Gold nanoparticles generated by thermolysis of "all-in-one" gold(i) carboxylate complexes

Article abstract of DOI:10.1039/c2dt11748g

Consecutive synthesis methodologies for the preparation of the gold(i) carboxylates [(Ph₃P)AuO₂CCH₂(OCH ₂CH₂)_nOCH₃] (n = 0-6) (6a-g) are reported, whereby selective mono-alkylation of diols HO(CH₂CH ₂O)_nH (n = 0-6), Williamson ether synthesis and metal carboxylate (Ag, Au) formation are the key steps. Single crystal X-ray diffraction studies of 6a (n = 0) and 6b (n = 1) were carried out showing that the P-Au-O unit is essentially linear. These compounds were applied in the formation of gold nanoparticles (NP) by a thermally induced decomposition process and hence the addition of any further stabilizing and reducing reagents, respectively, is not required. The ethylene glycol functionalities, providing multiple donating capabilities, are able to stabilise the encapsulated gold colloids. The dependency of concentration, generation time and ethylene glycol chain lengths on the NP size and size distribution is discussed. Characterisation of the gold colloids was performed by TEM, UV/Vis spectroscopy and electron diffraction studies revealing that Au NP are formed with a size of 3.3 (±0.6) to 6.5 (±0.9) nm in p-xylene with a sharp size distribution. Additionally, a decomposition mechanism determined by TG-MS coupling experiments of the gold(i) precursors is reported showing that 1 ^st decarboxylation occurs followed by the cleavage of the Au-PPh ₃ bond and finally release of ethylene glycol fragments to give Au-NP and the appropriate organics. The Royal Society of Chemistry 2012.

Full text of DOI:10.1039/c2dt11748g

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PAPER
Gold nanoparticles generated by thermolysis of “all-in-one” gold(I)
carboxylate complexes†
A. Tuchscherer,a D. Schaarschmidt,a S. Schulze,b M. Hietscholdb and H. Lang*a
Received 15th September 2011, Accepted 25th November 2011
DOI: 10.1039/c2dt11748g
Consecutive synthesis methodologies for the preparation of the gold(I) carboxylates [(Ph3P)-
AuO2CCH2(OCH2CH2)nOCH3] (n = 0–6) (6a–g) are reported, whereby selective mono-alkylation of
diols HO(CH2CH2O)nH (n = 0–6), Williamson ether synthesis and metal carboxylate (Ag, Au) formation
are the key steps. Single crystal X-ray diffraction studies of 6a (n = 0) and 6b (n = 1) were carried out
showing that the P–Au–O unit is essentially linear. These compounds were applied in the formation of
gold nanoparticles (NP) by a thermally induced decomposition process and hence the addition of any
further stabilizing and reducing reagents, respectively, is not required. The ethylene glycol functionalities,
providing multiple donating capabilities, are able to stabilise the encapsulated gold colloids. The
dependency of concentration, generation time and ethylene glycol chain lengths on the NP size and size
distribution is discussed. Characterisation of the gold colloids was performed by TEM, UV/Vis
spectroscopy and electron diffraction studies revealing that Au NP are formed with a size of 3.3 ( 0.6) to
6.5 ( 0.9) nm in p-xylene with a sharp size distribution. Additionally, a decomposition mechanism
determined by TG-MS coupling experiments of the gold(I) precursors is reported showing that 1st
decarboxylation occurs followed by the cleavage of the Au–PPh3 bond and finally release of ethylene
glycol fragments to give Au–NP and the appropriate organics.
including electrochemical8 and photochemical9 processes as well
as thermal decompositions of organometallic compounds10 were
applied to form Au NP, however, the chemical reduction of a
gold source in the presence of a stabiliser is the most common
one. A well-established synthesis protocol for preparing Au NP
was reported by Turkevich et al. using citrate as reducing and
stabilising component.11 Furthermore, the Brust-Schiffrin
method allows the reduction of chloroauric acid with sodium
borohydride in presence of an alkylthiol.12 For the synthesis of
high quality NP, stabilizing components featuring donating func-
tionalities or atoms such as N, O, P, and S are required, which
were attached on the particle surface and prevent aggregation. In
these respect, polyethylene glycols,13 polymers/block copoly-
mers,14 dendrimers,15 phosphanes,16 amines,17 thioethers18 and
surfactants19 are typically applied as stabilizing components.
Most published procedures for synthesising gold NP use Au(III)
sources, in which [AuCl4]− is the most common one. Only a few
synthesis procedures exist in which Au(I) species have been
applied as gold source. Schmid and co-workers showed that
Au55 clusters could be obtained by reducing [Au(PR3)Cl] with
B2H6.20 Stucky et al. demonstrated that [Au(PPh3)Cl] in pres-
ence of dodecanethiol and tert-butylamine-borane led to Au NP
with nearly mono-disperse size distribution.21 Furthermore, gold
NP could also be synthesised using [Au(tht)Cl)]22 (tht = tetrahy-
drothiophene), [Au(SMe2)Cl)]23 or [AuX] (X = Cl, Br)24 as
starting material in the presence of different sized alkylamines at
temperature between 60 and 120 °C. Nakamoto and co-workers
applied metal complexes of type [N(C14H29)(CH3)3]
1
Introduction
Intense efforts in the area of nanoparticles (NP) research have
been performed during recent decades with the aim of synthesis-
ing transition metal NP exhibiting defined structures and discrete
particle sizes between 1 and 100 nm as these colloids possess
unique physico-chemical properties. In this respect, especially
group-11 NP allow the design of new generations of nanodevices
and smart materials1 due to their exclusive optic,2 electric,3 mag-
netic4 and catalytic5 properties affected by the particle size,
shape, size distribution and particle-to-particle interactions.6 In
particular, gold colloids are excellent candidates as these
materials feature a high chemical stability and an intense colour.
In general, (gold) NP are accessible either by bottom-up or top-
down methodologies.7 A plurality of preparation methods
aFaculty of Natural Sciences, Institute of Chemistry, Department of
Inorganic Chemistry, Chemnitz University of Technology, Strasse der
Nationen 62, 09111 Chemnitz, Germany. E-mail: heinrich.lang@
chemie.tu-chemnitz.de; Fax: +49 (0)371 531 21219; Tel: +49 371 531
21210
bFaculty of Natural Sciences, Department of Solid Surfaces Analysis,
Chemnitz University of Technology, Reichenhainer Strasse 70, 09126
Chemnitz, Germany. E-mail: hietschold@physik.tu-chemnitz.de;
Fax: +49 (0)371 531 21639; Tel: +49 371 531 21630
†Electronic supplementary information (ESI) available: Electron diffrac-
tion pattern, TEM images, size distributions, UV/Vis, TGA and NMR
(1H, 13C{H}) data. CCDC reference numbers 815759–815760. For ESI
and crystallographic data in CIF or other electronic format see DOI:
10.1039/c2dt11748g
2738 | Dalton Trans., 2012, 41, 2738–2746
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Scheme 1 Synthesis protocol for the preparation of [(Ph3P)AuO2CCH2(OCH2CH2)nOCH3] (6a, n = 0; 6b, n = 1; 6c, n = 2; 6d, n = 3; 6e, n = 4; 6f,
n = 5; 6g, n = 6).
Table 1 νCO2 absorptions of 4a–g and gold complexes 6a–g
[Au(SC12H25)2] and [(PPh3)AuO2CC13H27)], respectively, for
Au–NP formation. Heating these species to 180 °C resulted in
the formation of Au particles of 26 nm size.25 Other complexes
including gold(I) benzimidazole and imidazoles led to particles
with an average size between 20 to 40 nm.26
We report here on the formation of gold NP by a bottom-up
methodology which does not require the addition of any further
reducing and stabilising components by using the “all-in-one”
gold(I) carboxylates [(Ph3P)AuO2CCH2(OCH2CH2)nOCH3] (n =
0–6) as precursors. These complexes contain the gold source,
and the reducing and stabilising parts in one molecule. The
influence of the ethylene glycol chain length, generation time
and precursor concentration on the Au NP size and size distri-
bution is discussed as well.
