Photophysical properties and electropolymerization of gold complexes of 3,3″-diethynyl-2,2′:5′,2″-terthiophene

Article abstract of DOI:10.1021/ic100961w

The preparation and crystal structures of 3,3″-diethynyl-2,2′: 5′,2″-terthiophene (A₂T₃) and three Au(I) complexes containing this ligand are reported. One of the complexes, Au ₂(dppm)(A₂T₃), has a short Au'Au distance (3.1969 A) because of an aurophilic interaction. UV/vis absorption and emission spectra of the complexes and ligand at 298 and 85 K and photoinduced electron transfer to methyl viologen are reported. A₂T₃ and two of the complexes may be electropolymerized, and the resulting gold-containing films were characterized by X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry.

Full text of DOI:10.1021/ic100961w

8802 Inorg. Chem. 2010, 49, 8802–8812
DOI: 10.1021/ic100961w
Photophysical Properties and Electropolymerization of Gold
Complexes of 3,300-Diethynyl-2,20:50,200-terthiophene
Angela M. Kuchison, Michael O. Wolf,* and Brian O. Patrick
Department of Chemistry, University of British Columbia, Vancouver, BC, V6T 1Z1, Canada
Received May 13, 2010
The preparation and crystal structures of 3,300-diethynyl-2,20:50,200-terthiophene (A2T3) and three Au(I) complexes containing
˚
this ligand are reported. One of the complexes, Au2(dppm)(A2T3), has a short Au-Au distance (3.1969 A) because of an
aurophilic interaction. UV/vis absorption and emission spectra of the complexes and ligand at 298 and 85 K and photoinduced
electron transfer to methyl viologen are reported. A2T3 and two of the complexes may be electropolymerized, and the resulting
gold-containing films were characterized by X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry.
Introduction
Functionalization of oligo- and polythiophenes can be
used to achieve an even greater range of materials properties.
For example, functionalization with simple alkyl and alkoxy
substituents results in greatly enhanced processablity and
solubility,12 while modification with more complex function-
alities such as molecular switches,13 crown ethers14-16 or
fullerenes,17 results in systems suitable for sensor or mole-
cular electronic (i.e., OFET, photovoltaic or OLED) applica-
tions. Metal complexes offer a large range of possible
functionality to oligo- and polythiophenes via their optical,
catalytic, and electronic properties.18-21 A particularly intrigu-
ing approach to metal modification of conjugated sys-
tems is to use the propensity of some metals such as gold
to weakly interact with other metal centers, either inter- or
intramolecularly. In carefully constructed systems, these
“aurophilic” interactions can strongly influence the degree
of conjugation in a pendant oligothiophene backbone,22
and thus dramatically influence the electronic behavior of
the oligothiophene. Aurophilic interactions may also give
rise to luminescent states which are useful in sensors23 and
Delocalized π electron systems found in conjugated
materials impart many interesting properties, including
high charge mobility and conductivity, luminescence, and
absorption in the UV/vis spectrum to these materials.
These properties have led to the use of conjugated materi-
als in applications such as organic photovoltaics,1 light emitt-
ing diodes (OLEDs)2 and field effect transistors (OFETs).3,4
Functionalized polythiophenes are some of the most exten-
sively studied conjugated polymers because of their excellent
suitability for a variety of electronic applications.5 Although
the extended conjugation found in polythiophenes is impor-
tant for some of these applications, oligothiophenes with
shorter, well-defined conjugation lengths are often useful in
evaluating the electronic absorption, emission, and electro-
chemical properties of related polymers. In some cases the
oligomers are also suitable for direct application in electronic
devices.6-11
*To whom correspondence should be addressed. E-mail: mwolf@
chem.ubc.ca.
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pubs.acs.org/IC
Published on Web 09/01/2010
2010 American Chemical Society

