Tuning supramolecular aurophilic structures: The effect of counterion, positive charge and solvent

Article abstract of DOI:10.1039/c6dt00865h

The synthesis of the cationic gold(i) complexes [Au(C≡CC₅H₄N)(CH₃-PTA)]X (X = I, 1; X = OTf, 4), [Au(C≡CC₅H₄N-CH₃)(PTA)]X (X = I, 2; X = OTf = 5; PTA = 1,3,5-triaza-7-phosphatricyclo[3.3.1.13.7]decane) and [Au(C≡CC₅H₄N-CH₃)(DAPTA)]X (X = I, 3; X = OTf = 6, DAPTA = 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane) results in cationic complexes with unexpected supramolecular assemblies in water ranging from rod-like structures (1) to vesicles (2 and 3) and square-like structures (5 and 6). These morphologies are completely different from the fibers previously obtained with their parent neutral complexes [Au(C≡C₅H₄N)(PTA)] and [Au(C≡C₅H₄N)(DAPTA)]. Nevertheless, the introduction of triflate as a counterion in 1 (complex 4) gives rise to the formation of a highly soluble complex in water which does not display any significant aggregation in solution. These results reveal the importance of the introduction of a positive charge on global supramolecular assemblies and how the counterion can also modify the resulting package. Interestingly, we have also proved that the aggregation of complexes 2, 3, 5 and 6 is also affected by the solvent with direct influence on their absorption and emission properties and the global morphology of the aggregates.

Full text of DOI:10.1039/c6dt00865h

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Tuning supramolecular aurophilic structures: the
effect of counterion, positive charge and solvent†
Cite this: DOI: 10.1039/c6dt00865h
a
a
a
a
b
Elisabet Aguiló, Raquel Gavara, Clara Baucells, Marta Guitart, João Carlos Lima,
c
a
Jordi Llorca and Laura Rodríguez*
The synthesis of the cationic gold(I) complexes [Au(CuCC
Au(CuCC N–CH
and [Au(CuCC N–CH
5
H
4
N)(CH
3
–PTA)]X (X = I, 1; X = OTf, 4),
[
5
H
4
3
)(PTA)]X (X = I, 2; X = OTf = 5; PTA = 1,3,5-triaza-7-phosphatricyclo[3.3.1.13.7]decane)
5
H
4
3
)(DAPTA)]X (X = I, 3; X = OTf = 6, DAPTA = 3,7-diacetyl-1,3,7-triaza-5-phospha-
bicyclo[3.3.1]nonane) results in cationic complexes with unexpected supramolecular assemblies in water
ranging from rod-like structures (1) to vesicles (2 and 3) and square-like structures (5 and 6). These mor-
phologies are completely different from the fibers previously obtained with their parent neutral complexes
5 4 5 4
[Au(CuC H N)(PTA)] and [Au(CuC H N)(DAPTA)]. Nevertheless, the introduction of triflate as a counter-
ion in 1 (complex 4) gives rise to the formation of a highly soluble complex in water which does not
display any significant aggregation in solution. These results reveal the importance of the introduction of a
positive charge on global supramolecular assemblies and how the counterion can also modify the result-
ing package. Interestingly, we have also proved that the aggregation of complexes 2, 3, 5 and 6 is also
affected by the solvent with direct influence on their absorption and emission properties and the global
morphology of the aggregates.
Received 3rd March 2016,
Accepted 10th March 2016
DOI: 10.1039/c6dt00865h
www.rsc.org/dalton
the development of entirely new materials with unusual topol-
ogies that lead to either unusual or enhanced properties.
Introduction
2
–4
Topology is becoming established in material science in the The self-assembly of small molecules has received great atten-
study of its affects on the physical properties of materials at tion in this field in the past decade, not only because of their
the nano-/mesoscale and in the study and design of materials fascinating and innumerable supramolecular morphologies
1
from a topological perspective. This incipient appreciation for (including spherical or cylindrical micelles, vesicles, toroids,
5
the importance of topology in the last few years has resulted in rods, ribbons, lamellar platelets, scrolls or nanotubes) but
a
Departament de Química Inorgànica i Orgànica, Universitat de Barcelona, Martí i
Franquès 1-11, 08028 Barcelona, Spain. E-mail: laura.rodriguez@qi.ub.es;
Fax: +34 934907725; Tel: +34 934039130
after 2 days (red line) of 2 in water (Fig. S16); emission spectra of 2 at three
different concentrations in water. λexc = 370 nm (Fig. S17); hypsochromic effect
with increasing polarity (negative solvatochromism) displayed in absorption
spectra of complex 2 (Fig. S18); plot of ˉν 0exp vs. ˉν 0calc for absorption data of com-
pound 3 (Fig. S19); plot of ˉν 0exp vs. ˉν 0calc for absorption data of compound 2
(Fig. S20); normalized emission spectra of 3 in different solvents (Fig. S21); nor-
malized emission spectra of 4 in different solvents (λexc = 370 nm) (Fig. S22); nor-
malized emission spectra of 5 in different solvents (λexc = 300 nm) (Fig. S23);
normalized excitation spectra of 2 in different solvents (Fig. S24); optical
b
LAQV-REQUIMTE, Departamento de Química, CQFB, Universidade Nova de Lisboa,
Monte de Caparica, Portugal
c
Institut de Tècniques Energètiques i Centre de Recerca en NanoEnginyeria,
Universitat Politècnica de Catalunya, Diagonal 647, 08028 Barcelona, Spain
†
Electronic supplementary information (ESI) available: Experimental section;
HR-ESI(+) mass spectrum of complex 1 (Fig. S1); HR-ESI(+) mass spectrum of
1
complex 2 (Fig. S2); HR-ESI(+) mass spectrum of complex 3 (Fig. S3); H-NMR
microscopy images of 2 in water (A), methanol (B), acetonitrile (C) and CHCl
(D) (Fig. S25); optical microscopy images of 3 in water (A), methanol (B), aceto-
nitrile (C) and CHCl (D) (Fig. S26); optical microscopy images of 5 in water (A),
methanol (B), acetonitrile (C) and CHCl (D) (Fig. S27); optical microscopy
images of 6 in water (A), methanol (B), acetonitrile (C) and CHCl (D) (Fig. S28);
3
1
1
spectrum of 2 in D
2
O (Fig. S4); H-NMR spectrum of 3 in D
2
O (Fig. S5); H-NMR
(Fig. S7); SEM
1
spectrum of 2 in CDCl
3
(Fig. S6); H-NMR spectrum of 3 in CDCl
3
3
images of dried samples of 2 (up) and 3 (bottom) (Fig. S8); Z potential values
3
−
5
measured for 5 × 10 M solutions of 2 and 3 in water by DLS measurements
3
1
(Fig. S9); H-NMR spectrum 4 in water (Fig. S10); HR-ESI(+) mass spectrum of
synthesis of N-methyl-4-ethynylpyridinum iodide (Scheme S1); synthesis of
N-methyl-4-ethynylpyridinum triflate (Scheme S2); synthesis of the N-methyl-4-
ethynylpyridinum perchlorate derivatives (Scheme S3); absorption and emission
(λexc = 370 nm) data of complexes 1–6 in water (Table S1); α, β, π* parameters for
the solvents used (Table S2); absorption data of the XLCT band of 2 and 3 in
different solvents (Table S3). See DOI: 10.1039/c6dt00865h
complex 5 (Fig. S11); HR-ESI(+) mass spectrum of complex 6 (Fig. S12); optical
microscopy images of aqueous dried samples of 5 (left) and 6 (right) (Fig. S13);
SEM images of aqueous dried samples of 5 (up) and 6 (bottom) (Fig. S14);
absorption spectra of 5 × 10− M solutions of complexes 1–6 in water (Fig. S15);
absorption spectra of freshly prepared ca. 1 × 10− M solution (solid line) and
5
4
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6
also due to their potential applications in material science, in
9
molecular devices or as mimics of biological systems or
7
,8
functions.