Compd.
νasym [cm−1
]
νsym [cm−1
]
Δν [cm−1
]
4a
4b
4c
4d
4e
1597
1597
1591
1605
1605
1603
1602
1598
1603
1599
1653
1614
1622
1651
1322
1323
1330
1322
1321
1321
1322
1434
1433
1434
1436
1436
1436
1437
275
274
261
283
284
282
280
164
170
165
217
178
186
214
4f
4g
6a
6b
6c10b
6d
6e
6f
6g
−
2
Results and discussion
6a–g the carboxylate ions RCO2 can bind to the appropriate
transition metals Ag or Au in a mono-dentate,28 chelating,29 or
μ-bridging30 fashion. The type of bonding is defined by Δν (Δν
= νasym − νsym).31 Mono-dentate-bonded R(O)CO− carboxylates
increase the separation of the corresponding νCO2 frequencies
relative to the values of the free carboxylate ion, usually taken
from the respective sodium or potassium salts.32 The νCO absorp-
tions for the silver- (4d–g) and gold complexes (6a–g) are given
in Table 1. As it can be seen from this Table, the Δν values of
4d–g are at ca. 280 cm−1 pointing to σ-binding of the carboxylic
group to silver. The Δν values of 6a–g are between 164 and
217 cm−1 indicating the same binding mode. The typical Δν
2.1. Synthesis and characterisation
The ethylene glycol-functionalised gold(I) carboxylates [(Ph3P)-
AuO2CCH2(OCH2CH2)nOCH3] (6a–g, n = 0–6) are available
via a four-step synthesis procedure as shown in Scheme 1.
Herein, ethylene glycol monomethyl ethers 2f–g were obtained
by the reaction of ethylene glycols 1f–g with methyl iodide in
presence of silver oxide, while 2d–e were purchased from com-
mercial suppliers. Addition of sodium hydride followed by bro-
moacetic acid to 2d–g gave the appropriate carboxylic acids 3d–
g (please note that 3a–c are commercially available). The silver
salts 4a–g were accessible by treatment of 3a–g with silver oxide
in yields between 60–80% (Experimental section). Transmetalla-
tion of 4a–g with [Au(Ph3P)Cl] (5) produced by concomitant
precipitation of [AgCl] the title gold(I) complexes 6a–g in excel-
lent to virtually quantitative yield. The identity of all newly pre-
pared compounds was proven by elemental analysis as well as
IR and NMR (1H, 13C{1H}, 31P{1H}) spectroscopy. Addition-
ally, high resolution ESI-TOF mass-spectrometry and single
crystal X-ray structure analysis (6a and 6b) were performed.
The reaction of 3a–g with silver oxide to afford 4a–g can be
monitored by IR spectroscopy, since the asymmetric νCO2
vibration typical for 3a–g at ca. 1757 cm−1 is bathochromic
shifted to ca. 1605 cm−1 in 4a–g, when the carboxylic group is
bonded to silver(I). Replacing Ag(I) by Au(I)(PPh3) (formation
of molecules 6a–g) induces a hypsochromic shift of the asym-
value for sodium acetate is 164 cm−1 33
Additionally, the
.
binding character of the carboxylato functionalities was proven
by single crystal X-ray diffraction studies of 6a and 6b, respect-
ively (vide infra).10b,34
Characteristic in the 13C{H} NMR spectra of 4d–g and 6a–g
is the appearance of the carboxylic carbon atom at ca. 177 ppm
for the silver species and at ca. 175 ppm for the corresponding
gold(I) systems (Experimental section).
The structures of 6a and 6b in the solid state were determined
by single crystal X-ray diffraction analysis (Fig. 1). Relevant
crystallographic and structural refinement data are summarised in
the Experimental section. Selected bond distances (Å) and
angles (°) are given in the caption of Fig. 1. Complex 6a crystal-
ˉ
lises in the triclinic space group P1, 6b in the monoclinic space
group P21/c. The P–Au–O unit is, as expected, linear with bond
angles of 174.81(9) (6a) and 178.29(18)° (6b). Similar species
metric νCO2 band to 1603–1652 cm−1 27
.
In complexes 4a–g and
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Fig. 1 Left: ORTEP diagram (50% probability level) of 6a with the atom numbering scheme. All hydrogen atoms are omitted for clarity. Selected
bond distances (Å) and angles (°): P1–Au1 2.2142(11), Au1–O1 2.087(3), O1–C1 1.252(6), C1–O2 1.231(7), P1–Au1–O1 174.81(9), O1–C1–C2
110.6(4), O1–C1–O2 127.4(5), O2–C1–C2 122.0(5). Right: ORTEP diagram (50% probability level) of 6b with the atom numbering scheme. All
hydrogen and disordered atoms are omitted for clarity. Selected bond distances (Å) and angles (°): P1–Au1 2.211(2), Au1–O1 2.047(6), O1–C1 1.265
(11), C1–O2 1.236(11), P1–Au1–O1 178.29(18), O1–C1–C2 124.6(11), O1–C1–O2 124.3(8), O2–C1–C2 109.4(11).
t
have recently been published, i.e. [Au(PPh3)O2CR] (R = Bu,
C2F5) and [Au(PPh3)OSO2CR] (R = Et, Ph) by Schmidbaur and
coworkers.35 The bond angle of the P–Au–O moiety and the
Au–O, P–Au, O–C and C–C bond distances of these species are
similar to that found for 6a and 6b.
following decomposition step includes the release of triphenyl-
phosphine as it could be verified by the detection of fragments
+
+
with m/z = 77 (C6H5 ) and 78 (C6H6 ), respectively. Finally, the
in situ formed organometallic gold(I) alkyl derivative [Au(CH2
(OCH2CH2)6OCH3)] decomposes via Au–C, C–C, and C–O
bond cleavage processes giving gold(0) and the appropriate
organics. Fragments with m/z = 26 (C2H2 ), 29 (C2H5 , CHO+)
+
+
+
2.2 TG and TG-MS studies
and 58 (C2H2O2 , C3H6O+) indicate the formation of CxHyOz
(x ≥ 3) species (Table 2). These in situ formed organics
together with PPh3 are most likely responsible for the narrow
size distribution of the gold nanoparticles (see below).36
The thermal behaviour of the newly synthesised gold(I) com-
plexes 6a–g was studied by TG and TG-MS coupling exper-
iments (TG = Thermogravimetry, MS = Mass Spectrometry), to
gain first information on the decomposition temperature and
mechanism of these species at atmospheric pressure. As an
example, the TG trace of 6g and its first derivation is depicted in
Fig. 2.
2.3 Gold nanoparticle formation and characterisation
For the generation of gold NP, p-xylene solutions of gold(I) com-
plexes 6a–g with concentrations of c = 1 × 10−2–8 × 10−4
M
In general, thermal degradation of complexes 6a–g starts at
ca. 220 °C and is completed at 370 °C. Complexes 6a–g decom-
pose in a three-step processes (ESI†). The appropriate weight
loss was determined by the residues in the TG pan. These results
point to the formation of small impurities (1.3–2.8%) which are
caused by by-products during the decomposition process. In
addition, TG measurements in an oxidative atmosphere were
carried out to minimize organic impurities. As can be seen from
the Table presented in the ESI,† the Δm/m0 values under O2
decreased compared with the measurements performed under
inert gas (N2) indicating that less impurities (0.2–0.6%) in the
gold bulk residue remained. Onset temperature and weight loss
caused by the thermal decomposition of the gold(I) complexes
6a–g are given in the ESI.†
Additionally, TG-MS experiments were carried out to get a
deeper insight into the decomposition mechanism of 6a–g. For
these studies, metal–organic 6g was selected, due to its longest
ethylene glycol chain as well as the best resolution of the TG
trace (Fig. 2, top). The first decomposition occurs between 220
and 275 °C showing only a typical fragment with m/z = 44
corresponding to CO2 clearly indicating that as initial step the
cleavage of the gold-oxygen bond occurs confirming decarboxy-
lation and formation of [(PPh3)AuCH2(OCH2CH2)6OCH3)]. The
Fig. 2 TG (TG = Thermogravimetry) (top) and selected mass-spectro-
metric scans (bottom) of 6g: m/z = 15 (CH3+); m/z = 26 (C2H2+); m/z =
29 (CHO+); m/z = 30 (CH2O+); m/z = 44 (CO2+); m/z = 58 (C2H2O2+);
+
m/z = 78 (C6H6+; amplified by factor 10), (gas flow Ar 40 mL min−1
,
heating rate 5 K min−1).