Article
Inorganic Chemistry, Vol. 49, No. 19, 2010 8803
Scheme 1. Synthesis of A2T3
luminescent displays.24 The presence of aurophilic inter-
actions can therefore affect the electronic properties of Au(I)
complexes with oligothiophene ligands, most notably the
luminescence that may be either dominated by emission from
a Au(I)-Au(I) state or an oligothiophene-based πrπ*
state.25 A variety of ligating groups such as carbenes,26
thiolates,27 phosphines,22,25,28 and acetylides29,30 have been
used to tether Au(I) centers to oligothiophenes.
Oligothiophenes can serve as monomers for the prepara-
tion of functionalized polythiophenes,11 and it is intriguing
to consider the possibility of polymerizing oligothiophenes
with pendant gold centers that are also involved in aurophilic
interactions. This may result in new photophysical behavior
and enhanced supramolecular interactions. Previously, we
preparedAu complexes where the metal centers were tethered
via β-phosphine substituents on adjacent thiophenes, and
these speciesexhibitedintramolecular Au-Au interactions.22
However, the combination of the steric bulk of the diphe-
nylphosphine groups and thepoorconjugation between adja-
cent thiophenes in these complexes prevented electropoly-
merization.22 Addition of a third thiophene ring between
terminal phosphine-bearing thiophenes resulted in structural
changes to the oligothiophene including improved conjuga-
tion, but no aurophilic interactions were observed because
of the steric bulk of the phosphines.28 Here we report a new
ligand system in which steric effects are reduced via the use of
acetylenes rather than diarylphosphines to bind the metals.
A terthiophene framework is used to allow planarization of
the conjugated backbone. We report three Au(I) complexes
with this new ligand, illustrating the effect of aurophilic inter-
actions and ligand conjugation on the photophysical and
electrochemical properties of the complexes.
Figure 1. Solid state molecular structure of A2T3. Hydrogens have been
omitted for clarity and thermal ellipsoids are drawn at 50% probability.
Crystals of A2T3 suitable for single crystal X-ray diffrac-
tion were grown from a CH2Cl2/hexanes solution. In the
solid state, the structure of the terthiophene moiety in
A2T3 (Figure 1) is quite similar to that of unsubstituted
2,20:50,200-terthiophene. A2T3 adopts a planar conforma-
tion with interannular torsion angles of 4.2 and 8.5°. By
comparison, 2,20:50,200-terthiophene has torsion angles
ranging from 6° to 9° in the solid state.32 The terthio-
phene32 and acetylene33 bond lengths and angles are un-
remarkable, and A2T3, like 2,20:50,200-terthiophene,32 packs
in a herringbone structure.
Reaction of A2T3 with PPh3AuCl results in the forma-
tion of the digold complex, (AuPPh3)2A2T3 (Scheme 2).
Crystals of (AuPPh3)2A2T3 suitable for X-ray diffraction
were grown from a CHCl3/hexanes solution, and the solid
state molecular structure is shown in Figure 2. The steric
bulk imposed by the AuPPh3 group increases the distor-
tion from planarity of the terthienyl backbone (inter-
annular torsion angle: 20.5°) in (AuPPh3)2A2T3 relative
to A2T3. A related complex in which AuPPh3 centers are
coordinated to the terminal (R, R00) positions of a terthio-
phene was prepared previously.29 In this case, the metal
places less steric demand on the planarity of the terthio-
phene backbone as evidenced by the small torsion angles
of 8.7° and 5.0° in the terthiophene group.29 Although the
Au atoms are on the same side of the A2T3 ligand in
(AuPPh3)2A2T3, the bulk of the PPh3 groups prevents an
aurophilic interaction.
Results and Discussion
Synthesis and Structures. The new diacetylene 3,300-di-
ethynyl-2,20:50,200-terthiophene (A2T3) was prepared from
3,300-dibromo-2,20:50,200-terthiophene (Br2T3).31 Double So-
nagashira coupling of trimethylsilylacetylene to Br2T3 gave
the trimethylsilyl protected intermediate, which was subse-
quently deprotected with n-Bu4NF to give A2T3 (Scheme 1).
(24) Yam, V. W.-W.; Cheng, E. C.-C. Top. Curr. Chem. 2007, 281, 269–
309.
(25) Stott, T. L.; Wolf, M. O.; Patrick, B. O. Inorg. Chem. 2005, 44, 620–
The PPh3 ligands in (AuPPh3)2A2T3 can be displaced
with less sterically demanding cyanide ligands to give
[n-Bu4N]2[(AuCN)2A2T3] (Scheme 2). Crystals of [n-Bu4N]2-
[(AuCN)2A2T3] were grown from an acetone/diethyl
ether solution, and the solid state molecular structure
is shown in Figure 3. The bond lengths and angles are
627.
(26) Powell, A. B.; Bielawski, C. W.; Cowley, A. H. J. Am. Chem. Soc.
2009, 131, 18232–18233.
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7387–7389.
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P. J.; Wong, W. Y. CrystEngComm 2002, 4, 405–412.
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Gray, T. G. Organometallics 2009, 28, 6171–6182.
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Staring, E. G. J. Synth. Met. 1989, 30, 381–389.
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Online 2002, E58, o777–o778.

