Luminescent metallogels of bis-cyclometalated alkynylgold(III) complexes

Article abstract of DOI:10.1021/ic3007519

A series of luminescent bis-cyclometalated alkynylgold(III) complexes have been synthesized and characterized. Some of the complexes have been demonstrated to exhibit gelation properties driven by π-π stacking and hydrophobic-hydrophobic interactions. The gelation properties have been investigated in detail through variable-temperature UV-vis absorption and emission studies, and the morphology of the gels has also been characterized by scanning electron microscopy and transmission electron microscopy.

Full text of DOI:10.1021/ic3007519

Article
pubs.acs.org/IC
Luminescent Metallogels of Bis-Cyclometalated Alkynylgold(III)
Complexes
Vonika Ka-Man Au, Nianyong Zhu, and Vivian Wing-Wah Yam*
Institute of Molecular Functional Materials [Areas of Excellence Scheme, University Grants Committee (Hong Kong)] and
Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong
S
* Supporting Information
ABSTRACT: A series of luminescent bis-cyclometalated alkynylgold(III) complexes have
been synthesized and characterized. Some of the complexes have been demonstrated to
exhibit gelation properties driven by π−π stacking and hydrophobic−hydrophobic
interactions. The gelation properties have been investigated in detail through variable-
temperature UV−vis absorption and emission studies, and the morphology of the gels has
also been characterized by scanning electron microscopy and transmission electron
microscopy.
metalated gold(III) complexes have been observed to exhibit
rich luminescence properties at both ambient and low
temperatures in various media. Very recently, another class of
luminescent gold(III) complexes with electron-rich pentafluor-
ophenyl moieties has been reported. Some of these complexes
were found to show room-temperature luminescence that
involved participation of the gold(III) metal center.29
INTRODUCTION
■
Over the past few decades, a rapid growth of interest in gold
chemistry has been observed.1−11 On the other hand, there has
been an enormous increase in attention drawn toward the
design and synthesis of novel supramolecular assemblies,10−19
especially those based on transition metal complex sys-
tems.16−24 Recently, our group has reported the interesting
photoluminescence and electroluminescence properties of bis-
cyclometalated gold(III) complexes, and it was found that the
presence of π−π stacking interactions among the complex
molecules could exert some influence on the emission as well as
the electrochemistry of this class of complexes.25 It is
anticipated that such π−π stacking interactions, together with
other intermolecular interactions such as van der Waals’ forces,
hydrogen bonding, and electrostatic attractions, may function
to facilitate the self-assembly of organogold(III) complexes. In
fact, the study of luminescent gold(III) complexes is rather
underdeveloped and underexplored, which is in contrast to that
of the related gold(I) and isoelectronic platinum(II)
systems.11b,c This probably stems from the presence of low-
energy d−d ligand field (LF) states as well as the electro-
philicity observed for the gold(III) metal center.11b,c In order to
enhance the luminescence behavior of gold(III) complexes, one
strategy has been through the introduction of strong σ-donating
ligands, which has been first demonstrated and reported by the
group of Yam on the preparation of stable gold(III) aryl
complexes that are found to emit even at room temperature in
solution.26 Later on, this concept has been further extended to
bis-cyclometalated gold(III) complexes that contain strongly σ-
donating alkynyl and N-heterocyclic carbene ligands.25 Mono-
cyclometalated bis-alkynylgold(III) complexes of arylpyridine
have also been reported very recently.27,28 These cyclo-
On the other hand, low-molecular-mass organic gelators
(LMOGs) represent a key area in the study of supramolecular
assembly because of their spontaneous and controlled self-
assembly phenomena.12−18,30,31 In many cases, LMOGs are
formed upon their self-assembly through a combination of non-
covalent interactions such as π−π stacking, hydrogen bonding,
hydrophobic−hydrophobic interactions and van der Waals’
forces, resulting in the formation of entangled self-assembled
fibrillar networks (SAFINs).13 Owing to these weak inter-
molecular interactions, the key advantage of using LMOGs as
molecular building blocks is their reversibility, which makes
them highly tunable and responsive to micro-environmental
changes.32−35 For example, LMOGs of pyrene-containing
oligopeptides have been shown to self-assemble to give one-
dimensional helical columnar structures that further lead to
three-dimensional fibrous networks.36 Luminescence color
switching was observed and was ascribed to the interplay of
the π−π stacking interactions of the pyrene moieties and the
intermolecular hydrogen bonding interactions of the oligopep-
tides.36
Stemming from the extensive studies on organogels, there
has been an increasing interest in the investigation of
Received: April 12, 2012
© XXXX American Chemical Society
A
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metallogels based on transition metal complex systems such as
platinum(II),37−40 gold(I),41 copper(I),42,43 rhenium(I),44 and
iron(II).45 In particular, luminescent metallogels represent a
remarkable class of gelators. The presence of metallophilic
interactions and/or non-covalent forces may lead to variation in
the gelating abilities and rich photophysical properties. An
elegant example based on trinuclear (pyrazolato)gold(I)
complexes with long alkyl side chains was reported recently,
with reversible RGB-color switching behavior of the gel, where
both aurophilic interactions and van der Waals’ forces have
been shown to be involved.41 Recent works by us have shown
that metallogels based on the platinum(II) and rhenium(I)
transition metal systems display rich luminescence behav-
ior.37,44 In one representative example, luminescence enhance-
ment has been observed at elevated temperatures for a series of
alkynylplatinum(II) metallogels bearing pincer ligands derived
from 2,6-bis(N-alkylbenzimidazol-2′-yl)pyridine.37c To the best
of our knowledge, corresponding work on gold(III) systems
has not been reported. It is believed that, with a judicious
selection of the coordinating ligands, luminescent gold(III)
complexes with gelation properties could be developed, and the
gelation properties could be readily modified through a fine
balance and an interplay of the non-covalent interactions
between these gelators and the solvent molecules. Herein, we
report the functionalization of the bis-cyclometalated gold(III)
chromophores with organogelating moieties for the preparation
of luminescent gold(III) metallogels.
synthesized by stirring a mixture of the chlorogold(III)
precursor [Au(R-C^N^C)Cl]46 and the respective 3,4,5-
(trialkoxyphenyl)acetylene47 in dichloromethane in the pres-
ence of Et3N and a catalytic amount of CuI at room
temperature under a nitrogen atmosphere according to that
reported previously by us.25 All of the complexes are found to
be air and thermally stable and soluble in common organic
solvents such as dichloromethane and chloroform. The
1
identities of all of the complexes have been confirmed by H
NMR spectroscopy, fast-atom-bombardment mass spectrome-
try (FAB-MS), and satisfactory elemental analyses. Their IR
spectra exhibited a ν(CC) absorption at 2137−2152 cm−1,
which is in accordance with the presence of the alkynyl ligand
in the terminal σ-coordination mode.
