A bis-spiropyran-containing multi-state [2]rotaxane with fluorescence output

Article abstract of DOI:10.1016/j.tet.2013.04.119

In this paper, a bis-spiropyran-functionalized [2]rotaxane with a 4-morpholin-naphthalimide fluorophore as stopper was designed, synthesized, and studied. The macrocycle can shuttle reversibly in response to external acid-base stimuli and the spiropyran functional group can be switched to its ring-opened merocyanine (MC) state. It has been shown that, by introducing two spiropyran units into the system, intercomponent interactions, such as electron transfer and energy transfer processes, between the SP or MC functional units and the fluorophore, can be altered in response to the combination of acid-base and photochemical stimuli, which can generate obvious UV/vis absorption and fluorescence spectral changes.

Full text of DOI:10.1016/j.tet.2013.04.119

Tetrahedron 69 (2013) 5319e5325
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Tetrahedron
journal homepage: www.elsevier.com/locate/tet
A bis-spiropyran-containing multi-state [2]rotaxane
with fluorescence output
*
Wei Zhou, Hui Zhang, Hong Li, Yu Zhang, Qiao-Chun Wang, Da-Hui Qu
Key Laboratory for Advanced Materials and Institute of Fine Chemicals, East China University of Science & Technology, Shanghai 200237, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 7 March 2013
Received in revised form 20 April 2013
Accepted 26 April 2013
Available online 2 May 2013
In this paper, a bis-spiropyran-functionalized [2]rotaxane with a 4-morpholin-naphthalimide fluo-
rophore as stopper was designed, synthesized, and studied. The macrocycle can shuttle reversibly in
response to external acidebase stimuli and the spiropyran functional group can be switched to its ring-
opened merocyanine (MC) state. It has been shown that, by introducing two spiropyran units into the
system, intercomponent interactions, such as electron transfer and energy transfer processes, between
the SP or MC functional units and the fluorophore, can be altered in response to the combination of
acidebase and photochemical stimuli, which can generate obvious UV/vis absorption and fluorescence
spectral changes.
Keywords:
Spiropyran
Rotaxane
Fluorescence
Supramolecular chemistry
Ó 2013 Elsevier Ltd. All rights reserved.
1. Introduction
interlocked molecular systems.12 In this paper, we report the de-
sign, preparation, characterization, and properties of
a bis-
Over the past few decades, mechanically interlocked mole-
cules,1 such as rotaxanes and catenanes, have become typical
candidates in the design of artificial molecular machines. Bistable
rotaxanes,2 which can change their shapes and properties in re-
sponse to external stimuli, have important potential to function as
molecular switches,3 molecular logic gates,4 and stimuli-responsive
materials5 when functional units are introduced into the rotaxane
molecule. Various photochemically and electrochemically active
units have been introduced into mechanically interlocked rotax-
anes to achieve specific functions and to realize intercomponent
interactions, such as electron transfer,6 energy transfer,7 charge
transfer interactions8 etc., most of them featuring an absorption or
fluorescent spectral changes as outputs that can be easily detected.
On the other hand, photochromic compounds, such as diary-
lethenes9 and spiropyrans,10 can alter their ability to absorb visible
radiation in response to optical stimuli and were exploited as im-
portant functional units to modulate the emission of compatible
fluorophores, using the ‘ON/OFF’ properties of the fluorescence to
store and/or transfer information in a nondestructive manner. In
most cases, the specific fluorophore was covalently linked to the
photochromic molecule (or linked to it through a spacer) to form
the dyad or the triad, or the macromolecular constructs.11 However,
this modulation has rarely been realized in mechanically
spiropyran-containing [2]rotaxane 1-H-SP, in which inter-
component transfer interactions, can be altered in response to the
combination of chemical and photochemical stimuli, along with
remarkable UV/vis absorption and fluorescence spectral changes.
2. Results and discussion
2.1. Molecular design and syntheses
The chemical structures and schematic representations of the
multistable [2]rotaxane 1-H-SP, bis-spiropyran-containing crown
ether 2-SP and its reversible photoswitching process, and
dumbbell-shaped thread component 3-H are shown in Scheme 1.
