred for 2 d at 358C. The solvent was
evaporated. FC (SiO2; CH2Cl2!CH2Cl2/EtOAc 98:2) and recycling GPC
(Jaigel-2H; CHCl3) afforded 3 (115 mg, 0.046 mmol, 45%) as a blue
solid. tR =20.4 min (Jaigel-2H; CHCl3, flow=4 mLminꢀ1); 1H NMR
(400 MHz, CDCl3): d=0.89–1.01 (m, 18H), 1.31–1.56 (m, 50H), 2.23 (s,
3H), 2.24 (s, 3H), 2.25–2.39 (m, 12H), 2.43–2.55 (m, 10H), 2.84 (t, J=
6.9 Hz, 4H), 5.61 (t, J=8.0 Hz, 2H), 5.70 (t, J=8.1 Hz, 2H), 7.23–7.55
(m, 22H), 7.72 (d, J=8.3 Hz, 2H), 7.77 (d, J=8.3 Hz, 2H), 7.87–7.92 (m,
4H), 8.25 (s, 4H), 8.80 ppm (d, J=8.0 Hz, 2H); 13C NMR (101 MHz,
CDCl3): d=12.03, 12.48, 12.67, 14.22, 14.72, 17.17, 18.19, 18.26, 20.57,
22.81, 28.08, 28.11, 29.50, 29.51, 30.58, 32.01, 32.02, 32.29, 32.81, 34.34,
34.44, 90.43, 90.57, 90.60, 91.02, 118.91, 123.21, 123.25, 123.27, 123.71,
123.91, 123.94, 125.26, 127.48, 128.27, 128.44, 128.51, 128.79, 129.13,
129.25, 129.56, 129.65, 130.63, 131.43, 131.86, 131.87, 131.95, 131.96,
132.32, 132.41, 132.50, 133.18, 133.82, 135.82, 136.26, 136.34, 136.98,
137.56, 138.19, 138.73, 139.14, 139.94, 140.84, 141.61, 151.10, 152.18,
152.37, 153.22, 154.31, 158.98, 161.61 ppm; 19F NMR (376 MHz, CDCl3):
d=ꢀ145.66 (q, J=31.5 Hz), ꢀ134.97 ppm (q, J=33.1 Hz); IR (ATR):
n˜ =2927, 2858, 1740, 1526, 1470, 1411, 1362, 1324, 1276, 1232, 1190, 1157,
1081, 977, 898, 839, 748, 707, 666, 629 cmꢀ1; UV/Vis (CHCl3): lmax (e)=
315 (126477), 529 (66248), 572 (24984), 620 nm (111728); HR-MALDI-
MS (DCTB): m/z (%): 2500.0978 (100) [M]+ (calcd for
C156H140B2F4N14O12+: 2500.0947).
X-ray crystal structure of 14: Crystal data at 123 K for
¯
C82H60BCl4F4N10O ·
(CH2Cl2), Mr =1573.807, triclinic, space group P1,
Z=1, a=7.92060(10), b=12.1909(2), c=
1calcd =1.455 gcmꢀ3
,
20.3353(4) ꢀ, a=102.6460(8), b=96.7771(9), g=107.0610(9)8, V=
1796.32(5) ꢀ3, m=0.312 mmꢀ1. Red-brown cube (linear dimensions ca.
0.18ꢃ0.099ꢃ0.069 mm). Number of measured and unique reflections:
32642 and 8232, respectively (Rint =0.083). Structure contains one mole-
cule of CH2Cl2. Final R(F)=0.0891, wR(F2)=0.1751 for 618 parameters
and 5924 reflections with I>2s(I) and 2.425<q<27.4858.
X-ray crystal structure of 16: Crystal data at 123 K for
C96H89ClI2N10O12·4ACHTUNGTRENNUNG(CH2Cl2), Mr =2203.79, monoclinic, space group P21/c,
1calcd =1.483 gcmꢀ3, Z=4, a=18.2270(3), b=23.1041(5), c=24.2627(5) ꢀ,
a=90.00, b=104.9292(10), g=90.008, V=9872.6(3) ꢀ3, m=0.947 mmꢀ1
(numeric absorption correction applied). Green-yellow plate (linear di-
mensions ca. 0.21ꢃ0.09ꢃ0.03 mm). Multiple layered, twinned crystal, but
no reasonable twin law found. Number of measured and unique reflec-
tions: 69005 and 19272, respectively (Rint =0.56). Only iodine and chlor-
ine atoms refined anisotropically because of limited data quality and
overlapping reflexions from the twinning. Structure contains four mole-
cules of CH2Cl2. Final R(F)=0.2788, wR(F2)=0.5603 for 588 parameters
and 10413 reflections with I>2s(I) and 2.425<q<26.0228.
X-ray crystal structure of 28: Crystal data at 173 K for C25H30BF2N3O2,
Mr =453.341, monoclinic, space group P21/n, 1calcd =1.258 gcmꢀ3, Z=4,
a=8.5829(3), b=24.5096(7), c=11.5112(3) ꢀ, a=90.00, b=98.844(2),
g=90.008, V=2392.74(12) ꢀ3, m=0.090 mmꢀ1. Purple plate (linear di-
mensions ca. 0.27ꢃ0.225ꢃ0.018 mm). Number of measured and unique
reflections: 17437 and 4340, respectively (Rint =0.109). Crystal was twin-
ned, refined twinning parameter 0.902:0.098. Final R(F)=0.1210,
wR(F2)=0.2756 for 299 parameters and 3428 reflections with I>2s(I)
and 2.425<q<25.3508.
Cavitand 4: K2CO3 (10 mg, 0.072 mmol) was added to a degassed solution
of 34 (90 mg, 0.055 mmol) and 14 (54 mg, 0.072 mmol) in Me2SO (6 mL).
The mixture was stirred for 4 h at 238C, after which it was poured into
H2O (200 mL). The resulting precipitate was collected by filtration,
washed with H2O (3ꢃ10 mL), and dried in vacuo. FC (SiO2; CH2Cl2!