2740 | Dalton Trans., 2012, 41, 2738–2746
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Table 2 TG–MS data of selected gaseous products formed by the
thermal decomposition of 6g
Mass number (m/z) Fragment
Intensity ion current (Amax)
13
15
26
29
30
31
42
43
44
45
58
59
77
78
CH+
CH3
C2H2
8 × 10−12
7 × 10−11
4 × 10−11
2 × 10−10
9 × 10−11
3 × 10−11
9 × 10−12
2 × 10−11
2 × 10−10
2 × 10−11
+
+
C2H5+, CHO+
C2H6+, CH2O+
CH3O+
C2H2O+
C2H3O+
+
CO2
C2H5O+
C2H2O2+, C3H6O+ 1 × 10−11
C2H3O+ 2+, C3H7O+ 5 × 10−12
Fig. 3 Time dependent UV/Vis spectra of Au NP generated by thermo-
lysis of 6e (c = 6.3 × 10−3 M) (UV/Vis spectra were taken every
30 min).
C6H5+
C6H6
2 × 10−12
8 × 10−12
have been prepared. p-Xylene was chosen as solvent due to its
non-coordinating character and its high boiling point.10b The
advantage of 6a–g, in contrast to other gold(I) sources for the
formation of Au NP is that neither a stabilising nor a reducing
reagent had to be added, since 6a–g contain the stabilising com-
ponents in form of the ethylene glycol and triphenylposphine
ligands. The reduction of gold(I) to gold(0) is performed by
homolytic bond cleavage and bond forming processes (vide
supra). Thermolysis of the appropriate gold(I) p-xylene solutions
resulted in a colour change from colourless to intensive purple
within 40 min indicating the formation of zero-valent Au NP.
These particles are stabilised both by the ethylene glycols and
triphenylphosphine as schematically shown in Scheme 2. Please
note, that for gold(I) carboxylates 6a and 6b no colloidal gold
could be obtained. This is caused by the too-small stabilising
organic matrix generated by 6a and 6b, respectively.
Optical characterisation of the Au NP solutions was performed
by UV/Vis spectroscopy. All colloidal gold solutions show the
typical strong plasmon band in the range of 450–650 nm caused
by the interaction of electromagnetic radiation with the electron
fluctuation of the gold NP (spectra are given in the ESI†). Time-
dependent UV/Vis experiments were carried out to monitor the
progress of NP formation as well as to determine complete con-
versions from appropriate solutions. As an example, 6e was
chosen due to its middle sized ethylene glycol chain. Therefore,
every five minutes a UV/Vis spectrum was recorded (Fig. 3).
The impact of the reaction time within thermolysis is the
growth of the characteristic plasmon band as it can be seen from
Fig. 3. The rise of intensity is caused by an increase of the par-
ticle number due to time progress of thermolysis. In addition, a
bathochromic shift of the plasmon band maximum is observed
indicating an increase of the gold NP size. This band was
determined by deconvolution of the absorption spectra using
four overlapping Gaussian-shaped absorptions.37
These fits are good enough to allow an almost exact overlay of
the sum of the spectral components with the experimental data.
From this data the time for complete decomposition was deter-
mined. As result, the maximum of the intensity was found after
140 min, representing complete decomposition of the precursor
6e. At this time the concentration of gold NP reached its
maximum (Fig. 4). Further heating resulted in particle agglo-
meration and larger particles accompanied by a decrease of the
total number of particles were observed.
Within the time range 0–140 min an almost linear increase of
the absorption maximum from 500 to 520 nm occurred (Fig. 4).
This represents an increase of the average gold NP size during
the whole decomposition process.38 Resulting from deconvolu-
tion, the plasmon full-width-at-half-maximum (FWHM) was
determined showing a linear decrease over time indicating a
closer size distribution of the obtained gold NP (Fig. 4).
The formation of Au NP from 6d–g was confirmed by elec-
tron diffraction studies. The gold NP have an fcc lattice structure.
The ring pattern could be indexed as derived from Au (111),
(200), (220), (222) and (311) lattice planes (ESI†).15e
The particle size, size distribution and shape of the Au NP
were determined by transition electron microscopy (TEM)
revealing an average size diameter between 3.3 ( 0.6)–6.5 ( 0.9)
nm depending on the ethylene glycol chain length of the
Fig. 4 Time-dependent FWHM (full-width-at-half-maximum) and
intensity of the plasmon band obtained by deconvolution of the time
dependent UV/Vis studies (6e) (c = 6.3 × 10−3 M).
Scheme 2 Thermolysis of 6a–g and schematic view of stabilised Au
NP.
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Table 3 Comparison of generated Au NP sizes after 1, 2 and 3 h
thermolysis
NP size [nm]
Compd.
1 h
2 h
3 h
a
a
6c10b
6d
6e
6f
6g
4.0 ( 1.0)
3.4 ( 0.4)
3.9 ( 0.9)
3.3 ( 0.6)
4.4 ( 0.7)
—
—
—
a
6.3 ( 0.8)
5.2 ( 0.6)
5.2 ( 0.6)
5.6 ( 1.1)
6.5 ( 0.9)
5.9 ( 0.7)
5.6 ( 1.2)
a No Au particles obtained, caused by the in situ formed small organic
matrix and hence agglomeration of the Au colloids takes place.
appropriate carboxylic ligand, the generation time and the pre-
cursor concentration. It has been shown that a magnification of
ethylene glycol chain length increases the stability of the NP
(Table 3). It should be mentioned that Au NP generated from 6c
are not stable for more than 1 h. For 6d the stability increases to
2 h caused by the larger organic framework which better can
prevent agglomeration under thermolysis conditions. Best results
were obtained applying 6e–g (Table 3).
In addition, the Au NP size depends on the concentration of
the appropriate precursor solution. For these studies we choose
6e with five –CH2OCH2– repeating units representing a complex
with sufficient donating functionalities for the stabilisation of the
formed Au NP. A high precursor concentration of 6e (1.6 × 10−2
M) resulted in the formation of an average particle size diameter
of 6.3 ( 0.8) nm, while low concentrations (7.8 × 10−4 M) pro-
duced smaller particles of 4.5 ( 0.9) nm diameter (Fig. 7). The
size distribution is not affected by changing the concentration,
which is in agreement with previous work.10b This effect is
caused by a higher particle density which leads to an higher
probability of colliding resulting in larger Au NP formation.
Typical TEM images and corresponding size distributions of the
obtained samples at different concentrations are presented in
Fig. 7.
Fig. 5 TEM images and size distributions of Au NP received by ther-
molysis after 2 h of 6d (A; 6.3 ( 0.8) nm) and 6g (B; 5.6 ( 1.1) nm)
(c = 6.3 × 10−3 M).