In the last few years, gold(I) complexes have represented an
emerging area of investigation within this field, as they show
1
0
weak Au(I)⋯Au(I) aurophilic interactions which can modulate
and govern the resulting assemblies and properties in very
11
different potential applications. Among the resulting supramole-
cular structures obtained with low molecular weight gold(I)
complexes, recent reports on hydrogelators should be
12–14
highlighted.
The formation of these gels has been driven
through non-covalent interactions, which are commonly van der
Chart 1 Positively charged species studied in this work.
Waals forces, hydrogen bonding, electrostatic attractions and π–π
12
stacking interactions, together with aurophilic interactions.
Our recent results on the formation of hydrogels from
26–30
properties of organometallic gold(I) complex crystals,
the
small organometallic complexes containing Au(I)–alkynyl
rearrangements that occur in solution, also affect the emission
1
5–17
moieties,
prompted us to go one step further in the design
of the aggregates.
and synthesis of novel supramolecular nanostructures pre-
pared by the self-assembly of small molecules. In particular,
we are interested in the understanding of how supramolecular
packing can be modulated by modifications of the chemical
structure or the environment of small gold(I) organometallic
precursors. The design and synthesis of novel self-assembling
Results and discussion
Synthesis and characterization
materials with tunable properties is challenging, but undeni- Complex 1 was obtained by the reaction of [Au(CuCC
ably crucial, and the understanding of the factors that control (PTA)] with CH I at low temperature (Scheme 1). Previously, we
such properties has aroused much interest in the last few carried out the reaction involving [Au(CuCC H N)] and
5 4
H N)
3
5
4
n
1
8–25
years.
We are mainly interested in gold(I) alkynyl com- (PTA-Me)I but this was not accomplished successfully. On the
plexes, due to their appealing stems from the two-coordinate other hand, positively charged complexes of the pyridyl unit
linear geometry of the metal atom and the linearity of the were also obtained by modifications of the synthetic pro-
alkynyl moiety, which together have made them ideal candi- cedures (Scheme 2). For this, the previous synthesis of the
dates for the exploration of self-assembling functional pro- organic ligand N-methyl-4-ethynylpyridinum iodide was necess-
3
1
perties and have drawn attention due to their wide range of ary (Scheme S1†). In these cases, the acac method was necess-
11
different properties. For these reasons, in this work, we ary to remove the terminal alkynyl proton, and complexes 2
report how the 3D assemblies of gold(I) derivatives previously and 3 were obtained with moderate yields (ca. 50–70%).
1
5,16
1
31
reported by us
can be modulated by the introduction of
Characterization of complexes 1–3 by H, P-NMR and IR
different factors. In fact, we have been able to tune the large spectroscopy, and mass spectrometry verified the successful
pre-organized fibrilar structures previously found and convert formation of these products. In all the cases, molecular peaks
them into rods, spherical vesicles or square-like morphologies, were displayed in the ESI-MS experiments (Fig. S1–S3†). The
among others, by the introduction of a positive charge to the corresponding CuC and CvN vibrations of the chromophoric
chemical structure either at the phosphine unit (complexes 1 units were also observed in the IR spectra in all the cases.
and 4 Chart 1) or at the pyridyl unit (complexes 2, 3, 5 and 6). Most importantly, the disappearance of the terminal alkynyl
1
The influence of the counterion of these positively charged proton detected by IR and H-NMR is clear evidence of the for-
complexes has also been explored together with the effect of mation of complexes 2 and 3. Additionally, the characteristic
the polarity of the solvents in the intermolecular interactions H and H protons of the pyridine together with the character-
α
β
2
giving rise to unprecedented changes in their photophysical istic patterns of PTA (2) or DAPTA (3) phosphines in D O were
1
and morphological properties. Very recently, the formation has observed in the H-NMR spectra of the complexes (Fig. S4 and
been reported of various structures with Au alkynyl amphi- S5†). The formation of aggregated samples in this solvent was
1
8
philic systems and different long alkyl chains. But the absence evidenced by the presence of different H
α β
and H pyridyl
1
5,16
of these long alkyl chains in our complexes make them par- protons where this moiety must be directly affected.
Only
ticularly appealing with regard to the study of their aggregation phosphine protons were detected in chloroform, due to the
processes. And, to the best of our knowledge, this is the first poor solubility of the ionic part of the molecules in apolar sol-
1
5–17,32–34
example, with this family of compounds, that shows how the vents (Fig. S6 and S7†).
Moreover, the more asym-
polarity of different solvents and the presence of different metric pattern of the methylated phosphine (1) was also
1
35–37
counterions can induce the formation of distinct supramolecular recorded by H-NMR in D
2
O (Fig. 1 top).
Interesting find-
O. The
1
structures in solution. On the other hand, as was observed ings were observed from H-NMR characterization in D
2
for the effect of solvent vapours on the resulting luminescent corresponding spectra of the three complexes clearly displayed
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5 4
Scheme 1 Synthesis of [Au(CuC H N)(PTA-Me)]I complex.
5 4 3 3
Scheme 2 Synthesis of [Au(CuC H N-Me)(PR )]I (PR = PTA, DAPTA) complexes.