CH2Cl2/EtOAc 98:2) and recycling GPC (Jaigel-2H; CHCl3) afforded 4
(84 mg, 0.037 mmol, 66%) as a dark blue solid. tR =20.7 min (Jaigel-2H;
CHCl3, flow=4 mLminꢀ1); 1H NMR (400 MHz, CDCl3): d=0.91–1.01
(m, 18H), 1.31–1.53 (m, 44H), 1.59 (s, 6H), 2.23 (s, 3H), 2.27 (s, 3H),
2.24–2.38 (m, 12H), 2.48 (s, 6H), 2.52–2.66 (m, 4H), 2.89 (t, J=6.9 Hz,
4H), 5.61 (t, J=7.2 Hz, 2H), 5.69 (t, J=8.0 Hz, 2H), 7.14–7.38 (m, 16H),
7.44 (t, J=7.7 Hz, 2H), 7.85–7.91 (m, 4H), 8.25 (s, 2H), 8.26 (s, 2H),
8.82 ppm (d, J=8.0 Hz, 2H); 13C NMR (101 MHz, CDCl3): d=12.15,
12.61, 12.70, 14.22, 14.75, 17.24, 18.08, 18.13, 18.38, 18.43, 20.67, 22.81,
28.07, 28.10, 29.50, 29.51, 30.65, 32.01, 32.02, 32.25, 32.86, 34.37, 34.48,
118.90, 123.91, 127.56, 128.22, 128.33, 128.42, 128.68, 128.78, 128.93,
129.13, 129.20, 129.31, 129.52, 129.58, 129.69, 130.50, 132.40, 133.19,
133.69, 135.81, 136.92, 137.05, 137.94, 137.99, 138.07, 138.29, 138.35,
138.40, 138.50, 139.96, 140.82, 141.65, 151.20, 152.19, 152.45, 153.22,
154.52, 158.90, 158.93, 161.31 ppm; 19F NMR (376 MHz, CDCl3): d=
ꢀ146.04, ꢀ145.45, ꢀ136.63, ꢀ135.88, ꢀ134.23, ꢀ133.51 ppm; IR (ATR):
n˜ =2926, 2857, 2361, 2341, 1741, 1528, 1468, 1444, 1412, 1358, 1325, 1275,
1231, 1189, 1157, 1114, 1101, 1081, 1043, 978, 962, 899, 840, 826, 796, 757,
728, 695, 682, 668; 648 cmꢀ1; UV/Vis (CHCl3): lmax (e)=316 (81000), 390
CCDC-779392 (11), -779393 (13), -779394 (14), -779395 (16), and -779396
(28) contain the supplementary crystallographic data for this paper.
These data can be obtained free of charge from The Cambridge Crystal-
lographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Synthetic procedures: Compounds 1[9,13], 5[9], 7[9], 8[9], 10[9], 11[9], 12[10]
,
15[9], 17[16], 18[16], 19[9], 21[9], 23[9], 26[17], 30[11b], 33[8] were prepared accord-
ing to literature procedures.
Cavitand 2: [Pd
ACHTUNGTRENNUNG
were added to
a
9
(190 mg, 0.0860 mmol), and DIPEA (0.30 mL, 1.7 mmol) in THF (5 mL)
and CHCl3 (5 mL). The mixture was stirred for 3 d at 358C. The solvent
was evaporated. FC (SiO2; CH2Cl2 ! CH2Cl2/EtOAc 98:2) and recycling
GPC (Jaigel-2H; CHCl3) afforded 2 (90 mg, 0.033 mmol, 39%) as a blue
solid. tR =19.7 min (Jaigel-2H; CHCl3); 1H NMR (400 MHz, CDCl3): d=
0.87–1.02 (m, 18H), 1.28–1.55 (m, 50H), 2.19–2.38 (m, 12H), 2.23 (s,
6H), 2.45–2.56 (m, 10H), 2.85 (t, J=6.9 Hz, 4H), 5.62 (t, J=8.0 Hz, 2H),
5.70 (t, J=8.0 Hz, 2H), 7.27–7.51 (m, 22H), 7.57–7.77 (m, 12H), 7.83–
7.94 (m, 4H), 8.25 (s, 4H), 8.80 ppm (d, J=8.0 Hz, 2H); 13C NMR
(101 MHz, CDCl3): d=12.03, 12.48, 12.67, 14.22, 14.72, 17.17, 18.19,
18.26, 20.57, 22.81, 28.08, 28.11, 29.50, 29.51, 30.58, 32.01, 32.02, 32.29,
32.81, 34.34, 34.44, 90.43, 90.57, 90.60, 91.02, 118.91, 123.21, 123.25,
(15000), 528 (77000), 572 (21000), 619 nm (106000); HR-MALDI-MS
+
(DCTB): m/z (%): 2300.0361 (100) [M]+ (calcd for C140H132B2F4N14O12
:
2300.0319).
{3-Ethyl-5-[(4-ethyl-3,5-dimethyl-2H-pyrrol-2-ylidene-kN){4-[(4-ethynyl-
phenyl)-ethynyl]phenyl}methyl]-2,4-dimethyl-1H-pyrrolato-kN}(di
ACHTUNGTRENNUNGfluACHTUNGTRENNUNGo-
A
ACHTUNGTRENNUNG
Chem. Eur. J. 2010, 16, 12590 – 12602
ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
12599

F. Diederich et al.
cooled to ꢀ788C. nBu4NF (1m in THF, 1.4 mL, 1.4 mmol) was added to
the solution, and the resulting mixture was stirred for 30 min at ꢀ788C.