X-ray Crystal Structures. Single crystals of [Au(C^N^C)-
(CCC6H2(OCH3)3-3,4,5)] (1) and [Au(tBuC^N^CtBu)-
(CCC6H2(OCH3)3-3,4,5)] (5) were obtained by layering
of n-hexane onto a concentrated dichloromethane solution of
the respective complex, and their crystal structures were
determined by X-ray crystallography. Crystal structure
determination data are summarized in Table 1. The selected
Table 1. Crystal and Structure Determination Data of
Complexes 1 and 5
[Au(C^N^C)(CC
C6H2(OCH3)3-3,4,5)]
[Au(tBuC^N^CtBu)(CC
C6H2(OCH3)3-3,4,5)] (5)
·1/2C6H14 (1·1/2C6H14)
empirical formula
C28H22AuNO3·1/2
C6H14
C36H38AuNO3
RESULTS AND DISCUSSION
fw
660.52
729.64
■
temp, K
wavelength, Å
cryst syst
space group
a, Å
296(2)
0.71073
monoclinic
P21/n
302(2)
0.71073
monoclinic
P21/c
Synthesis and Characterization. The bis-cyclometalated
alkynylgold(III) complexes 1−10, as shown in Chart 1, were
Chart 1
8.5855(2)
23.4736(7)
13.1607(4)
90
17.1549(7)
14.2495(6)
13.0516(6)
90
b, Å
c, Å
α, deg
β, deg
100.066(2)
90
100.8060(10)
90
γ, deg
volume, cm3
Z, Å3
2611.48(13)
4
3133.9(2)
4
density (calcd), g
1.680
1.546
cm−3
cryst size, mm3
index ranges
0.34 × 0.18 × 0.06
−10 ≤ h ≤ 10
−27 ≤ k ≤ 27
−15 ≤ l ≤ 15
36857/4613
0.49 × 0.18 × 0.05
−20 ≤ h ≤ 19
−15 ≤ k ≤ 16
−15 ≤ l ≤ 15
17192/5510
reflns collected/
unique
GOF on F2
1.032
1.069
final R indices [I > R1 = 0.0357, wR2 =
R1 = 0.0182, wR2 = 0.0410
2σ(I)]
0.0848
largest diff peak
1.324 and −0.899
0.295 and −0.550
and hole, e Å−3
bond distances and bond angles are tabulated in Table 2. The
perspective views of the crystal structures of 1 and 5 are
depicted in Figure 1, and their crystal packing diagrams are
shown in Figure 2. The gold(III) metal center coordinates to
the tridentate cyclometalating R-C^N^C ligand, with the
remaining site occupied by an alkynyl ligand to give a distorted
square-planar geometry, characteristic of d8 metal complexes.
The C−Au−N angles of 80.5−81.4° about the gold(III) metal
B
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Table 2. Selected Bond Lengths (Å) and Angles (deg) for Complexes 1 and 5 with Estimated Standard Deviations (esd’s) Given
in Parentheses
[Au(C^N^C)(CCC6H2(OCH3)3-3,4,5)]·1/2C6H14 (1·1/2C6H14)
[Au(tBuC^N^CtBu)(CCC6H2(OCH3)3-3,4,5)] (5)
Bond Lengths (Å)
Au(1)−C(1)
Au(1)−C(12)
Au(1)−C(28)
Au(1)−N(1)
C(1)−C(2)
1.998(7)
2.061(8)
2.070(7)
2.005(5)
1.142(8)
Au(1)−C(1)
Au(1)−C(12)
Au(1)−C(28)
Au(1)−N(1)
C(1)−C(2)
1.969(3)
2.064(3)
2.075(3)
2.002(2)
1.193(4)
Bond Angles (deg)
C(12)−Au(1)−C(28)
N(1)−Au(1)−C(1)
Au(1)−C(1)−C(2)
N(1)−Au(1)−C(12)
N(1)−Au(1)−C(28)
C(1)−C(2)−C(3)
161.9(3)
C(12)−Au(1)−C(28)
N(1)−Au(1)−C(1)
Au(1)−C(1)−C(2)
N(1)−Au(1)−C(12)
N(1)−Au(1)−C(28)
C(1)−C(2)−C(3)
162.10(12)
176.85(10)
174.7(3)
179.3(2)
177.2(6)
81.4(3)
80.5(2)
177.3(7)
81.04(10)
81.06(11)
178.5(3)
Figure 2. Crystal packing diagrams of (a) 1 and (b) 5, showing the
“dimeric” configuration.
[Au(R-C^N^C)] motif is essentially coplanar, and the Au−C
(2.061−2.075 Å) and Au−N (2.002−2.005 Å) bond distances
are similar to those found in other related complexes.25 The
Au−CC and CC−C angles of 174.7−177.2° and 177.3−
178.5° only show a minor deviation from the ideal 180°,
establishing a slightly distorted linear arrangement, with the
Au−C (1.969−1.998 Å) and CC bond distances (1.142−
1.193 Å) similar to those found in the related cyclometalated
alkynylgold(III) systems.25,27 Because the shortest Au···Au
distances (5.3311 and 5.8769 Å) between adjacent molecules
are found to be longer than the sum of the van der Waals radii
for two gold(III) centers, no significant Au···Au interactions
Figure 1. Perspective views of (a) 1 and (b) 5 with atomic numbering
schemes. H atoms have been omitted for clarity. Thermal ellipsoids are
drawn at the 30% probability level.
center are found to deviate from the ideal 90° because of the
restricted bite angle of the tridentate R-C^N^C ligands. The
C
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occur in the crystal lattices of the complexes. The molecules are
arranged in a head-to-tail fashion in the crystal lattice, with
some π−π stacking interactions of 3.4288−3.5649 Å between
the [Au(C^N^C)] moieties.
Electrochemistry. The cyclic voltammograms of 1−10 in
dichloromethane (0.1 mol dm−3 nBu4NPF6) generally show one
quasi-reversible reduction couple at −1.31 to −1.61 V vs SCE
and an irreversible oxidation wave at +1.09 to +1.27 V vs SCE.
The electrochemical data are summarized in Table 3.