1
Fig. 1 H-NMR spectrum of complex 1 in D
2
O (top) and in CDCl
3
(bottom). H
β
protons in the spectrum below are buried under the CDCl
3
signal.
the characteristic protons of the phosphines while protons of
In 1, the phosphine groups are expected to point towards
the ethynylpyridyl chromophore could only be observed (and water molecules while the more hydrophobic ethynylpyridyl
with very low intensity) in diluted conditions (Fig. 1 top). moieties are expected to pack closely to each other through
Similar behaviour was recently observed for the hydrophobic interactions. In the case of 2 and 3, the presence
1
5
[
5 4
Au(CuC H N)(PTA)] complex which is proof that aggrega- of a positive charge at the pyridyl groups is expected to promote
tion occurs in this solvent, and the organic chromophoric unit a different aggregation pattern, where the positively charged
must be directly involved. In the absence of aggregation, (as unit is located towards the water molecules. This hypothesis
1
observed in CDCl
3
, Fig. 1 bottom) the H-NMR spectrum was also confirmed by the Z potential values measured by
shows the correct integration ratio of 2 : 6 between the pyridyl Dynamic Light Scattering (DLS) experiments (see below).
a
H and phosphine protons. For the reasons detailed above,
some kinds of supramolecular assemblies were also expected
for 1–3 in water. Nevertheless, the lack of the expected gel be-
Analysis of the aggregates by electron microscopy and optical
microscopy
haviour of the solutions did not indicate the formation of long Scanning electron microscopy was used as an important tool
fibers promoting gelification in these cases (see below).
for gaining insight into the supramolecular assemblies of
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these complexes and to analyse the effect of the positive Dynamic light scattering
moiety (1–3) in the resulting, and unpredictable, three-dimen-
DLS experiments were carried out on the spherical samples
sional supramolecular packing. The rod aggregates of 1 were
about 20–30 μm long; the individual spherical aggregates of 2
and 3 measured around 20 nm and the presence of a multi-
layer system (typical of vesicles), containing in some cases
hollows (darker colour) with an empty inner, was detected for
−5
(
vesicles) using 5 × 10 M solutions and indicated that the
expected size of the vesicles was around 20 nm with a positive
Z potential value of around +25 and +15 mV for 2 and 3,
respectively (Fig. S9†). These data suggest that the positive
charge may be pointing outwards in the vesicles’ structure.
The lowest positive value measured for 3 could be attributed to
the larger steric hindrance of the DAPTA phosphine which
must be related to the different packing structure (see below).
2
(Fig. 2). Moreover, the spherical aggregates seemed to
agglomerate to sizes of ca. 200 nm or greater (Fig. S8†). Cryo-
genic transmission electron microscopy (cryo-TEM) images
provided key evidence for verification of the presence of the
micellar-vesicles topologies of 2 and 3 in solution (Fig. 2D).
Interestingly, these morphologies seem to be maintained in
larger structures and are detectable by optical microscopy
DLS experiments carried out at different concentrations
−5
showed that the smaller vesicles’ size are detected at ca. 10
M
(
∼20 nm), and they agglomerate up to ca. 130–140 nm at
−4
ca. 1 × 10 M concentration (Fig. 4), in agreement with data
retrieved from SEM experiments (see above). Thus, we suspect
that the spherical shape is maintained both in solution and in
dried samples.
(Fig. 3).
Hence, it seems clear that cationic charges produce a clear
effect on the global morphology of the supramolecular assem-
blies and preclude the formation of long empty fibers pre-
viously observed for their neutral analogous complexes
To the best of our knowledge, this type of vesicles topology
is the first example of weak interactions with low molecular
weight complexes reported in the literature. Only small
micelles have very recently been found with a Au(I)-metallo-
1
5
16
[
Au(CuC H N)(PTA)] and [Au(CuC H N)(DAPTA)].
5 4 5 4
3
8
amphiphile in buffered water.
Effect of counteranion on the resulting package. The nature
of the counterion can affect the resulting supramolecular
3
9
package as observed in other gold supramolecular structures.
With this in mind, the complex [Au(CuC N)(PTA-Me)]OTf
4) was synthesized following a procedure similar to the one
5
H
4
(
used to obtain 1 but using MeOTf instead of MeI. The result-
ing product was observed to be highly soluble in polar solvents
1
and is shown in the corresponding H-NMR spectrum in D O,
2
which shows all the protons of the molecule in the correct
integrating ratio (Fig. S10†). Thus, no significant aggregation
was expected and consequently, complex 4 does not seem to
give rise to the formation of highly preorganized and ordered
structures.
The synthesis of N-methyl-4-pydidylethynyl triflate ligand
was also performed following a similar procedure that for the
synthesis of the iodide ligand (Scheme S2†) in order to investi-
gate whether the counteranion could induce changes in the
spherical-type aggregates observed for 2 and 3. The introduc-
Fig. 2 Scanning electron microscopy images of dried samples of 1 (A),
2
(B) and 3 (C). Cryogenic transmission electron microscopy image of tion of other counteranions such as perchlorate was also
−4
sample of a 5 × 10 M aqueous solution of 2 (D).
attempted (see Scheme S3†) but the very low yield (∼2%) of the
Fig. 3 Optical microscopy images of dried samples of 1 (A), 2 (B) and 3 (C).
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Fig. 4 Diameter of vesicles in different solutions of 2 in water at different concentrations measured by DLS (left); DLS distribution at two different
−5
−3
concentrations: 5 × 10 M, black line, and 1 × 10 M, red line (right).
resulting organic precursor and the oily nature of the obtained molecule involved in the aggregate. Calculation of the CPP
gold(I) derivatives precluded their correct isolation and corres- values corresponding to the cationic part of the molecules
ponding studies.
(involved directly in the packing formation) was carried out by
3
)] measuring the length of each molecule based on
The reaction of the triflate ligand with [Au(acac)(PR
(
PR = PTA, DAPTA) was accomplished by the same procedure simple Spartan models (Fig. 6). The calculated CPP values
3
+
shown in Scheme 2 for iodide derivatives and the resulting were 0.51, 1.01 and 4.07 for [Au(CuC-C H N)(CH PTA)] ,
5
4
3
+
[Au(CuC
5
H
4
N-Me)(PR
3
)]OTf (PR
3
= PTA (5), DAPTA (6)) were [Au(CuC-C
5
H
4
N-CH
3
)(PTA)]
and
5 4 3
[Au(CuC-C H N-CH )
+
successfully obtained in moderate-high yields (ca. 70–80%) in (DAPTA)] , respectively. This is in agreement with the for-
agreement with characterization data (Fig. S11 and S12†). mation of hexagonal preferred aggregate structures for the
Optical microscopy images of dried aqueous samples of 5 and complex with the cationic charge located at the phosphine
6
showed the formation of large structures presenting square- (Fig. 6 left) and lamellar aggregates (Fig. 6 middle) and
like concentric shapes (Fig. 5A and S13†). SEM characterization reversed micelles (Fig. 6 right) for the aggregation of com-
confirms this fact and enabled us to measure their size as plexes with the positive charge at the pyridyl moiety and PTA
4
0
ca. 20–40 μm (Fig. 5B and C and S14†). It could be seen that and DAPTA phosphines, respectively. Lamellar structures
the use of a different counteranion (triflate instead of iodide) tend to minimize the interactions between water molecules
modulates the formation of different supramolecular and the hydrophobic parts that are inside the lamellar phase.