Subsequently, AcOH (0.1 mL, 1.7 mmol) was added at ꢀ788C and the
mixture was warmed to 238C. The mixture was filtered through a plug of
SiO2, eluted with CH2Cl2, and the solvent was removed to afford 6
(0.44 g, 0.87 mmol, 77%) as a red solid. Rf =0.30 (SiO2; CH2Cl2/cyclohex-
ane 1:1); m.p.: 235–2458C (decomp); 1H NMR (400 MHz, CDCl3): d=
0.99 (t, J=7.5 Hz, 6H), 1.33 (s, 6H), 2.31 (q, J=7.5 Hz, 4H), 2.54 (s,
6H), 3.20 (s, 1H), 7.30 (d, J=8.4 Hz, 2H), 7.46–7.55 (m, 4H), 7.66 ppm
(d, J=8.4 Hz, 2H); 13C NMR (101 MHz, CDCl3): d=12.03, 12.68, 14.76,
17.22, 79.29, 83.30, 90.17, 90.83, 122.40, 123.47, 123.67, 128.74, 130.67,
131.66, 132.31, 132.40, 133.11, 136.27, 138.34, 139.29, 154.21 ppm;
19F NMR (376 MHz, CDCl3): d=ꢀ145.78 ppm (q, J=32.8 Hz); IR
(ATR): n˜ =3273, 2963, 2927, 2869, 1537, 1473, 1403, 1388, 1371, 1315,
and eluted with CH2Cl2 to afford 14 (0.29 g, 0.39 mmol, 99%) as a black
solid. Rf =0.25 (SiO2; CH2Cl2/cyclohexane 3:1); m.p.: 310–3208C
(decomp); 1H NMR (400 MHz, CDCl3): d=1.50 (s, 6H), 2.24 (s, 6H),
2.57 (t, J=7.0 Hz, 4H), 2.89 (t, J=7.0 Hz, 4H), 7.24–7.34 (m, 6H), 7.43
(t, J=7.0 Hz, 2H), 8.81 ppm (d, J=8.0 Hz, 2H); 13C NMR (101 MHz,
CDCl3): d=12.60, 18.34, 20.65, 30.69, 127.50, 128.23, 128.54, 128.87 (t, J=
12.1 Hz), 129.31, 129.33, 129.62, 132.38, 133.81, 136.13, 138.01, 138.28,
138.36, 140.87, 143.52, 151.15, 154.53, 160.90 ppm; 19F NMR (376 MHz,
CDCl3): d=ꢀ135.03 ppm (q, J=34.0 Hz); IR (ATR): n˜ =2926, 1738,
1605, 1549, 1522, 1467, 1434, 1385, 1367, 1339, 1320, 1273, 1231, 1196,
1157, 1080, 1061, 1031, 1013, 961, 908, 874, 829, 812, 767, 742, 728, 714,
705, 650, 627, 610 cmꢀ1; UV/Vis (CHCl3): lmax (e)=316 (58000), 395
(9000), 571 (23000), 618 nm (111000); HR-MALDI-MS (3-HPA): m/z
+
(%): 743.1843 (100) [M]+ (calcd for C41H30BCl2F2N5O2
: 743.1838),
1263, 1182, 1159, 1115, 1050, 971, 836, 806, 760, 738, 702, 650, 608 cmꢀ1
;
724.1864 (61) [MꢀF]+ (calcd for C41H30BCl2FN5O2+: 724.1854).
(3-Ethyl-5-{(4-ethyl-3,5-dimethyl-2H-pyrrol-2-ylidene-kN)[4-({4-[(trimNGUNETRNGTUHAC eth-
UV/Vis (CHCl3): lmax (e)=302 (39000), 529 nm (74000); HR-MALDI-
+
MS (3-HPA): m/z (%): 504.2549 (100) [M]+ (calcd for C33H31BF2N2
504.2548), 485.2555 (87) [MꢀF]+ (calcd for C33H31BFN2+: 485.2564).
:
AHCTUNGTRENNUNG
A
ACHTUNGTRENNUNG
{2-[{4-[(4-Ethynylphenyl)ethynyl]phenyl}(3-methyl-4,5-dihydro-2H-ben-
zo[g]indol-2-ylidene-kN)methyl]-3-methyl-4,5-dihydro-1H-benzo[g]indo-
(0.016 g, 0.087 mmol) were added to a degassed solution of 7 (0.70 g,
1.7 mmol), 18 (0.55 g, 1.8 mmol), and DIPEA (1.8 mL, 10 mmol) in THF
(50 mL). The mixture was stirred for 3 d at 238C, then filtered through
Celite and purified by FC (SiO2; CH2Cl2/cyclohexane 1:1) to afford 20
(0.77 g, 1.3 mmol, 77%) as a red solid. Rf =0.30 (SiO2; CH2Cl2/cyclohex-
ane 1:1); m.p.: 155–1608C (decomp); 1H NMR (400 MHz, CDCl3): d=
0.26 (s, 9H), 0.99 (t, J=7.5 Hz, 7H), 1.33 (s, 6H), 2.31 (q, J=7.5 Hz,
4H), 2.54 (s, 6H), 7.29 (d, J=8.4 Hz, 2H), 7.45–7.51 (m, 4H), 7.65 ppm
(d, J=8.4 Hz, 2H); 13C NMR (101 MHz, CDCl3): d=0.06, 12.03, 12.68,
14.74, 17.23, 90.42, 90.78, 96.75, 104.67, 123.05, 123.48, 123.79, 128.76,
130.71, 131.59, 132.14, 132.38, 133.12, 136.24, 138.36, 139.35, 154.22 ppm;
19F NMR (376 MHz, CDCl3): d=ꢀ145.81 (q, J=33.0 Hz) ppm; IR
(ATR): n˜ =2960, 1538, 1474, 1404, 1315, 1249, 1182, 1115, 1072, 975, 835,
759, 705 cmꢀ1; UV/Vis (CHCl3): lmax (e)=308 (38000), 529 nm (67000);
HR-MALDI-MS (3-HPA): m/z (%): 576.2940 (83) [M]+ (calcd for
C36H39BF2N2Si+: 576.2944), 557.2956 (100) [MꢀF]+ (calcd for
C36H39BFN2Si+: 557.2960).