[2]Rotaxane 1-H-SP has several key features: a bis-spiropyran-
functionalized dibenzo-24-crown-8 (DB24C8) crown ether macro-
cycle was interlocked into the rotaxane thread, which contains
a long-distance alkyl chain that separates two distinguishable
binding sites, namely dibenzylammonium (DBA)13 and N-methyl-
triazolium (MTA)2d,14 recognition sites for DB24C8. The stoppers are
a 4-morpholin-naphthalimide fluorescent moiety on one side-
demployed because of its desirable spectroscopic propertiesdand
a 3,5-dimethoxyl benzene stopper group on the other side. The
DB24C8 macrocycle has been proved to have a better affinity for the
DBA station than for the MTA one, and no affinity at all for the N-
benzylamine moiety, thus allowing the shuttling movement in re-
sponse to acidebase stimuli.15 As shown in Schemes 1 and 2, UV
light irradiation of spiropyran (SP) can induce heterolytic cleavage
* Corresponding author. Tel./fax: þ86 2164252288; e-mail address: dahui_qu@
ecust.edu.cn (D.-H. Qu).
0040-4020/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2013.04.119

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W. Zhou et al. / Tetrahedron 69 (2013) 5319e5325
Scheme 3. Preparation of compound 6, 10, and 2-SP.
a moderate yield (65%) via the esterification of spiropyran car-
boxylic acid 11 and benzyl alcohol 12.
The synthesis of [2]rotaxane 1-H-SP was illustrated in Scheme 4.
Using the copper(I)-catalyzed Huisgen alkyneeazide 1,3-dipolar
cycloaddition16 as the stopping strategy of rotaxane preparation,
the target [2]rotaxane 1-H-SP was successfully obtained. A mixture
of alkyne 6 and crown ether 2-SP in dry CH2Cl2 was stirred for
10 min at room temperature, after which azide 10 and [Cu(CH3CN)4]
PF6 were added to the solution, and the mixture continued to stir for
24 h to form the rotaxane 1-H-SP in 45% isolated yield. The thread
component 3-H was also prepared as a reference compound in
a similar strategy in the absence of crown ether 2-SP. [2]Rotaxane 1-
H-SP, and the thread component 3-H were well-characterized by 1H
NMR, 13C NMR spectroscopies and HR-ESI mass spectrometry
(Supplementary data). The HR-ESI mass spectra of [2]rotaxane 1-H-
SP and 3-H gave sharp peaks at m/z 1052.4816 [Mꢀ2PF6]2þ and
435.7376 [Mꢀ2PF6]2þ, respectively, in excellent agreement with the
calculated value (1052.4810 and 435.7373, respectively).
Scheme 1. The chemical structures and schematic representations of a photochromic
rotaxane 1-H-SP,
a bis-spiropyran-containing crown ether 2-SP, and a dumbbell-
shaped thread component 3-H.
Scheme 2. Schematic representations and interconversions between the four states of
rotaxane 1-H-SP in response to different combinations of chemical and photochemical
stimuli.
of the spiro carboneoxygen bond, to generate ring-opened mer-
ocyanine (MC) structure. Moreover, the acidebase stimuli can drive
the reversible shuttling motion of spiropyran-functionalized
DB24C8 macrocycle between two distinguishable stations. On the
basis of the facts, the alterations of intercomponent interactions
between the functional units, such as photoinduced electron
transfer (PET) and electron energy transfer (EET) processes, can be
realized in one molecular platform under different stimuli combi-
nations of two external inputs (Scheme 2).
The synthetic route for key intermediates 2-SP, 6, and 10 was
shown in Scheme 3. As described in Scheme 3, aldehyde 4 and
benzylamine 5 were refluxing in toluene, and then the afforded
white Schiff base was reduced with NaBH4 in methanol, followed
by acidification, and ion exchange to give the alkyne 6 in a 66%
yield. The click reaction between the known compounds alkyne 7
and azide 8 gave 9 in a 70% yield, and subsequent methylation and
ion exchange with NH4PF6 aqueous solution to obtain 10 with
a secondary MTA recognition site in a high yield (90%). Bis-
spiropyran-containing crown ether 2-SP was prepared in
Scheme 4. Preparation of compound 3-H and [2]rotaxane 1-H-SP.
