Cyclam-cored dendrimers appended with four dendrons of two different types: Intradendrimer energy transfer

Article abstract of DOI:10.1002/asia.201000170

We have synthesized two cyclam-cored dendrimers appended with dendrons of two different types by proper protection/deprotection of the cyclam unit. The resulting dendrimers contain six naphthyl and two dansyl units (N6D2) or two dansyl and six naphthyl un

Full text of DOI:10.1002/asia.201000170

FULL PAPERS
DOI: 10.1002/asia.201000170
Cyclam-Cored Dendrimers Appended with Four Dendrons of Two Different
Types: Intradendrimer Energy Transfer
Giacomo Bergamini,[a] Angela Sottilotta,[a] Mauro Maestri,[a] Paola Ceroni,*[a] and
Fritz Vçgtle*[b]
Abstract: We have synthesized two
cyclam-cored dendrimers appended
with dendrons of two different types by
proper protection/deprotection of the
cyclam unit. The resulting dendrimers
contain six naphthyl and two dansyl
units (N6D2) or two dansyl and six
naphthyl units (N2D6) at the periph-
ery. Their photophysical properties
have been compared to those of a den-
drimer containing 8 dansyl units (D8)
and a previously investigated dendri-
mer containing 8 naphthyl units (N8).
The absorption spectra are those ex-
pected on the basis of the number of
chromophores, demonstrating that no
ground state interaction takes place.
The emission spectra of N2D6 and
N6D2 show naphthalene localized and
naphthalene excimer emission similar
to those observed in the case of N8, to-
gether with a much stronger dansyl
emission with maximum at 525 nm.
Addition of CF3SO3H to dendrimer
solutions in CH3CN/CH2Cl2 1:1 (v/v)
leads to protonation of the aliphatic
amine units of the cyclam core at first
and then of the aromatic amine of each
dansyl chromophores. Cyclam can be
diprotonated and this affects dansyl ab-
sorption and, most significantly, emis-
sion bands by a charge perturbation
effect. Each dansyl unit is independent-
ly protonated in both dendrimers. The
most interesting photophysical feature
of these heterofunctionalized cyclam-
cored dendrimers is the occurrence of
an
intradendrimer
photoinduced
energy transfer from naphthyl to
dansyl chromophores of two different
dendrons (interdendron mechanism).
The efficiency of this process is 50%
for N6D2 and it can be increased up to
75% upon protonation of the cyclam
core and formation of N6D2ACHTUNGTRENNUNG
(2H+).
This arises from the fact that protona-
tion of the amine units of the cyclam
prevents formation of exciplexes upon
naphthyl excitation, thus shutting down
one of the deactivation processes of
the fluorescent naphthyl excited state.
Keywords: dansyl
· dendrimer ·
exciplex · naphthalene · protona-
tion
Introduction
based on, or containing metal ions have been prepared and
investigated.[2] The study of these novel hybrid species has
considerably expanded the scope of metal coordination
chemistry. Coupling luminescence with metal coordination
can be exploited for a variety of purposes, which include in-
vestigation of dendrimer structure,[3] encapsulated metal
nanoparticles,[4] light harvesting,[5] stepwise complexation,[6]
and reversible metal complex assembly.[7] In most cases,
metal ion coordination by a dendrimer takes place on units
that are present along the dendrimer branches (e.g., amine,
imine, or amide groups) or appended at the dendrimer pe-
riphery (e.g., terpyridine, cathecolamide ligands). When
multiple identical coordinating units are present, dendrimers
give rise to metal complexes of variable stoichiometry and
unknown structures. Apart from porphyrin-based dendrim-
ers, few examples of luminescent dendrimers with a well de-
fined metal-coordinating site have been reported so far,[8]
and most of them contain 1,4,8,11-tetraazacyclotetradecane
(cyclam).[9]
Dendrimers[1] constitute a class of multibranched molecules
that can—by design—exhibit a high degree of order but also
a high degree of complexity: selected chemical units can be
placed in predetermined sites of the dendritic architecture.
Dendrimer chemistry was initially developed in the field of
organic chemistry. More recently, a number of dendrimers
[a] Dr. G. Bergamini, A. Sottilotta, Prof. M. Maestri, Prof. P. Ceroni
Dipartimento di Chimica “G. Ciamician”
Universitꢀ di Bologna
via Selmi 2, I-40126 Bologna (Italy)
Fax : (+39)051-2099456
E-mail: paola.ceroni@unibo.it
[b] Prof. F. Vçgtle
Kekulꢁ-Institut fꢂr Organische Chemie und Biochemie der Universi-
tꢃt Bonn
Gerhard-Domagk Strasse 1
53121 Bonn (Germany)
1884
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Chem. Asian J. 2010, 5, 1884 – 1895

Cyclam is one of the most ex-
tensively investigated ligands in
coordination chemistry:[10] it is
flexible enough to complex a
wide variety of metal ions.
Moreover, the ease of substitu-
tion on the nitrogen atoms of
the cyclam ring opens up a
large array of derivatives. Both
cyclam and its 1,4,8,11-tetra-
methyl derivative in aqueous
solution can be mono and di-
protonated and can coordinate
metal ions such as CoII, NiII,
CuII, ZnII, CdII, and HgII with
very large stability constants.[10]
Furthermore, cyclam and its de-
rivatives have been studied in
medical applications,[11] as carri-
ers of metal ions to tumors,[12]
as imaging contrast agents,[13]
for radioactive diagnosis and
treatment,[14]
as
anti-HIV
agents,[15] and, most recently, as
neuroprotective or neurorescue
agents for the treatment of Alz-
heimerꢅs disease.[16]
In the present paper, we have
synthesized three new dendrim-
ers containing (a) 8 dansyl (5-
dimethylamino-1-naphthalene-
sulphonamido), (b) six dansyl
and two naphthyl, and (c) two
dansyl and six naphthyl units at
the periphery, hereafter named
D8, N6D2, and N2D6, respec-
tively (Scheme 1), on the basis
of the number of dansyl (D)
and naphthyl (N) chromo-
phores at the periphery. These
dendrimers are particularly in-
teresting because they are deco-
Scheme 1.
Results and Discussion
rated with photoactive units and contain a cyclam core, so
that coordination of protons and metal ions can be detected
by changes in the photophysical properties. Moreover,
N6D2 and N2D6 are among few examples of dendrimers
constituted by two different types of dendrons,[17] which in
the present case are photoactive. This opens up the possibili-
ty of interdendron energy and/or electron transfer processes
within the same dendrimer molecule. For the sake of clarity,
the photophysical properties of the new dendrimers and the
effect of protonation have been compared to a previously
reported dendrimer containing 8 naphthyl units (N8), and a
dansyl model compound (D in Scheme 1).