lato-kN}ACHTUNGTRENNUNG(difluoro)boron (9): A solution of 22 (0.50 g, 0.72 mmol) in THF
(60 mL) was cooled to ꢀ788C. nBu4NF (1m in THF, 0.9 mL, 0.9 mmol)
was added to the solution, and the resulting mixture was stirred for
30 min at ꢀ788C. Subsequently, AcOH (0.06 mL, 1 mmol) was added at
ꢀ788C and the mixture was warmed to 238C. The crude product was
washed with CHCl3 (5 mL) and THF (2 mL) to afford
9 (0.39 g,
0.62 mmol, 86%) as a dark brown-green solid. Rf =0.44 (SiO2; CH2Cl2/cy-
clohexane 1:1); m.p.: 330–3408C (decomp); 1H NMR (400 MHz, CDCl3):
d=1.41 (s, 3H), 2.54 (t, J=7.0 Hz, 2H), 2.88 (t, J=7.0 Hz, 2H), 3.20 (s,
1H), 7.22–7.34 (m, 4H), 7.37–7.47 (m, 4H), 7.48–7.56 (m, 4H), 7.71 (d,
J=8.3 Hz, 2H), 8.81 ppm (d, J=7.9 Hz, 2H); 13C NMR not available due
to low solubility of the solid; 19F NMR (376 MHz, CDCl3): d=
ꢀ135.00 ppm (d, J=33.6 Hz); IR (ATR): d=3290, 2939, 2899, 2838,
1604, 1560, 1519, 1466, 1429, 1390, 1368, 1340, 1322, 1308, 1273, 1229,
1190, 1169, 1152, 1109, 1082, 1059, 1042, 1013, 966, 945, 849, 834, 820,
769, 747, 726, 713, 705, 671, 651, 634 cmꢀ1; UV/Vis (CHCl3): lmax (e)=320
(95000), 571 (27000), 618 nm (119000); HR-MALDI-MS (3-HPA): m/z
(%): 624.2553 (82) [M]+ (calcd for C43H31BF2N2+: 624.2548), 605.2560
(100) [MꢀF]+ (calcd for C43H31BFN2+: 605.2564).
Difluoro(3-methyl-2-{(3-methyl-4,5-dihydro-2H-benzo[g]indol-2-ylidene-
kN)[4-({4-[(trimethylsilyl)ethynyl]phenyl}ethynyl)phenyl]methyl}-4,5-di-
hydro-1H-benzo[g]-indolato-kN)boron
(22):
[Pd
G
(0.066 g,
0.057 mmol), and CuI (0.011 g, 0.057 mmol) were added to a degassed so-
lution of 10 (0.60 g, 1.14 mmol), 18 (0.36 g, 1.2 mmol), and DIPEA
(1.2 mL, 6.9 mmol) in THF (50 mL). The mixture was stirred for 3 d at
238C, then filtered through Celite and purified by FC (SiO2; CH2Cl2/cy-
clohexane 2:3) to afford 22 (0.57 g, 0.82 mmol, 72%) as a black solid.
Rf =0.55 (SiO2; CH2Cl2/cyclohexane 1:1); m.p.: 265–2758C (decomp);
1H NMR (400 MHz, CDCl3): d=0.27 (s, 9H), 1.40 (s, 6H), 2.54 (t, J=
7.0 Hz, 4H), 2.88 (t, J=7.0 Hz, 4H), 7.21–7.27 (m, 2H), 7.28–7.35 (m,
2H), 7.37–7.54 (m, 8H), 7.70 (d, J=8.2 Hz, 2H), 8.81 ppm (d, J=8.0 Hz,
2H); 13C NMR (101 MHz, CDCl3): d=0.06, 12.48, 20.61, 30.66, 90.60,
90.75, 96.79, 104.65, 123.00, 123.50, 124.01, 127.49, 128.22, 128.51, 128.80
(t, J=11.6 Hz), 129.20, 129.60, 131.61, 132.16, 132.30, 132.47, 133.88,
136.03, 136.55, 138.93, 140.83, 151.06 ppm; 19F NMR (376 MHz, CDCl3):
d=ꢀ134.97 ppm (q, J=32.9 Hz); IR (ATR): n˜ =2933, 2163, 1604, 1556,
1525, 1464, 1435, 1400, 1367, 1326, 1307, 1275, 1231, 1195, 1156, 1118,
1083, 1014, 965, 945, 863, 827, 768, 706, 657, 631 cmꢀ1; UV/Vis (CHCl3):
lmax (e)=318 (93000), 571 (26000), 618 nm (120000); HR-MALDI-MS
(3-HPA): m/z (%): 696.2936 (100) [M]+ (calcd for C46H39BF2N2Si+:
696.2944), 677.2969 (68) [MꢀF]+ (calcd for C46H39BFN2Si+: 677.2960).
[2,3-Dichloro-6-{4-[(4-ethyl-3,5-dimethyl-1H-pyrrol-2-yl-kN)(4-ethyl-3,5-
dimethyl-2H-pyrrol-2-ylidene-kN)methyl]-2,6-dimethylphenyl}-5H-pyr
ACHTUNGERTNrNUNG o-
A
E
N
ACHTUNGTRENNUNG
(0.90 g, 4.11 mmol) and 31 (1.66 g, 3.91 mmol) in THF (60 mL) was
heated to 408C for 30 min. After cooling to 238C, (COCl)2 (0.40 mL,
4.7 mmol) and pyridine (0.95 mL, 12 mmol) were added and the resulting
mixture was stirred for 16 h at 508C. The solvent was evaporated, and
the crude product was filtered through a plug of SiO2 and eluted with
CH2Cl2 to afford 13 (2.39 g, 3.83 mmol, 98%) as a red solid. Rf =0.20
(SiO2; CH2Cl2/cyclohexane 3:1); m.p.: 330–3408C (decomp); 1H NMR
(400 MHz, CDCl3): d=1.01 (t, J=7.6 Hz, 6H), 1.43 (s, 6H), 2.20 (s, 6H),
2.33 (q, J=7.5 Hz, 4H), 2.54 (s, 6H), 7.18 ppm (s, 2H); 13C NMR
(101 MHz, CDCl3): d=12.18, 12.69, 14.74, 17.26, 18.31, 128.83, 129.10,
130.62, 133.20, 137.87, 138.01, 138.48, 138.69, 143.50, 154.29, 154.49,
160.89 ppm; 19F NMR (376 MHz, CDCl3): d=ꢀ145.81 ppm (q, J=
32.9 Hz); IR (ATR): n˜ =2962, 2929, 2869, 1795, 1733, 1537, 1474, 1404,
1383, 1369, 1316, 1265, 1232, 1186, 1114, 1061, 1043, 974, 869, 830, 812,
758, 744, 712, 630, 611 cmꢀ1; UV/Vis (CHCl3): lmax (e)=378 (7000),
529 nm (71000); HR-MALDI-MS (3-HPA): m/z (%): 623.1838 (100)
[M]+ (calcd for C31H30BCl2F2N5O2+: 623.1838), 604.1848 (63) [MꢀF]+
(calcd for C31H30BCl2FN5O2+: 604.1854).