Compared to literature methods dealing with thermally
induced Au, NP generated from Au(I) precursors showed that the
particles obtained by the “single source” methodology described
herein are smaller and more narrow size distributed. Particles
synthesised by Stuky et al. and Nakamoto et al. are in almost the
same range (3.5–8.3 nm), however different stabilising com-
ponents (primary alkylamines or dodecanethiole) and reducing
reagents (e.g., butylamine borane) are needed.21,23
Significantly larger particles (20 to 40 nm), in contrast to our
methodology,
were
received
using
[C14H29N(CH3)3]
[Au(SC12H25)2], [(PPh3)AuO2CC13H27)] or gold-benzimidazole/
imidazoles as gold(I) source.22,26 Nearly mono-disperse particles
were obtained from Au(I) halides (Cl, Br) in oelamine within 4
and 12 nm size.24 The Au NP received by our method are not
monodisperse but exhibited a relatively small size distribution.
However, the approach discussed here requires neither additional
stabiliser nor reducing reagents and hence a simplification of the
gold NP preparation is achieved.
Furthermore it was found that different ethylene glycol chain
lengths result in a slight decrease of the average size for the
same generation time. A higher number of donating functional-
ities results in a more efficient stabilisation of the Au NP and
thus in slower particle growth (Fig. 5). An extension of the gen-
eration time from one to three hours resulted in an increase of
the Au NP sizes due to gradually agglomeration, as seen in
Fig. 6 using exemplary 6f as gold source.
Remarkable of the methodology described herein is the sharp
size distribution obtained by thermolysis of metal-organics 6c–g.
Studies on the stability of the Au NP showed that the particles
generated by these gold(I) complexes are stable for at least 5 h
under thermolysis conditions (138 °C). In contrast, the stability
on the respective Au NP increases significantly to more than two
weeks at ambient temperature.
Removing the solvent resulted in agglomeration of the respect-
ive Au nanoparticles and hence redispersion of the colloids was
not possible. The obtained particle sizes are in a similar range to
the Brust-Schiffrin method, as well as to the synthesis strategies
using different low molecular mass colloid stabilisers such as
oligo ethers, sodium citrate or low generation dendrimers.12
Fig. 6 TEM images and size distributions of Au NP obtained by ther-
molysis of 6f after 1 h (A; 3.3 ( 0.6) nm) and 3 h (B; 5.9 ( 0.7) nm)
(c = 6.3 × 10−3 M) in p-xylene.
2742 | Dalton Trans., 2012, 41, 2738–2746
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stabilisation upon thermolysis without addition of any further
stabilising and reducing components in a non-coordinating
solvent like p-xylene. TG-MS coupling experiments showed that
as initial step decarboxylation of the carboxylate occurs, fol-
lowed by elimination of PPh3 providing [AuCH2O(CH2CH2O)n-
CH3]. Finally, the respective gold(I) alkyl species decompose via
Au–C, C–C, and C–O homolytic bond cleavage and formation
processes providing the appropriate ethylene glycol-based organ-
ics to stabilise the gold colloids together with PPh3. Depending
on the ethylene glycol chain length, the generation time and the
concentration, Au NP sizes between 3.3 ( 0.6) and 6.5 ( 0.9)
nm were formed. It was found that longer ethylene glycol chain
lengths increase the stability of Au NP at thermolysis conditions
(138 °C, refluxing p-xylol). Additionally, the particle growth is
slower for longer chain lengths. The best stabilising effect is
observed with chain lengths ≥3 –OCH2CH2– repeating units.
The particle size is influenced by the concentration of the stock
solution, whereby higher concentrations (1.6 × 10−2 M) resulted
in the formation of larger particles (6.3 ( 0.8) nm), due to an
increased probability of particle colliding. In contrast, lower con-
centrations (7.8 × 10−4 M) produced smaller Au NP (4.5 ( 0.9)
nm), due to less probability of colliding and hence limited par-
ticle growth.
Fig. 7 TEM images and size distributions of Au NP received by ther-
molysis of 6e at different concentrations: c = 7.8 × 10−4 M (A; 4.5
( 0.9) nm); c = 6.3 × 10−3 M (B; 5.2 ( 0.6) nm); c = 1.6 × 10−2 M (C;
6.3 ( 0.8) nm).
4
Experimental
4.1 Materials and instruments
All synthesis procedures were performed under argon atmos-
phere with the solvents and reagents degassed prior to use. Mol-
ecules 2e–g were prepared according to the procedure described
by Saufé et al.44 Carboxylic acids 3d–g were prepared following
the synthesis method reported by Kunz et al.45 Silver oxide was
prepared according to standard methods.46 Silver(I) carboxylates
4a–c were synthesized in analogy to the methodology described
by Steffan et al.47 All other chemicals were commercially avail-
able and were used without further purification. 1H NMR spectra
were recorded with a Bruker Avance III 500 spectrometer operat-
ing at 500.30 MHz in the Fourier transform mode; 13C{1H}
NMR spectra were recorded at 125.80 MHz and the 31P{1H}
spectra at 202.53 MHz. Chemical shifts are reported in parts per
million (δ) relative to tetramethylsilane for 1H and 13C{1H}
NMR spectra, and external 85% H3PO4 for 31P{1H} NMR
spectra. The melting points of analytical pure samples (sealed
off in N2 purged capillaries) were determined using a Gallen-
kamp MFB 595 010 M melting point apparatus. Microanalyses
were performed with a Thermo FLASHEA 1112 Series instru-
ment. Infrared spectra were recorded with a FT-Nicolet IR 200
spectrometer. UV/Vis absorption spectra were recorded using a
Thermo Genesys 6 spectrophotometer. High resolution mass
spectra were recorded using a micrOTOF QII Bruker Daltonite
workstation. Transmission Electron Microscopy (TEM) imaging
was performed with a PHILIPS CM 20 instrument operated at
200 kV. TG-MS experiments were determined by using a
Mettler Toledo TGA/DSC1 1600 system with an MX1 balance
coupled with a Pfeiffer Vacuum MS ThermoStar GSD 301
T2 mass spectrometer. TG experiments were performed on a
Mettler Toledo TGA/DSC1 1100 system with an UMX1
balance.
The advantage of the “all-in-one” precursor for gold colloid
formation and stabilisation, [(Ph3P)AuO2CCH2(OCH2CH2)n-
OCH3] (n = 0–6), over so far well-established Au(I) and Au(III)
species24–26 is that the gold carboxylates 6a–g combine the gold
source with the stabilizing and reducing components in one mol-
ecule. For this reason, no additional stabiliser and reducing com-
ponent, which may contaminate the NP stock solutions, had to
be added. For example, H[AuCl4] releases chloride within the
reducing process, while the addition of a reducing reagent such
as Na[BH4] to hydrogen tetrachloroaurate produce H3[BO4] and
NaCl as impurities.39
The unique properties of the “all-in-one” gold(I) ethylene
glycol carboxylate precursors [(Ph3P)AuO2CCH2(OCH2CH2)n-
OCH3] (n = 0–6) enable a variety of uses. One is the use of the
respective gold(I) carboxylates 6c–g in spin- and spray-coating
processes for gold deposition. A further benefit of 6c–g is their
use as particle-free MOD ink for inkjet printing of gold layers
and patterns similar to the method recently described for a
similar silver precursor.40 The respective gold(I) carboxylates are
also of interest in catalysis. Claus et al. showed that the hydro-
genation of citral is catalyzed by gold41 and silver42,43 particles.
Therefore, silica carriers have been loaded with the gold(I) car-
boxylates producing, after a calcination process, gold-coated or
gold NP-coated silica (depending on temperature). These studies
are at present under development.
3
Conclusions
The newly synthesized gold(I) carboxylates 6c–g (n = 2–6) can
successfully be used as precursors for gold NP generation and
This journal is © The Royal Society of Chemistry 2012
Dalton Trans., 2012, 41, 2738–2746 | 2743

View Article Online
4.2 Synthesis
177.7 (s, OCOCH2). HRMS: m/z: calcd for C15H29AgO9:
461.0935; found 461.0938 [M+H]+.