Unprotonated Species
Absorption Spectra
The absorption spectra of the investigated dendrimers are
reported in Figure 1. The cyclam core does not absorb
below 230 nm, while the benzene units appended to the
dansyl chromophores exhibit a negligible absorption (e<
200mÀ1 cmÀ1 in the 240–270 nm region),[18] so that the chro-
mophores are dimethoxybenzene, naphthalene, and dansyl
units. The absorption spectrum of N8 is dominated by the
naphthalene pp* transition with maximum at 275 nm. The
absorption spectrum of D8 is very similar to that of the
model compound D, apart from a small red-shift in the
lower energy band at approximately 350 nm, which involves
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P. Ceroni, F. Vçgtle et al.
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the absorption spectra of the investigated dendrimers are
those expected on the basis of the number of dimethoxyben-
zene, naphthalene, and dansyl chromophores, demonstrating
that no ground state interaction takes place in the dendrim-
ers between the various chromophoric units.
Emission Properties
Upon excitation at 350 nm, D8, N6D2, and N2D6 show a
strong fluorescence band at 525 nm, identical for the three
dendrimers and slightly red shifted and lower in intensity
compared to that of D (Figure 2, Table 1). This emission
Figure 1. Absorption spectra of the dendrimers D8, N2D6, N6D2, and
N8 (black lines) compared to model compound D (gray line) in CH3CN/
CH2Cl2 solutions at 298 K.
a charge-transfer transition from the amine group to the ar-
omatic moiety.[19] This result can be rationalized on the basis
of the polarity effect exerted on this charge-transfer band: a
different environment is experienced by the dansyl chromo-
phore in the dendritic structure compared to that of the
model compound in the solvent mixture. The absorption
spectra of N6D2 and N2D6 show two bands with maxima
at (a) approximately 260 nm owing to a pp* transition in-
volving naphthalene, dansyl, and, to a lower extent, dime-
thoxybenzene chromophores, and (b) 347 nm, typical of the
dansyl chromophore, red shifted compared to the model
compound D, as observed in the case of dendrimer D8
(Table 1). Apart from the small red-shift of the dansyl band,
Figure 2. Normalized emission spectra of N8 (dotted line, lex =280 nm),
D8 (dashed line, lex =350 nm), and D (gray line, lex =350 nm) in air-equi-
librated CH3CN/CH2Cl2 solutions at 298 K.
arises from the same charge-transfer transition of the lowest
energy absorption band. An increase in the polarity of the
environment is known to decrease the emission quantum
yield and to cause a red-shift of the maximum of the emis-
sion wavelength.[19] This result is in agreement with the ab-
sorption measurements and demonstrates that the dansyl
chromophore experiences a more polar environment in the
dendritic structure than in the CH3CN/CH2Cl2 1:1 (v/v) mix-
ture. The excited-state lifetime is approximately 15 ns for
D8, N6D2, N2D6, and D (Table 1).
Upon excitation at 280 nm, D8 shows the same emission
spectrum observed upon excitation at 350 nm, while N6D2
and N2D6 exhibit the typical dansyl emission band together
with a much weaker emission with a maximum at 337 nm,
practically coincident in shape and position with the emis-
sion observed for N8, while no dimethoxybenzene emission,
with maximum at 305 nm, is registered. As previously re-
ported,[20] N8 exhibits three types of emission bands (dotted
line in Figure 2), assigned to naphthyl localized excited
states (lmax =337 nm), naphthyl excimers (shoulder at ca
390 nm), and naphthyl–amine exciplexes (lmax =480 nm). In
the case of N6D2 and N2D6, the naphthalene based emis-
sion at 337 nm is strongly quenched,[21] and the exciplex
band is not visible because of the overlap with the much
stronger dansyl emission. The naphthalene emission decay is
multiexponential (in the ns-timescale) for N6D2 and N2D6,
Table 1. Absorption and emission data of the investigated dendrimers in
an air-equilibrated CH3CN/CH2Cl2 1:1 (v/v) solution at 298 K. For com-
parison purposes, photophysical data of model compound D are report-
ed.
absorption
emission
lmax [nm] fem
lmax [nm] e [104 mÀ1 cmÀ1
]
t [ns]
[a]
N8
N8
275
276
265
347
4.8
4.8
5.2
0.77
5.2
0.77
9.1
2.4
9.1
2.4
12
3.5
12
3.5
1.3
0.39
337
337
337
525
337
540
337
525
337
540
525
0.008
–
–
–
[a]
(2H+)
0.032
N6D2
N6D2
N2D6
N2D6
D8
0.003[b]
0.34[c]
15.2[d]
–
E
0.004[b]
0.27[c]
352
257
347
<0.001[b]
0.34[c]
–
15.4[d]
–
(2H+) 257
<0.001[b]
0.28[c]
352
257
347
257
351
253
339
0.34[c]
14.0[d]
–
D8
D
A
533
510
0.27[c]
0.36[c]
14.0[d]
[a] Multiexponential decays in the nanosecond time range. [b] lex
=
280 nm. Emission quantum yield of the naphthalene chromophore. Emis-
sion spectra have been corrected for reabsorption (see Experimental Sec-
tion). [c] lex =350 nm. Emission quantum yield of the dansyl chromo-
phore. [d] lex =350 nm; lem =530 nm
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Cyclam-Cored Dendrimers and Intradendrimer Energy Transfer
as previously observed for N8, in agreement with the multi-
ple emission bands.
Effects of Protonation
D8, N2D6, and N6D2 dendrimers have two different proto-
nation sites: the cyclam core and the dansyl units.[20a] The
former (aliphatic amine units) is expected to be more basic
than the latter (aromatic amine units).
Cyclam is known to undergo protonation in aqueous solu-
tion[22] as well as in other solvents.[23] In aqueous solution,
the four successive pKa values are 11.6, 10.6, 1.61, and
2.42,[24] showing that cyclam can be easily mono- and di-pro-
tonated, but further protonation is difficult. It is also inter-
esting to note that the fourth pKa value is larger than the
third one, a result related to protonation-induced structural
rearrangements.
Protonation of the dansyl group brings about profound
and clearly recognizable changes of the absorption and
emission spectra because of the charge transfer nature of
the dansyl bands. More specifically, protonation of model
compound D causes the disappearance of the absorption
bands with maxima at 339 and 253 nm, and of the emission
band with lmax =510 nm, and the concomitant appearance of
the absorption band with a maximum at 290 nm, accompa-
nied by a smaller feature with lmax =330 nm and emission
(lmax =337 nm, F=0.002, t<0.5 ns) band of protonated
dansyl.
Figure 3. Emission spectra of a 2.5ꢆ10À5 m solution of N8 in CH3CN/
CH2Cl2 1:1 (v/v) upon titration with CF3SO3H: 0 equiv (solid thick line),
3 equiv (dashed thick line). lex =275 nm (isosbestic point). Inset shows
normalized emission intensity changes at 337 (empty diamonds), 390
(solid diamonds), and 480 nm (empty triangles).