Compound 24: [PdACTHUNTRGNE(UNG PPh3)4] (47 mg, 0.041 mmol), and CuI (8 mg,
0.04 mmol) were added to a degassed solution of 6 (155 mg, 0.308 mmol),
11 (0.75 g, 0.41 mmol), and DIPEA (1.4 mL, 8.2 mmol) in THF (30 mL).
The mixture was stirred for 2 d at 238C, after which the solvent was
evaporated. FC (SiO2; CH2Cl2!CH2Cl2/EtOAc 98:2) and recycling GPC
(Jaigel-2H; CHCl3) afforded 24 (216 mg, 0.098 mmol, 24%) as a red
solid. tR =20.6 min (Jaigel-2H; CHCl3, flow=4 mLminꢀ1); m.p.: 260–
2708C (decomp); 1H NMR (400 MHz, CDCl3): d=0.94 (q, J=6.7 Hz,
12H), 1.00 (t, J=7.6 Hz, 6H), 1.35 (s, 6H), 1.29–1.56 (m, 38H), 2.17 (s,
3H), 2.23 (s, 3H), 2.20–2.39 (m, 12H), 2.55 (s, 6H), 5.62 (t, J=7.0 Hz,
2H), 5.70 (t, J=8.1 Hz, 2H), 7.27–7.35 (m, 10H), 7.46–7.72 (m, 10H),
[2,3-Dichloro-6-{2,6-dimethyl-4-[(3-methyl-4,5-dihydro-1H-benzo[g]in-
dol-2-yl-kN)(3-methyl-4,5-dihydro-2H-benzo[g]indol-2-ylidene-kN)meth-
ACHTUNGTRENNUNGyl]ACHTUNGTRENNUNGphenyl}-5H-pyrroloACHTUNGTRENNUNG[3,4-b]pyrazine-5,7ACHTUNGTREN(NUNG 6H)-dionato]ACHTUNGTNRUEGN(difluoro)boron
(14): A solution of 33 (0.110 g, 0.50 mmol) and 32 (0.213 g, 0.391 mmol)
in THF (10 mL) was heated to 408C for 30 min. After cooling to 238C,
(COCl)2 (0.04 mL, 5 mmol) and pyridine (0.01 mL, 1 mmol) were added
and the resulting mixture was stirred for 16 h at 508C. The solvent was
evaporated, and the crude product was filtered through a plug of SiO2
12600
www.chemeurj.org
ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 12590 – 12602

Cavitands
FULL PAPER
7.83–7.90 (m, 4H), 8.24 (s, 2H), 8.25 ppm (s, 2H); 13C NMR (101 MHz,
CDCl3): d=12.06, 12.70, 14.23, 14.79, 17.22, 17.79, 17.95, 18.15, 18.26,
22.81, 28.07, 28.10, 29.51, 29.52, 29.85, 32.00, 32.01, 32.24, 32.79, 34.30,
34.39, 90.40, 90.42, 90.68, 90.92, 91.25, 96.72, 118.88, 123.04, 123.07,
123.28, 123.36, 123.69, 123.87, 125.28, 128.43, 128.50, 128.72, 128.83,
128.98, 129.55, 130.65, 131.79, 131.83, 131.90, 132.41, 133.10, 135.79,
135.81, 136.09, 136.23, 136.94, 136.97, 137.51, 137.54, 137.91, 138.35,
139.26, 139.29, 139.89, 139.90, 141.51, 141.57, 152.12, 152.14, 152.34,
153.18, 154.19, 158.98, 161.46, 161.59 ppm; 19F NMR (376 MHz, CDCl3):
d=ꢀ145.77 ppm (d, J=32.8 Hz); IR (ATR): n˜ =2926, 2857, 2360, 1740,
1539, 1479, 1446, 1412, 1359, 1323, 1258, 1235, 1190, 1157, 1115, 1101,
1064, 979, 898, 837, 760, 709, 689, 668, 618 cmꢀ1; UV/Vis (CHCl3): lmax
2508C; 1H NMR (400 MHz, CDCl3): d=0.99 (t, J=7.6 Hz, 6H), 1.34 (s,
6H), 2.31 (q, J=7.6 Hz, 4H), 2.38 (s, 6H), 2.53 (s, 6H), 7.11 ppm (s,
2H); 13C NMR (101 MHz, CDCl3): d=12.30, 12.70, 14.71, 17.22, 17.65,
129.10, 130.43, 130.95, 133.36, 137.70, 138.02, 138.09, 152.21, 154.66 ppm;
19F NMR (376 MHz, CDCl3): d=ꢀ145.84 ppm (q, J=32.9 Hz); IR
(ATR): n˜ =2965, 2927, 2869, 1746, 1602, 1526, 1474, 1406, 1368, 1311,
1263, 1222, 1180, 1159, 1117, 1038, 974, 929, 867, 827, 758, 607 cmꢀ1; UV/
Vis (CHCl3): lmax (e)=379 (8000), 531 nm (73000); HR-MALDI-MS (3-
+
HPA): m/z (%): 453.2397 (100) [M]+ (calcd for C25H30BF2N3O2
453.2399), 434.2410 (86) [MꢀF]+ (calcd for C25H30BFN3O2+: 434.2415).
