Liquid-crystalline thiol- and disulfide-based dendrimers for the functionalization of gold nanoparticles: Preliminary communication

Article abstract of DOI:10.1002/hlca.200890253

Liquid-crystalline dendrons carrying either a thiol or disulfide function which display nematic, smectic A, columnar, or chiral nematic phases have been synthesized. Their mesomorphic properties are in agreement with the nature of the mesogenic units and structure of the dendrons. The first-generation poly(aryl ester) dendron containing two cyanobiphenyl mesogenic units was used to functionalize gold nanoparticles. For full coverage, a smectic-like supramolecular organization on the nanometer scale is observed, when the gold nanoparticles are spread onto carbon-coated copper grids. This result indicates that the dendritic ligands reported here act as self-organization promoters.

Full text of DOI:10.1002/hlca.200890253

Helvetica Chimica Acta – Vol. 91 (2008)
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Liquid-Crystalline Thiol- and Disulfide-Based Dendrimers for the
Functionalization of Gold Nanoparticles
Preliminary Communication
by Ste´phane Freina), Julien Boudonb), Mireille Vonlanthena), Toralf Scharfc), Joaquꢀn Barbera´ d),
Georg Sꢁss-Finka), Thomas Bꢁrgi*b), and Robert Deschenaux*a)
a
´
ˆ
) Institut de Chimie, Universite de Neuchatel, Avenue de Bellevaux 51, Case postale 158,
ˆ
CH-2009 Neuchatel (e-mail: robert.deschenaux@unine.ch)
b
´
ˆ
ˆ
) Institut de Physique, Universite de Neuchatel, Avenue de Bellevaux 51, CH-2000 Neuchatel
(e-mail: thomas.buergi@unine.ch)
c
´
ˆ
ˆ
) Institut de Microtechnique, Universite de Neuchatel, Rue A.-L. Breguet 2, CH-2000 Neuchatel
d
´
´
) Quꢀmica Organica, Facultad de Ciencias-Instituto de Ciencia de Materiales de Aragon,
Universidad de Zaragoza-CSIC, E-50009 Zaragoza
Liquid-crystalline dendrons carrying either a thiol or disulfide function which display nematic,
smectic A, columnar, or chiral nematic phases have been synthesized. Their mesomorphic properties are
in agreement with the nature of the mesogenic units and structure of the dendrons. The first-generation
poly(aryl ester) dendron containing two cyanobiphenyl mesogenic units was used to functionalize gold
nanoparticles. For full coverage, a smectic-like supramolecular organization on the nanometer scale is
observed, when the gold nanoparticles are spread onto carbon-coated copper grids. This result indicates
that the dendritic ligands reported here act as self-organization promoters.
Introduction. – Rational design of novel supramolecular materials for applications
in optics, electronics, catalysis, and biomedical sciences is still a challenge [1], current
interest with this aim being focused on the synthesis of thermotropic liquid-crystalline
gold nanoparticles [2 – 5]. Decorated gold nanoparticles are one of the most promising
candidates for self-organization leading to bulk metamaterials, i.e., materials with
nonconventional electromagnetic properties. It has already been shown that regular
arrangements of metallic particles on different length scales can lead to negative
magnetic permeability [6]. This opens the pathway to metamaterials in the visible light
region, provided that the following conditions are fulfilled: the distance and
organization of the particles have to be controlled, and there should be a possibility
to compensate optical absorption by incorporation of active agents to allow energy
transfer [7]. The first condition is fulfilled by the self-organization within the liquid-
crystal phase itself, while the second one can be fulfilled by adding fluorescence dyes
into the liquid-crystal materials.
To generate mesomorphism, gold nanoparticles were functionalized with liquid-
crystalline thiol derivatives [2 – 4] via a ligand-exchange reaction from dodecane-1-
thiol-stabilized gold nanoparticles [8]. Only in one case, the mesophase displayed by
the materials could be identified [4]: an enantiotropic nematic phase was obtained for
gold nanoparticles partly decorated with laterally-branched mesogens; the latter
ꢁ 2008 Verlag Helvetica Chimica Acta AG, Zꢂrich