packages: squares for triflate complexes instead of micelles/ At the same time, the positively charged head groups induce a
vesicles, observed for iodide derivatives (Table 1).
curvature, closing the structure, which also minimizes the
Analysis of the packing parameter and relation to the repulsion between the positively charged head groups and
4
1
observed geometry. The critical packing parameter (CPP) is results in the formation of a vesicle. This is in agreement
known to be an important tool for the determination of the with the characterization images obtained by SEM (see above).
geometry of micellar types of aggregates. CPP is based on the Finally, the high steric hindrance of the DAPTA phosphine
calculation of the ratio v/(lmax × a) where v is the volume of one must be responsible for the formation of reversed micelles,
molecule, lmax is the length of the hydrophobic part and a is instead of vesicles, where the most bulky group (phosphine) is
the area of a cross section of the more hydrophilic part of the located outside the cavity. The presence of amines in this
Fig. 5 Optical microscopy images of aqueous dried samples of 6 (A). SEM images of aqueous dried samples of 5 (B) and 6 (C).
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Table 1 Summary of the different supramolecular assemblies of complexes 1–6 in water
−
X = I (1)
Rods
X = OTf− (4)
No significant aggregation
PR
PR
PR
PR
3
3
3
3
= PTA; X = I− (2)
Vesicles
Square-like
Vesicles
−
= PTA; X = OTf− (5)
= DAPTA; X = I (3)
= DAPTA; X = OTf− (6)
Square-like
+
Fig. 6 Critical packing parameters (CPPs) and preferred aggregate structures for geometrical packing of [Au(CuC-C
5
H
4
N)(CH
3
PTA)] (left),
+
+
[
5 4 3 5 4 3
Au(CuC-C H N-CH )(PTA)] (middle) and [Au(CuC-C H N-CH )(DAPTA)] (right).
phosphine makes this location possible since amine may be solution and it is not mandatory to maintain the possible
protonated at neutral aqueous pH. packing in the solid state in the aggregates obtained in solu-
It is known that simple inorganic counterions are very tion. They are more similar to micellar type structures than to
loosely associated with micelles. They are very mobile and crystalline type structures in terms of the hydrophobic/hydro-
there is no specific complex formed with a defined distance philic balance, interactions with solvent and electrostatic
from the external part of the micelle. Thus, iodide counterions repulsions that determine the shapes of the aggregates.
of 1–3 are not expected to affect the resulting packages and
CPP could give a reasonable explanation for the packing.
Effect of the solvent on the resulting package. Diluted solu-
tions of complexes 2 and 3 present different colours in polar
We are not convinced that the same is true for triflate and apolar solvents. Hence, the effect of the polarity of the
derivatives 4–6, due to their lower water solubility and the evi- solvent on the resulting spectroscopic properties and mor-
dence for a possible anion–π interaction with compound 4 (see phology was investigated.
below). The very different structures of the aggregates of 5 and
Absorption and emission characterization in water
6
suggests that the packing must take into account the poss-
ible intercalation of triflate in the aggregates, nevertheless, we Absorption and emission spectra of complexes 1–6 were
cannot prove this. In such a case (triflate intercalation in the recorded in water at ca. 10− M concentration and the results
structure), repulsions between the positive moieties may be are summarized in Table S1,† Fig. 7, S15† and Fig. 8. The
less important and for this, the resulting packages are absorption spectrum of 1 presents an intense absorption at
extended structures of lamellar phase giving rise to square-like ca. 265–300 assigned to intraligand (IL) π–π* (CuCpy) transitions
5
1
1,15,16,42,43
samples instead of vesicles.
based on the literature.
This transition exhibits
In order to gain more information about the packing of our some broadening (not completely vibronically resolved) which
structures, several attempts were made to grow single crystals is indicative of an aggregation process where the Au–CuCpy
1
5
suitable for X-ray diffraction but they were unsuccessful. In moiety is directly involved. Thus, π–π stacking together with
any case, it seems credible that the observed assemblies aurophilic interactions are expected to be present in solution
studied in this work are globally the result of aggregation in and should be responsible for the formation of the rod-like
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to reorganization of the iodide anions in the aggregates with
time.
A different profile was displayed for 4 (Fig. S16†). The
highest recorded extinction coefficient is in agreement with
the lack of formation of aggregates. Nevertheless, the profile is
not completely understood since it resembles the spectra of
the methylated pyridyl derivatives (2, 3, 5 and 6) but the
1
H-NMR spectra does not show any upfield shift typical for
1
this coordination. The largest H-NMR downfield shift of H
α
and H
β
protons of 4 together with the smaller calculated coup-
ling constants, are in agreement with a possible anion–π stack-
48
ing disposition. Thus, the triflate counterion could interact
with the aromatic pyridyl ring giving a red-shifted and un-
resolved absorption band. These interactions may be favoured
for this counterion possibility because of hydrogen bonding and
Fig. 7 Absorption spectra of 5 × 10− M solutions of complexes 1, 2 could be the reason for the different package observed by SEM.
5
and 6 in water.
Emission spectra, recorded upon excitation of all the
samples at 370 nm, displayed the presence of a broad band
around 450 nm (or vibronically structured with progressive
spacings at ca. 2000 cm− , in the case of 1) and an additional
band near 600 nm for the PTA derivatives 1, 2 and 5 (Fig. 8).
The vibronical resolved observed in 1 let us assign this higher
1
3
energy band to an intra-ligand [π–π*(alkynyl)] emission
origin. This resolution was lost for the methylated pyridyl
derivatives 2, 3, 5 and 6, as was observed for other methyl–pyri-
4
5,46,49
dinium compounds.
The lower energy emissions may be
attributed to MMLCT transitions within the aggregates as
recently observed for platinum alkynyl derivatives and for the
emission spectra recorded at different concentrations
5
0,51
(
Fig. S17†).
The recorded yellow emission was also in
agreement with this assignment and with the fact that approxi-
mation of Au centers increases the emission in this region of
4
2
the spectrum. An XLCT origin should be ruled out since it is
also observed for triflate derivatives and also for aged solutions
where the XLCT absorption band disappears.
Fig. 8 Emission spectra of 2.5 × 10− M solutions of complexes 1–6 in
5
water (λexc = 370 nm).