2.2. 1H NMR measurements
The direct comparison of 1H NMR spectra (Fig. 1) of crown ether
2-SP, [2]rotaxane 1-H-SP, and thread component 3-H in CDCl3

W. Zhou et al. / Tetrahedron 69 (2013) 5319e5325
5321
the peaks for the MTA protons H21, H22, H23 were shifted with
Dd¼0.54, 0.21, and ꢀ0.33 ppm, respectively. Moreover, the peaks
for the protons H2, H3 on the dimethoxybenzene stopper shifted
downfield with Dd¼0.09 and 0.14 ppm, respectively. The macro-
cycle shuttled back around the ammonium station upon reproto-
nation of the amine with the addition of 1.2 equiv CF3CO2H, which
was evidenced by the regeneration of the original 1H NMR spec-
trum (Fig. 2c). Thus, using the 1H NMR spectroscopy, the reversible
acidebase shuttling motion of the [2]rotaxane 1-H-SP has been
demonstrated.
2.3. The photophysical properties of 1-H-SP, 2-SP, and 3-H
The photophysical properties of bis-spiropyran-containing
crown ether 2-SP and the dumbbell 3-H were investigated. Irradi-
ation of 2-SP in dichloromethane solution with 365 nm for 2 min
can reach the photostationary state (PSS) and result in an increase
in an absorption band at 500e650 nm (Fig. 3a), which indicates the
appearance of the ring-opened isomer 2-MC, with its structure
shown in Scheme 1. The system can be recovered to its original
SP state and the solution becomes colorless when placed in dark
for 5 min.
Fig. 1. Partial 1H NMR spectra (400 MHz, CDCl3, 298 K) of (a) crown ether 2-SP, (b) [2]
rotaxane 1-H-SP, (c) thread component 3-H. The assignments correspond to the
structures as shown in Scheme 1.
indicates the localization of the DB24C8 at DBA station. As shown in
Fig. 1, the methylene protons H4 and H6 in the DBA station of the
rotaxane (Fig.1b) were shifted downfield (Dd¼0.69 ppm) compared
with those of dumbbell 3-H (Fig. 1c), meanwhile, the peaks of
protons H1, H2, H3 on the dimethoxybenzene stopper shifted up-
field (Dd¼ꢀ0.20, ꢀ0.16, and ꢀ0.11 ppm, respectively) due to the
shielding effect of macrocycle 2-SP. Moreover, the protons (H21, H22
,
H23) on the MTA unit have the same chemical shifts as the ones on
dumbbell 3-H, and the peaks of protons HB, HC on the DB24C8
experienced upfield shift (Dd¼ꢀ0.12, ꢀ0.29 ppm, respectively)
compared with the ones of macrocycle 2-SP (Fig. 1a) due to
a combination of [NeH/O] and [CeH/O] hydrogen bonds. All this
evidence proved the fact that the DB24C8 ring exhibited a pre-
dominant selectivity for the encirclement of the DBA recognition
site.
It has been reported that 1,8-diazabicyclo[5þ.4.0]undec-7-ene
(DBU) is strong enough to deprotonate the NH2 center.15 Addi-
tion of 1.1 equiv DBU resulted in the moving of the DB24C8 toward
the MTA recognition site, generating 1-SP (shown in Scheme 2). The
peaks for the methylene protons H4, H6 on the DBA recognition site
are shifted upfield (with a Dd of ꢀ0.51 ppm) as a result of both the
deprotonation of the neighboring ammonium and the shuttling of
the macrocycle (Fig. 2b). Due to association with the DB24C8 ring,
Fig. 3. (a) UV/vis spectral change of compound 2-SP in CH2Cl2 (2ꢁ10ꢀ5 M) at room
temperature upon irradiation at 365 nm to reach the PSS. (b) Partial fluorescence
spectrum of 3-H in CH2Cl2 (2ꢁ10ꢀ5 M) excited with 410 nm and UV/vis spectrum of 2-
SP in CH2Cl2 (2ꢁ10ꢀ5 M) upon irradiation at 365 nm for 2 min to reach the PSS.
The absorption spectrum of compound 3-H showed an ab-
sorption band with lmax at 410 nm and the fluorescence emission
displayed a band with lem at 522 nm when excited at 410 nm
(Fig. S1). The absolute fluorescence quantum of dumbbell 3-H was
0.52, which was hardly changed upon addition of 3 equiv DBU. It is
reasonable because the DBA center is far away from the fluorescent
stopper and deprotonation of the ammonium center does not affect
Fig. 2. Partial 1H NMR spectra (400 MHz, CDCl3, 298 K) of (a) [2]rotaxane 1-H-SP
(1ꢁ10ꢀ2 M), (b) deprotonation with addition of 1.1 equiv of DBU to sample a, (c) re-
protonation with addition of 1.2 equiv of TFA to sample b.