[AgO2CCH2(OCH2CH2)3OCH3] (4d). Freshly prepared silver
oxide (0.52 g, 0.22 mmol) was suspended in ethanol (20 mL)
and this mixture was slowly treated with HO2CCH2(OCH2-
CH2)3OCH3 (1d) (1.00 g, 0.44 mmol) diluted in ethanol (5 mL).
Afterwards, the reaction mixture was heated to 50 °C for 2 h.
After cooling it to ambient temperature it was filtered through a
pad of Celite. The solution was reduced to 3 mL and an excess
of nhexane (80 mL) was added. The suspended solution was dec-
anted and the thus obtained residue was dried in oil pump
vacuum to afford pale brown waxy 4d. Yield: 1.14 g (79% based
on 3d) Mp: 109 °C. Anal. calcd for C9H17AgO6 (329.10): C
32.85, H 5.21 found: C 32.52, H 5.24. FT-IR (KBr, cm−1): 2896
[(Ph3P)AuO2CCH2OCH3] (6a). To triphenylphosphine gold(I)
chloride (0.9 g, 1.82 mmol) dissolved in toluene (20 mL) was
added 4a (0.36 g, 1.82 mmol) in an single portion. The slurry
was stirred for 12 h at ambient temperature in the absence of
light, followed by filtration of the reaction mixture through a pad
of Celite. Afterwards, the remaining residue was washed twice
with toluene (15 mL). Evaporation of all volatiles from the elute
in oil-pump vacuum gave colourless 6a. Yield: 0.92 g (92%
based on 4a). Mp: 152 °C. Anal. calcd. for C21H20AuO3P
(548.32): C 46.00, H 3.68 found: C 46.27, H 3.56. FT-IR (KBr,
cm−1): 2925(m), 1598 (s), 1434 (s), 1271 (m) 1101 (s), 710 (m),
691 (m).1H NMR (CDCl3) 3.44 (s, 3 H), 4.01 (s, 2 H),
7.44–7.53 (m, 15 H). 13C NMR (CDCl3) 58.8, 72.6, 128.4 (d,
1
(s), 1605 (s), 1425 (w), 1411 (w), 1322 (m), 1107 (s). H NMR
(500 MHz, CD3OD): δ = 3.35 (s, 3H, s, 3 H, OCH3), 3.53 (m, 2
H, CH2), 3.61 (m, 2 H, CH2), 3.64 (m, 4 H, CH2), 3.69 (m, 4 H,
CH2), 4.00 (s, 2 H, OCOCH2). 13C NMR (125 MHz, CD4O) δ =
59.5 (s, OCH3), 71.2–71.5 (6 C, CH2), 73.0 (s, OCOCH2), 177.4
(s, OCOCH2). HRMS: m/z: calcd for C9H18AgO6: 329.0149;
found 329.0138 [M+H]+.
1
p
iC, JCP = 64.54 Hz), 129.1 (d, JCP = 11.9 Hz), 131.9 (d, C,
4JCP = 2.54 Hz), 133.0 (d, JCP = 13.59 Hz), 175.0. 31P NMR
(202 MHz, CDCl3) 27.61. HRMS: m/z: calcd for
C39H35Au2O3P2: 1007.1387; found: 1007.1414 [M+Ph3PAu]+.
[(Ph3P)AuO2CCH2OCH2CH2OCH3] (6b). Colourless 6b was
prepared according to the synthesis procedure described for 6a.
In this respect, [Au(PPh3)Cl] (0.5 g, 1.01 mmol) was reacted
with 4b (0.24 g, 1.01 mmol). Yield: 0.52 g (86% based on 4b).
Mp: 111 °C. Anal. calcd. for C23H24AuO4P (592.37): C 46.63,
H 4.08 found: C 46.24, H 4.09. FT-IR (KBr, cm−1): 2922 (m),
1603 (s), 1477 (w), 1460 (w), 1433 (m), 1099 (s), 711 (m), 692
[AgO2CCH2(OCH2CH2)4OCH3] (4e). Pale brown 4e was iso-
lated as described for the synthesis of 4d. Thus, silver oxide
(0.44 g, 0.2 mmol) was reacted with HO2CCH2(OCH2CH2)4-
OCH3 (1e) (1.00 g, 0.4 mmol) Yield: 1.15 g (77% based on 3e)
Mp: 106 °C. Anal. calcd for C11H21AgO7 (371.15): C 35.41, H
5.67 found: C 35.73, H 5.78. FT-IR (KBr, cm−1): 2896 (s), 1605
(s), 1424 (w), 1409 (w), 1321 (m), 1102 (s). 1H NMR (CD3OD):
δ = 3.33 (s, 3H, s, 3 H, OCH3), 3.56 (m, 2H, CH2), 3.65 (m, 14
H, CH2), 3.88 (s, 2H, OCOCH2). 13C NMR (125 MHz, CD4O)
δ = 59.6 (s, OCH3), 71.1–71.5 (8 C, CH2), 72.9 (s, OCOCH2),
177.7 (s, OCOCH2). HRMS: m/z: calcd for C11H21AgO7:
373.0411; found 373.0365 [M+H]+.
1
(m). H NMR (CDCl3) 3.39 (s, 3 H), 3.61 (m, 2 H), 3.77 (m, 2
H), 4.15 (s, 2 H), 7.43–7.52 (m, 15 H). 13C NMR (CDCl3) 59.0,
i
1
70.3, 71.38, 72.0, 128.5 (d, C, JCP = 64.48 Hz), 129.2 (d, JCP
= 12.04 Hz), 132.0 (d, pC, 4JCP = 2.45 Hz), 134.2 (d, JCP = 13.5
Hz), 175.4. 31P NMR (202 MHz, CDCl3) 27.64. HRMS: m/z:
calcd for C23H24AuO4P: 593.1150; found: 593.1155 [M+H]+.
[AgO2CCH2(OCH2CH2)5OCH3] (4f). Pale brown 4f was iso-
lated as described for the synthesis of 4d. Thus, silver oxide
(0.19 g, 0.80 mmol) was reacted with HO2CCH2(OCH2CH2)5-
OCH3 (1f) (0.50 g, 1.6 mmol). Yield: 0.43 g (64% based on 3f)
Mp: 106 °C. Anal. calcd for C13H25AgO8 (417.20): C 37.43, H
6.04 found: C 37.06, H 6.34. FT-IR (KBr, cm−1): 2899 (s), 1603
(s), 1425 (w), 1408 (w), 1321 (m), 1106 (s). 1H NMR (CD3OD):
δ = 3.27 (s, 3H, OCH3), 3.52 (m, 2 H, CH2), 3.60 (m, 2 H,
CH2), 3.66 (m, 16 H, CH2), 3.89 (s, 2 H, OCOCH2). 13C NMR
(125 MHz, CD4O) δ = 59.3 (s, OCH3), 70.9 (s, CH2) 71.1–71.4
(8 C, CH2), 71.6 (s, CH2), 73.0 (s, OCOCH2), 177.6 (s,
OCOCH2). HRMS: m/z: calcd for C13H25AgO8: 417.0673;
found 417.0667 [M+H]+.
[(Ph3P)AuO2CCH2(OCH2CH2)3OCH3] (6d). The colourless
oil 6d was obtained according to the synthesis procedure
described for 6a. In this respect, [Au(PPh3)Cl] (1.0 g,
2.02 mmol) was reacted with 4d (0.67 g, 2.02 mmol). Yield:
1.31 g (96% based on 4d). Anal. calcd. for C27H32AuO6P
(680.48): C 47.66, H 4.74 found: C 47.29, H 4.81. FT-IR (NaCl,
cm−1): 2877 (s), 1653 (s), 1480 (m), 1436 (m), 1102 (s), 712
(m), 695 (m). 1H NMR (CDCl3): δ = 3.37 (s, 3H, s, 3 H,
OCH3), 3.54 (m, 2H, CH2), 3.68 (m, 8 H, CH2), 3.77 (m, 2 H,
CH2), 4.14 (s, 2H, OCOCH2), 7.45–7.56 (m, 15 H, CH). 13C
NMR (CDCl3) δ = 59.2 (s, OCH3), 70.6–70.8 (6 C, CH2), 72.1
i
1
(s, OCOCH2), 128.7 (d, C, JCP = 64.51 Hz), 129.4 (d, JCP
=
11.87 Hz), 132.2 (d, pC, 4JCP = 2.12), 134.3 (d, JCP = 13.48 Hz),
176.0 (s, OCOCH2). 31P NMR (202 MHz, CDCl3) 27.84.