Absorption and emission in solvents of different polarity
It was observed that complexes 2 and 3 displayed different
colours when dissolved in water and in chloroform. In order to
structures. A lower intensity broad band or tail above 300 nm check the effect of the solvents in the corresponding solutions,
can be assigned to a σ*Au⋯Au–π* transition according to theore- 1 × 10− M samples of complexes 2, 3 and their triflate ana-
tical studies carried out recently for analogous neutral com- logous 5 and 6 in solvents of different polarity were prepared
3
4
2,44
plexes.
0 nm red-shifted and without vibronical resolution. In the case solvent effect was observed by the naked eye for 1 and 4. As
of 2, 3, 5 and 6, this is due to the methylated pyridyl group.
displayed in Fig. 9, the solutions of 3 present a wide range of
The intra-ligand absorption band of 2–6 is about and their absorption and emission spectra were recorded. No
2
Another band around 400 nm was recorded for the PTA different colours, and for this, their solvatochromic behaviour
complexes 2 and 5. This band is probably due to the absorp- and the corresponding spectroscopic properties and the result-
tion of aggregated species since PTA complexes aggregate ing package were investigated.
more easily than their DAPTA analogues. An additional tran-
sition around 450 nm was recorded for fresh solutions of prepared samples in the different solvents and the multipara-
Absorption and emission spectra were measured for freshly
5
2
2
and 3 and has been tentatively assigned to XLCT transitions metric method of Kamlet and Taft, in which UV-Vis absorp-
(
X = halide), as reported in the literature for other organo- tion and emission energies are correlated with different
4
5,46
This charge transfer transition is solvent properties according to eqn (1), was applied.53–57 In
metallic compounds.
favoured by the coordination of an electron withdrawing group this equation, ˉν is the value of the absorption and/or emission
0
4
7
(
Au–phosphine) to the pyridinium moiety and was observed energies in a reference solvent (cyclohexane; α = β = π* = 0),
to disappear in aged solutions (Fig. S16†). This is probably due α is an index of the solvent’s ability to act as a hydrogen-bond
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Fig. 9 1 × 10− M solutions of 3 in solvents of different polarity (1, water; 2, methanol; 3, acetonitrile; 4, chloroform; 5, THF; 6, toluene; 7,
3
cyclohexane).
donor (or electron pair acceptor) toward a solute and β is a the solvatochromic effect was not detected. A large negative
measure of the ability of a bulk solvent to act as a hydrogen- solvatochromism (hypsochromic effect) was observed for 2 and
bond acceptor (or electron-pair donor), π* is an index of the 3 (62 nm and 65 nm respectively (∼155 000 cm− )) due to stabi-
solvent polarity/polarizability which measures the solvent’s lization of the ground state in more polar solvents during the
ability to stabilize a neighbouring charge or dipole through transition. Kamlet–Taft multiparametric fitting (Table 2 and
non-specific dielectric interactions and δ is the polarizability Fig. S19 and S20†) shows that the polarity/polarizability
correction for different classes of solvent (aliphatic, aromatic (measured by π* parameter) is the main effect on this hypso-
or halogenated). Often, the contribution of δ is negligible chromic shift (larger p value), which means that the stabili-
leading to the simplified eqn (2), from which the parameters zation by H-bonding of the ground state is less important and
a, b and p (corresponding to the responses of the appropriate even less for the DAPTA derivative, 3. Nevertheless, the ability
solute molecular property to the relevant solvent property) can to establish or to accept H-bonds between solvent and solute is
be retrieved through a multiparametric fitting for various sol- not negligible. In fact, both a and b values are positive, and
1
vents. α, β and π* are tabulated values (Table S2†).
indicate a stabilization of the ground state, increasing the
energy of the transition.
Interesting findings may be retrieved from emission spectra
recorded for all different solvents upon excitation at the lowest
energy absorption band (ca. 370 nm). Two different emission
ꢀ
ˉν ¼ ˉν 0 þ aα þ bβ þ pðπ þ dδÞ
ð1Þ
ð2Þ
ˉν ¼ ˉν 0 þ aα þ bβ þ pπꢀ
The absorption band around 450 nm of compounds 2 and bands at ca. 450 nm and 550 nm were recorded for all of the
in water was observed to be strongly dependent upon solvent complexes as exemplified for 2 in Fig. 11 (see also Fig. S21–
3
polarity (Table S3† and Fig. 10 and S18†). Interestingly, this S23† for the other complexes). In the case of 2 and 5, the
band does not appear for triflate derivatives (5 and 6) which is general observed trend is that the lowest energy emission band
−
in agreement with the previous XLCT assignment (X = I ), and increases in intensity with the solvent polarity. In the less polar
solvents, such as chloroform, THF, toluene and cyclohexane,
the band at 550–600 nm drastically disappears. By comparison
1
5,16
with previous studies
the broad emission shape of both
bands seems to be assigned to emissive aggregates. The lowest
energy emission band recorded in polar solvents may indicate
the formation of larger structures in these media in agreement
with NMR data. A particular case is the emission spectrum
recorded in cyclohexane (less polar solvent) which displays a
different profile with a vibronically structured shape (see
Fig. 11). This could be attributed to the emission of a
15,16
monomer, which is in agreement with previous works.
values, in cm− , as well as slope and correlation
1
Table 2 a, b, p and ν
¯
0
coefficients obtained from Kamlet–Taft multiparametric fitting of the
absorption data
2
Compound
a
b
p
ˉν
0
Slope
r
Fig. 10 Normalized absorption spectra of complex
3 recorded in
different solvents. Hypsochromic effect with increasing polarity (nega-
tive solvatochromism) is shown.
2
3
942
726
959
707
2537
3288
17 789
17 430
1
1
0.99
0.99
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Fig. 11 Normalized emission spectra of 5 × 10−5 M solutions of 2 in
different solvents (λexc = 370 nm).
Fig. 12 SEM images of dried samples of 5 in water (A), methanol (B),
acetonitrile (C) and CHCl (D).
3
Excitation spectra collected at the emission maxima display Conclusions
two different bands centred at ca. 350 nm (more apolar sol-
We have demonstrated how to modulate the resulting supra-
molecular morphology of gold(I) alkynyl complexes by carrying
out different modifications of their chemical structure and
environment. The effect of the introduction of a positive
charge let us create rod-like structures with cationic charge
located at the PTA phosphine (complex 1). This morphology
completely changes to the formation of vesicles or reversed
micelles when this charge is located on the pyridyl unit (com-
plexes 2 and 3).