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W. Zhou et al. / Tetrahedron 69 (2013) 5319e5325
the fluorescent moiety. This also helps to study the photophysical
properties of the [2]rotaxane 1-H-SP. It should be noted that there
is obvious overlap between the emission spectrum of 3-H and the
absorption spectrum of ring-opened isomer 2-MC (Fig. 3b), as
a result, it is possible that the EET process from the excited MA
fluorophore to the 2-MC moiety could occur, if the two components
are sufficiently close to each other.17
of ring-opened MC units 1-MC. The emission intensity of 1-MC
decreased 38% (d in Scheme 5), and the absolute fluorescence
quantum yield was 0.09. Indeed, the MC component can activate an
EET process and lead to a partial fluorescence quenching. None-
theless, the emission spectrum of 1-MC does not show the char-
acteristic fluorescence of 2-MC at 643 nm (Fig. S2). The lack of
sensitized fluorescence suggests that the transfer of energy from
the excited fluorophore to the MC photochrome is not particularly
efficient. In fact, the HOMO value of MC,18 reported as ꢀ5.4 eV to
ꢀ4.5 eV, indicating that the photoinduced transfer of one electron
from the photochrome to the excited fluorophore is exoergonic.
Presumably, both of the electron transfer process and energy
transfer pathway contribute to the nonradiative deactivation of the
excited fluorophore.17
Restarting from 1-H-SP, irradiation at 365 nm resulted in the
formation of 1-H-MC, the emission intensity decreased 22% at the
PSS (b in Scheme 5), and the absolute fluorescence quantum yield
of 1-H-MC dropped to 0.28, both of which indicate a less efficient
PET and EET processes between the two functional units. The less
efficient PET and EET processes can be ascribed to the long distance
between the naphthalimide fluorophore and opened-form MC
units. To this PSS solution, 1.1 equiv DBU was added to generate 1-
MC, in which opened-form merocyanine-containing macrocycle
was shuttling to the MTA recognition station (route c in Scheme 5),
and the emission intensity decreased 55% compared to that of the
PSS mixture (c in Scheme 5). This obvious change was due to an
efficient PET and EET processes between the two functional units.
It should be mentioned that the photochemistry of photochro-
mic spiropyran was unaffected by the addition of DBU, as evidenced
by nearly the same PSS absorption spectra of 1-H-SP and 1-SP
(Fig. S3). It should also be noted that the two strategies to generate
1-MC from 1-H-SP, namely route aþd and route bþc (Scheme 5),
gave almost the same absorption and fluorescence spectra (Fig. 4).
Then we focused on the physical properties of the [2]rotaxane 1-
H-SP in response to chemical and photochemical stimuli. The
emission intensity of the rotaxane 1-H-SP is around 92% of that of
the dumbbell 3-H, and the absolute fluorescence quantum yield of
1-H-SP is 0.41, whereas that of 3-H is 0.52. Presumably, the pho-
toinduced electron transfer from the photochrome to the excited
fluorophore is responsible for the decrease in quantum yield. The
HOMO and LUMO values of the N-ethyl-4-morpholin-naph-
thalimide fluorophore,12 were calculated as ꢀ5.6 eV and ꢀ2.1 eV,
respectively, and the HOMO value of SP,18 reported by several lit-
erature as ꢀ5.3 eV to ꢀ4.7 eV. Therefore, it was possible that an
electron from the HOMO of the SP photochrome was transferred to
the vacancy in the HOMO of the excited 4-morpholin-naph-
thalimide fluorophore, which partially quenched the fluorescence
of the 4-morpholin-naphthalimide moiety. As shown in Scheme 5,
the dichloromethane solution of 1-H-SP was added of excess DBU,
which could induce the shuttling motion of the macrocycle 2-SP to
the MTA recognition station, generating 1-SP (route a), then irra-
diated the sample at 365 nm to reach the PSS to give 1-MC isomer
(route d), with the photochromic functional unit in a ring-opened
merocyanine state. The other route can also generate 1-MC. Start-
ing from 1-H-SP, firstly irradiation at 365 nm resulted in the for-
mation of 1-H-MC (route b), then followed by addition of excess
DBU to the mixture to yield 1-MC (route c). Each route was char-
acterized using UV/vis absorption and fluorescence emission
spectroscopies, as discussed below.