HRMS: m/z: calcd for C27H32AuO6P: 681.1675; found:
681.1686 [M+H]+.
[AgO2CCH2(OCH2CH2)6OCH3] (4g). Pale brown 4g was iso-
lated as described for the synthesis of 4d. In this respect, silver
oxide (0.16 g, 0.7 mmol) was reacted with HO2CCH2(OCH2-
CH2)6OCH3 (1g) (0.50 g, 1.4 mmol). Yield: 0.46 g (71% based
on 3g). Mp: 105 °C. Anal. calcd for C15H29AgO9 (461.15): C
39.06, H 6.34 found: C 38.86, H 5.99. FT-IR (KBr, cm−1): 2900
[(Ph3P)AuO2CCH2(OCH2CH2)4OCH3] (6e). The colourless
oil 6e was synthesized as described for 6a. Thus, [Au(PPh3)Cl]
(0.64 g, 1.3 mmol) was reacted with 4e (0.50 g, 1.3 mmol).
Yield: 0.83 g (89% based on 4e). Anal. calcd. for C29H36AuO7P
(724.53): C 48.07, H 5.01 found: C 47.92, H 5.14. FT-IR (NaCl,
cm−1): 2876 (m), 1614 (s), 1479 (m), 1436 (m), 1102 (s), 713
(m), 693 (m). 1H NMR (CDCl3): δ = 3.37 (s, 3H, s, 3 H,
OCH3), 3.54 (m, 2H, CH2), 3.65 (m, 12 H, CH2), 3.75 (m, 2 H,
1
(s), 1602 (s), 1422 (w), 1409 (w), 1322 (m), 1106 (s). H NMR
(CD3OD): δ = 3.33 (s, 3H, OCH3), 3.52 (m, 2 H, CH2), 3.63 (m,
22 H, CH2), 3.86 (s, 2 H, OCOCH2). 13C NMR (125 MHz,
CD4O) δ = 59.2 (s, OCH3), 70.8 (s, CH2), 71.0 (s, CH2), 71.1 (s,
CH2), 71.2–71.5 (8 C, CH2), 71.6 (s, CH2), 73.0 (s, OCOCH2),
2744 | Dalton Trans., 2012, 41, 2738–2746
This journal is © The Royal Society of Chemistry 2012

View Article Online
CH2), 4.13 (s, 2H, OCOCH2), 7.44–7.56 (m, 15 H, CH). 13C
NMR (CDCl3) δ = 59.1 (s, OCH3), 70.5–71.3 (8 C, CH2), 72.0
collected on an Oxford Gemini S diffractometer at 100 K using
Cu-Kα (λ = 1.54184 Å) radiation. The structures were solved by
direct methods and refined by full-matrix least square procedures
on F2.48 All non-hydrogen atoms were refined anisotropically
and a riding model was employed in the refinement of the hydro-
gen atom positions. For 6b a minor disorder in the ethylene
glycol chain (ratio 0.60 : 0.40) has been observed. CCDC refer-
ence numbers 815759–815760. For crystallographic data in CIF
or other electronic format see DOI: 10.1039/c2dt11748g
i
1
(s, OCOCH2), 128.7 (d, C, JCP = 64.95 Hz), 129.3 (d, JCP
=
11.92 Hz), 132.3 (d, pC, 4JCP = 2.39), 134.7 (d, JCP = 13.49 Hz),
175.2 (s, OCOCH2). 31P NMR (202 MHz, CDCl3) 27.62.
HRMS: m/z: calcd For C29H36AuO7PNa: 747.1756; found:
747.1757 [M+Na]+.
[(Ph3P)AuO2CCH2(OCH2CH2)5OCH3] (6f). The colourless
oil 6f was synthesized according to the methodology described
for 6a. Thus, [Au(PPh3)Cl] (0.35 g, 0.08 mmol) was reacted
with 4f (0.41 g, 0.08 mmol). Yield: 0.55 g (85% based on 4f).
Anal. calcd. for C31H40AuO8P (768.58): C 48.44, H 5.25 found:
C 48.61, H 5.17. FT-IR (NaCl, cm−1): 2872 (s), 1622 (s), 1480
Crystal data for 6a. C23H24AuO4P, M = 592.36 g mol−1
,
crystal dimensions 0.25 × 0.18 × 0.18 mm, T = 100 K, monocli-
nic, P21/c, a = 8.9363(2), b = 24.5432(6), c = 9.8595(3) Å, β =
92.335(2)°, V = 2160.64(10) Å3, Z = 4, ρc = 1.821 g cm−3, μ =
13.714 mm−1, θ range = 4.84– 61.99°, reflections collected:
8041, independent: 3306 (Rint = 0.0351), R1 = 0.0405, wR2 =
0.1181 [I > 2σ(I)].
1
(w), 1436 (m), 1102(s), 712 (m), 694 (m). H NMR (CDCl3): δ
= 3.37 (s, 3H, s, 3 H, OCH3), 3.54 (m, 2H, CH2), 3.64 (m, 14 H,
CH2), 3.71 (m, 2 H, CH2), 3.77 (m, 2 H, CH2), 4.14 (s, 2H,
OCOCH2), 7.44 ≥ 7.55 (m, 15 H, CH). 13C NMR (CDCl3) δ =
60.0 (s, OCH3), 70.4–70.6 (10 C, CH2), 71.9 (s, OCOCH2),
Crystal data for 6b. C21H20AuO3P, M = 548.31 g mol−1
,
crystal dimensions 0.25 × 0.20 × 0.20 mm, T = 100 K, triclinic,
i
1
128.6 (d, 3 C, JCP = 64.24 Hz), 129.2 (d, 6 CH, JCP = 12.22
ˉ
P1, a = 7.1087(3), b = 11.0927(4), c = 11.9697(5) Å, α =
4
Hz), 132.0 (d, 3pCH, JCP = 2.55), 134.2 (d, 6 CH, JCP = 13.52
91.716(3), β = 98.636(3), γ = 91.676(3)°, V = 932.20(6) Å3, Z =
2, ρc = 1.953 g cm−3, μ = 15.789 mm−1, θ range = 3.99–62.18°,
reflections collected: 8014, independent: 2931 (Rint = 0.0189),
R1 = 0.0277, wR2 = 0.0726 [I > 2σ(I)].
Hz), 175.3 (s, OCOCH2).31P NMR (202 MHz, CDCl3) 27.76.
HRMS: m/z: calcd for C31H40AuO8PNa: 791.2019; found:
791.2064 [M+Na]+.
[(Ph3P)AuO2CCH2(OCH2CH2)6OCH3] (6g). The colourless
oil 6g was synthesized as described for 6a. In this respect,
[Au(PPh3)Cl] (0.35 g, 0.08 mmol) was reacted with 4g (0.38 g,
0.08 mmol). Yield: 0.61 g (99% based on 4g). Anal. calcd. for
C33H44AuO9P (812.64): C 48.77, H 5.46 found: C 48.59, H
5.48. FT-IR (NaCl, cm−1): 2871 (s), 1651 (s), 1481 (w), 1437
Acknowledgements
We gratefully acknowledge the Deutsche Forschungs-
gemeinschaft (IRTG, GRK 1215 - Materials and Concepts for
Advanced Interconnects and Nanosystems) and the Fonds der
Chemischen Industrie for generous financial support.