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ligands showed a monotropic nematic phase. Alternatively, gold nanoparticles were
partly functionalized with non-mesomorphic second-generation poly(benzyl ether)
¯
dendrons [5] also via a ligand-exchange reaction to give an enantiotropic Im3m cubic
phase.
We designed mesomorphic materials by functionalizing [60]fullerene (nematic,
chiral nematic, smectic A, smectic C, columnar phases) [9], [60]fullerene – ferrocene
dyads (smectic A phase) [10], and diruthenium clusters (nematic and smectic A
phases) [11] with liquid-crystalline dendrimers. The nature of the mesophases and the
supramolecular organization within the liquid-crystal state could be controlled via the
structure of the mesomorphic units, and the structure and size (generation) of the
dendrons. Therefore, structural engineering at the molecular level led to materials with
tailored-made mesomorphic properties.
Based on this experience, we envisaged to apply this concept to gold nanoparticles.
Indeed, gold nanoparticles are three-dimensional molecular objects, such as [60]fuller-
ene, ferrocene, and organometallic clusters, the self-organization behavior of which
could also be generated and controlled by use of liquid-crystalline dendrons [12]. We
report herein the synthesis, characterization, and liquid-crystalline properties of thiol-
and disulfide-based dendrons, and the functionalization of gold nanoparticles with one
of the ligands.
Results and Discussion. – 1. Design. This study focuses on the preparation of first-
(i.e., 1, 2, and 8), second- (i.e., 3, 4, 5, and 6), and third- (i.e., 7) generation dendrons
containing either a thiol or disulfide group (Schemes 1 – 5). The disulfide function (two
anchor sites) was selected to design ligands having stronger binding constants than the
thiol derivatives (one anchor site). Thus, eight ligands were designed and classified
within three families according to their structures: 1) poly(aryl ester) dendrons
functionalized with mesomorphic cyanobiphenyl units (i.e., compounds 1 – 4;
Schemes 1 and 2), 2) poly(benzyl ether) dendrons carrying alkyl chains (i.e.,
compounds 5 – 7; Schemes 3 and 4), and 3) a poly(aryl ester) dendron carrying
optically-active mesogens (i.e., compound 8, Scheme 5).
2. Synthesis. The preparation of compounds 1 – 8 is presented in Schemes 1 – 5. They
are obtained by esterification of first- (i.e., 9 and 13), second- (i.e., 10 and 11), or third-
(i.e., 12) generation HO-based dendrons with either 11-sulfanylundecanoic acid (!1,
3, and 5) or lipoic acid (¼1,2-dithiolane-3-pentanoic acid; ! 2, 4, 6, 7, and 8) under
standard reaction conditions. The syntheses of the precursors 9 [13], 10 [13], and 13 [14]
had already been published, and the precursors 11 [15a] and 12 [15a] have been
prepared as described in the literature.
3. Liquid-Crystalline Properties. The liquid-crystalline and thermal properties of
compounds 1 – 8 were investigated by polarized optical microscopy (POM) and
differential scanning calorimetry (DSC). The phase-transition temperatures and
enthalpies are reported in Table 1.
Dendrons 1 – 4 gave rise to a smectic A phase in agreement with the nature of the
mesomorphic cyanobiphenyl units which tend to be oriented parallel to each other, the
consequence of which was the formation of layers [9][13]. For the first-generation
dendrons 1 and 2, an additional nematic phase was also obtained. The second-
generation poly(benzyl ether) dendrons 5 and 6, carrying either a SH or a disulfide

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Helvetica Chimica Acta – Vol. 91 (2008)
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Scheme 3
a) 11-Sulfanylundecanoic acid, DPTS, DCC, CH2Cl2, r.t., 24 h; 34%. b) Lipoic acid, DPTS, DCC, 4-ppy,
CH2Cl2, r.t., 24 h; 67%.
group, did not show mesomorphic properties, suggesting that these groups associated to
the flexible alkyl chain cannot be oriented correctly in the center of the columns for
mesomorphism to occur, most likely, because the size of the dendron was not large
enough to surround the flexible chain in such a way that discs were formed. This was
confirmed by the fact that third-generation dendron 7, which also carries a disulfide
group, displayed columnar mesomorphism. The columnar phase displayed by 7 was
characterized by XRD. The patterns contain a set of three sharp maxima in the small-
angle region and a broad, diffuse halo in the wide-angle region (Table 2). The small-

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Scheme 4
a) Lipoic acid, DPTS, DCC, CH2Cl2, r.t., 72 h; 79%.