C^N^C ligand, and similar assignments have also been made in
other related alkynylgold(III) complexes.25 Complex 5 was
observed to show the most negative potential at −1.61 V, which
is in agreement with the assignment because the electron-rich
tert-butyl substituents on the cyclometalating ligand would raise
the energy of the π* orbital and cause the complex to be
reduced with more difficulty, leading to a more negative
potential. Extended π conjugation upon the introduction of an
aryl substituent on the central pyridine ring of the R-C^N^C
ligand stabilizes the π* orbital and leads to a less negative
reduction potential for complexes 6 and 7. The replacement of
the phenyl moieties in the R-C^N^C ligand by naphthyl groups
does not cause a significant change in the energy of the π*
orbital, as revealed by the similar potentials in 1−4 and 8−10,
probably supportive of the greater localization of the lowest
unoccupied molecular orbital (LUMO) on the pyridine moiety
of the R-C^N^C ligand. On the other hand, the irreversible
oxidative waves at +1.09 to +1.27 V are assigned to a ligand-
centered oxidation of the alkynyl ligand.25
UV−Vis Absorption Spectroscopy. The electronic
absorption spectra of the complexes show a high-energy
absorption band at 306−324 nm and a vibronically structured
absorption band at 363−412 nm with extinction coefficients on
the order of 103−104 dm3 mol−1 cm−1. The photophysical data
for complexes 1−10 are summarized in Table 4 and the
representative electronic absorption spectra of complexes 5−7
and 10 are depicted in Figure 3. The absorption energy of the
low-energy band is found to be quite insensitive to the nature
of the alkynyl ligands. The vibrational progressional spacings of
the low-energy band at ca. 1200−1400 cm−1 are in agreement
with the typical skeletal vibrational frequencies of the
cyclometalating R-C^N^C ligand. Similar absorption bands
could also be observed in the chloro precursor46 and the related
alkynylgold(III) complexes.25,27 The lower-energy band is
assigned as a metal-perturbed intraligand (IL) π−π* transition
a
Table 3. Electrochemical Data for 1−10
b
c
complex oxidation Epa/V vs SCE
reduction E1/2/V vs SCE (ΔEp/mV)
1
2
3
4
5
6
7
8
9
10
+1.16
+1.20
+1.17
+1.18
+1.27
+1.17
+1.12
+1.10
+1.15
+1.09
−1.54 (77)
−1.54 (79)
−1.54 (72)
−1.53 (65)
−1.61 (71)
−1.36 (74)
−1.31 (73)
−1.56 (77)
−1.57 (86)
−1.56 (85)
a
In a dichloromethane solution with 0.1 M nBu4NPF6 as the
supporting electrolyte at room temperature; working electrode, glassy
b
carbon; scan rate 100 mV s−1. Epa refers to the anodic peak potential
c
for the irreversible oxidation waves. E1/2 = (Epa + Epc)/2; Epa and Epc
are peak anodic and peak cathodic potentials, respectively. ΔEp = |Epa
− Epc|.
Complexes with the same tridentate cyclometalating R-
C^N^C ligands are found to show similar potentials for the
reduction couples. For example, complexes 1−4 bearing the
unsubstituted C^N^C ligand all exhibit reduction couples at ca.
−1.54 V vs SCE. In view of such an observation, the reduction
couples are ascribed to the ligand-centered reduction of the R-
Table 4. Photophysical Data for 1−10
a
absorption
emission
b
complex
λmax/nm (εmax/dm3 mol−1 cm−1
)
medium (T/K)
λmax/nm (τ0/μs)
573 (0.1)
Φem
c
1
312 (12970), 322 (12115), 363 (4890), 381 (5080), 401 (3595)
312 (18765), 322 (17320), 366 (9025), 382 (9355), 400 (7230)
312 (13785), 324 (11925), 364 (5010), 382 (5430), 400 (4075)
312 (14765), 324 (13295), 366 (5790), 382 (6185), 400 (4250)
314 (18700), 324 (17195), 372 (6305), 390 (6740), 412 (5635)
306 (21090), 370 (5615), 390 (6160), 408 (4600)
310 (18845), 382 (3450), 400 (3380)
CH2Cl2 (298)
9.9 × 10−3
c,d
glass (77)
CH2Cl2 (298)
470, 503, 536, 576 (207)
597 (0.2)
c
c
2
8.7 × 10−3
8.1 × 10−3
5.2× 10−3
4.6 × 10−3
2.8 × 10−3
8.6 × 10−3
6.5 × 10−2
1.2 × 10−2
9.4 × 10−2
c,d
glass (77)
CH2Cl2 (298)
486, 522, 558 (144)
602 (6.4)
3
c,d
glass (77)
CH2Cl2 (298)
470, 504, 534, 586 (262)
604 (0.2)
4
c,d
glass (77)
CH2Cl2 (298)
471, 502, 537 (180)
484, 516, 556 (0.1)
478, 510, 547 (257)
639 (0.2)
5
c,d
glass (77)
CH2Cl2 (298)
c
c
c
c
c
6
c,d
glass (77)
CH2Cl2 (298)
511, 538 (102)
7
563, 606, 659 (13)
498, 536, 577 (3373)
559, 602, 660sh (64)
554, 602, 653 (235)
559, 604, 657sh (12)
564, 610 (2807)
c,d
glass (77)
CH2Cl2 (298)
8
306 (53765), 346 (22205), 376 (5865), 394 (7015)
344 (8340), 378 (3520), 396 (3835)
c,d
glass (77)
CH2Cl2 (298)
9
c,d
glass (77)
CH2Cl2 (298)
10
302 (49670), 376 (21200), 396 (27775)
559, 601, 657sh (35)
567, 616, 668sh (279)
c,d
glass (77)
a
b
c
In dichloromethane at 298 K. The luminescence quantum yield, measured at room temperature using quinine sulfate as a standard. Vibronic-
d
structured emission band. In EtOH−MeOH−CH2Cl2 (40:10:1, v/v).
D
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tert-butyl and naphthyl groups in the R-C^N^C ligand, which
causes the energy levels of the π orbital of the R-C^N^C ligand
to be higher-lying than that of the π orbital of the alkynyl
ligands. As a result, an emission originating from an IL origin
would be preferred to that with a LLCT origin. In the presence
of the more conjugated naphthyl moieties in place of phenyl
moieties in the cyclometalating R-C^N^C ligand, better
delocalization over the cyclometalating ligand would be
expected. A pronounced red shift in emission is observed in
complex 6 relative to complexes 1−4, as well as in complexes
7−10 relative to complex 5. With increasing conjugation, it is
probable that the highest occupied molecular orbital (HOMO)
π orbital would be destabilized, while the LUMO π* orbital
would be stabilized, such that the resulting HOMO−LUMO
energy gap would be reduced to cause a red shift in emission.