:
{2-[(3,5-Dimethyl-4-nitrophenyl)(3-methyl-4,5-dihydro-2H-benzo[g]indol-
2-ylidene-kN)methyl]-3-methyl-4,5-dihydro-1H-benzo[g]indolato-kN}(di-
(e)=328 (82000), 529 (69000); HR-MALDI-MS (3-HPA): m/z (%):
ACHUTNGRENfNUG luACHTUNGTRENNUNoG ACHTUNRTGENNrGUN o)ACHTUNGRTENbNUNG oron (29): A catalytic amount of TFA (0.02 mL, 0.3 mmol) was
+
2203.8151 (34) [M]+ (calcd for C129H118BF2IN12O12
:
2203.8132),
added and the solution stirred for 3 h at 238C, to a solution of 27 (0.50 g,
2.8 mmol) and 30 (1.01 g, 5.80 mmol) in CH2Cl2 (200 mL) at 238C. The
solution was washed with a saturated aqueous NaHCO3 solution, brine,
dried over MgSO4, and filtered. The solvent was evaporated, and the re-
sulting solid was dissolved in toluene (200 mL). A suspension of DDQ
(0.67 g, 2.9 mmol) in toluene (200 mL) was added, and the mixture was
stirred for 1 h at 238C. Then, TEA (1.6 mL, 11 mmol) and BF3·Et2O
(2.8 mL, 22 mmol) were added and the mixture was heated to 758C for
40 min. After cooling to 238C, the mixture was filtered through a plug of
SiO2, eluted with CH2Cl2 and the solvent was evaporated. The crude
product was purified by FC (SiO2; CH2Cl2/cyclohexane 1:1) to afford 29
(1.1 g, 1.9 mmol, 69%) as a dark green solid. Rf =0.54 (SiO2; CH2Cl2/cy-
clohexane 1:1); m.p.: 330–3408C (decomp); 1H NMR (400 MHz, CDCl3):
d=1.42 (s, 6H), 2.42 (s, 6H), 2.55 (t, J=7.0 Hz, 4H), 2.89 (t, J=7.0 Hz,
4H), 7.22 (s, 2H), 7.24–7.28 (m, 2H), 7.28–7.35 (m, 2H), 7.39–7.46 (m,
2H), 8.80 ppm (d, J=8.0 Hz, 2H) ppm; 13C NMR (101 MHz, CDCl3): d=
12.76, 17.69, 20.63, 30.63, 127.52, 128.27, 128.38, 128.88 (t, J=11.6 Hz),
129.58, 129.77, 131.05, 132.52, 133.60, 135.63, 137.20, 138.42, 140.89,
151.35, 152.36 ppm; 19F NMR (376 MHz, CDCl3): d=ꢀ135.06 ppm (q,
J=34.1 Hz); IR (ATR): n˜ =2934, 2899, 2837, 2359, 2339, 1605, 1556,
1519, 1468, 1435, 1397, 1385, 1357, 1341, 1324, 1304, 1276, 1230, 1189,
1161, 1104, 1082, 1069, 1042, 1028, 1012, 950, 911, 893, 873, 866, 819, 779,
747, 732, 706, 676, 649, 633, 622 cmꢀ1; UV/Vis (CHCl3): lmax (e)=311
(15000), 316 (51000), 395 (10000), 573 (26000), 621 nm (116000); HR-
2184.8202 (100) [MꢀF]+ (calcd for C129H118BFIN12O12+: 2184.8151).
Compound 25: [PdACHTUNGTRENNUNG(PPh3)4] (47 mg, 0.041 mmol), and CuI (8 mg,
0.04 mmol) were added to a degassed solution of 7 (124 mg, 0.308 mmol),
11 (0.75 g, 0.41 mmol), and DIPEA (1.4 mL, 8.2 mmol) in THF (30 mL).
The mixture was stirred for 16 h at 238C, after which the solvent was
evaporated. FC (SiO2; CH2Cl2!CH2Cl2/EtOAc 98:2) and recycling GPC
(Jaigel-2H; CHCl3) afforded 25 (192 mg, 0.091 mmol, 22%) as a red
solid. tR =20.7 min (Jaigel-2H; CHCl3, flow=4 mLminꢀ1); m.p.: 280–
2908C (decomp); 1H NMR (400 MHz, CDCl3): d=0.94 (q, J=6.7 Hz,
12H), 1.01 (t, J=7.5 Hz, 6H), 1.38 (s, 6H), 1.29–1.55 (m, 38H), 2.16 (s,
3H), 2.24 (s, 3H), 2.21–2.41 (m, 12H), 2.56 (s, 6H), 5.62 (t, J=7.1 Hz,
2H), 5.70 (t, J=8.1 Hz, 2H), 7.27–7.38 (m, 10H), 7.49 (s, 1H), 7.50 (s,
1H), 7.67 (s, 2H), 7.74 (d, J=8.3 Hz, 2H), 7.83–7.92 (m, 4H), 8.24 (s,
2H), 8.25 ppm (s, 2H); 13C NMR (101 MHz, CDCl3): d=12.12, 12.71,
14.22, 14.79, 17.26, 17.83, 17.94, 18.19, 18.27, 22.81, 28.08, 28.11, 29.50,
29.51, 29.85, 32.01, 32.02, 32.29, 32.81, 34.32, 34.42, 89.62, 90.42, 96.67,
118.91, 123.59, 123.90, 125.19, 128.47, 128.53, 128.85, 128.90, 129.14,
129.52, 130.70, 131.60, 132.37, 132.53, 133.16, 135.83, 135.84, 136.17,
136.47, 136.99, 137.01, 137.48, 137.64, 137.94, 138.37, 139.26, 139.31,
139.94, 141.54, 141.61, 152.16, 152.17, 152.38, 153.21, 154.27, 159.01,
161.45, 161.60 ppm; 19F NMR (376 MHz, CDCl3): d=ꢀ145.76 ppm (q,
J=32.4 Hz); IR (ATR): n˜ =2925, 2856, 2361, 2341, 1740, 1712, 1530,
1477, 1444, 1412, 1361, 1327, 1264, 1231, 1191, 1158, 1115, 1101, 1083,
1019, 978, 899, 838, 761, 709, 689, 668, 652, 604 cmꢀ1; UV/Vis (CHCl3):
lmax (e)=529 (68000); HR-MALDI-MS (3-HPA): m/z (%): 2103.7745
(86) [M]+ (calcd for C121H114BF2IN12O12+: 2103.7821), 2084.7743 (100)
[MꢀF]+ (calcd for C121H114BFIN12O12+: 2084.7834).
3,5-Dimethyl-4-nitrobenzaldehyde (27): Alcohol 26 (4.47 g, 24.7 mmol) in
CH2Cl2 (3 mL) was added to a suspension of PCC (9.6 g, 44 mmol) in
CH2Cl2 (100 mL). The resulting dark suspension was stirred for 1 h at
238C after which Et2O (120 mL) and Celite were added to the reaction
mixture to form a black slurry, which was filtered through a plug of SiO2
and eluted with CH2Cl2. Upon removal of solvent, 27 (3.94 g, 22.0 mmol,
89%) was obtained as a tan solid. Rf =0.41 (SiO2; CH2Cl2/cyclohexane
2:1); m.p.: 50–518C (Lit:[28] 52–548C); 1H NMR (400 MHz, CDCl3): d=
2.38 (s, 6H), 7.65 (s, 2H), 9.99 ppm (s, 1H); 13C NMR (101 MHz, CDCl3):
d=17.38, 130.23, 130.77, 136.81, 155.23, 190.81 ppm; HR-EI-MS (70 eV):
m/z: 179.0577 [M]+ (calcd for C9H9NO3+: 179.0582).