All the experiments have been carried out in CH3CN/
CH2Cl2 1:1 (v/v) solution upon addition of CF3SO3H. The
number of acid equivalents is calculated per dendrimer. For
all the investigated dendrimers, absorption and emission
spectral changes are completely reversible upon addition of
a base (tributylamine).
Protonation of N8: It has already been reported[21] that
protonation of the cyclam core of N8 causes negligible
changes in the absorption spectra, and profound changes of
the intensity and shape of the emission bands (Figure 3): dis-
appearance of the exciplex band, and a strong increase in
the intensities of the naphthyl localized and excimer bands.
These changes reach a plateau at 2 equiv of acid, suggesting
that the tetraamine cyclam core undergoes only two proto-
nation reactions under the present experimental conditions.
The decrease of the exciplex-band intensity mirrors the in-
crease of naphthyl localized emission at 337 nm. Indeed, the
two protons are likely shared by the four nitrogen atoms,
thus preventing exciplex formation and reviving naphthyl
emission as shown in Figure 4.
Protonation of D8: The absorption spectrum of D8 shows
modest changes up to 2 equivalents of acid: slight red-shift
and intensity decrease of the lowest energy band. Upon fur-
ther addition of acid (up to ca. 10 eqs.), strong changes take
place, typical of the dansyl protonation. Two families of isos-
bestic points are observed in the range 0–2 equivalents and
2–10 equivalents. The plots of normalized absorption at 295
and 352 nm (solid symbols in Figure 5a) show a mirrorlike
trend with no changes up to 2 equivalents and plateau
Figure 4. Absorption (a) and emission spectra (b) of a 1.2ꢆ10À5 m solu-
tion of D8 in CH3CN/CH2Cl2 1:1 (v/v) upon titration with CF3SO3H:
0 equiv (solid thick line), 12 equiv (dashed thick line). lex =276 nm (iso-
sbestic point).
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337 nm; (c) slight decrease and red-shift of the dansyl emis-
sion band upon addition of the first two acid equivalents are
registered; (d) the emission at 337 nm increases very slowly
at the beginning of the titration and does not reach a pla-
teau up to 15 equivalents of acid.
The effect on the intensity and position of the dansyl
band caused by the first two protons together with the very
small red-shift and decrease of the dansyl absorbance at
347 nm can be ascribed to the effect of the positively
charged core (protonated cyclam) on the charge-transfer
transition of the appended dansyl units.
The difference between absorption and emission plots
demonstrates the occurrence of excited state processes: the
emission intensity at 525 nm becomes negligible after addi-
tion of approximately 8 protons, that is, when, as shown by
the absorption spectrum, more than 20% of the dansyl units
are still unprotonated. This arises from electron-transfer
quenching of the dansyl excited states by protonated dansyl
units, as previously observed for other partially protonated
polydansyl dendrimers.[25]
The anomalous behavior of the emission of protonated
dansyl at 337 nm, on the other hand, is not observed for
model compound D, and it cannot be a simple quenching
(regardless of the mechanism) by the moiety appended to
the dansyl unit because all the quantities in Figure 5 are nor-
malized to the values obtained at the end of the titration. It
can be accounted for by assuming that the excited state of
protonated dansyl exhibits a lower proton affinity than the
ground state, as previously observed for other cyclam-cored
dendrimers containing dansyl chromophores.[26]
Protonation of N2D6: The absorption spectral changes of
N2D6 upon protonation (Figure 6) are very similar to those
of D8. The emission spectra show a red-shift and a decrease
of the dansyl emission at 525 nm and an increase of the pro-
tonated dansyl emission, superimposed to the naphthalene
emission at 337 nm. The first two protons are located on the
cyclam core and small changes of dansyl absorption and
emission bands occur because of charge perturbation effects.
Figure 5. Normalized absorption changes at 295 (solid squares), 352 nm
(solid circles), and emission intensity changes at 337 (empty diamonds)
and 525 nm (empty triangles) upon excitation at 276 and 318 nm, respec-
tively, during the titration of CH3CN/CH2Cl2 1:1 (v/v) solutions of a) N8,
b) N2D6, and c) N6D2 with CF3SO3H.
Absorption changes reach
a plateau at approximately
8 equivalents of acid (solid symbols in Figure 5b), as expect-
ed for independent protonation of the cyclam core and of
the six dansyl units. Emission intensity changes (Figure 5b)
do not parallel the corresponding absorption changes and
are qualitatively similar to those observed in the case of D8.
Therefore, the same interpretation of the quenching of
dansyl emission at 525 nm and protonated dansyl emission
at 337 nm discussed in the previous case is applicable.
values reached at approximately 10 equivalents of acid.
These results demonstrate that two distinct protonation pro-
cesses take place: the former on the cyclam core (2 protons
per cyclam) as expected, and the latter on the eight dansyl
chromophores. Each dansyl unit is protonated independent-
ly, as proved by the maintenance of the isosbestic points be-
tween 2 and 10 equivalents.
Upon excitation at 276 nm, where the absorbance is prac-
tically constant throughout the acid titration, the dansyl
emission band decreases and exhibits a red-shift, while a
new band, typical of the protonated dansyl units, arises at
Protonation of N6D2: Absorption and emission spectral
changes are similar to those reported for N2D6, apart from
the fact that absorption changes reach a plateau at approxi-
mately 4 equivalents (Figure 5c), in agreement with
a
337 nm.
A
closer inspection of the emission intensity
double protonation of the cyclam core, and of monoproto-
nation of the two dansyl units.
changes (empty symbols in Figure 5a) show that: (a) they
are not superimposed to the corresponding absorption
changes, contrary to the behavior of model compound D;
(b) the decrease of the dansyl emission at 525 nm does not
mirror the increase of protonated dansyl emission at
Upon protonation of the cyclam core and formation of
N6D2ACHTNUGRTNEUNG
(2H+), changes in the naphthalene emission are ex-
pected on the basis of the behavior observed for D8 and N8,
but naphthalene and protonated dansyl emission are com-
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Chem. Asian J. 2010, 5, 1884 – 1895

Cyclam-Cored Dendrimers and Intradendrimer Energy Transfer
cause of its very low molar absorption coefficient (lmax
=
275 nm, e=2200mÀ1 cmÀ1) compared to naphthalene
(e275nm =6000mÀ1 cmÀ1) and dansyl units (lmax =253 nm, e=
12300mÀ1 cmÀ1), which precludes a quantitative estimation
of the efficiency of energy and/or electron transfer process-
es.