Changing the counterion from iodide to triflate gives rise to
a different supramolecular package and results in the for-
mation of square-like assemblies (complexes 5 and 6) in water,
while the higher solubility of the triflate analogues of 1
(complex 4) precludes the formation of aggregates. Hence, we
can modulate the formation of different types of 3D structures
formed by the establishment of weak interactions between
molecules (mainly aurophilic interactions).
The solutions of complexes 2, 3, 5 and 6 in different sol-
vents enables us to demonstrate that this parameter also
affects the resulting supramolecular package as could be seen
by the corresponding emission spectra and microscopy
images. Moreover, Kamlet–Taft multiparametric analysis of the
XLCT absorption band of complexes 2 and 3 indicates that the
observed negative solvatochromism in absorption is mainly
due to polarity/polarizability effects while solvent polarity
affects the resulting emission of the aggregates.
vents) and an additional band 450 nm (only observed in more
polar solvents) corresponding to absorption of the less and
more aggregated samples (see Fig. S24†).
No emission bands were displayed for 3 and 6 in less polar
solvents upon excitation of the samples at 370 nm (absorption
of larger aggregates). Excitation of these samples at the lower
absorption wavelength (ca. 300 nm) gives rise to emission
bands centred at ca. 350 nm and 450 nm. This fact is in agree-
ment with the higher solubility of the DAPTA complexes with
respect to the analogous PTA derivatives.
Analysis of the samples with different solvents using
microscopic techniques
The dried samples were also observed under optical
microscopy and SEM in order to correlate the morphology of
the aggregates with the observed absorption and emission
bands. No supramolecular structures could be detected for the
samples prepared in cyclohexane, which together with the lack
of the broad emission at 550–600 nm, corroborates the fact
that emissive aggregates are responsible for this emission. On
the other hand, different topologies were detected in the
remaining solvents, which means that in all cases supramole-
cular structures were obtained and that these different shapes
can be correlated with the different spectroscopic emission
patterns recorded (Fig. 12 and S25–28†).
It is accepted in the literature that the presence of aurophi-
lic interactions can produce long wavelength luminescent crys-
5
8–60
tals that are responsive to changes in their environment.
Experimental section
General procedures
In particular, many gold crystalline complexes display solvo- or
vapoluminescence that is a result of uptake of solvent mole-
cules into the solid phase. Nevertheless, to the best of our All experiments were carried out under prepurified N using
2
knowledge, this is the first report where it is shown how sol- standard Schlenk techniques. All of the solvents were distilled
vents promote the formation of different supramolecular from appropriated drying agents. Commercial reagents
shapes of gold(I) alkynyl aurophilic aggregates.
1,3,5-triaza-7-phosphatricyclo[3.3.1.13.7]decane (PTA, Aldrich
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9
7%), 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane ately after solution preparation as the coloring of these varies
(
(
DAPTA, Aldrich 97%), MeI (Aldrich, 99%) and MeCF SO
with time.
3
3
Aldrich, 99%) were used as received. Literature methods were
Synthesis of [Au(acac)(PTA)] (1a). Solid Tl(acac) (76 mg,
6
0
used to prepare N-methyl-4-ethynylpyridine iodide, [AuCl 0.25 mmol) was added to a solution of [AuCl(PTA)] (100 mg,
6
1
61
62
(
(
PTA)], [AuCl(DAPTA)], [Tl(acac)] and [Au(CuC-C H N) 0.25 mmol) in acetone (10 ml). After four days of stirring at
5 4
1
5
PTA)]. A similar procedure to that previously reported for room temperature, the resulting white suspension was filtered.
N-methyl-4-ethynylpyridine iodide was used for the synthesis The solution was concentrated to ca. 5 ml and n-hexane
6
3
of N-methyl-4-ethynylpyridine triflate, but MeCF SO was (10 ml) was added to precipitate [Au(acac)(PTA)] as a white
3
3
used instead of MeI.
solid which was filtered off and dried in vacuum. Yield: 71%
1
(
3
82 mg). H-NMR (400 MHz, CDCl ): 4.60–4.46 (AB q, J = 12
Hz, 6H, N–CH –N), 4.28 (s, 6H, N–CH –P), 2.25–2.12 (m, 8H,
Physical measurements
2
2
3
1
1
CH
−
3
–(CO)–CH
2
–(CO)–CH
3
). P{ H}-NMR (162 MHz, CDCl
3
):
Infrared spectra were recorded with an FT-IR 520 Nicolet
45.1. IR (KBr, cm− ): 1635 (CvO).
1
1
31
1
Spectrophotometer. H-NMR (δ(TMS) = 0.0 ppm), P{ H}-NMR
δ(85% H PO ) = 0.0 ppm) spectra were obtained with a Varian
Synthesis of [Au(acac)(DAPTA)] (2a). Solid Tl(acac) (90 mg,
(
3
4
0
0
.30 mmol) was added to a solution of [AuCl(DAPTA)] (120 mg,
.30 mmol) in acetone (10 ml). After four days of stirring at
Mercury 400, Bruker 400 and Bruker DMX 500. ES(+) mass
spectra were recorded with a Fisons VG Quatro spectrometer.
Absorption spectra were recorded with a Varian Cary 100 Bio
UV-spectrophotometer and emission spectra with a Horiba-
Jobin-Ybon SPEX Fluorolog 3.22 and Nanolog spectrofluori-
meters. Microspectrofluorimetry measurements were carried
out with a MicroSPEX instrument with the Spex Fluorog appar-
atus 3.22 connected to an Olympus BX51 M confocal micro-
scope (Universidade Nova de Lisboa). Fluorescence microscopy
was carried out with an Axioplan 2ie Zeiss imaging microscope
equipped with a NikonDXM1200F digital camera (Universi-
dade Nova de Lisboa) and a Leica DMIRB fluorescence micro-
scope (Universitat de Barcelona). Optical microscopy was
carried out with an Olympus BX51. Scanning electron
microscopy was carried out at 5 kV using a Neon40 Crossbeam
Station (Zeiss) equipped with a field emission gun. Cryo-trans-
mission electron microscopy measurements were carreid out
with a Tecnai G2 F20 (FEI) 200 kV FEG TEM cryomicroscope. A
Horiba Scientific Nanoparticle Analyzer SZ-100 (Universidade
Nova de Lisboa) operating at 25 °C was used to obtain the DLS
measurements.
room temperature, the white suspension was filtered. The
resulting solution was concentrated to ca. 5 ml and n-hexane
(
10 ml) was added to precipitate [Au(acac)(DAPTA)] as a white
solid which was filtered off and dried in vacuum. Yield: 73%
1
(
99 mg). H-NMR (400 MHz, CDCl
3
): 5.80 (d, J = 20.0 Hz, 1H,
–P), 4.96 (d,
N–CH –N), 5.60 (dd, J = 20.0/12.0 Hz, 1H, N–CH
2
2
J = 16.0 Hz, 1H, N–CH –N), 4.80–4.60 (m, 2H, N–CH –P + N–
2
2
CH
2
–N), 4.15 (dt, J = 20.0/4.0, 1H, N–CH
2
–P), 4.07 (d, J = 20.0
2 2
Hz, 1H, N–CH –N), 3.87 (s, 2H, N–CH –P), 3.57 (dt, J = 20.0/4.0
Hz, 1H, N–CH –P), 3.85 (s, 3H, N–CH ), 1.85 (s, 6H, CO–CH ),
2
3
3
3
1
1
2
(
.25–2.12 (m, 8H, CH
162 MHz, CDCl
3
–(CO)–CH
2
–(CO)–CH
3
).