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Scheme 5
a) Lipoic acid, DPTS, DCC, 4-ppy, CH2Cl2, r.t., 24 h; 71%.
Table 1. Phase-Transition Temperatures (T) and Enthalpy Changes (DH) of Compounds 1 – 8
Compound
Tg [8]a)
Transitionb)
T [8]c)
DH [kJ/mol]
1
17
SmA ! N
N ! I
162
175
161
183
189
200
72
56
104
103
0.4
1.5
0.1
2
22
SmA ! N
N ! I
1.6
3
4
5
6
7
8
30
39
SmA ! I
SmA ! I
Cr! I
13.6
13.2
107.6
3.4
8.7
2.0
Cr! I
–d)
12
Colh ! I
N* ! I
a) Glass-transition temperature. b) SmA ¼ smectic A phase, N ¼ nematic phase, Colh ¼ hexagonal
columnar phase, N* ¼ chiral nematic phase, I ¼ isotropic liquid, Cr¼ crystalline or semi-crystalline
material. c) Transition temperatures are given at the onset of the observed peaks. d) Not detected.

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pffiffi
angle maxima correspond to a reciprocal spacing ratio of 1 : 3 : 2, which can be
indexed as the (1 0), (1 1), and (2 0) reflections of a two-dimensional hexagonal lattice.
The broad halo arises from the liquid-like arrangement of the conformationally-
disordered hydrocarbon chains. Its diffuse character confirmed the mesomorphic
nature of this mesophase. Using density estimations, it was possible to deduce the
number of molecules of compound 7 per column stratum or disc. The relationship
between the density (1) of the compound in the Colh phase and the number of
molecules (Z) in the unit cell is given by the following equation:
1 ¼ (M/N)/(V/Z)
where M is the molar mass of the compound, N the Avogadroꢃs number, and V the unit
pffiffi
cell volume: V ¼ ð 3=2Þa2c ꢀ 10ꢁ24 for a hexagonal lattice (a: hexagonal lattice
constant; c: stacking distance). A reflection corresponding to c was not observed in the
X-ray patterns, most likely, because there is no regular stacking within the column.
However, it can reasonably be assumed that the intracolumnar distance is close to
4.4 ꢄ, which is the distance corresponding to the diffuse halo (Table 2). Thus, for Z ¼ 1,
the calculated density was 0.85 g cmꢁ3, a reasonable value for an organic compound.
Therefore, considering a slice of column (or disc) with a thickness of 4.4 ꢄ, it is clear
that there is one molecule of compound 7 per slice or disc. The formation of columnar
phases from 7 is in agreement with the nature of the dendrons [15]. Finally, the first-
generation ligand 8, which contains optically-active laterally-branched mesogens [16],
showed the formation of a chiral nematic phase.
Table 2. X-Ray Data of the Hexagonal Columnar Phase Displayed by Compound 7a)
dmeas [ꢄ]
I
hk
dcalc [ꢄ]
Phase parameters at room temperature
41.2
24.1
20.4
4.4
vs
m
m
10
11
20
41.2
23.8
20.6
a ¼ 47.6 ꢄ
S ¼ 1961 ꢄ2
br.
a) dmeas and dcalc are the measured and calculated diffraction spacings, resp.; I is the intensity of the
reflection (vs: very strong, m: medium, br.: broad); hk are the indexations of the reflections
corresponding to the two-dimensional hexagonal lattice of the Colh phase; a is the lattice parameter of
X
pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
2
1
Nhk
h2 þ k2 þ hkÞ, where Nhk
pffiffi
the hexagonal columnar phase (a ¼
ꢀ< d10 > with < d10 >¼
ð
dhk
ꢂ
3
h;k
is the number of hk reflections; 3 in this case); S is the lattice area (S ¼ a ꢀ< d10 > for Colh). The
experiments were performed at 258 both in the virgin state and after thermal treatment; the results are
the same under both conditions.
The liquid-crystalline phases could be identified by POM from their characteristic
textures (nematic phase: schlieren texture; smectic A phase: focal-conic fan texture and
homeotropic areas; columnar phase: pseudo-focal conic texture; chiral nematic phase:
plane texture; see Figs. 1 – 4 for illustrative examples).
4. Functionalization of Gold Nanoparticles. The functionalization of gold nano-
particles was achieved by two alternative protocols: 1) the direct synthesis [8] (! I;