3. Conclusion
In conclusion, a novel [2]rotaxane with two spiropyran photo-
chromic functional groups has been prepared and well-
characterized. The rotaxane 1-H-SP can respond to different com-
binations of chemical and photochemical stimuli, and displays
multiple states with distinguishable fluorescence output. In 1-H-SP
and 1-SP, the PET process between the SP unit and the naph-
thalimide fluorescent unit can be tuned by acidebase stimuli. In 1-
H-MC and 1-MC, both of the PET and EET processes interaction
between the MC unit and the naphthalimide fluorescent unit can be
chemically regulated. Most importantly, the reversible alteration of
intercomponent interactions (such as energy transfer, electron
transfer) in a rotaxane system can take advantage of UV/vis ab-
sorption spectroscopy and fluorescence emission spectroscopy,
which are easy to be detected. This kind of multi-state molecular
shuttle holds the potential to construct multi-level molecular ma-
chines and complicated logic gates.
Scheme 5. Schematic representations and interconversions between the four states of
rotaxane 1-H-SP, and the fluorescence spectral changes for rotaxane 1-H-SP in re-
sponse to different combinations of chemical and photochemical stimuli. The fluo-
rescence spectral changes a, b, c, d correspond to routes a, b, c, d, respectively.
Excitation wavelength was 410 nm.
4. Experimental
4.1. General
13
1H NMR and C NMR spectra were measured on a Bruker AV-
€
Starting from 1-H-SP, upon addition of 1.1 equiv DBU to convert
1-H-SP to 1-SP (route a in Scheme 5), the absorption spectrum had
no obvious change, however, the emission intensity decreased 45%,
meanwhile, the absolute fluorescence quantum yield of 1-SP
dropped to 0.18. This change can be attributed to an efficient PET
process from two SP photochromic groups to the excited state of 4-
morpholin-naphthalimide fluorophore. Irradiation at 365 nm could
convert 1-SP into 1-MC (route d in Scheme 5), and resulted in a new
absorption band at 500e650 nm corresponding to the generation
400 spectrometer. The electronic spray ionization (ESI) mass
spectra were tested on an LCT Premier XE mass spectrometer. The
UV/vis absorption spectra and fluorescence spectra were obtained
on a Varian Cary 100 spectrometer and a Varian Cary Eclipse (1-cm
quartz cell used), respectively. The photoirradiation was carried on
a CHF-XM 500-W high-pressure mercury lamp in a sealed Ar-
saturated 1 cm quartz cell. The distance between the lamp and
the sample cell was 20 cm. Photostationary states were ensured by

W. Zhou et al. / Tetrahedron 69 (2013) 5319e5325
5323
solution, which resulted in a suspension. The precipitate was col-
lected by suction filtration. Recrystallization from MeOH gave 6
(0.72 g, 66%) as a white solid: mp¼160e161 ꢂC. 1H NMR (400 MHz,
CD3SOCD3, 298 K):
d
¼9.07 (s, 2H), 7.43 (d, J¼8.7 Hz, 2H), 7.06 (d,
J¼8.7 Hz, 2H), 6.67 (d, J¼2.2 Hz, 2H), 6.55 (t, J¼2.2 Hz, 1H), 4.84 (d,
J¼2.3 Hz, 2H), 4.10 (d, J¼2.5 Hz, 4H), 3.76 (s, 6H), 3.58 (t, J¼2.3 Hz,
1H). 13C NMR (100 MHz, CD3SOCD3, 298 K):
d¼160.5, 157.6, 133.8,
131.5, 124.3, 114.9, 107.6, 100.4, 79.0, 78.3, 55.3, 49.9, 49.5. HRMS
(ESI) (m/z): ½M ꢀ PF6ꢀꢃþ calcd for C19H22NO3, 312.1600; found,
312.1596.
4.4. Synthesis of compound 9
A mixture of compound 7 (1.00 g, 3.12 mmol), 1,10-dec-
anediazide 8 (1.4 g, 6.3 mmol), CuI (0.12 g, 0.63 mmol), and N,N-
diisopropylethylamine (0.78 g, 6.3 mmol) in anhydrous THF
(20 mL) was stirred at room temperature for 12 h under nitrogen
atmosphere. The resulting suspension was filtered, and the filtrate
was evaporated under reduced pressure. The residue was parti-
tioned in H2O/CH2Cl2. The organic layer was dried over Na2SO4 and
filtered, and the filtrate was evaporated to dryness. The residue was
purified via column chromatography (SiO2, CH2Cl2/petroleum
ether¼5/1) to give 9 (1.68 g, 70%) as a green solid: mp¼109e110 ꢂC.