Comparison of the emission spectra of N8, D8, and N6D2
upon excitation at 280 nm shows that in the case of N6D2
(where 20% of light is absorbed by the dansyl chromo-
phores for the latter dendrimer), the naphthalene emission
is quenched by 50% and dansyl emission is sensitized with
an efficiency of 50%. Therefore, upon excitation of the six
naphthalene units, besides the formation of excimers and ex-
ciplexes, intradendrimer photoinduced energy transfer to
the dansyl units takes place with an efficiency of 50%. The
interdendrimer dynamic mechanism is precluded by the
short lifetime of the naphthalene excited state (t<10 ns)
and by the small concentration of the dendritic species. For
N2D6, a higher efficiency of the intradendrimer naphtha-
lene-to-dansyl energy transfer is expected on the basis of
the higher number of acceptor dansyl units per donor naph-
thalene chromophore: from 1:3 in the former to 3:1 in the
latter case. However, careful estimation of the energy trans-
fer efficiency is precluded by the very low absorption coeffi-
cient of the two naphthalene units compared to the six
dansyl units: for example, at 280 nm, the fraction of light ab-
sorbed by the naphthyl units is approximately 25%.
Figure 6. Absorption (a) and emission spectra (b) of a 1.2ꢆ10À5 m solu-
tion of N2D6 in CH3CN/CH2Cl2 1:1 (v/v) upon titration with CF3SO3H:
0 equiv (solid thick line), 10 equiv (dashed thick line). lex =276 nm (iso-
sbestic point).
Upon protonation of the cyclam core, changes in the effi-
ciency of the intradendrimer energy transfer are expected
for N6D2 and N2D6 because exciplex formation is prevent-
ed. Comparison of the dansyl emission intensity during acid
titration of N6D2 solutions upon excitation at 276 nm, an
isosbestic point where 75% of light is absorbed by the naph-
thyl chromophores, and at 350 nm, an isosbestic point where
only dansyl absorbs light, shows different trends. In particu-
lar, upon excitation at 350 nm, a decrease is observed be-
cause of charge perturbation effects, while upon excitation
at 276 nm, dansyl emission increases by approximately 2
equivalents of acid and then decreases (Figure 7). This
result is consistent with an increase in the naphthalene-to-
dansyl energy transfer efficiency, as evidenced by the com-
parison between absorption and excitation spectra. From a
pletely superimposed, thus preventing a separation of the
two contributions (Figure 7). Changes in the efficiency of
the naphthalene-to-dansyl energy transfer, on the other
hand, can be evaluated (see below).
quantitative point of view, in the case of N6D2ACTHNUTRGNEUNG
(2H+), the
naphthalene emission is quenched by 75% and dansyl emis-
sion is sensitized with an efficiency of 75%. Protonation of
the cyclam core brings about a substantial increase in the in-
tradendrimer energy transfer because the excited naphthyl
unit is no longer engaged in exciplex formation.
Figure 7. Normalized emission intensity at 525 nm upon excitation at 276
(solid circles) and 350 nm (open circles) of N6D2 in CH3CN/CH2Cl2 1:1
(v/v) upon titration with CF3SO3H.
Conclusions
Intradendrimer Energy Transfer
N6D2 and N2D6 dendrimers contain three types of chro-
mophores: dimethoxybenzene, naphthalene, and dansyl
groups with a decreasing energy of the fluorescent singlet
excited state (S1) in the reported order. Selective excitation
of dimethoxybenzene units is precluded in both cases be-
A family of first generation dendrimers based on a cyclam
core and appended with fluorescent dendrons has been syn-
thesized: they contain eight dansyl (D8), six napthyl and
two dansyl (N6D2), and two napthyl and six dansyl units
(N2D6) at the periphery. The last two dendrimers have a
Chem. Asian J. 2010, 5, 1884 – 1895
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1889

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2 days at RT. The organic phase is then washed with water (2ꢆ), saturat-
ed sodium hydrogen carbonate, and water, dried over sodium sulphate
and removed in vacuo. The crude product is purified by column chroma-
tography (SiO2; dichloromethane/ethyl acetate 1:1) yielding a yellow
solid (2.4 g, 55%). 1H NMR: (400 MHz, CDCl3, 258C), d=2.79 (s, 12H,
Janus-like structure since their core have been appended
with two different types of dendrons by proper protection/
deprotection of the cyclam during the synthesis. They show
absorption spectra owing to the overlap of the different
chromophoric units, namely dimethoxybenzene, naphtha-
lene, and dansyl, demonstrating that no ground state inter-
action among the chromophores takes place. The emission
spectra are quite complex, exhibiting both weak naphthyl lo-
calized and naphthyl excimer emissions in the UV spectral
region and a very strong green dansyl emission.
These dendrimers contain a single coordinating unit and
luminescent chromophores, so that interaction with protons
brings about profound changes to the photophysical proper-
ties. They show two distinct
NACTHNUTRGNEUNG
(CH3)2), 4.13 (s, 2H, Ar-CH2OH), 6.45 (d, 2H, 4JHH =1.89 Hz, Ar-H),
4
3
6.72 (t, 1H, JHH =1.89 Hz, Ar-H), 7.07 (d, 2H, JHH =7.45 Hz, dansyl-H),
3
3
7.25 (t, 2H, JHH =8.46 Hz, dansyl-H), 7.41 (t, 2H, JHH =8.46 Hz, dansyl-
H), 7.52 (s, br, 2H, N-H), 8.00 (d, 2H, 3JHH =7.33 Hz, dansyl-H), 8.23 (d,
2H, 3JHH =8.57 Hz, dansyl-H), 8.41 ppm (d, 2H, 3JHH =8.46 Hz, dansyl-
H); 13C NMR: (100.6 MHz, CDCl3, 258C), d=45.37 (N
ACTHUNGTRNEUNG(CH3)2), 63.95
(Ar-CH2OH), 110.48, 114.45, 115.30, 118.59, 123.18, 128.62, 129.48,
129.72, 130.34, 130.87, 133.99, 137.69, 143.20, 151.88 ppm (CAr); FAB-MS:
m/z (%): 604.1 (M+H+, 100); C31H32N4O5S2: (604.74)
3,5-Bis(N-benzyl-5’-dimethylaminonaphthalene-1’-sulfonamido)benzyl
alcohol (2):
protonation sites: the first on
the aliphatic amine units of the
cyclam core and the second on
the aromatic amine units of the
dansyl chromophores. Cyclam,
as previously reported, under-
goes two protonations, while
dansyl units are independently
monoprotonated in each den-
drimer.
N2D6 and N6D2 exhibit par-
ticularly interesting photophysi-
3,5-Bis(5’-dimethylaminonaphthalene-1’-sulfonamido)benzyl alcohol
1
cal properties because of the occurrence of interdendron
energy transfer processes within the same dendrimer (static
intradendrimer mechanism). In particular, in the case of
N6D2, we can modulate the efficiency of the naphthyl to
dansyl energy transfer efficiency from 50% to 75% by pro-
tonation of the cyclam core.