1
(m), 1103 (s), 712 (m), 695 (m). H NMR (CDCl3): δ = 3.37 (s,
3H, s, 3 H, OCH3), 3.54 (m, 2H, CH2), 3.65 (m, 18 H, CH2),
3.71 (m, 2 H, CH2), 3.76 (m, 2 H, CH2), 4.13 (s, 2H, OCOCH2),
7.46–7.56 (m, 15 H, CH). 13C NMR (CDCl3) δ = 59.0 (s,
OCH3), 70.4–70.7 (12 C, CH2), 71.9 (s, OCOCH2), 128.6 (d, iC,
1JCP = 63.77 Hz), 129.2 (d, CH, JCP = 11.90 Hz), 132.0 (d,
Notes and references
1 (a) H. Wohltjen and A. W. Snow, Anal. Chem., 1998, 70, 2856;
(b) A. G. Kanaras, F. S. Kamounah, K. Schaumburg, C. J. Kiely and
M. Brust, Chem. Commun., 2002, 2249; (c) O. D. Velev and S. Gupta,
Adv. Mater., 2009, 21, 1897; (d) M. Calderón, M. A. Quadir, M. Strumia
and R. Haag, Biochimie, 2010, 92, 1242.
2 (a) D. Compton, L. Cornish and E. van der Lingen, Gold Bull., 2003, 36,
10; (b) S. Link, A. Beeby, S. F. Gerald, M. A-El-Sayed, T. G. Schaaff and
R. L. Whetten, J. Phys. Chem. B, 2002, 106, 3410; (c) G. Palui, S. Ray
and A. Banerjee, J. Mater. Chem., 2009, 19, 3457; (d) S. Link and
M. A. El-Sayed, Int. Rev. Phys. Chem., 2000, 19, 409.
4
pCH, JCP = 2.33), 134.2 (d, CH, JCP = 13.59 Hz), 175.3 (s,
OCOCH2). 31P NMR (202 MHz, CDCl3) 28.65. HRMS: m/z:
calcd for C33H44AuO9P: 813.2461; found: 813.2489 [M+H]+.
4.3 Gold nanoparticle generation
3 (a) D. L. Feldheim and C. D. Keating, Chem. Soc. Rev., 1998, 27, 1;
(b) V. D. Nithya and R. K. Selvan, Phys. B, 2011, 406, 24;
(c) A. K Singh, Adv. Powder Technol., 2010, 21, 609.
4 (a) S. Laurent, D. Forge, M. Port, A. Roch, C. Robic, L. V. Elst and R.
N. Muller, Chem. Rev., 2008, 108, 2064; (b) Q. Ge, J. Su, T.-S. Chung
and G. Amy, Ind. Eng. Chem. Res., 2011, 50, 382; (c) B. Zhang,
B. Chen, Y. Wanga, F. Guo, Z. Li and D. Shi, J. Colloid Interface Sci.,
2011, 353, 426; (d) Z-A. Lin, J-N. Zheng, F. Lin, L. Zhang, Z. Caic and
G-N. Chen, J. Mater. Chem., 2011, 21, 518.
5 (a) M. Haruta and M. Daté, Appl. Catal., A, 2001, 222, 427; (b) A. Villa,
G. M. Veith and L. Prait, Angew. Chem., Int. Ed., 2010, 49, 4499–4502;
(c) R. Narayanan and M. A. El-Sayed, J. Phys. Chem. B, 2005, 109,
12663; (d) G. Kyriakou, S. K. Beaumont, S. M. Humphrey, C. Antonetti
and R. M. Lambert, ChemCatChem, 2010, 2, 1444; (e) V. Calò, A. Nacci,
A. Monopoli and P. Cotugno, Chem.–Eur. J., 2009, 15, 1272; (f) V. Calò,
A. Nacci and A. Monopoli, J. Mol. Catal. A: Chem., 2004, 214, 45.
6 (a) J. Zhou, J. Ralstron, R. Sedev and D. A. Battie, J. Colloid Interface
Sci., 2009, 331, 251–262; (b) S-A. Dong, S-P. Zhou and Mater, Mater.
Sci. Eng., B, 2007, 140, 153; (c) S. Park and K. Hamad-Schifferli,, Curr.
Opin. Chem. Biol., 2010, 14, 616; (d) M. Wang and M. Thanou, Pharma-
col. Res., 2010, 62, 90; (e) A. Ethirajan and K. Landfester, Chem.–Eur.
For gold NP formation, Au(I) complexes 6c–g were dissolved in
p-xylene (c = 1.6 × 10−2 M, 6.3 × 10−3 M, 7.8 × 10−4 M) and
the appropriate reaction solution was stirred for 10 min at
ambient temperature. Afterwards, it was heated rapidly to reflux.
Within 1 h of heating the colour changed from colourless to
purple. After heating, the appropriate reaction solution was
rapidly cooled to ambient temperature using an ice bath. The cor-
responding colloidal gold solutions were used as obtained
without further purification, since no reducing and further stabi-
lising components were used.
4.4 Crystal structure determinations
Single crystals of 6a and 6b suitable for X-ray diffraction analy-
sis were obtained by crystallisation from concentrated diethyl
ether solutions containing 6a or 6b at −30 °C. Data were
This journal is © The Royal Society of Chemistry 2012
Dalton Trans., 2012, 41, 2738–2746 | 2745

View Article Online
J., 2010, 16, 9398; (f) R. Costi, A. E. Saunders and U. Banin, Angew.
Chem., Int. Ed., 2010, 49, 4878; (g) C. Marambio-Jones and
E. M. V. Hoek, J. Nanopart. Res., 2010, 12, 1531.
7 (a) E. Gaffet, M. Tachikart, O. E. Kedim and R. Rahouadj, Mater.
Charact., 1996, 36, 185; (b) G. M. Whitesides and J. C. Love, Sci. Am.,
2001, 39; (c) S. Eustis and M. A. El-Sayed, Chem. Soc. Rev., 2006, 35,
209; (d) N. N. Kariuki, J. Luo, M. M. Maye, S. A. Hassan, T. Menard, H.
R. Naslund, Y. H. Lin, C. M. Wang, M. H. Engelhard and C. J. Zhong,
Langmuir, 2004, 20, 11240; (e) N. R. Jana, L. Gearheart and C.
J. Murphy, Chem. Mater., 2001, 13, 2313.
22 S. Gomez, K. Philippot, V. Colliere, B. Chaudret, F. Senocq and
P. Lecante, Chem. Commun., 2000, 1945–1946.
23 M. Yamamoto, Y. Kashiwagi and M. Nakamoto, Z. Naturforsch., 2009,
64b, 1305–1311.
24 X. Lu, H.-Y. Tuan, B. A. Korgel and Y. Xia, Chem.–Eur. J., 2008, 14,
1584–1591.
25 M. Nakamoto, M. Yamamoto and M. Fukusumi, Chem. Commun., 2002,
1622–1623.
26 S. J. Hsu, K. M. Hsu, Max K. Leonga and Ivan J. B. Lin, Dalton Trans.,
2008, 1924–1931.
8 (a) C. Fu, H. Zhou, D. Xie, L. Sun, Y. Yin, J. Chen and Y. Kuang,
Colloid Polym. Sci., 2010, 288, 1097; (b) B. Nikoobakht, Z. L. Wang and
M. A. El-Sayed, J. Phys. Chem. B, 2000, 104, 8635; (c) Y. Y. Yu, S.
S. Chang, C. L. Lee and C. R. Chris Wang, J. Phys. Chem. B, 1997, 101,
6661.
27 D. I. Nichols and A. S. Charleston, J. Chem. Soc. A, 1969, 2581.
28 (a) F. A. Cotton and W. H. Tbsley, Inorg. Chem., 1982, 21, 300;
(b) M. A. Gil, W. Maringgele, S. Dechert and F. Meyer, Z. Anorg. Allg.
Chem., 2007, 633, 2178.