P{ H}-NMR
): −48.3. IR (KBr, cm− ): 1675 (CvO).
1
3
Synthesis of [Au(CuC-C H N)(CH PTA)]I (1). CH I (0.12 ml,
5
4
3
3
0.19 mmol) was added dropwise to
a
solution of
5 4 2 2
[Au(CuC-C H N)(PTA)] (60 mg, 0.13 mmol) in CH Cl (10 ml)
at −40 °C. The suspension was allowed to warm to room temp-
erature for 4 hours. The resulting pale yellow solution was con-
centrated to ca. 5 ml, and diethyl ether (10 ml) was added to
1
precipitate a pale yellow solid. Yield: 80% (73 mg). H-NMR
(
400 MHz, D
J = 8.0 Hz, 2H, Hβ-pyr), 5.08–4.90 (AB m, 4H, N–CH
.69–4.59 (AB m, 2H, N–CH –N), 4.56–4.44 (m, 2H, P–CH –N ),
2
O, ppm): 8.46 (d, J = 8.0 Hz, 2H, Hα-pyr), 7.41 (d,
+
2
–N ),
Preparation of the samples
+
4
2
2
+
Optical and fluorescence microscopy measurements. 1 mg 4.33–4.06 (AB, m, 4H, N–CH
2
–P), 2.86 (s, 3H, N –CH
3
).
O, ppm): −57.2. IR (KBr, cm ): 3425
the measurements, a drop of each solution was placed onto a (C–H (CH )), 2100 (CuC), 1664 (CvN). ES-MS (+) m/z: 471.10
3
1
−1
of each compound was dissolved in 5 ml of each solvent. For
P-NMR (162 MHz, D
2
3
microscope slide and evaporated to dryness.
SEM measurements. 4 × 10 M solutions of the complexes calc. %: C: 29.33, H, 3.77, N: 9.12; Found %: C: 29.42, H: 3.80,
4
([M]+, calc.: 471.10). Elemental analyses for C15H23AuIN P
−4
were used. A drop of each solution was deposited onto a N: 9.31.
silicon plate and evaporated to dryness by contact with air.
This process was carried out in the same way for all of the (PTA)] (40 mg, 0.08 mmol) was added to a solution of
different solvents. N-methyl-4-ethynylpyridine (10 mg, 0.08 mmol) in THF
5 4 3
Synthesis of [Au(CuC-C H N-CH )(PTA)]I (2). Solid [Au(acac)
Polarity effect studies. The solvents used were double-dis- (10 ml). After 1 hour of stirring at room temperature, the
tilled water, methanol p.a. (Fluka), acetonitrile p.a. (Fluka), resulting red solution was concentrated, and diethyl ether
THF (appropriate drying agents), chloroform p.a. (Fluka), (10 ml) was added to precipitate a dark red solid. Yield: 75%
1
toluene (appropriate drying agents) and cyclohexane p.a. (30 mg). H-NMR (400 MHz, D
2
O): 8.10 (d, J = 12.0 Hz, 2H,
(Panreac).
Hα-pyr), 7.61 (d, J = 12.0 Hz, 2H, Hβ-pyr), 4.67–4.50 (AB q, J =
To prepare solutions of 2, 3, and 5, 6, 1 mg of each com- 16.0 Hz, 6H, N–CH –N), 4.37 (s, 6H, N–CH –P), 3.88 (s, 3H,
2
2
3
1
−1
3 3
pound was dissolved in 5 ml of each solvent, then the mother CH ). P-NMR (162 MHz, CDCl , ppm): −48.2. IR (KBr, cm ):
solutions were diluted to half concentration and the spectra 3425 (C–H), 2104 (CuC), 1640 (CvN). ESI-MS (+) m/z: 471.10
were recorded. All of the measurements were made immedi- ([M]+, calc.: 471.10). Elemental analyses for C H AuIN P
1
5
23
4
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2 2 2
calc. %: C: 29.33, H, 3.77, N: 9.12; Found %: C: 29.44, H: 3.81, 1H, N–CH –N), 4.79–4.69 (m, 2H, N–CH –P + N–CH –N),
N: 9.28.
Synthesis of [Au(CuC-C
Au(acac)(DAPTA)] (44 mg, 0.09 mmol) was added to a solution
of N-methyl-4-ethynylpyridine (10 mg, 0.09 mmol) in THF 2116 (CuC), 1635 (CvN). ESI-MS(+): m/z: 543.12 ([M]+, calc:
10 ml). After 1 hour of stirring at room temperature, the 543.12). Elemental analyses for C18 23AuF PS calc. %: C:
resulting red solution was concentrated, and diethyl ether 31.22, H, 3.35, N: 8.09, S: 4.63; Found %: C: 30.97, H: 3.45, N:
4.51–3.68 (m, 8H, N–CH –P (1H) + N–CH –N (1H), N–CH –P
2
2
2
5
H
4
N-CH
3
)(DAPTA)]I (3). Solid (2H) + N–CH
2
3 3
–P (1H) + N–CH (3H)), 2.10 (m, 6H, CO–CH ).
3
1
1
−1
[
3
P{ H}-NMR (162 MHz, CD OD, ppm): −17.8. IR (KBr, cm ):
(
H
3 4 5
N O
(
(
10 ml) was added to precipitate a dark red solid. Yield: 50% 7.95, S: 4.61.