Future investigations will be aimed at studying the com-
plexation ability of these dendrimers towards transition
metal ions and lanthanide ions.
(850 mg, 1.4 mmol) was dissolved in DMF (40 mL), and potassium car-
bonate (970 mg, 7 mmol) was added. A solution of 500 mg (2,9 mmol,
0.35 mL) benzylbromide in 20 mL DMF was then added drop wise and
the reaction mixture was stirred for 3 days at RT. The reaction mixture
was then filtered, the solvent removed in vacuo and the rest taken up in
chloroform. The organic phase was then washed with water, saturated
sodium hydrogen carbonate, and again water, dried over sodium sulphate
and solvent removed in vacuo. The crude product was purified by
column chromatography (SiO2; dichloromethane/ethyl acetate 4:1) yield-
ing a yellow solid (830 mg, 75%). 1H NMR: (300 MHz, CDCl3, 258C),
d=2.88 (s, 12H, NACTHNUTRGNE(UNG CH3)2), 4.08 (s, 2H, Ar-CH2OH), 4.63 (s, 4H, CH2N),
6.61 (d, 2H, 4JHH =2.08 Hz, Ar-H), 6.87 (t, 1H, 4JHH =2.07 Hz, Ar-H),
7.04–7.19 (m, 14H, benzyl-H, dansyl-H), 7.37 (t, 2H, 3JHH =8.49 Hz,
3
dansyl-H), 7.91 (d, 2H, 3JHH =8.10 Hz, dansyl-H), 8.00 (d, 2H, JHH
=
Experimental Section
7.34 Hz, dansyl-H), 8.52 ppm (d, 2H, 3JHH =8.48 Hz, dansyl-H);
13C NMR: (100.6 MHz, CDCl3, 258C), d=45.43 (N
(CH3)2), 54.38
Synthesis of the Dendrons
(CH2N), 63.97 (Ar-CH2OH), 115.13, 119.79, 123.10, 126.48, 127.63,
127.87, 128.38, 128.69, 128.90, 129.86, 130.26, 130.74, 130.86, 133.87,
135.71, 139.44, 142.01, 151.64 ppm (CAr); FAB-MS: m/z (%): 784.3
(M+H+, 100); C45H44N4O5S2: (784.98)
3,5-Bis(5’-dimethylaminonaphthalene-1’-sulfonamido)benzyl
(1):
alcohol
3,5-Bis(N-benzyl-5’-dimethylamino-
naphthalene-1’-sulfonamido)benzyl
bromide (3):
3,5-Bis(N-benzyl-5’-dimethylamino-
naphthalene-1’-sulfonamido)-benzyl
alcohol 2 (3.1 g, 3.6 mmol) and CBr4
(1.7 g, 5.1 mmol) were dissolved in
abs. tetrahydrofuran (20 mL) under
argon atmosphere. To this mixture, tri-
phenylphosphine (1.4 mg, 5.1 mmol)
was added portion wise. After approx-
3,5-Diaminobenzylalcohol-dihydrochloride (1.6 g, 7.2 mmol) and triethyl-
amine (3.0 g, 4.1 mL, 30 mmol) are suspended in abs. chloroform (40 mL)
and a solution of dansylchloride (4.2 g) in chloroform (100 mL) is added
dropwise over a period of 2.5 h. The reaction mixture is then stirred for
imately 20 min, the reaction mixture was poured onto ice waterACHTUNGTRENNUNG(25 mL),
which was then extracted with chloroform (3ꢆ). The organic phase was
then washed with saturated sodium hydrogen carbonate (2ꢆ) and water,
dried over sodium sulphate, and the solvent removed in vacuo. The crude
1890
www.chemasianj.org
ꢄ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Asian J. 2010, 5, 1884 – 1895

Cyclam-Cored Dendrimers and Intradendrimer Energy Transfer
1,4,8-Tris(trifluoroacetyl)-1,4,8,11-tet-
raazacyclotetradecane
1.0 mmol), potassium
4
(500 mg,
carbonate
(730 mg, 5.2 mmol), and 3,5-bis(2’-oxy-
methyl-naphthyl)benzylbromide
5
(550 mg, 1.1 mmol) were stirred in
DMF (30 mL) at RT for 3 days. The
precipitate was filtered off, the filtrate
evaporated, and the residue dissolved
in chloroform. After washing with
product was purified by column chromatography (SiO2; dichlorome-
thane/ethyl acetate 40:1) yielding a yellow solid (2.8 g, 85%). 1H NMR:
(400 MHz, CDCl3, 258C), d=2.87 (s, 12H, NACTHNURGTNEG(UN CH3)2), 3.85 (s, 2H, Ar-
water and saturated sodium hydrogen carbonate solution, the solution
was dried over sodium sulfate and chloroform evaporated in vacuo.
Column chromatographic purification delivered the colorless solid
(560 mg, 61%). DC (SiO2): Rf =0.3 (dichloromethane/ethyl acetate 25:1
v/v); 1H NMR: (400 MHz, CDCl3, 258C), d=1.57–1.69 (m, 2H, CH2),
1.95–2.15 (m, 2H, CH2), 2.31–2.47 (m, 2H, CH2N), 2.57–2.70 (m, 2H,
CH2N), 3.27–3.45 (m, 12H, CH2N), 3.54 (s, 2H, Ar-CH2N), 5.17 (s, 2H,
Naph-CH2), 5.21 (s, 2H, Naph-CH2), 6.47 (s, 2H, Ar-H), 6.66 (s, 1H, Ar-
H), 7.43–7.55 (m, 6H, Naph-H), 7.77–7.86 ppm (m, 8H, Naph-H); FAB-
MS: m/z (%): 891.3 (M+H+, 100); C45H43F9N4O5: (890.83).