MALDI-MS (3-HPA): m/z (%): 573.2406 (100) [M]+ (calcd for
+
C35H30BF2N3O2
:
573.2399), 554.2420 (47) [MꢀF]+ (calcd for
C35H30BFN3O2+: 554.2415).
{4-[(4-Ethyl-3,5-dimethyl-1H-pyrrol-2-yl-kN)(4-ethyl-3,5-dimethyl-2H-pyr-
ACHUTGTNRENNrGU ol-2-ylidene-kN)methyl]-2,6-dimethylanilinato}HCATUNGTREN(NGUN difluoro)boron (31): Hy-
drazine monohydrate (2.9 mL, 93 mmol) and Pd/C (10%, 0.49 g,
0.46 mmol) were added to a degassed solution of 28 (2.1 g, 4.6 mmol) in
THF (50 mL) and EtOH (100 mL). The mixture was heated to reflux for
40 min, then cooled to 238C. Celite was added, and the mixture was fil-
tered through a plug of Celite. The solvent was evaporated, and the resi-
due was purified by FC (SiO2; CH2Cl2/cyclohexane 1:1!4:1), affording
31 (1.8 g, 4.3 mmol, 92%) as a dark red solid. Rf =0.20 (SiO2; CH2Cl2/cy-
clohexane 3:1); m.p.: 240–2458C; 1H NMR (400 MHz, CDCl3): d=0.99
(t, J=7.6 Hz, 6H), 1.37 (s, 6H), 2.22 (s, 6H), 2.30 (q, J=7.6 Hz, 4H),
2.52 (s, 6H), 3.72 ppm (s, 2H), 6.81 (s, 2H); 13C NMR (101 MHz, CDCl3):
d=12.16, 12.58, 14.78, 17.23, 17.69, 122.34, 125.11, 128.06, 131.54, 132.44,
138.69, 141.75, 143.14, 153.05 ppm; 19F NMR (376 MHz, CDCl3): d=
ꢀ145.84 ppm (q, J=33.3 Hz); IR (ATR): n˜ =3493, 3410, 2969, 2926,
2869, 1623, 1539, 1474, 1403, 1388, 1371, 1313, 1258, 1184, 1159, 1113,
1076, 1038, 971, 867, 798, 756, 728, 705, 668, 637 cmꢀ1; UV/Vis (CHCl3):
lmax (e)=379 (9000), 525 nm (79000); HR-MALDI-MS (3-HPA): m/z
(%): 423.2643 (100) [M]+ (calcd for C25H32BF2N3+: 423.2657), 404.2656
(92) [MꢀF]+ (calcd for C25H32BFN3+: 404.2673).
{2-[(3,5-Dimethyl-4-nitrophenyl)(4-ethyl-3,5-dimethyl-2H-pyrrol-2-yli-
dene-kN)-methyl]-4-ethyl-3,5-dimethyl-1H-pyrrolato-kN}ACTHNUTRGNE(UNG difluoro)boron
(28): A catalytic amount of TFA (0.1 mL, 1 mmol) was added to a solu-
tion of 27 (2.0 g, 11 mmol) and 3-ethyl-2,4-dimethyl-1H-pyrrole (3.0 g,
23 mmol) in CH2Cl2 (700 mL) at 238C, and the resulting solution was
stirred for 3 h at 238C. The solution was washed with a saturated aqueous
NaHCO3 solution, brine, dried over MgSO4, and filtered. The solvent
was evaporated, and the resulting solid was dissolved in toluene
(400 mL). A suspension of DDQ (2.68 g, 11.7 mmol) in toluene (200 mL)
was added, and the mixture was stirred for 1 h at 238C. Then, TEA
(6.3 mL, 45 mmol) and BF3·Et2O (8.0 mL, 65 mmol) were added, and the
mixture was heated to 758C for 40 min. After cooling to 238C, the mix-
ture was filtered through a plug of SiO2, eluted with CH2Cl2 and the sol-
vent was evaporated. The crude product was purified by FC (SiO2;
CH2Cl2/cyclohexane 2:1) to afford 28 (3.53 g, 7.79 mmol, 70%) as a me-
{2,6-Dimethyl-4-[(3-methyl-4,5-dihydro-1H-benzo[g]indol-2-yl-kN)(3-meth-
yA
G
U
N
R
T
N
U
H
l-4,5-dihydro-2H-benzo[g]indol-2-ylidene-kN)methyl]anilinato}(di
GfNUTRETUNGACH luoNUGTRENUNGACHT GrNUGTRETUNACH o)-
AHCTUNGERTGbNNUN oron (32): Hydrazine monohydrate (0.42 mL, 14 mmol) and Pd/C (10%,
0.29 g, 0.27 mmol) was added to a degassed solution of 29 (390 mg,
0.680 mmol) in THF (10 mL) and EtOH (20 mL),. The mixture was
heated to reflux for 32 h. After cooling to 238C, Celite was added and
the mixture was filtered through a plug of Celite. The solvent was evapo-
rated, and the residue was purified by FC (SiO2; CH2Cl2/cyclohexane
ACHTUNGTRENNUNGtallic green solid. Rf =0.48 (SiO2; CH2Cl2/cyclohexane 1:1); m.p.: 237–
Chem. Eur. J. 2010, 16, 12590 – 12602
ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
12601