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Fig. 1. Thermal-polarized optical micrograph of the texture displayed by 1 in the nematic phase upon
cooling the sample from the isotropic liquid to 1738
Fig. 2. Thermal-polarized optical micrograph of the focal-conic fan texture displayed by 4 in the smectic A
phase upon cooling the sample from the isotropic liquid to 1998

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Fig. 3. Thermal-polarized optical micrograph of the pseudo-focal conic texture displayed by 7 in the
columnar phase upon cooling the sample from the isotropic liquid to 828
Fig. 4. Thermal-polarized optical micrograph of the texture displayed by 8 in the nematic chiral phase
upon cooling the sample from the isotropic liquid to 998

Helvetica Chimica Acta – Vol. 91 (2008)
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Scheme 6), and 2) the ligand-exchange reaction [17] (! II; Scheme 7). From the point
of view of functionalization, the direct method [8] leads to full coverage of the
nanoparticles surface with the desired thiol derivative; on the other hand, the ligand-
exchange reaction [17] allows to control the loading of the desired thiol derivative on
the gold surface. In this preliminary study, both reactions were carried out with ligand 1.
Scheme 6
a) Tetraoctylammonium bromide (TOAB), toluene/H2O 4 :1, r.t., a few min. b) Compound 1, 30 min,
then NaBH4, toluene, r.t., inert atmosphere, 24 h; 3%.
Scheme 7
a) TOAB, toluene/H2O 4 :1, r.t., a few min. b) Dodecane-1-thiol, 30 min, then NaBH4, toluene, r.t., 1 h,
30%. c) Compound 1, CH2Cl2, r.t., inert atmosphere, 72 h; 50%.
The direct synthesis led to nanoparticles I with an average diameter of 1.2 ꢃ
0.4 nm1) (Fig. 5). A few considerably larger particles (up to 7 nm) were visible in
the TEM image (Fig. 5). The ligand-exchange reaction (synthesis of gold nanoparticles
with dodecane-1-thiol, followed by exchange of dodecane-1-thiol with 1) led to
nanoparticles II with an average diameter of 1.7 ꢃ 0.4 nm2) (Fig. 6). The main
advantages of the latter approach are: 1) the size of the gold nanoparticles can be
controlled (first step), and 2) the ligands ratio can be adjusted (second step).
1
)
)
Size and size distribution were estimated from a sample of 1755 particles (minimum size: 0.74 nm,
maximum size: 6.98 nm).
Size and size distribution were estimated from a sample of 2575 particles (minimum size: 0.70 nm,
maximum size: 5.31 nm).
2

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Fig. 5. TEM Micrograph showing rows of 1.2-nm gold nanoparticles I
Fig. 6. TEM Micrograph showing 1.7-nm gold nanoparticles II
Different techniques were used to purify the nanoparticles, depending on the
preparation method. For the direct synthesis, the nanoparticles were purified by size-
exclusion chromatography (see Exper. Part). For the exchange reaction, the nano-
particles covered with dodecane-1-thiol were purified by membrane filtration and the
final materials by ultrafiltration (see Exper. Part). In addition, the particle core size was

Helvetica Chimica Acta – Vol. 91 (2008)
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estimated to be lower than ca. 2 nm by UV/VIS spectroscopy (no plasmon band located
at ca. 520 nm) and further validated by TEM observations (Figs. 5 and 6).
1
The structure and purity of the gold nanoparticles were confirmed by H-NMR
spectroscopy (Figs. 7 and 8): broadening of the peaks for the thiol derivatives grafted
on the gold surface and disappearance of the CH2SH signal [8][18] evidenced that the
ligands are grafted onto the gold surface. For II, the relative amount of ligand 1 with
respect to dodecane-1-thiol was estimated from the spectrum of the mixed system (part
D of Fig. 8), and was found to be ca. 40%. Finally, the absence of sharp peaks indicated
the absence of free thiol in the samples.
Fig. 7. 1H-NMR Spectra (in CD2Cl2) of compound 1 (a) and gold nanoparticles I (b)
5. Self-Organization Behavior. Compound 1 attached to gold nanoparticles
promoted an unexpected organization on carbon-coated copper grids: the particles
arrange in evenly spaced rows (Fig. 5). In this organization, the particle cores within
one row are closely packed, and separated from each other by less than 1 nm. The
separation between the rows is ca. 6.5 nm, which corresponds to 1.3 times the length of
compound 1 (L ¼ 5.3 nm) in its fully extended conformation. This can be interpreted as
the formation of layers, as for smectic phases, with interdigitation of the cyanobiphenyl
mesogenic units from one layer to the adjacent one. Interestingly, decreasing the
dendrimer loading on the gold particle surface from 100 to 40% results in a less
pronounced organization (not shown) or even in a complete loss of organization
(Fig. 6). Thus, compound 1 acts as a self-organization promoter of gold particles,
provided that sufficient loading is reached. Such organized structures may find
applications in optical devices such as in optical waveguides or diffraction gratings due
to the large local variation of the refractive index. Particularly interesting is the fact
that, by this method, very short periodicities can be obtained.
Conclusions. – We have synthesized liquid-crystalline thiol- and disulfide-based
ligands which display mesomorphism, in agreement with their structures. In this