Gelation Studies. The gelation properties of the complexes
have been tested in various organic solvents by the “stable to
inversion of a test tube” method. The gelation properties of the
complexes studied are summarized in Table 5. A range of
Figure 3. Electronic absorption spectra of complexes 4, 6, 7, and 10 in
dichloromethane at 298 K.
of the bis-cyclometalating ligand, with some charge-transfer
character from the peripheral phenyl moieties to the central
pyridine moiety.
Luminescence Spectroscopy. Upon excitation at λ ≥ 330
nm, the complexes are found to exhibit intense emission in
dichloromethane solution at 298 K. Selected solution emission
spectra are shown in Figure 4. Considering the emission spectra
Table 5. Summary of Gelation Properties in Various Organic
a
Solvents
complex DMSO methanol
hexane
cyclohexane benzene toluene
2
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
P
P
P
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
3
P
4
Gs (4.6)
Gs (4.6)
6
Gu
P
P
7
P
8
P
Gu
Gu
9
P
10
Gu (20.3) Gu (25.1)
a
Gs = opaque stable gel over 1 week; Gu = unstable gel only stable for
a few minutes; P = precipitation; S = soluble; I = insoluble. The values
in parentheses are the critical gelation concentrations in mg/mL at 25
°C.
Figure 4. Emission spectra of complexes 3, 5, and 10 in
dichloromethane at 298 K.
organic solvents, from polar dimethyl sulfoxide (DMSO) to
non-polar benzene, have been tested. Complexes 4 and 10 are
found to show good gelation behaviors in non-polar organic
solvents such as n-hexane and cyclohexane and give opaque
pale yellow gels. However, the other complexes fail to form any
gels in the solvents tested, probably because of an imbalance in
the intermolecular interactions, especially hydrophobic−hydro-
phobic and π−π stacking interactions, between the complex
molecules. In particular, the metallogels formed by 4 are highly
stable and the critical gelation concentration (cgc) is rather low
in hexane and cyclohexane, as shown in Figure 5. On the other
hand, the other complexes give only precipitation or insoluble
suspensions in these solvents (Table 5).
Electron microscopy was performed on the xerogels (air-
dried gels) of the complexes in order to study their
morphologies. Xerogels have been employed for the study of
a number of organogels31,36 and metallogels37−42,44 to
investigate their structures by microscopic techniques and
have been regarded as a good representation of the real gel
structures. Scanning electron microscopy (SEM) and trans-
mission electron microscopy (TEM) images have been
recorded for the hexane and cyclohexane xerogels (air-dried
gel) formed by complex 4, as well as the hexane xerogel formed
by complex 10. As in typical organogels and metallogels,12,14
the gel states of the complexes demonstrated a network of
of complexes 1−4 and 6, which all contain an ancillary
(trialkoxyphenyl)alkynyl ligand, the complexes are found to
exhibit a broad, structureless emission band at 573−639 nm.
Complexes 1−4, which contain the same unsubstituted C^N^C
ligand, show emission energies that increase from 573 to 604
nm with an increase in the alkoxy chain lengths of the alkynyl
ligands. Complex 6, with an additional difluorophenyl moiety,
is found to show an emission band at lower energy at 639 nm.
Owing to the electron-rich nature of the (trialkoxyphenyl)-
alkynyl ligands, these structureless emission bands are
tentatively assigned as originated from an excited state of
triplet ligand-to-ligand charge-transfer (3LLCT) [π(CCC6-
H4(OR)3-3,4,5) → π*(R-C^N^C)] character. However, the
presence of (trialkoxyphenyl)alkynyl groups would not always
lead to the occurrence of the triplet LLCT emission, as shown
in complexes 5 and 7−10, which exhibit a vibronically
structured emission band at 484−660 nm. With reference to
the emission studies of related bis-cyclometalated gold(III)
complexes in the literature,25 this vibronic-structured emission
3
band can be assigned as originated from an IL [π → π*(R-
C^N^C)] state, with some charge-transfer character from the
aryl moieties to the pyridine moiety of the R-C^N^C ligand.
The disappearance of the structureless LLCT emission band
could be attributed to the presence of the electron-donating
E
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Figure 7. (a) SEM and (b) TEM images of the xerogels prepared from
the cyclohexane gel of complex 4.
In order to clearly observe the gel-to-sol phase transition
behavior, temperature-dependent UV−vis absorption studies
have been performed for complex 4. Upon gel-to-sol phase
transition at elevated temperatures, complex 4 shows an
obvious increase in the color intensity from very pale yellow gel
to yellow sol. When the temperature is increased from 10 to 40
°C in hexane, the UV−vis absorption spectra feature a drop in
absorbance of the absorption tail at ca. 430 nm and beyond.
The vibronically structured absorption bands at 393 and 414
nm gradually merge into a broad absorption band. Beyond 40
Figure 5. Photographs of (a) the hexane gel and (b) the cyclohexane
gel of 4 with the corresponding sol forms at elevated temperature
([Au] = 4.6 mg/mL in both cases).
entangled fibrous structures in a micrometer scale, as shown in
the SEM and TEM images in Figures 6 and 7.
Figure 6. (a) SEM and (b) TEM images of the xerogels prepared from the hexane gel of complex 4.
F
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°C, a new vibronic band starts to appear at 381 and 401 nm. A
further increase in temperature up to 48 °C, which is the sol−
gel phase transition temperature (Tgel), leads to the complete
disappearance of the absorption shoulder. Further heating
results only in an increase in the absorbance and very few
changes in the shape of the UV−vis absorption spectra. Similar
observations have been obtained for the temperature-depend-
ent UV−vis spectroscopic studies of complex 4 in cyclohexane.
Complex 4 forms a pale yellow gel in cyclohexane and would
give a more intensely colored yellow sol upon a gel-to-sol phase
transition at higher temperatures. Initially, in the hexane gel at
10 °C, complex 4 features vibronically structured absorption
bands at 395 and 415 nm and an absorption shoulder at 430
nm. When the temperature is increased, the UV−vis absorption
spectra also display a drop in the intensity of the absorption tail
beyond 430 nm. The vibronically structured band gradually
disappears and new vibronic bands are developed at 385 and
400 nm when the temperature is above 23 °C. At the phase
transition temperature of 35 °C, the absorption shoulder
completely disappears, and the absorbance of the new
vibronically structured band is found to increase with
temperature. The UV−vis absorption spectral traces at various
temperatures in hexane and cyclohexane are depicted in Figures
8 and S1 in the Supporting Information (SI), respectively. With
vibronic-structured emission bands at 496 and 526 nm upon
transition to the sol form when the temperature is increased to
30 °C, which is assignable to a 3IL [π → π*(C^N^C)] excited
state. The observation of both the IL and LLCT bands suggests
that the two states are rather close-lying in energy. At elevated
temperatures, both bands show a drop in the emission intensity.