1H NMR (400 MHz, CDCl3, 298 K):
d
¼8.61 (dd, J¼7.3, 0.9 Hz, 1H),
8.55 (d, J¼8.1 Hz, 1H), 8.42 (dd, J¼8.4, 0.9 Hz, 1H), 7.71 (dd, J¼8.3,
7.4 Hz, 1H), 7.61 (s, 1H), 7.23 (d, J¼8.1 Hz, 1H), 5.50 (s, 2H), 4.27 (t,
J¼7.3 Hz, 2H), 4.04 (t, J¼7.9 Hz, 4H), 3.21e3.29 (m, 6H), 1.80e1.89
(m, 2H), 1.53e1.62 (m, 2H), 1.20e1.37 (m, 12H). 13C NMR (100 MHz,
CDCl3, 298 K):
d
¼164.1, 163.6, 155.8, 143.7, 132.8, 131.4, 130.3, 129.9,
126.1, 125.8, 123.0, 116.9, 114.9, 66.9, 53.4, 51.4, 50.2, 35.1, 30.2, 29.2,
29.2, 29.0, 28.9, 28.8, 26.6, 26.4. HRMS (ESI) (m/z): [MþH]þ calcd for
C29H37N8O3, 545.2989; found, 545.2985.
Fig. 4. (a) UV/vis spectral of 1-H-SP, route aþd and route bþc. (b) Fluorescence spectra
of 1-H-SP, route aþd and route bþc (CH2Cl2, 2ꢁ10ꢀ5 M). Excitation wavelength was
410 nm.
4.5. Synthesis of compound 10
A solution of 9 (1 g, 1.84 mmol) in CH3I (15 mL) was stirred at
40 ꢂC for 12 h. The reaction mixture was cooled to room temper-
ature, and CH3I was evaporated off in vacuo. The residue was dis-
solved in MeOH (15 mL), followed by the addition of saturated
NH4PF6 solution. After the mixture was stirred for 2 h, the mixture
was extracted with CH2Cl2 (3ꢁ20 mL). The combined organic layer
was evaporated, and the residue was purified via column chro-
matography (SiO2, CH2Cl2/MeOH¼100/1) to give 10 (1.16 g, 90%) as
a green powder: mp¼140e141 ꢂC. 1H NMR (400 MHz, CDCl3,
monitoring composition changes in time by taking UV spectra at
distinct intervals until no changes were observed. The absolute
quantum yields of fluorescence were measured by using a Fluo-
romax-4 fluorescence spectrophotometer equipped with the
quantum yield measuring accessory and report generator program.
4.2. Materials
Chemicals were used as received from Acros, Aldrich, Fluka, or
Merck. All solvents were in reagent grade, which were dried
and distilled prior to use according to standard procedures.
The molecular structures were confirmed via 1H NMR, 13C
NMR, and high-resolution ESI mass spectroscopy. Compounds
5,12 7,19 8,12 11,11b 126c were synthesized according to the previous
reports.
298 K):
d
¼8.56 (dd, J¼7.3, 0.9 Hz, 1H), 8.50 (d, J¼8.1 Hz, 1H),
8.40e8.46 (m, 2H), 7.71 (dd, J¼8.3, 7.5 Hz,1H), 7.22 (d, J¼8.2 Hz,1H),
5.50 (s, 2H), 4.56 (s, 3H), 4.44e4.55 (m, 2H), 3.95e4.08 (m, 4H),
3.15e3.36 (m, 6H), 1.99 (m, 2H), 1.52e1.60 (m, 2H), 1.19e1.42 (m,
12H). 13C NMR (100 MHz, CDCl3, 298 K):
d
¼164.1, 163.5, 156.7, 140.0,
133.5, 131.9, 131.3, 130.8, 130.0, 125.9, 125.9, 122.1, 115.5, 115.0, 66.8,
54.2, 53.4, 51.4, 38.5, 31.8, 29.2, 29.0, 28.9, 28.7, 28.7, 26.6, 26.0.
HRMS (ESI) (m/z): ½M ꢀ PF6ꢀꢃþ calcd for C30H39N8O3, 559.3145;
found, 559.3144.