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Fig. 8. 1H-NMR Spectra of dodecane-1-thiol (a; in CDCl3), dodecane-1-thiol-stabilized gold nano-
particles (b; in CDCl3), compound 1 (c; in CD2Cl2), and gold nanoparticles II (d; in CD2Cl2)
preliminary study, one of these ligands was used to stabilize and organize gold
nanoparticles, the other ligands could also provide stabilization and organization of
gold nanoparticles as well as of other metallic nanoparticles. The gold nanoparticles
obtained in this study did not show mesomorphism. However, a surface organization on
the nanometer scale was observed when spreading the materials onto a carbon-coated
copper grid. Our results open up the design of organometallic materials with
temperature-dependent optical properties by a bottom-up approach.

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The authors thank the Swiss National Science Foundation (Grants No. 200021-109176 and 200020-
117676) and the CICYT-FEDER Spanish project CTQ2006-15611-C02-01 for financial support.
Experimental Part
General. UV/VIS Spectra: Varian Cary 50 spectrophotometer; in CH2Cl2 before normalization.
1H-NMR Spectra: Bruker 400 spectrometer with the solvent as an internal reference (chemical shifts d in
ppm). Polarized optical microscopy (POM): Zeiss-Axioskop polarizing microscope equipped with a
Linkam THMS-600 variable-temp. stage, under N2. Transition temp. and enthalpies were determined on
a Mettler-Toledo 822e differential-scanning calorimeter at a rate of 108/min under He/N2. The XRD
patterns were obtained with a pinhole camera (Anton-Paar) operating with a point-focussed Ni-filtered
Cu/Ka beam. The samples were held in Lindemann glass capillaries (1-mm diameter) and heated, when
necessary, with a variable-temp. oven. The capillary was perpendicular to the X-ray beam, and the
patterns were collected on a flat photographic film perpendicular to the beam. Spacings were obtained
via Braggꢃs law. Transmission electron microscopy (TEM): Philips C200 electron microscope operating
at 200 kV. The nanoparticles were dissolved in CH2Cl2, and the samples were prepared by drop-casting
the soln. onto a 300-mesh carbon-coated copper grid. TEM Images were analyzed with the help of Image
J, a free, public-domain program that is useful for the rapid counting of large numbers of particles [19];
further information is provided on the american NIH-dedicated website: http://rsb.info.nih.gov/ij.
Synthesis of 1. To a soln. of 9 [13] (4.85 g, 4.45 mmol) and 11-sulfanylundecanoic acid (486 mg,
2.23 mmol) in dry CH2Cl2 (250 ml) at 08 were added 4-(dimethylamino)pyridinium para-toluenesulfo-
nate (DPTS) (655 mg, 2.23 mmol), N,N’-dicyclohexylcarbodiimide (DCC) (2.30 g, 11.13 mmol), and 4-