This could be explained by the fact that, in the gel state, the
rigidity of the media would increase and result in a reduction of
molecular vibrations and motions, such that the non-radiative
deactivation pathways could be retarded. However, at higher
temperatures, the non-radiative decay would become more
facile. The emission spectral changes of complex 4 at various
temperatures are depicted in Figures 9 and S2 in the SI.
Figure 9. Corrected emission spectra of the hexane gel of complex 4
upon an increase in the temperature from 10 to 40 °C.
CONCLUSION
■
A bis-cyclometalated alkynylgold(III) system has been found to
form metallogels with detectable absorption and emission
changes during the sol−gel transition, which can serve as a
probe for micro-environmental changes. Microscopic analyses
of the xerogels display a network of fibrous structures. With a
judicious choice of coordinating ligands, the interplay of non-
covalent interactions such as π−π stacking and hydrophobic−
hydrophobic interactions can be readily adjusted for a rational
design of metallogels based on the gold(III) system.
Figure 8. UV−Vis absorption spectral traces of the sol−gel phase
transition of complex 4 in hexane upon an increase in the temperature
from 10 to 50 °C. Inset: spectral traces at 20, 40, and 50 °C.
EXPERIMENTAL SECTION
reference to the electronic absorption studies of these
complexes, the vibronically structured bands are assigned as
the IL transition of the cyclometalating C^N^C ligand. The
exhibition of an isosbestic point at 408−410 nm suggests a
clean conversion from the supramolecular assemblies to the
monomeric species upon a gel-to-sol transition at elevated
temperature. On the other hand, complex 10 shows a less
dramatic color change upon sol−gel phase transition in
cyclohexane or hexane, and the gels are less stable than those
of complex 4. Upon an increase in the temperature, the yellow
gel of complex 10 would gradually become a sol, which is also
yellow in color.
■
Materials and Reagents. Potassium tetrachloroaurate(III) was
purchased from ChemPur. The chlorogold(III) precursor complexes,
[Au(R-C^N^C)Cl], were prepared according to a literature
procedure,46 using the commercially available 2,6-diphenylpyridine
or its derivatives synthesized by the Krohnke procedure of pyridine
̈
synthesis.48 3,4,5-Tris(alkoxyphenyl)acetylenes were prepared accord-
ing to a reported procedure.47 Copper(I) iodide was obtained from
Lancaster and triethylamine from Acros. All solvents were purified and
distilled using standard procedures before use. All other reagents were
of analytical grade and were used as received.
Physical Measurements and Instrumentation. UV−Vis
spectra were obtained on a Hewlett-Packard 8452A diode-array
spectrophotometer. 1H NMR spectra were recorded on a Bruker DPX-
300 (300 MHz) or Bruker DPX-400 (400 MHz) Fourier transform
NMR spectrometer with chemical shifts recorded relative to
tetramethylsilane (Me4Si). Positive FAB-MS spectra were recorded
on a Finnigan MAT95 mass spectrometer. Elemental analyses for the
metal complexes were performed on the Carlo Erba 1106 elemental
analyzer at the Institute of Chemistry, Chinese Academy of Sciences,
in Beijing. Steady-state excitation and emission spectra were recorded
on a Spex Fluorolog-2 model F111 fluorescence spectrofluorometer
equipped with a Hamamatsu R-928 photomultiplier tube. Photo-
The corresponding variable-temperature emission properties
of the hexane and cyclohexane gels have also been investigated
for complex 4. The complex shows similar emission bands in
both solvents. Upon excitation at the isosbestic point at ca. 410
nm at 10 °C, an emission band is observed at 570−620 nm,
3
which is assigned as originated from the LLCT [π(CC
C6H4(OR)3-3,4,5) → π*(C^N^C)] excited state. When the
temperature is raised, the intensity of the emission band is
found to drop. In cyclohexane, the complex shows additional
G
dx.doi.org/10.1021/ic3007519 | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
physical measurements in low-temperature glass were carried out with
the sample solution loaded in a quartz tube inside a quartz-walled
Dewar flask. Liquid nitrogen was placed in the Dewar flask for low-
temperature (77 K) photophysical measurements. Excited-state
lifetimes of solution samples were measured using a conventional
laser system. The excitation source used was the 355-nm output (third
harmonic, 8 ns) of a Spectra-Physics Quanta-Ray Q-switched GCR-
150 pulsed Nd:YAG laser (10 Hz). Luminescence quantum yields
were measured by the optical dilute method reported by Demas and
Crosby.49 A degassed aqueous solution of quinine sulfate in 1.0 N
sulfuric acid (Φ = 0.546, excitation wavelength at 365 nm) was used as
the reference and corrected for the refractive index of the solution.49b
All solution samples for photophysical studies were freshly prepared
under a high vacuum in a 10-cm3 round-bottomed flask equipped with
a side-arm 1-cm fluorescence cuvette and sealed from the atmosphere
by a Rotaflo HP6/6 quick-release Teflon stopper. Solutions were
rigorously degassed on a high-vacuum line in a two-compartment cell
with no less than four successive freeze−pump−thaw cycles. Cyclic
voltammetric measurements were performed by using a CH
Instruments, Inc., model CHI 600A electrochemical analyzer. The
electrolytic cell used was a conventional two-compartment cell.
Electrochemical measurements were performed in dichloromethane
Synthesis. General Procedure for Syntheses of Alkynylgold(III)
Complexes. The alkynylgold(III) complexes were synthesized
according to a reported procedure, as summarized below.25 A mixture
of the gold(III) precursor complex, [Au(R-C^N^C)Cl] (0.50 mmol),
was suspended in dichloromethane (35 mL) in the presence of a
catalytic amount of copper(I) iodide (10 mg, 0.05 mmol). The
appropriate acetylene (0.75 mmol) and triethylamine (2 mL) were
then added. The resulting mixture was stirred at room temperature for
3 h, after which the mixture was evaporated to dryness. The solid
residue was purified by column chromatography on silica gel using
dichloromethane as the eluent. Subsequent recrystallization from the
slow diffusion of diethyl ether or n-pentane vapor into the
concentrated dichloromethane solution yielded the respective complex
as yellow solids.