4.3. Synthesis of compound 6
A mixture of compound 4 (0.4 g, 2.4 mmol) and 5 (0.39 g,
2.4 mmol) was refluxed overnight in toluene (30 mL). The solvent
was removed under reduced pressure. The residue was dissolved in
methanol, and NaBH4 (0.29 g, 7.2 mmol) was added in small por-
tions under ice-bath. The mixture was stirred at room temperature
for a further 6 h. Water was added to quench the excess NaBH4. The
mixture was extracted with CH2Cl2. The combined organic layer
was dried over Na2SO4. After concentrating in vacuo, the white
solid was dissolved in MeOH (20 mL), and HCl (6 M, 2 mL) was
added. After stirring for a few minutes, the solvent was removed
under reduced pressure. The residue was dissolved in CH2Cl2
(20 mL), followed by the addition of saturated NH4PF6 aqueous
4.6. Synthesis of compound 3-H
A mixture of 6 (30 mg, 0.04 mmol), 10 (27.4 mg, 0.06 mmol), and
[Cu(CH3CN)4]PF6 (11.2 mg, 0.03 mmol) was stirred in dry CH2Cl2
(1 mL) at room temperature for 24 h. After removal of the solvent,
the residue was purified via column chromatography (SiO2, CH2Cl2/
MeOH¼15/1) to give compound 3-H (27.8 mg, 60%) as a yellow
solid: mp¼105e106 ꢂC. 1H NMR (400 MHz, CD3COCD3, 298 K):
d
¼8.90 (s, 1H), 8.64 (dd, J¼8.5, 1.0 Hz, 1H), 8.58 (dd, J¼7.3, 1.0 Hz,
1H), 8.52 (d, J¼8.1 Hz, 1H), 8.08 (s, 1H), 7.85 (dd, J¼8.4, 7.4 Hz, 1H),
7.51 (d, J¼8.0 Hz, 2H), 7.43 (d, J¼8.1 Hz, 1H), 7.11 (d, J¼8.2 Hz, 2H),
6.74 (s, 2H), 6.55 (s, 1H), 5.64 (s, 2H), 5.19 (s, 2H), 4.73 (t, J¼7.2 Hz,

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W. Zhou et al. / Tetrahedron 69 (2013) 5319e5325
2H), 4.67 (s, 3H), 4.47 (m, 4H), 4.40 (t, J¼7.1 Hz, 2H), 3.94e4.01 (m,
4H), 3.79 (s, 6H), 3.28e3.35 (m, 4H), 1.96e2.04 (m, 2H), 1.84e1.92
(m, 2H), 1.31 (m, 12H). 13C NMR (100 MHz, CD3COCD3, 298 K):
and the Scientific Research Foundation for the Returned Overseas
Chinese Scholars, State Education Ministry for financial support.
d
¼170.9, 164.8, 164.1, 162.3, 160.4, 159.2, 157.6, 141.1, 140.7, 133.8,
Supplementary data
132.5, 132.3, 132.1,132.0, 130.7,126.9, 126.8, 123.5, 116.7,116.0,116.0,
116.0, 108.5, 101.6, 67.3, 62.4, 55.8, 54.6, 54.3, 50.6, 39.2, 32.7, 30.9,
27.0, 26.5. HRMS (ESI) (m/z): ½M ꢀ 2PF6ꢀꢃ2þ calcd for C49H61N9O6,
435.7373; found, 435.7376.
Characterization data; UV/vis absorption and fluorescence
spectra, and other materials. Supplementary data related to this
article can be found at http://dx.doi.org/10.1016/j.tet.2013.04.119.
4.7. Synthesis of compound 2-SP
References and notes
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To the mixture of compound 11 (0.20 g, 0.53 mmol) and 12
(0.10 g, 0.21 mmol) in CH2Cl2 (100 mL), EDCI (0.12 g, 0.6 mmol) and
DMAP (12.05 mg, 0.1 mmol) were added. The mixture was stirred
overnight and then washed the mixture with brine (3ꢁ50 mL). The
organic layer was dried over anhydrous sodium sulfate. The com-
bined organic layer was evaporated, and the residue was purified
via column chromatography (SiO2, CH2Cl2/MeOH¼200/1) to give 2-
SP (0.17 g, 65%) as a brown powder: mp¼75e76 ꢂC. 1H NMR
(400 MHz, CDCl3, 298 K)
d
¼7.95e8.02 (m, 4H), 7.15e7.21 (m, 2H),
7.07 (d, J¼6.5 Hz, 2H), 6.86 (m, 10H), 6.70 (d, J¼8.7 Hz, 2H), 6.60 (d,
J¼7.7 Hz, 2H), 5.79 (d, J¼10.4 Hz, 2H), 4.93 (s, 4H), 4.07e4.16 (m,
8H), 3.90 (m, 8H), 3.81 (s, 8H), 3.45e3.82 (m, 4H), 2.53e2.76 (m,
4H), 1.24 (s, 6H), 1.09 (s, 6H). 13C NMR (100 MHz, CDCl3, 298 K):
d
¼171.7, 159.4, 150.7, 150.5, 146.2, 141.0, 136.0, 130.0, 128.3, 127.8,
125.8, 123.1, 122.7, 121.9, 121.9, 119.8, 118.6, 118.5, 117.7, 115.5, 106.8,
106.7, 71.8, 71.7, 71.1, 71.1, 69.8, 69.8, 66.2, 52.8, 39.3, 33.7, 25.7, 19.7.