pyrrolidinopyridine (4-ppy; spatula tip). The mixture was stirred for 24 h at r.t., and the solvent was
evaporated under vacuum. Purification of the crude material by column chromatography (CC; silica gel
63 – 200 mm; CH2Cl2) and precipitation from CH2Cl2 with MeOH gave pure 1 (1.32 g, 46%).
Compounds 2 – 8 were synthesized according to the above procedure, and were purified by CC (silica
gel 63 – 200 mm) with CH2Cl2 (for 2, 3, 4, 7, and 8) or CH2Cl2/heptane (for 5 and 6) as eluent. The chemical
yields are indicated in the Scheme captions.
Data of Bis[10-(4-{[(4’-cyanobiphenyl-4-yl)oxy]carbonyl}phenoxy)decyl] 5-[(11-Sulfanylundeca-
1
noyl)oxy]benzene-1,3-dicarboxylate (1)3). H-NMR (400 MHz, CD2Cl2): 8.49 (t, 1 arom. H); 8.11 (d, 4
arom. H); 7.89 (d, 2 arom. H); 7.73 (d, 4 arom. H); 7.71 (d, 4 arom. H); 7.65 (d, 4 arom. H); 7.31 (d, 4 arom.
H); 6.97 (d, 4 arom. H); 4.31 (t, 2 CO2CH2); 4.03 (t, 2 CH2O); 2.57 (t, CH2CO2); 2.48 (q, CH2SH); 1.83 –
1.69 (m, 2 CO2CH2CH2, 2 CH2CH2O, CH2CH2CO2, CH2CH2SH); 1.37 – 1.26 (m, 36 aliph. H). Anal. calc.
for C79H88N2O12S (1289.62): C 73.58, H 6.88, N 2.17, S 2.49; found: C 73.48, H 6.68, N 2.31, S 2.33.
Data of Bis[10-(4-{[(4’-cyanobiphenyl-4-yl)oxy]carbonyl}phenoxy)decyl] 5-{[5-(1,2-Dithiolan-3-yl)-
1
pentanoyl]oxy}benzene-1,3-dicarboxylate (2)3). H-NMR (400 MHz, CD2Cl2): 8.50 (t, 1 arom. H); 8.11
(d, 4 arom. H); 7.91 (d, 2 arom. H); 7.73 (d, 4 arom. H); 7.71 (d, 4 arom. H); 7.65 (d, 4 arom. H); 7.31 (d, 4
arom. H); 6.98 (d, 4 arom. H); 4.32 (t, 2 CO2CH2); 4.03 (t, 2 CH2O); 3.62 – 3.55 (m, CH); 3.20 – 3.07 (m,
SCH2); 2.61 (t, CH2CO2); 2.49 – 2.41 (m, SCH2CHa); 1.95 – 1.88 (m, SCH2CHb); 1.82 – 1.68 (m,
2 CO2CH2CH2, CH2CH2CO2, 2 CH2CH2O, CHCH2); 1.46 – 1.30 (m, 26 aliph. H). Anal. calc. for
C76H80N2O12S2 (1277.59): C 71.45, H 6.31, N 2.19, S 5.02; found: C 71.27, H 6.40, N 2.24, S 5.03.
Data of 3. 1H-NMR (400 MHz, CD2Cl2): 8.89 (t, 1 arom. H); 8.59 (t, 2 arom. H); 8.22 (d, 2 arom. H);
8.12 (d, 8 arom. H); 8.10 (d, 4 arom. H); 7.74 (d, 8 arom. H); 7.72 (d, 8 arom. H); 7.67 (d, 8 arom. H); 7.32
(d, 8 arom. H); 6.98 (d, 8 arom. H); 4.35 (t, 4 CO2CH2); 4.04 (t, 4 CH2O); 2.64 (t, CH2CO2); 2.49 (q,
CH2SH); 1.84 – 1.75 (m, 4 CO2CH2CH2, 4 CH2CH2O, CH2CH2CO2, CH2CH2SH); 1.47 – 1.30 (m, 60
aliph. H). Anal. calc. for C155H158N4O26S (2525.04): C 73.73, H 6.31, N 2.22, S 1.27; found: C 73.35, H 6.35,
N 2.17, S 1.43.
Data of 4. 1H-NMR (400 MHz, CD2Cl2): 8.89 (t, 1 arom. H); 8.59 (t, 2 arom. H); 8.23 (d, 2 arom. H);
8.12 (d, 8 arom. H); 8.10 (d, 4 arom. H); 7.74 (d, 8 arom. H); 7.72 (d, 8 arom. H); 7.67 (d, 8 arom. H); 7.32
3
)
As representative nomenclature examples, the systematic names of compounds 1, 2, 5, and 6 are
provided.