CH2Br), 4.63 (s, 4H, CH2N), 6.60 (d, 2H, 4JHH =2.02 Hz, Ar-H), 6.85 (t,
1H, 4JHH =1.89 Hz, Ar-H), 7.01–7.03 (m, 4H, benzyl-H, dansyl-H), 7.12–
7.19 (m, 8H, benzyl-H), 7.27 (t, 2H, 3JHH =8.71 Hz, dansyl-H), 7.35 (t,
2H, 3JHH =8.46 Hz, dansyl-H), 7.93 (d, 2H, 3JHH =7.33 Hz, dansyl-H),
8.00 (d, 2H, 3JHH =8.71 Hz, dansyl-H), 8.51 ppm (d, 2H, 3JHH =8.59 Hz,
dansyl-H); 13C NMR: (100.6 MHz, CDCl3, 258C), d=31.4 (Ar-CH2Br),
45.46 (NACHTUNGTRENNUNG(CH3)2), 54.36 (CH2N), 115.31, 119.67, 123.09, 127.71, 128.20,
128.43, 128.63, 128.75, 129.53, 129.88, 130.12, 130.82, 130.99, 133.69,
135.52, 138.48, 139.57, 151.68 ppm (CAr); FAB-MS: m/z (%): 848.2
(M+H+, 100); C45H43BrN4O5S2: (847.88)
1-(3,5-bis(2’-oxymethylnaphthyl)benzyl)-1,4,8,11-tetraazacyclotetrade-
cane (7):
Synthesis of the Dendrimers
1,4,8-Tris(trifluoroacetyl)-11-(3,5-bis(2’-oxymethylnaphthyl)benzyl)-
1,4,8,11-tetraazacyclotetradecane 6 (400 mg, 0.45 mmol) and sodium car-
bonate (570 mg, 5.4 mmol) were dissolved in methanol–water mixture
(30 mL, 4:1, v/v) and heated under reflux for 3 h. The mixture was then
stirred overnight at RT. The product
1,4,8-Tris(trifluoroacetyl)-1,4,8,11-tetraazacyclotetradecane (4):
was poured into water (50 mL) and
then extracted several times with
chloroform. The organic phase was
dried over sodium sulfate and the sol-
vent evaporated in vacuo. The result-
ing raw product was used for the next
Cyclam (1.0 g, 5 mmol) and 500 mg (5 mmol, 0.7 mL) triethylamine were
dissolved in methanol (5 mL). Trifluoroacetic acid ethylester 4 (3.6 g,
25 mmol, 3 mL) in methanol (5 mL) was dropped slowly into this solu-
tion and then stirred for 5 h at RT. The solvent was removed by distilla-
tion and the remainder taken up in diethyl ether. The organic phase was
washed several times with a saturated solution of sodium hydrogen car-
bonate and then dried over sodium sulfate. After the solvent was re-
moved under reduced pressure and the remainder purified at a short fil-
tration column, a colorless hygroscopic product (2.8 g) was obtained. DC
(SiO2): Rf =0.6 (ethyl acetate); 1H NMR:(400 MHz, CDCl3, 258C), d=
1.76–1.87 (m, 2H, CH2), 2.07–2.31 (m, 2H, CH2), 2.59–2.70 (m, 2H,
CH2N), 2.90–2.95 (m, 2H, CH2N), 3.43–3.74 ppm (m, 12H, CH2N); GC-
MS: Rt =9.90 min; m/z (%)=488 (M+, 20); C16H21F9N4O3: (488.35)
1
step without further purification. H NMR: (400 MHz, CDCl3, 258C), d=
1.62 (brt, 2H, CH2), 1.79 (brt, 2H, CH2), 2.46–2.77 (m, 16H, CH2N),
3.49 (s, 2H, Ar-CH2N), 5.19 (s, 4H, Naph-CH2), 6.59 (s, 1H, Ar-H), 6.71
(s, 2H, Ar-H), 7.42–7.55 (m, 6H, Naph-H), 7.79–7.89 ppm (m, 8H, Naph-
H); 13C NMR: (100.6 MHz, CDCl3, 258C), d=26.30, 28.63 (CH2), 47.54,
47.81, 48.99, 49.15, 49.30, 51.08, 53.37,
1,4,8-Tris(trifluoroacetyl)-11-(3,5-bis(2’-oxymethylnaphthyl)benzyl)-
1,4,8,11-tetraazacyclotetradecane (6):
54.74 (NCH2), 58.03 (Ar-CH2N), 70.25
(Naph-CH2), 100.06, 108.94, 125.28,
126.06, 126.24, 126.28, 127.74, 127.95,
128.34, 133.09, 133.35, 134.58, 141.74,
159.92 ppm (CAr); FAB-MS: m/z (%):
603.1 (M+H+, 100); C39H46N4O2:
(602.81).
1-(3,5-bis(2’-oxymethylnaphthyl)ben-
zyl)-4,8,11-trisACTHNUTRGNE(NUG 3,5-bis(N-benzyl-5’-
dimethylaminonaphthalen-1’-sulfona-
mido)benzyl)-1,4,8,11-tetraazacyclo-
tetradecane (N2D6)
Chem. Asian J. 2010, 5, 1884 – 1895
ꢄ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemasianj.org
1891

P. Ceroni, F. Vçgtle et al.
FULL PAPERS
1-(3,5-bis(2’-oxymethylnaphthyl)ben-
zyl)-1,4,8,11-tetraazacyclo-tetrade-
cane 7 (100 mg, 1.66ꢆ10À4 mol), 3,5-
bis(N-benzyl-5’-dimethylamino-naph-
thalen-1’-sulfonamido)benzyl
bro-
mide 3 (563 mg, 6.64ꢆ10À4 mol) and
potassium carbonate (230 mg, 1.66ꢆ
10À3 mol) were dissolved in DMF
(30 mL) and stirred for 3 days at RT.
The organic phase was then washed
with water and saturated sodium hy-
drogen carbonate, dried over sodium
sulphate and solvent removed in
vacuo. The crude product was puri-
fied by column chromatography
(SiO2; dichloromethane/methanol 10:1) yielding a yellow foam (300 mg,
62%). 1H NMR: (300 MHz, CDCl3, 258C), d=1.25 (brs, 4H, CH2), 1.80
(brt, 2H, CH2N), 1.88–1.93 (m, 4H, CH2N), 1.99 (s, 4H, CH2N), 2.09
(brt, 2H, CH2N), 2.19 (brt, 2H, CH2N), 2.30 (brt, 2H, CH2N), 2.76 (s,
(420 mg, 0.49 mmol) were stirred at RT for 3 days in DMF (30 mL).
After washing with water and column chromatographic purification, a
yellowish product (240 mg, 47% yield) was obtained. DC (SiO2): Rf =0.3
(dichloromethane/ethyl acetate 15:1 v/v); 1H NMR: (400 MHz, CDCl3,
258C), d=1.48 (s, 2H, CH2), 1.99 (s, 2H, CH2), 2.59 (s, 2H, CH2N), 2.87
(s, 12H, NACTHNUGTRNE(UGN CH3)2), 2.94–3.63 (16H, CH2N, Ar-CH2N), 4.55 (s, 4H, CH2-
N-SO2), 6.72 (s, 2H, Ar-H), 6.77 (s, 1H, Ar-H), 6.88–6.97 (m, 4H, benzyl-
H), 7.09–7.19 (m, 8H, benzyl-H, dansyl-H), 7.29 (t, 2H, 3JHH =8.47 Hz,
2H, Ar-CH2N), 2.79, 2.80, 2.82 (s, 36H, NACTHNURGTNEG(UN CH3)2), 2.88 (s, 2H, Ar-
CH2N), 2.94 (s, 2H, Ar-CH2N), 3.25 (s, 2H, Ar-CH2N), 4.53, 4.57 (s, 12H,
CH2-N-SO2), 5.09 (s, 4H, Naph-CH2), 6.56 (t, 1H, Ar-H), 6.59 (t, 1H, Ar-
H), 6.64 (t, 4H, Ar-H), 6.70 (d, 6H, Ar-H), 6.88–7.08 (m, 36H, benzyl-H,
dansyl-H), 7.17–7.29 (m, 12H, dansyl-H), 7.40–7.45 (m, 6H, Naph-H),
7.70–8.03 (m, 20H, Naph-H, dansyl-H), 8.41–8.47 ppm (m, 6H, dansyl-
3
dansyl-H), 7.45 (t, 2H, 3JHH =8.47 Hz, dansyl-H), 7.98 (d, 4H, JHH
=
8.66 Hz, dansyl-H), 8.54 ppm (d, 2H, 3JHH =8.48 Hz, dansyl-H); FAB-
H); 13C NMR: (100.6 MHz, CDCl3, 258C), d=45.39 (N
ACTHUNGTRNEUNG(CH3)2), 48.78,
MS: m/z (%): 1255.4 (M+H+, 75); C61H63N8O7S2: (1255.32).