[Au(C^N^C)(CCC6H2(OCH3)3-3,4,5)] (1; HC^N^CH = 2,6-
Diphenylpyridine). 1 was synthesized from [Au(C^N^C)Cl] (231
mg, 0.50 mmol) and 3,4,5-(trimethoxyphenyl)acetylene (144 mg, 0.75
mmol) according to the general procedure. The target complex 1 was
obtained as yellow crystals. Crystals of diffraction quality were
obtained from the layering of hexane onto a concentrated dichloro-
methane solution of the complex. Yield: 161 mg (52%). 1H NMR (400
MHz, CDCl3, 298 K): δ 3.88 (s, 3H, −OCH3), 3.91 (s, 6H, −OCH3),
6.86 (s, 2H, −CCC6H2−), 7.25 (t, 2H, J = 7.3 Hz, phenyl of
C^N^C), 7.40 (t, 2H, J = 7.3 Hz, phenyl of C^N^C), 7.53 (d, 2H, J =
8.0 Hz, pyridine of C^N^C), 7.59 (d, 2H, J = 7.3 Hz, phenyl of
C^N^C), 7.92 (t, 1H, J = 8.0 Hz, pyridine of C^N^C), 8.08 (d, 2H, J =
7.3 Hz, phenyl of C^N^C). Positive FAB-MS: m/z 617 ([M]+). IR
(KBr): 2137 cm−1 [ν(CC)]. Elem anal. Calcd for C28H22AuNO3
(found): C, 54.47 (54.43); H, 3.59 (3.96); N, 2.27 (2.26).
n
solutions with 0.1 M Bu4NPF6 as the supporting electrolyte at room
temperature. The reference electrode was a Ag/AgNO3 (0.1 M in
acetonitrile) electrode, and the working electrode was a glassy carbon
electrode (CH Instruments, Inc.) with a platinum wire as the counter
electrode. The working electrode surface was first polished with a 1-
μm alumina slurry (Linde), followed by a 0.3-μm alumina slurry, on a
microcloth (Buehler Co.). The ferrocenium/ferrocene couple
(FeCp2+/0) was used as the internal reference.50 All solutions for
electrochemical studies were deaerated with prepurified argon gas just
before measurements.
[Au(C^N^C)(CCC6H2(OC12H25)3-3,4,5)] (2). 2 was synthesized
from [Au(C^N^C)Cl] (231 mg, 0.50 mmol) and 3,4,5-
(tridodecoxyphenyl)acetylene (491 mg, 0.75 mmol) according to the
general procedure. The target complex 2 was obtained as yellow solids.
Gelation Studies. A gelation test was carried out by suspending a
weighed sample of the gold(III) metallogelator in a measured volume
of a particular organic solvent inside a screw-capped sample vial. The
suspension was heated until all of the solids were dissolved. The
sample vial was cooled in air to room temperature and then left to
stand for a period of time. The gelation properties were evaluated by
the “stable-to-inverion of a test tube” method. The temperature-
dependent electronic absorption spectra and variable-temperature
steady-state emission and excitation spectra were obtained using a
Varian Cary 50 UV−vis spectrophotometer and a Spex Fluorolog-3
model FL3-211 spectrofluorometer, respectively, with a Varian Cary
single-cell Peltier thermostat to control the working temperature. A
quartz cuvette with a 2-mm path length has been used for the
measurements. SEM experiments were performed either on a Leo1530
field-emission-gun scanning electron microscope or a Hitachi S-3400N
variable-pressure scanning electron microscope operating at 4.0−8.0 or
12 kV, respectively. TEM experiments were performed on a Philips
Tecnai G2 20 S-TWIN transmission electron microscope with an
accelerating voltage of 200 kV. The TEM images were obtained by
Gatan MultiScan model 794. Both types of experiments were
conducted at the Electron Microscope Unit of the University of
Hong Kong. The SEM and TEM samples were prepared by dropping
dilute gels onto a silicon wafer. Slow evaporation of the solvents in air
for 10 min led to xerogels. All of the samples for SEM experiments
were sputter-coated with a gold thin film.
Crystal Structure Determination. Single crystals of 1 and 5
suitable for X-ray diffraction studies were grown by layering of n-
hexane onto a concentrated dichloromethane solution of the complex.
The X-ray diffraction data were collected on a Bruker Smart CCD
1000, using graphite-monochromatized Mo-Kα radiation (λ = 0.71073
Å). The structure was solved by direct methods, employing the
SHELXS-97 program.51 Full-matrix least-squares refinement on F2 was
used in the structure refinement. The positions of H atoms were
calculated based on the riding mode with thermal parameters equal to
1.2 times those of the associated C atoms and participated in the
calculation of the final R indices. In the final stage of least-squares
refinement, all non-H atoms were refined anisotropically.
1
Yield: 270 mg (50%). H NMR (400 MHz, CD2Cl2, 298 K): δ 0.86
(m, 9H, −CH3), 1.27 (m, 48H, −CH2−), 1.48 (m, 6H, −CH2−), 1.82
(m, 6H, −CH2−), 4.01 (m, 6H, −OCH2−), 6.77 (s, 2H, −CC
C6H2−), 7.24 (dt, 2H, J = 1.1 and 7.3 Hz, phenyl of C^N^C), 7.36 (dt,
2H, J = 1.1 and 7.3 Hz, phenyl of C^N^C), 7.50 (d, 2H, J = 8.0 Hz,
pyridine of C^N^C), 7.59 (d, 2H, J = 7.3 Hz, phenyl of C^N^C), 7.88
(t, 1H, J = 8.0 Hz, pyridine of C^N^C), 7.99 (d, 2H, J = 7.3 Hz,
phenyl of C^N^C). Positive FAB-MS: m/z 1080 ([M]+). IR (KBr):
2137 cm−1 [ν(CC)]. Elem anal. Calcd for C61H88AuNO3·1/2H2O
(found): C, 67.26 (67.29); H, 8.24 (7.91); N, 1.29 (1.25).
[Au(C^N^C)(CCC6H2(OC16H33)3-3,4,5)] (3). 3 was synthesized
from [Au(C^N^C)Cl] (231 mg, 0.50 mmol) and 3,4,5-
(trihexadecoxyphenyl)acetylene (618 mg, 0.75 mmol) according to
the general procedure. The target complex 3 was obtained as yellow
1
solids. Yield: 499 mg (80%). H NMR (300 MHz, CDCl3, 298 K): δ
0.91 (m, 18H, −CH3 and −CH2−), 1.26 (m, 60H, −CH2−), 1.48 (m,
9H, −CH2−), 1.80 (m, 6H, −CH2−), 3.99 (m, 6H, −OCH2−), 6.83
(s, 2H, −CCC6H2−), 7.28 (d, 2H, J = 7.3 Hz, phenyl of C^N^C),
7.40 (t, 2H, J = 7.3 Hz, phenyl of C^N^C), 7.50 (d, 2H, J = 8.1 Hz,
pyridine of C^N^C), 7.57 (d, 2H, J = 7.3 Hz, phenyl of C^N^C), 7.88
(t, 1H, J = 8.1 Hz, pyridine of C^N^C), 8.10 (d, 2H, J = 7.3 Hz,
phenyl of C^N^C). Positive FAB-MS: m/z 1249 ([M]+). IR (KBr):
2137 cm−1 [ν(CC)]. Elem anal. Calcd for C73H112AuNO3·H2O
(found): C, 69.22 (69.22); H, 9.07 (8.99); N, 1.11 (1.08).