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Helvetica Chimica Acta – Vol. 91 (2008)
(d, 8 arom. H); 6.98 (d, 8 arom. H); 4.35 (t, 4 CO2CH2); 4.04 (t, 4 CH2O); 3.64 – 3.57 (m, CH); 3.20 – 3.08
(m, SCH2); 2.67 (t, CH2CO2); 2.50 – 2.42 (m, SCH2CHa); 1.96 – 1.87 (m, SCH2CHb); 1.82 – 1.76 (m,
4 CO2CH2CH2, 4 CH2CH2O, CHCH2); 1.47 – 1.35 (m, 52 aliph. H). Anal. calc. for C152H150N4O26S2
(2512.96): C 72.65, H 6.02, N 2.23, S 2.55; found: C 72.37, H 6.07, N 2.21, S 2.60.
Data of 3,5-Bis[(3,4,5-tris{[4-(dodecyloxy)benzyl]oxy}benzyl)oxy]benzyl 11-sulfanylundecanoate
(5)3). 1H-NMR (400 MHz, CD2Cl2): 7.31 (d, 8 arom. H); 7.29 (d, 4 arom. H); 6.88 (d, 8 arom. H); 6.78 –
6.73 (m, 8 arom. H); 6.60 (d, 2 arom. H); 6.56 (t, 1 arom. H); 5.06 – 5.02 (m, CO2CH2Ar, 4 OCH2Ar); 4.93
(m, 4 OCH2Ar); 3.97 – 3.86 (m, 6 OCH2); 2.49 (t, CH2CO2); 2.32 (q, CH2SH); 1.81 – 1.72 (m,
6 OCH2CH2, CH2CH2CO2); 1.44 – 1.27 (m, 122 aliph. H); 0.89 (t, 6 Me). Anal. calc. for C146H220O16S
(2263.36): C 77.48, H 9.80, S 1.42; found: C 77.18, H 9.84, S 1.56.
Data of 3,5-Bis[(3,4,5-tris{[4-(dodecyloxy)benzyl]oxy}benzyl)oxy]benzyl 5-(1,2-dithiolan-3-yl)pen-
tanoate (6)3). 1H-NMR (400 MHz, CDCl3): 7.31 (d, 8 arom. H); 7.27 (d, 4 arom. H); 6.87 (d, 8 arom. H);
6.76 (d, 4 arom. H); 6.73 (s, 4 arom. H); 6.59 (d, 2 arom. H); 6.56 (t, 1 arom. H); 5.06 (s, CO2CH2Ar); 5.02
(s, 4 OCH2Ar); 4.92 (s, 2 OCH2Ar); 4.91 (s, 2 OCH2Ar); 3.97 – 3.90 (m, 6 OCH2CH2); 3.53 – 3.48 (m,
CH); 3.15 – 3.03 (m, SCH2); 2.42 – 2.30 (m, CH2CO2 , SCH2CHa); 1.81 – 1.72 (m, 6 OCH2CH2,
CH2CH2CO2, CHCH2, SCH2CHb); 1.44 – 1.27 (m, 110 aliph. H); 0.88 (t, 6 Me). Anal. calc. for
C143H212O16S2 (2251.37): C 76.29, H 9.49, S 2.85; found: C 76.26, H 9.34, S 2.74.
Data of 7. 1H-NMR (400 MHz, CD2Cl2): 7.31 (d, 16 arom. H); 7.22 (d, 8 arom. H); 6.87 (d, 16 arom.
H); 6.75 (s, 8 arom. H); 6.72 (d, 8 arom. H); 6.69 (d, 4 arom. H); 6.61 – 6.58 (m, 3 arom. H); 6.56 (t, 2
arom. H); 5.03 (s, CO2CH2Ar); 5.00 (s, 2 OCH2Ar); 4.98 (s, 8 OCH2Ar); 4.94 (s, 4 OCH2Ar); 4.87 (s,
4 OCH2Ar); 3.94 – 3.89 (m, 12OCH2CH2); 3.52 – 3.48 (m, CH); 3.09 – 3.01 (m, SCH2); 2.37 – 2.32 (m,
SCH2CHa, CH2CO2); 1.83 – 1.81 (m, SCH2CHb); 1.77 – 1.73 (m, 12 OCH2CH2); 1.65 – 1.60 (m, CHCH2,
CH2CH2CO2); 1.44 – 1.27 (m, 218 aliph. H); 0.87 (t, 12 Me). Anal. calc. for C285H416O32S2 (4418.53): C
77.47, H 9.49, S 1.45; found: C 77.47, H 9.50, S 1.38.
Data of 8. 1H-NMR (400 MHz, CD2Cl2): 8.48 (t, 1 arom. H); 8.25 (d, 4 arom. H); 8.00 (d, 2 arom. H);