49.62, 49.99, 50.23, 50.47, 50.86, 51.01 (CH2N), 54.38, 54.49 (CH2-N-SO2),
58.50, 59.48 (Ar-CH2N), 70.12 (Naph-CH2), 100.59, 107.80, 115.17, 119.59,
119.64, 119.69, 123.02, 125.28, 125.99, 126.16, 126.26, 127.23, 127.43,
127.57, 127.69,127.94, 128.03, 128.28, 128.45, 128.55, 128.60, 128.62,
128.78, 129.80, 129.84, 130.14, 130.16, 130.62, 130.68, 130.77, 133.03,
133.28, 134.09, 134.20, 134.48, 135.77, 135.80, 135.85, 138.96, 139.07,
140.99, 141.14, 141.18, 143.02, 151.59, 151.61, 151.65, 159.97 ppm (CAr);
MALDI-TOF-MS: m/z (%): 2903.8
1-(3,5-Bis(N-benzyl-5’-dimethylaminonaphthalene-1’-sulfonamido)ben-
zyl)-1,4,8,11-tetraazacyclotetradecane (9):
1-(3,5-Bis(N-benzyl-5’-dimethylaminonaphthalene-1’-sulfonamido)-
benzyl)-1,4,8,11-tetraazacyclotetradecane
8 (240 mg, 0.19 mmol) and
sodium carbonate (240 mg, 2.3 mmol) were dissolved in methanol/water
(M+H+); C174H172N16O14S6: (2903.72).
1,4,8-Tris(trifluoroacetyl)-11-(3,5-
bis(N-benzyl-5’-dimethylaminonaph-
thalene-1’-sulfonamido)ben-
zyl)1,4,8,11-tetraazacyclotetradecane
(8):
1,4,8-Tris(trifluoroacetyl)-1,4,8,11-tet-
raazacyclotetradecane
0.41 mmol), potassium
4
(200 mg,
carbonate
(283 mg, 2.1 mmol), and 3,5-bis(N-
benzyl-5’-dimethylaminonaphthalene-
1’-sulfonamido)benzylbromide
3
1892
www.chemasianj.org
ꢄ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Asian J. 2010, 5, 1884 – 1895

Cyclam-Cored Dendrimers and Intradendrimer Energy Transfer
mixture (30 mL, 4:1, v/v), then heated under reflux for 3 h. After addi-
tional stirring at RT over night, work up yielded the raw product which
was used without further purification. 1H NMR: (300 MHz, CDCl3,
258C), d=1.50 (brs, 2H, CH2), 1.67 (brs, 2H, CH2), 1.90 (brs, 2H,
tered, the solvent removed in vacuo, and the rest taken up in chloroform.
The organic phase was then washed with water and saturated sodium hy-
drogen carbonate, dried over sodium sulphate, and solvent removed in
vacuo. The crude product was purified by column chromatography (SiO2;
dichloromethane/methanol 15:1) yielding a yellow foam (116 mg, 45%).
1H NMR: (300 MHz, CDCl3, 258C), d=1.43 (brs, 2H, CH2), 1.66 (brs,
2H, CH2), 2.05 (brs, 2H, CH2N), 2.13 (brs, 2H, CH2N), 2.30–2.53 (m,
3
CH2N), 1.96 (brt, 2H, JHH =5.46 Hz, CH2N), 2.44 (s, 4H, CH2N), 2.57 (s,
2H, CH2N), 2.65 (brt, 2H, 3JHH =5.08 Hz, CH2N), 2.72 (brs, 4H, CH2N),
2.86 (s, 12H, NACHTUNGTRENNUNG(CH3)2), 3.09 (s, 2H, Ar-CH2N), 4.63 (s, 4H, CH2-N-SO2),
6.60 (d, 2H, 4JHH =1.88 Hz, Ar-H), 6.78 (t, 1H, 4JHH =1.89 Hz, Ar-H),
7.00–7.04 (m, 4H, benzyl-H), 7.10–7.17 (m, 8H, benzyl-H, dansyl-H),
12H, CH2N), 2.78 (s, 12H, NACHTNUTRGNEUNG(CH3)2), 2.86 (s, 2H, Ar-CH2N), 3.18 (s, 2H,
Ar-CH2N), 3.38 (s, 4H, Ar-CH2N), 4.51 (s, 4H, CH2-N-SO2), 4.96, 5.00,
5.12 (s, 12H, Naph-CH2), 6.50 (s, 2H, Ar-H), 6.57 (s, 1H, Ar-H), 6.61 (s,
4H, Ar-H), 6.65 (s, 2H, Ar-H), 6.72 (s, 3H, Ar-H), 6.93–7.09 (m, 12H,
benzyl-H, dansyl-H), 7.18 (t, 2H, 3JHH =7.72 Hz, dansyl-H), 7.26 (t, 2H,
dansyl-H), 7.38–7.48 (m, 18H, Naph-H), 7.74–7.81 (m, 24H, Naph-H),
7.91 (d, 2H, 3JHH =7.35 Hz, dansyl-H), 7.96 (d, 2H, 3JHH =8.67 Hz,
dansyl-H), 8.43 ppm (d, 2H, 3JHH =8.48 Hz, dansyl-H); 13C NMR:
3
3
7.25 (t, 2H, JHH =8.67 Hz, dansyl-H), 7.33 (t, 2H, JHH =8.47 Hz, dansyl-
H), 7.94 (d, 2H, 3JHH =7.34 Hz, dansyl-H), 8.03 (d, 2H, 3JHH =8.67 Hz,
dansyl-H), 8.49 ppm (d, 2H, 3JHH =8.48 Hz, dansyl-H); 13C NMR:
(100.6 MHz, CDCl3, 258C), d=25.80, 28.54 (CH2), 45.44 (NACTHNUTRGNEUNG(CH3)2),
47.02, 47.65, 48.24, 48.81, 49.32, 50.99, 51.05, 53.73 (NCH2), 54.42 (Ar-
CH2N-SO2), 55.54 (Ar-CH2N), 115.23, 119.68, 123.03, 127.58, 127.83,
128.12, 128.33, 128.81, 129.35, 129.86, 130.16, 130.66, 131.01, 134.02,
135.82, 138.81, 138.99, 151.65 ppm (CAr); FAB-MS: m/z (%): 967.4
(M+H+, 100); C55H66N8O4S2: (967.29).