29 (a) J. N. Van Niekerk, F. R. L. Schoening and J. H. Talbot, Acta Crystal-
logr., 1953, 6, 720; (b) N. W. Alcock and V. L. Tracy, Acta Crystallogr.,
1971, B35, 406.
9 E. I. Isaeva, M. Y. Kim, V. V. Gorbunova and T. B. Boitsova,
Russ. J. Gen. Chem., 2007, 77, 812.
10 (a) S. F. Jahn, T. Blaudeck, A. Jakob, P. Ecorchard, T. Rüffer, H. Lang
and R. R. Baumann, Chem. Mater., 2010, 22, 3067; (b) A. Tuchscherer,
D. Schaarschmidt, S. Schulze, M. Hietschold and H. Lang, Inorg. Chem.
Commun., 2011, 14, 676.
11 J. Turkevitch, P. C. Stevenson and J. Hillier, Discuss. Faraday Soc.,
1951, 11, 55–75.
30 (a) Y. B. Koh and G. G. Christoph, Inorg. Chem., 1978, 17, 2590;
(b) J. E. Davis, B. M. Gatehouse and K. S. Murray, J. Chem. Soc.,
Dalton Trans., 1973, 2523.
31 G. B. Deacon and R. J. Phillips, Coord. Chem. Rev., 1980, 33, 227–250.
32 K. Nakamoto, Infrared Spectra of Inorganic and Coordination Com-
pounds, Wiley, New York, 1963, 198.
12 M. Brust, M. Walker, D. Bethell, D. Schiffrin and R. Whyman, J. Chem.
Soc., Chem. Commun., 1994, 801–802.
33 G. B. Deacon, F. Huber and R. J. Phillips, Inorg. Chim. Acta, 1985, 104,
41–45.
13 (a) V. Delmas, S. Grugeon, R. Herrera Urbina, P-Y. Silvert and
K. Tekaia-Elhsissen, Nanostruct. Mater., 1999, 11, 1277; (b) C-H. Wang,
C-J. Liu, C-L. Wang, T.-E. Hua, J. M. Obliosca, K. H. Lee, Y Hwu,
C-S. Yang, R-S. Liu, H-M. Lin, J-H. Je and G Margaritondo, J. Phys. D:
Appl. Phys., 2008, 41, 1; (c) M. Maccarini, G. Briganti, S. Rucareanu,
X.-D. Lui, R. Sinibaldi, M. Sztucki and R. B. Lennox, J. Phys. Chem. B,
2010, 114, 6937.
14 (a) J. Zhou, J. Ralston, R. Sedev and D. A. Beattie, J. Colloid Interface
Sci., 2009, 331, 251; (b) G. A. Nimola and K. Pandian, Colloids Surf., A,
2006, 290, 138; (c) G. V. Ramesh, S. Porel and T. P. Radhakrishnan,
Chem. Soc. Rev., 2009, 38, 2646; (d) R. M. Stoltenberg, C. Liu and
Z. Bao, Langmuir, 2011, 27 (1), 445.
15 (a) E. Boisselier, A. K. Diallo, L. Salmon, C. Ornelas, J. Ruiz and
D. Astruc, J. Am. Chem. Soc., 2010, 132, 2729; (b) F. Gröhn, B. J. Bauer,
Y. A. Akpalu, C. L. Jackson and E. J. Amis, Macromolecules, 2000, 33,
6042; (c) K. Esumi, Top. Curr. Chem., 2003, 227, 31; (d) R. Haag and
F. Vögtle, Angew. Chem., Int. Ed., 2004, 43, 272; (e) S. Dietrich,
S. Schulze, M. Hietschold and H. Lang, J. Colloid Interface Sci., 2011,
359, 454–460.
16 (a) H. D. Jin, A. Garrison, T. Tseng, B. K. Paul and C.-H. Chang, Nano-
technology, 2010, 21, 445604; (b) S. K. Mallissery and D. Gudat, Dalton
Trans., 2010, 39, 4280.
34 (a) S. J. Lee, S. W. Han, M. Yoon and K. Kim, Vib. Spectrosc., 2000, 24,
265–275; (b) G. B. Deacon and R. J. Phillips, Coord. Chem. Rev., 1980,
33, 227–250.
35 (a) P. Römbke, A. Schier and H. Schmidbaur, J. Chem. Soc., Dalton
Trans., 2001, 2482–2486; (b) P. Römbke, A. Schier and H. Schmidbaur,
Z. Naturforsch, 2002, 57b, 605–609.
36 (a) E. J. Fernandez, J. Garcia-Barrasa, A. Laguna, J. M. Lopez-de-Luzur-
iaga, M. Monge and C. Torres, Nanotechnology, 2008, 19 (18), 185602;
(b) I.-K. Shim, Y. I. Lee, K. J. Lee and J. Joung, Mater. Chem. Phys.,
2008, 110 (2–3), 316–321.
37 (a) A. Hildebrandt, D. Schaarschmidt and H. Lang, Organometallics,
2011, 30, 556; (b) M. Lohan, P. Ecorchard, T. Rüffer, F. Justaud,
C. Lapinte and H. Lang, Organometallics, 2009, 28, 1878.
38 W. Haiss, N. T. K Thanh, J. Aveyard and D. G. Fernig, Anal. Chem.,
2007, 79, 4215.
39 J. Lu, D. B. Dreisinger and W. C. Cooper, Hydrometallurgy, 1997, 45,
305–322.
40 S. F. Jahn, T. Blaudeck, A. Jakob, P. Ecorchard, T. Rüffer, P. Schmidt,
H. Lang and R. R. Baumann, Chem. Mater., 2010, 22, 3067–3071.
41 M. Bron, A. Knop-Gericke, D. Teschner, A. Scheybal, M. Hävecker,
R. Födisch, D. Hönicke, R. Schlögl and P. Claus, J. Catal., 2005, 234,
37.
17 (a) Y. G. Kim, S.-K. Oh and R. M. Crooks, Chem. Mater., 2004,
16, 167; (b) Y. Chen, Y.-M. Zhang and Y. Liu, Chem. Commun., 2010,
46, 5622.
42 P. Claus, Appl. Catal., A, 2005, 291, 222.
43 M. Steffan, A. Jakob, P. Claus and H. Lang, Catal. Commun., 2009, 10,
437.
18 (a) A. G. Kanaras, F. S. Kamounah, K. Schaumburg, C. J. Kiely and
M. Brust, Chem. Commun., 2002, 2294; (b) T. Peterle, P. Ringler and
M. Mayor, Adv. Funct. Mater., 2009, 19, 3497; (c) T. Peterle, A. Leifert,
J. Timper, A. Sologubenko, U. Simon and M. Mayor, Chem. Commun.,
2008, 3438.
44 A. Bouzide and G. Sauvé, Tetrahedron Lett., 1997, 38 (34), 5945.
45 O. Zech, M. Kellermeier, S. Thomaier, E. Maurer, R. Klein, C. Schreiner
and W. Kunz, Chem.–Eur. J., 2009, 15, 1341–1345.
46 M. Tanabe and R. H. Peters, Org. Synth., 1990, 60, 92 (1981, Coll.
Vol. 7, 386).
19 (a) H. Hiramatsu and F. E. Osterloh, Chem. Mater., 2004, 16, 2509;
(b) M. Y. Han and C. H. Quek, Langmuir, 2000, 16, 362.
20 G. Schmid, Chem. Rev., 1992, 92, 1709–1727.
21 N. Zheng, J. Fan and G. D. Stucky, J. Am. Chem. Soc., 2006, 128, 6550–
6551.
47 M. Steffan, A. Jakob, P. Claus and H. Lang, Catal. Commun., 2009, 10,
437–441.
48 (a) G. M. Sheldrick, Acta Crystallogr., Sect. A: Found. Crystallogr.,
1990, 46, 467; (b) G. M. Sheldrick, SHELXL-97, Program for Crystal
Structure Refinement, 1997, Universität Göttingen.
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