1
23 mg). H-NMR (400 MHz, D
2
O): 8.80 (d, J = 12.0 Hz, 2H,
H
α-pyr), 7.70 (d, J = 12.0 Hz, 2H, Hβ-pyr), 5.65 (d, J = 20.0 Hz, 1H,
N–CH –N), 5.40 (dd, J = 20.0/12.0 Hz, 1H, N–CH –P), 5.10 (d,
2
2
Acknowledgements
J = 16.0 Hz, 1H, N–CH
2
2
–N), 4.70–3.88 (m, 7H, N–CH –P + N–
CH
2
–N + N–CH
2
–P + N–CH
2
–N + N–CH
2
1
–P + N–CH
2
–P), 3.76 (s, The support and sponsorship provided by COST Action
3
1
3
H, N–CH ), 1.85 (s, 6H, CO–CH ). P{ H}-NMR (162 MHz, CM1005 is acknowledged. Authors are also grateful to the
3
3
−
1
CDCl , ppm): −17.2. IR (KBr, cm ): 3430 (C–H), 2100 (CuC), Ministerio de Ciencia e Innovación of Spain (Project ENE2015-
3
1
5
3
937 (CvO), 1634 (CvN). ESI-MS (+) m/z: 543.12 ([M]+, calc.: 63969-R). This work was also supported by the Associated
43.12). Elemental analyses for C H AuIN O P calc. %: C: Laboratory for Sustainable Chemistry-Clean Processes and
1
7
23
4 2
0.46, H, 3.46, N: 8.36; Found %: C: 30.49, H: 3.49, N: 8.41.
3
Synthesis of [Au(CuC-C N)(CH PTA)](CF SO )
Technologies-LAQV which is financed by national funds from
FCT/MEC (UID/QUI/50006/2013) and co-financed by the ERDF
5
H
4
3
3
(
4). CH CF SO (4.1 μl, 0.36 mmol) was added dropwise to a under the PT2020 Partnership Agreement (POCI-01-0145-
3
3
3
solution of [Au(CuC-C
5 4
H N)(PTA)] (11 mg, 0.24 mmol) in FEDER-007265). J. Ll. is a Serra Húnter Fellow and is grateful
CH Cl (10 ml) at −40 °C. The suspension was allowed to to the ICREA Academia program. This research was supported
2
2
warm to room temperature for 4 hours. The resulting pale by a Marie Curie Intra-European Fellowship within the 7th
yellow solution was concentrated to ca. 5 ml, and diethyl ether European Community Framework Programme (R. G.).
(
(
10 ml) was added to precipitate a yellow solid. Yield: 80%
1
15 mg). H-NMR (400 MHz, D O, ppm): 8.60 (d, J = 6.4 Hz,
2
2
4
2
H, Hα-pyr), 7.85 (d, J = 6.4 Hz, 2H, Hβ-pyr), 5.10–4.92 (AB m,
References
+
2 2
H, N–CH –N ), 4.69–4.59 (AB m, 2H, N–CH –N), 4.54–4.45 (m,
+
H, P–CH –N ), 4.34–4.12 (AB, m, 4H, N–CH –P), 2.89 (s, 3H,
1 S. Gupta and A. Saxena, MRS Bull., 2014, 39, 266.
2 D. Massiot, R. J. Messinger, S. Cadars, M. Deschamps,
V. Montouillout, N. Pellerin, E. Veron, M. Allix, P. Florian
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3 X. Zou, H. Ren and G. Zhu, Chem. Commun., 2013, 49,
3911.
2
31
2
+
1
N –CH
3
). P{ H}-NMR (162 MHz, D
cm ): 3433 (C–H (CH
F). ES-MS (+) m/z: 471.10 ([M]+, calc.: 471.10). Elemental ana-
lyses for C16 23AuF PS calc. %: C: 30.43, H, 3.55, N: 7.89,
2
O, ppm): −43.6. IR (KBr,
−
1
3
)), 2113 (CuC), 1629 (CvN), 1264 (C–
H
3 4 3
N O
S: 4.51; Found %: C: 3.59, H: 3.45, N: 7.80, S: 4.70.
Synthesis of [Au(CuC-C H N-CH )(PTA)](CF SO ) (5). Solid
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5 M. J. Mayoral Muñoz and G. Fernández, Chem. Sci., 2012, 3,
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5
4
3
3
3
[
Au(acac)(PTA)] (60 mg, 0.13 mmol) was added to a solution of
N-methyl-4-ethynylpyridine triflate (43 mg, 0.15 mmol) in THF
10 ml). After 1 hour of stirring at room temperature the solu-
(
tion was concentrated to half volume and diethyl ether (10 ml)
6 E. Y.-H. Hong, H.-L. Wong and V. W.-W. Yam, Chem.
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9 C. P. Collier, E. W. Wong, M. Belohradsky, F. M. Raymo,
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was added to precipitate a dark green solid. Yield: 68%
1
(
55 mg). H NMR (CD OD, 400 MHz, ppm): 8.53 (d, J = 5.9 Hz,
3
2
H, Hα-pyr), 7.87 (d, J = 6.2 Hz, 2H, Hβ-pyr), 4.71–3.85 (m, 15H,
3
1
1
N–CH
2
–N + N–CH
2
–P + N–CH
3
). P{ H}-NMR (162 MHz,
−1
CD OD, ppm): −27.0. IR (KBr, cm ): 2109 (CuC), 1636
3
+
(
CvN). ESI-MS(+) m/z: 471.10 ([M] calc: 471.10). Elemental
analyses for C16 23AuF PS calc. %: C: 30.20, H, 3.64, N:
.89, S: 5.04; Found %: C: 30.52, H: 3.60, N: 7.81, S: 5.21.
Synthesis of [Au(CuC-C N-CH )(DAPTA)](CF SO
Au(acac)(DAPTA)] (25 mg, 0.05 mmol) was added to a solution
of N-methyl-4-ethynylpyridine triflate (15 mg, 0.05 mmol) in 11 J. C. Lima and L. Rodríguez, Chem. Soc. Rev., 2011, 40,
THF (5 ml). After 1 hour of stirring at room temperature the 5442.
solution was concentrated to half volume and diethyl ether 12 J. C. Lima and L. Rodríguez, Inorganics, 2015, 3, 1.
H
3 4 3
N O
7
5
H
4
3
3
3
) (6). Solid 10 H. Schmidbaur and A. Schier, Chem. Soc. Rev., 2012, 41,
370.
[
(
(
10 ml) was added to precipitate a dark green solid. Yield: 70% 13 A. Y.-Y. Tam and V. W.-W. Yam, Chem. Soc. Rev., 2013, 42,
1
22 mg). H NMR (CD
3
OD, 400 MHz, ppm): 8.64 (d, J = 6.5 Hz,
1540.
2
1
H, Hα-pyr), 7.79 (d, J = 6.6 Hz, 2H, Hβ-pyr), 5.71 (d, J = 13.9 Hz, 14 P. Casuso, A. Pérez-San Vicente, H. Iribar, A. Gutiérrez-
H, N–CH –N), 5.54 (m, 1H, N–CH –P), 5.08 (d, J = 14.7 Hz,
Rivera, A. Izeta, I. Loinaz, G. Cabañero, H.-J. Grande,
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