7.88 (d, 2 arom. H); 7.61 (d, 4 arom. H); 7.54 (d, 4 arom. H); 7.35 (d, 4 arom. H); 7.25 (d, 4 arom. H); 6.97
(d, 4 arom. H); 6.57 – 6.53 (m, 4 arom. H); 4.28 (t, 2 CO2CH2); 4.06, 4.00 (2t, 4 OCH2CH2); 3.92 – 3.80 (m,
2 CHCH2O); 3.61 – 3.54 (m, CH); 3.20 – 3.06 (m, SCH2); 2.57 (t, CH2CO2); 2.48 – 2.40 (m, SCH2CHa);
1.90 – 1.69 (m, 2 CO2CH2CH2, CH2CH2CO2, 4 CH2CH2O, 2 CH, SCHCH2, SCH2CHb); 1.60 – 1.46 (m,
2 MeCH2CH, 30 aliph. H); 1.03 (d, 2 MeCH); 0.96 (t, 2 MeCH2CH); 0.90 (t, 2 MeCH2CH2). Anal. calc.
for C106H126O20S2 (1784.25): C 71.35, H 7.12, S 3.59; found: C 71.09, H 7.14, S 3.41.
General Procedure for the Synthesis of the Gold Nanoparticles. Chemicals were purchased from
Sigma-Aldrich and NaBH4 from Acros Organics.
Synthesis of I. According to the two-phase method [8] with a ratio of 1, 3.5, 3, and 20 equiv. for
HAuCl4 · 3 H2O, tetraoctylammonium bromide (TOAB), 1, and NaBH4, resp. Purification of the
particles was performed with Bio-Rad Bio-Beads S-X1 (1% cross-linked; separated molecular weights:
600 – 14000 Da).
Synthesis of II. To a moderately stirred CH2Cl2 (5 ml) soln. containing dodecane-1-thiol-stabilized
gold nanoparticles [8] (50 mg, 3.8 mmol, purified over Sartorius-regenerated cellulose membranes with a
0.2-mm pore size) was added a soln. of 1 (240 mg, 0.19 mmol) in CH2Cl2 (5 ml). The mixture was stirred
under inert atmosphere at r.t. for 72 h, and filtered (Millipore solvent-resistant ultrafiltration device with
30-kDa regenerated cellulose ultrafiltration membrane under a 2.2 bar N2 pressure). The soln. containing
II was evaporated to dryness.
Data of I. 1H-NMR (400 MHz, CD2Cl2): 8.46 (br. s, 1 arom. H); 8.12 (br. s, 4 arom. H); 7.87 (br. s, 2
arom. H); 7.66 (br. s, 12 arom. H); 7.30 (br. s, 4 arom. H); 6.95 (br. s, 4 arom. H); 4.28 (br. s, 2 CO2CH2);
3.99 (br. s, 2 CH2O); 2.55 (br. s, CH2CO2); 1.74 (br. s, 10 aliph. H); 1.30 (br. s, 38 aliph. H).
Data of II. 1H-NMR (400 MHz, CD2Cl2; integration with respect to the signals of ligand 1): 8.46 (br.
s, 1 arom. H); 8.10 (br. s, 4 arom. H); 7.87 (br. s, 2 arom. H); 7.70 and 7.63 (2 br. s, 12 arom. H); 7.29 (br. s, 4
arom. H); 6.96 (br. s, 4 arom. H); 4.28 (br. s, 2 CO2CH2); 4.00 (br. s, 2 CH2O); 2.55 (br. s, CH2CO2); 1.75
(br. s, 10 aliph. H); 1.65 – 0.97 (72 aliph. H); 0.85 (br. s, 5 aliph. H).

Helvetica Chimica Acta – Vol. 91 (2008)
2337
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Received August 19, 2008