[Au(C^N^C)(CCC6H2(OC18H37)3-3,4,5)] (4). 4 was synthesized
from [Au(C^N^C)Cl] (231 mg, 0.50 mmol) and 3,4,5-
(trioctadecoxyphenyl)acetylene (681 mg, 0.75 mmol) according to
the general procedure. The target complex 4 was obtained as pale
yellow solids. Yield: 373 mg (56%). 1H NMR (300 MHz, CD2Cl2, 298
K): δ 0.80 (m, 9H, −CH3), 1.18 (m, 66H, −CH2−), 1.45 (m, 24H,
−CH2−), 1.72 (m, 6H, −CH2−), 3.91 (m, 6H, −OCH2−), 6.71 (s,
2H, −CCC6H2−), 7.23 (dt, 2H, J = 1.2 and 7.9 Hz, phenyl of
C^N^C), 7.33 (dt, 2H, J = 1.2 and 7.9 Hz, phenyl of C^N^C), 7.43 (d,
2H, J = 7.9 Hz, phenyl of C^N^C), 7.48 (d, 2H, J = 7.9 Hz, pyridine of
C^N^C), 7.55 (dd, 2H, J = 1.2 and 7.9 Hz, phenyl of C^N^C), 7.85 (t,
1H, J = 7.9 Hz, pyridine of C^N^C), 7.95 (dd, 2H, J = 1.2 and 7.9 Hz,
phenyl of C^N^C). Positive FAB-MS: m/z 1332 ([M]+). IR (KBr):
H
dx.doi.org/10.1021/ic3007519 | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
2 1 4 5 c m − 1 [ ν ( C  C ) ] . E l e m a n a l . C a l c d f o r
C79H124AuNO3·1/2CH2Cl2 (found): C, 69.43 (69.82); H, 9.16
(9.16); N, 1.02 (1.25).
0.88 (m, 6H, −CH3), 1.26 (m, 75H, −CH3 and −CH2−), 1.45 (m,
6H, −CH2−), 1.80 (m, 6H, −CH2−), 3.91 (m, 6H, −OCH2−), 6.66
(s, 2H, −CCC6H2−), 7.53 (m, 4H, naphthyl of C^N^C), 7.89 (m,
5H, naphthyl and pyridine of C^N^C), 8.00 (m, 4H, naphthyl and
pyridine of C^N^C), 8.36 (d, 2H, J = 8.5 Hz, naphthyl of C^N^C).
Positive FAB-MS: m/z 1349 ([M]+). IR (KBr): 2145 cm−1 [ν(C
C)]. Elem anal. Calcd for C81H116AuNO3 (found): C, 72.13 (72.19);
H, 8.67 (8.67); N, 1.04 (1.34).
[Au(tBuC^N^CtBu)(CCC6H2(OCH3)3-3,4,5)] [5; HtBuC^N^CtBuH
= 2,6-Bis(4-tert-butylphenyl)pyridine]. 5 was synthesized from
[Au(tBuC^N^CtBu)Cl] (287 mg, 0.50 mmol) and 3,4,5-
(trimethoxyphenyl)acetylene (144 mg, 0.75 mmol) according to the
general procedure. The target complex 5 was obtained as yellow
crystals. Crystals of diffraction quality were obtained from layering of
hexane onto a concentrated dichloromethane solution of the complex.
Yield: 164 mg (45%). 1H NMR (400 MHz, CDCl3, 298 K): δ 1.39 (s,
[Au(CNp^N^CNp)(CCC6H2(OC18H37)3-3,4,5)] (10). 10 was synthe-
sized from [Au(CNp^N^CNp)Cl] (281 mg, 0.50 mmol) and 3,4,5-
(trioctadecoxyphenyl)acetylene (681 mg, 0.75 mmol) according to the
general procedure. The target complex 10 was obtained as pale yellow
t
18H, Bu), 3.89 (s, 3H, −OCH3), 3.90 (s, 6H, −OCH3), 6.88 (s, 2H,
1
solids. Yield: 107 mg (15%). H NMR (300 MHz, CDCl3, 298 K): δ
−CCC6H2−), 7.29 (dd, 2H, J = 2.0 and 8.0 Hz, phenyl of C^N^C),
7.41 (d, 2H, J = 8.0 Hz, pyridine of C^N^C), 7.51 (d, 2H, J = 8.0 Hz,
phenyl of C^N^C), 7.82 (t, 1H, J = 8.0 Hz, pyridine of C^N^C), 8.22
(d, 2H, J = 2.0 Hz, phenyl of C^N^C). Positive FAB-MS: m/z 730
([M]+). IR (KBr): 2137 cm−1 [ν(CC)]. Elem anal. Calcd for
C36H38AuNO3 (found): C, 59.26 (59.11); H, 5.25 (5.20); N, 1.92
(2.15).
0.86 (m, 12H, −CH3 and −CH2−), 1.25 (m, 84H, −CH2−), 1.86 (m,
9H, −CH2−), 4.07 (m, 6H, −OCH2−), 6.97 (s, 2H, −CCC6H2−),
7.53 (m, 4H, naphthyl of C^N^C), 7.81 (d, 2H, J = 7.8 Hz, pyridine of
C^N^C), 7.90 (m, 3H, naphthyl and pyridine of C^N^C), 8.01 (m,
4H, naphthyl of C^N^C), 8.37 (m, 2H, naphthyl of C^N^C). Positive
FAB-MS: m/z 1433 ([M]+). IR (KBr): 2152 cm−1 [ν(CC)]. Elem
anal. Calcd for C87H128AuNO3 (found): C, 72.92 (73.16); H, 9.00
(9.04); N, 0.98 (1.39).