HRMS (ESI) (m/z): [MþH]þ calcd for C68H73N4O18, 1233.4920;
found, 1233.4924.
4.8. Synthesis of compound 1-H-SP
A mixture of 6 (20 mg, 0.04 mmol) and crown ether 2-SP
(98.6 mg, 0.08 mmol) was stirred in dry CH2Cl2 (1 mL) at room
temperature for
2 h. After 10 (28.1 mg, 0.04 mmol) and
[Cu(CH3CN)4]PF6 (11.2 mg, 0.03 mmol) were added to the solution,
the mixture was stirred for 2 days. After removal of the solvent, the
residue was purified via column chromatography (SiO2, CH2Cl2/
MeOH¼15/1) to give compound 1-H-SP (43 mg, 45%) as a brown
solid: mp¼135e136 ꢂC. 1H NMR (400 MHz, CDCl3, 298 K)
¼8.55 (d,
d
J¼7.5 Hz, 1H), 8.49 (d, J¼8.2 Hz, 1H), 8.43 (m, 2H), 7.85e8.00 (m,
5H), 7.67e7.72 (m, 1H), 7.52 (s, 2H), 7.14e7.23 (m, 5H), 7.07 (d,
J¼7.4 Hz, 2H), 6.79e6.90 (m, 8H), 6.66e6.76 (m, 6H), 6.59 (d,
J¼7.7 Hz, 2H), 6.41 (s, 2H), 6.21 (s, 1H), 5.83 (d, J¼10.3 Hz, 2H), 5.52
(s, 2H), 5.11 (s, 2H), 4.91 (s, 4H), 4.54 (s, 3H), 4.40e4.53 (m, 6H), 4.31
(m, 2H), 4.08 (m, 8H), 4.01 (d, J¼4.2 Hz, 4H), 3.79 (s, 8H), 3.62 (m,
4H), 3.57 (s, 6H), 3.52 (s, 8H), 3.27 (d, J¼4.2 Hz, 4H), 2.54e2.82 (m,
4H), 1.96 (m, 6H), 1.31 (m, 10H), 1.24 (s, 6H), 1.10 (s, 6H). 13C NMR
(100 MHz, CDCl3, 298 K)
d 171.7, 164.1, 163.5, 160.8, 159.4, 156.6,
147.4, 147.3, 147.3, 146.2, 140.9, 139.9, 135.9, 133.4,131.9, 131.2, 130.9,
130.0, 129.0, 128.2, 127.9, 125.9, 125.9, 125.7, 123.5, 122.7, 122.1,
121.9, 121.8, 119.7, 118.6, 115.5, 115.4, 115.0, 114.0, 112.9, 112.3, 106.7,
106.7, 106.6, 100.1, 70.6, 70.1, 68.2, 68.1, 66.8, 66.1, 55.0, 54.1, 53.3,
52.5, 52.2, 52.2, 39.2, 38.5, 33.8, 33.5, 31.9, 31.7, 29.7, 29.6, 29.3, 29.1,
28.9, 28.8, 28.45, 28.5, 28.2, 28.2, 25.7, 25.6, 24.3, 22.6, 19.7, 14.1.
HRMS (ESI) (m/z): ½M ꢀ 2PF6ꢀꢃ2þ calcd for C117H133N13O24
,
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Acknowledgements
We thank the NSFC/China (21272073 and 21190033), the Na-
tional Basic Research 973 Program (2011CB808400), the Founda-
tion for the Author of National Excellent Doctoral Dissertation of
China (200957), the Fok Ying Tong Education Foundation (121069),
the Fundamental Research Funds for the Central Universities, the
Innovation Program of Shanghai Municipal Education Commission,

W. Zhou et al. / Tetrahedron 69 (2013) 5319e5325
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