F. Diederich et al.
1:1), yielding 32 (190 mg, 0.349 mmol, 51%) as a dark red solid. Rf =0.38
(SiO2; CH2Cl2/cyclohexane 3:1); m.p.: 330–3408C (decomp.); 1H NMR
(400 MHz, CDCl3): d=1.46 (s, 6H), 2.25 (s, 6H), 2.54 (t, J=7.0 Hz, 4H),
2.87 (t, J=7.0 Hz, 4H), 3.77 (s, 2H), 6.90 (s, 2H), 7.21–7.31 (m, 4H),
7.38–7.44 (m, 2H), 8.80 ppm (d, J=8.0 Hz, 2H) ppm; 13C NMR
(101 MHz, CDCl3): d=12.63, 17.69, 20.61, 30.73, 122.40, 125.43, 127.39,
128.10, 128.55, 128.70, 128.83, 129.20, 131.73, 134.79, 136.48, 140.62,
141.58, 143.47, 150.34 ppm; 19F NMR (376 MHz, CDCl3): d=
ꢀ134.79 ppm (q, J=34.1 Hz); IR (ATR): n˜ =3486, 3401, 3037, 2921,
2833, 1635, 1547, 1522, 1466, 1433, 1402, 1386, 1367, 1327, 1307, 1275,
1235, 1194, 1169, 1157, 1086, 1047, 1021, 976, 958, 944, 919, 876, 828, 750,
732, 720, 710, 683, 668, 632, 608 cmꢀ1; UV/Vis (CHCl3): lmax (e)=311
(53000), 401 (8000), 566 (24000), 613 nm (109000); HR-MALDI-MS (3-
HPA): m/z (%): 543.2654 (100) [M]+ (calcd for C35H32BF2N3+: 543.2657),
524.2675 (39) [MꢀF]+ (calcd for C35H32BFN3+: 524.2673).
[6] M. Frei, F. Marotti, F. Diederich, Chem. Commun. 2004, 1362–1363.
[7] V. A. Azov, F. Diederich, Y. Lill, B. Hecht, Helv. Chim. Acta 2003,
86, 2149–2155.
[8] V. A. Azov, P. Skinner, Y. Yamakoshi, P. Seiler, V. Gramlich, F. Die-
derich, Helv. Chim. Acta 2003, 86, 3648–3670.
[9] V. A: Azov, A. Schlegel, F. Diederich, Bull. Chem. Soc. Jpn. 2006,
79, 1926–1940.
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Compound 34: K2CO3 (64 mg, 0.46 mmol) was added to a degassed solu-
tion of 12 (0.50 g, 0.46 mmol) and 13 (0.22 g, 0.35 mmol) in Me2SO
(30 mL). The mixture was stirred for 4 h at 238C, after which it was
poured into H2O (300 mL). The resulting precipitate was collected by fil-
tration, washed with H2O (3ꢃ10 mL), and dried in vacuo. Recycling
GPC (Jaigel-2H; CHCl3) afforded 34 (43 mg, 0.026 mmol, 6%) as a red
solid. tR =21.8 min (Jaigel-2H; CHCl3, flow=4 mLminꢀ1); m.p.: 250–
2608C (decomp); 1H NMR (400 MHz, CDCl3): d=0.88–0.96 (m, 12H),
1.05 (t, J=7.5 Hz, 6H), 1.19 (s, 3H), 1.26 (s, 3H), 1.27–1.51 (m, 32H),
2.26 (s, 6H), 2.15–2.47 (m, 12H), 2.58 (s, 6H), 4.30 (t, J=7.7 Hz, 1H),
5.62 (t, J=7.6 Hz, 3H), 7.07 (s, 1H), 7.13 (s, 2H), 7.16 (s, 2H), 7.22 (s,
1H), 7.27–7.31 (m, 2H), 7.33 (s, 2H), 7.42 (t, J=7.7 Hz, 2H), 7.68 (d, J=
7.8 Hz, 2H), 8.09 (d, J=8.3 Hz, 2H), 8.31 ppm (s, 2H); 13C NMR
(101 MHz, CDCl3): d=12.11, 12.73, 14.22, 14.81, 17.31, 17.84, 18.34,
22.82, 28.06, 28.13, 29.49, 29.54, 29.85, 32.01, 32.02, 32.04, 32.51, 32.75,
33.75, 33.91, 34.17, 34.55, 110.83, 118.78, 123.76, 123.95, 127.34, 128.15,
128.67, 128.84, 129.17, 129.35, 129.57, 130.65, 130.75, 133.24, 135.72,
137.50, 137.60, 137.66, 138.29, 138.50, 138.95, 139.60, 139.96, 141.73,
151.45, 152.29, 152.63, 152.73, 152.80, 152.99, 154.33, 158.79, 161.28 ppm;
19F NMR (376 MHz, CDCl3): d=ꢀ146.26, ꢀ145.08 ppm; IR (ATR): n˜ =
3365 (w, br), 2926, 2856, 2360, 2341, 1741, 1540, 1479, 1410, 1359, 1323,
1263, 1222, 1189, 1159, 1115, 1066, 1042, 978, 897, 862, 842, 796, 757, 728,
682, 668, 649, 604 cmꢀ1; UV/Vis (CHCl3): lmax (e)=528 nm (66000); HR-
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show the cavitands as solvates with acetone inside the cavity of 11
and CH2Cl2 inside the cavity of 16 (Figure 1SI in the Supporting In-
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to study the conformations of BODIPY dyes, see: A. C. Benniston,
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[22] Degradation of both dye moieties was observed at higher TFA con-
centrations (see Figure 11SI–13SI in the Supporting Information),
whereby degradation of the acceptor was even faster than that of
the donor. As a consequence of these findings, measurements of the
fluorescence spectra in the titration experiments were performed as
quickly as possible after mixing the cavitand with TFA (after ca.
20 s). Because slight degradation of the BODIPY-dye moieties
could not be avoided, and because the acceptor dye degrades more
quickly than the donor dye, the absolute FRET efficiencies for cavi-
tands 1–4 are artificially low under these conditions. However, be-
cause a uniform experimental protocol was used throughout these
measurements, the relative FRET efficiencies within the cavitand
series are internally consistent.
MALDI-MS (3-HPA): m/z (%): 1627.7922 (27) [M]+ (calcd for
+
C99H104BF2N9O10
:
1627.7967), 1608.7921 (100) [MꢀF]+ (calcd for
C99H104BFN9O10+: 1608.7992).
Acknowledgements
This work was supported by a grant from the Swiss National Science
Foundation (SNF). I.P. acknowledges the receipt of a Novartis Master
Fellowship and a fellowship from the Studienstiftung des deutschen
Volkes. B.B. is supported by a Kekulꢄ fellowship of the Fonds der Chemi-
schen Industrie. We thank Dr. Vladimir Azov (University of Bremen) for
helpful discussions, and Dr. Melanie Chiu and Dr. Nicolas Marion for re-
viewing the manuscript.
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Received: June 9, 2010
Published online: September 23, 2010
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