[Au{C^N(2,5-F2C6H3)^C}(CCC6H2(OC18H37)3-3,4,5)] [6; HC^N-
(2,5-F2C6H3)^CH = 2,6-Diphenyl-4-(2,5-difluorophenyl)pyridine]. 6
was synthesized from [Au{C^N(2,5-F2C6H3)^C}Cl] (287 mg, 0.50
mmol) and 3,4,5-(trioctadecoxyphenyl)acetylene (681 mg, 0.75
mmol) according to the general procedure. The target complex 6
ASSOCIATED CONTENT
* Supporting Information
■
S
1
was obtained as yellow solids. Yield: 520 mg (72%). H NMR (300
Crystallographic data for the structures of 1 and 5, temperature-
dependent UV−vis absorption spectral traces, and emission
spectra of the sol−gel phase transition of complex 4 in
cyclohexane. This material is available free of charge via the
Internet at http://pubs.acs.org.
MHz, CDCl3, 298 K): δ 0.88 (m, 9H, −CH3), 1.25 (m, 84H,
−CH2−), 1.48 (m, 6H, −CH2−), 1.82 (m, 6H, −CH2−), 3.98 (m, 6H,
−OCH2−), 6.83 (s, 2H, −CCC6H2−), 7.28−7.33 (m, 5H,
−C6H3F2-2,5 and phenyl of C^N^C), 7.43 (t, 2H, J = 7.2 Hz, phenyl
of C^N^C), 7.63 (m, 4H, −C6H3F2-2,5 and pyridine of C^N^C), 8.13
(d, 2H, J = 7.2 Hz, phenyl of C^N^C). Positive FAB-MS: m/z 1445
([M]+). IR (KBr): 2137 cm−1 [ν(CC)]. Elem anal. Calcd for
C85H126AuF2NO3·3H2O (found): C, 68.11 (68.15); H, 8.88 (8.68); N,
0.93 (0.96).
AUTHOR INFORMATION
Corresponding Author
*E-mail: wwyam@hku.hk.
■
[Au{C^N(4-MeC6H4)^CNp}(CCC6H2(OC16H33)3-3,4,5)] (7; HC^N-
(4-MeC6H4)^CNpH = 4-(4-Methylphenyl)-2-(2-naphthyl)-6-phenyl-
pyridine). 7 was synthesized from [Au{C^N(4-MeC6H4)^CNp}Cl]
(301 mg, 0.50 mmol) and 3,4,5-(trihexadecoxyphenyl)acetylene (618
mg, 0.75 mmol) according to the general procedure. The target
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
1
complex 7 was obtained as yellow crystals. Yield: 465 mg (67%). H
V.W.-W.Y. acknowledges support from The University of Hong
Kong and the URC Strategic Research Theme on Molecular
Materials. This work has been supported by the University
Grants Committee Areas of Excellence Scheme (AoE/P-03/
08), the Collaborative Research Fund (HKUST2/CRF/10),
and the General Research Fund (HKU 7060/09P and HKU
7063/10P) from the Research Grants Council of Hong Kong
Special Administrative Region, People's Republic of China.
V.K.-M.A. acknowledges the receipt of a postgraduate student-
ship from The University of Hong Kong. Dr. A. Y.-Y. Tam is
gratefully acknowledged for his helpful discussions on gelation
studies. Dr. L. Szeto is gratefully acknowledged for technical
assistance in the crystal structure determination of 1. We also
thank the Electron Microscope Unit at The University of Hong
Kong for their technical assistance.
NMR (400 MHz, CDCl3, 298 K): δ 0.88 (m, 24H, −CH3 and
−CH2−), 1.26 (m, 54H, −CH2−), 1.43 (m, 9H, −CH2−), 1.78 (m,
9H, −CH2−), 2.47 (s, 3H, −CH3), 3.91 (m, 6H, −OCH2−), 6.67 (s,
2H, −CCC6H2−), 7.37 (d, 2H, J = 8.1 Hz, −C6H4−), 7.41 (d, 1H, J
= 8.1 Hz, −C6H4−), 7.57 (m, 2H, phenyl of C^N^C), 7.69 (m, 4H,
naphthyl and phenyl of C^N^C), 7.82 (m, 1H, naphthyl of C^N^C),
7.93 (m, 2H, pyridine of C^N^C), 7.99 (m, 1H, naphthyl of C^N^C),
8.08 (m, 1H, naphthyl of C^N^C), 8.16 (m, 1H, naphthyl of C^N^C).
Positive FAB-MS: m/z 1389 ([M]+). IR (KBr): 2152 cm−1
[ν(CC)]. Elem anal. Calcd for C84H120AuNO3·5H2O (found): C,
68.22 (68.24); H, 8.86 (9.04); N, 0.95 (0.88).
[Au(CNp^N^CNp)(CCC6H2(OC14H28)3-3,4,5)] (8; HCNp^N^CNpH =
2,6-Di-2-naphthylpyridine). 8 was synthesized from [Au-
(C^N p N^CN p )Cl] (281 mg, 0.50 mmol) and 3,4,5-
(tritetradecoxyphenyl)acetylene (554 mg, 0.75 mmol) according to
the general procedure. The target complex 8 was obtained as pale
yellow solids. Yield: 202 mg (32%). 1H NMR (300 MHz, CDCl3, 298
K): δ 0.88 (m, 6H, −CH3), 1.26 (m, 69H, −CH3 and −CH2−), 1.82
(m, 6H, −CH2−), 3.97 (m, 6H, −OCH2−), 6.71 (s, 2H, −C
CC6H2−), 7.54 (m, 4H, naphthyl of C^N^C), 7.91 (m, 4H, naphthyl
of C^N^C), 8.00 (m, 3H, naphthyl and pyridine of C^N^C), 8.38 (d,
2H, J = 8.6 Hz, naphthyl of C^N^C), 8.65 (s, 2H, pyridine of
C^N^C). Positive FAB-MS: m/z 1265 ([M]+). IR (KBr): 2137 cm−1
[ν(CC)]. Elem anal. Calcd for C75H101AuNO3·3C5H12 (found):
C,73.14 (73.34); H, 9.34 (9.10); N, 0.95 (1.35).
DEDICATION
■
Dedicated to Professor Dieter Fenske on the occasion of his
70th birthday.
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[Au(CNp^N^CNp)(CCC6H2(OC16H33)3-3,4,5)] (9). 9 was synthe-
sized from [Au(CNp^N^CNp)Cl] (281 mg, 0.50 mmol) and 3,4,5-
(trihexadecoxyphenyl)acetylene (618 mg, 0.75 mmol) according to the
general procedure. The target complex 9 was obtained as pale yellow
1
solids. Yield: 513 mg (76%). H NMR (400 MHz, CDCl3, 298 K): δ
I
dx.doi.org/10.1021/ic3007519 | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
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