(100.6 MHz, CDCl3, 258C), d=45.39 (NACHTNUTRGNEUGN(CH3)2), 49.92, 50.22, 50.36,
50.74, 51.48 (CH2N), 54.38 (CH2-N-SO2), 58.35, 59.10, 59.67 (Ar-CH2N),
70.03, 70.14, 70.28 (Naph-CH2), 100.71, 100.85, 100.94, 107.72, 107.87,
108.02, 115.13, 119.74, 123.04, 125.32, 125.42, 125.99, 126.02, 126.14,
126.17, 126.21, 126.26, 126.28, 126.36, 127.50, 127.71, 127.74, 127.97,
128.26, 128.33, 128.55, 128.66, 129.81, 130.19, 130.57, 130.79, 133.05,
133.08, 133.29, 133.33, 134.20, 134.52, 134.55, 135.93, 139.01, 141.06,
142.81, 143.04, 143.21, 151.55, 159.89, 159.93, 162.36 ppm (CAr); FAB-MS:
m/z (%): 2175.1 (M+H+); C142H132N8O10S2: (2174.75).
1,4,8-TrisACHTUNGTRENNUNG(3,5-bis(2’-oxymethylnaphthyl)benzyl)-11-(3,5-bis(N-benzyl-
5’-dimethylaminonaphthalene-1’-sulfonamido)benzyl)-1,4,8,11-tetra-
azacyclotetradecane (N6D2):
1-(3,5-Bis(N-benzyl-5’-dimethylaminonaphthalene-1’-sulfonamido)ben-
zyl)-1,4,8,11-tetraazacyclotetradecane 9 (120 mg; 0.12 mmol), 3,5-bis(2’-
oxymethyl-naphthyl)benzyl bromide 5 (330 mg, 0.67 mmol), and potassi-
um carbonate (170 mg, 1.21 mmol) were dissolved in DMF (30 mL) and
stirred under argon for 3 days at RT. The reaction mixture was then fil-
1,4,8,11-TetraACTHNUGRTNEUNG(3,5-bis(N-benzyl-5’-dimethylaminonaphthalene-1’-sul-
fonamido)benzyl)-1,4,8,11-tetraazacyclotetradecane (D8):
Chem. Asian J. 2010, 5, 1884 – 1895
ꢄ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemasianj.org
1893

P. Ceroni, F. Vçgtle et al.
FULL PAPERS
Cyclam (11 mg, 5.5ꢆ10À5 mol), 3,5-bis(N-benzyl-5’-dimethylamino-naph-
thalen-1’-sulfonamido)benzyl bromide 3 (300 mg, 0.35 mmol), and potas-
sium carbonate (60 mg, 0.44 mmol) were dissolved in acetonitrile
(30 mL) and stirred for 6 days at RT. The reaction mixture was then fil-
tered, the solvent removed in vacuo, and the rest taken up in chloroform.
The organic phase was then washed with water and saturated sodium hy-
drogen carbonate, dried over sodium sulphate, and removed in vacuo.
The crude product is purified by column chromatography (SiO2; di-
chloromethane/methanol 15:1) yielding a yellow foam (140 mg, 77%).
1H NMR: (400 MHz, CDCl3, 258C), d=1.15 (s, 4H, CH2), 1.83 (s, 8H,
Dend, J. Locklin, D. Patton, A. Baba, R. C. Advincula, J. Am.
Chem. Soc. 2005, 127, 1744.
[5] For some recent examples, see for example: a) C. Giansante, P.
Ceroni, V. Balzani, F. Vçgtle, Angew. Chem. 2008, 120, 5502;
Angew. Chem. Int. Ed. Engl. 2008, 47, 5422; b) J. B. Oh, M.-K. Nah,
Y. H. Kim, M. S. Kang, J.-W. Ka, K. Kym, Adv. Funct. Mater. 2007,
17, 413; c) B.-L. Li, Z.-T. Liu, G.-J. Deng, Q.-H. Fan, Eur. J. Org.
Chem. 2007, 508; d) N. S. Baek, Y. H. Kim, S.-G. Roh, B. K. Kwak,
H. K. Kim, Adv. Funct. Mater. 2006, 16, 1873; e) L. Shen, M. Shi, F.
Li, D. Zhang, X. Li, E. Shi, T. Yi, Y. Du, C. Huang, Inorg. Chem.
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CH2N), 1.96 (s, 8H, CH2N), 2.81 (s, 48H, NACTHNURGTNEG(UN CH3)2), 2.85 (s, 8H, Ar-
CH2N), 4.55 (s, 16H, CH2-N-SO2), 6.66 (s, 4H, Ar-H), 6.74 (s, 8H, Ar-
H), 6.91–7.00 (m, 40H, benzyl-H), 7.06 (d, 8H, 3JHH =7.5 Hz, dansyl-H),
7.21 (t, 8H, 3JHH =8.5 Hz, dansyl-H), 7.25 (t, 8H, 3JHH =7.8 Hz, dansyl-
H), 7.92 (d, 8H, 3JHH =6.8 Hz, dansyl-H), 8.01 (d, 8H, 3JHH =8.7 Hz,
dansyl-H), 8.45 ppm (d, 8H, 3JHH =8.5 Hz, dansyl-H); 13C NMR:
(100.6 MHz, CDCl3, 258C), d=45.46 (NACHTNUGTRNE(UNG CH3)2), 50.65 (CH2N), 54.46
(CH2-N-SO2), 58.53 (CH2N), 115.22, 119.62, 123.01, 127.08, 127.53,
128.07, 128.27, 128.44, 128.52, 129.85, 130.13, 130.68, 130.73, 134.18,
135.77, 139.11, 141.33, 151.64 ppm (CAr); MALDI-TOF-MS: m/z (%):
3266.3 (M+H+); C190H192N20O16S8: (3268.2).
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The experiments were carried out in CH3CN/CH2Cl2 1:1 (v/v) solutions
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Perkin–Elmer l40 spectrophotometer. Fluorescence spectra were ob-
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coefficient, fluorescence lifetime, and log K values, 10% on the fluores-
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Received: March 4, 2010
Published online: June 10, 2010
Chem. Asian J. 2010, 5, 1884 – 1895
ꢄ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemasianj.org
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