8804 Inorganic Chemistry, Vol. 49, No. 19, 2010
Kuchison et al.
Figure 3. Solid state molecular structure of [n-Bu4N]2[(AuCN)2A2T3].
Hydrogens have been omitted for clarity and thermal ellipsoids are drawn
at 50% probability.
Figure 2. Solid state molecular structure of (AuPPh3)2A2T3. Hydrogens
have been omitted for clarity and thermal ellipsoids are drawn at 50%
probability.
internannular torsion angles of 19.0° and 20.4° in [n-Bu4N]2-
[(AuCN)2A2T3].
Reaction of (AuPPh3)2A2T3 with diphenylphosphino-
methane (dppm) results in the formation of Au2(dppm)-
(A2T3). Crystals of this complex were grown from a
CHCl3-CH2Cl2-acetone solution, and the structure is
shown in Figure 4. Here, the dppm bridges the two metal
centers, forcing the Au centers into close proximity and
resulting in an aurophilic interaction37 with a Au(1)-
Au(2) distance of 3.1969(2)A. The small bite angle of the
dppm forces the Au-acetylide groups to deviate from
linearity (C-C-Au = 167.5(3)° and 174.3(4)°). In con-
trast, (AuPPh3)2A2T3 has a C-C-Au angle of 176.5(3)°
and [n-Bu4N]2[(AuCN)2A2T3] has C-C-Au angles of
177.0(3)° and 174.9(4)° (note: C(16B)-C(17B)-Au(2B)
is 169(8)°). Of these three Au complexes, Au2(dppm)-
(A2T3) has the most planar terthiophene backbone with
interannular torsion angles of 3.8° and 1.4°. As in (AuPPh3)2-
A2T3, all of the S atoms in Au2(dppm)(A2T3) are anti to
each other. In this case, this conformation minimizes the
distance between Au centers and allows the Au-Au
interaction in Au2(dppm)(A2T3). In contrast, other phos-
phino-Au-thienyl complexes with intramolecular auro-
philic interactions have torsion angles of ∼100° between
adjacent rings and Au-Au distances of 3.0879(7) and
Scheme 2. Synthesis of (AuPPh3)2A2T3, [n-Bu4N]2[(AuCN)2A2T3]
and Au2(dppm)(A2T3)
similar to those found in related species.29,34,35 Despite
the decreased steric bulk in [n-Bu4N]2[(AuCN)2A2T3], no
aurophilic interactions are observed with the shortest
distance between Au centers being 7.5 A. This is surpris-
ing, given that Au(I)-Au(I) interactions are often ob-
served in cationic and anionic Au(I) complexes with low
steric bulk around the Au centers.36 The syn orientation
of the thiophene rings in the terthiophene backbone of
[n-Bu4N]2[(AuCN)2A2T3] prevents the Au centers from
approaching one another. This contrasts with the anti
conformation observed in both A2T3 and (AuPPh3)2-
A2T3. In addition, a [n-Bu4N]þ counterion is intercalated
between adjacent Au atoms in the [(AuCN)2A2T3]2- unit.
The planarity of the terthiophene backbone is not signi-
ficantly altered in the solid state of [n-Bu4N]2[(AuCN)2-
A2T3] relative to (AuPPh3)2A2T3, as evident from the
3.3322(4) A.22
Electronic Spectroscopy
UV/vis Absorption Spectra. The UV/vis absorption
spectra of A2T3, (AuPPh)3A2T3, [n-Bu4N]2[(AuCN)2-
A2T3], and Au2(dppm)(A2T3) are shown in Figure 5.
The spectra are dominated by strong πfπ* transitions.
The spectrum of A2T3 has two absorption bands (Table 1)
slightly red-shifted from the corresponding bands in
the spectrum of 2,20:50,200-terthiophene (λmax = 250 and
354 nm)38 since unsubstituted terthiophene does not
benefit from the additional conjugation afforded by the
acetylene groups. Coordination of the Au centers to the
acetylene results in small shifts of the highest energy
(34) Katz, M. J.; Leznoff, D. B. J. Am. Chem. Soc. 2009, 131, 18435–
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(35) Rosenzweig, A.; Cromer, D. T. Acta Crystallogr. 1959, 12, 709–712.
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Article
Inorganic Chemistry, Vol. 49, No. 19, 2010 8805
increased conjugation along the terthiophene backbone
imposed by the molecular geometry. Additional bands
between 300 and 330 nm in the spectra of Au2(dppm)-
(A2T3), (AuPPh3)2A2T3, and [n-Bu4N]2[(AuCN)2A2T3]
may be due to metal-perturbed intraligand transitions.
Several other gold acetylide complexes have bands with
contributions of a similar nature.39-42
Low temperature UV/vis spectra of the molecules in
MeOH/EtOH glasses were obtained to gain further in-
sight into their electronic behavior. In an EtOH/MeOH
(4:1) solution at room temperature, the absorption spec-
tra of all the compounds are similar to those obtained
in CH2Cl2. In a frozen MeOH/EtOH glass at 85 K,
increased vibronic coupling is observed for all the com-
pounds (Figure 6). The lowest energy electronic transition
for all the compounds, observed as a single broad band
at room temperature, separates into several bands at 85 K
with ∼1400-1490 cm-1 spacing. This vibronic coupling
is attributed to thiophene ring vibrations43 and C-C
stretches.44 Low temperature studies on 2,20:50,200-terthio-
phene show similar vibronic structure.38,45 In the case of
A2T3 and [n-Bu4N]2[(AuCN)2A2T3] there appear to be
additional sharp bands in the lower energy region of the
spectrum. These may be due to C-H vibronic coupling or
the presence of multiple structural conformations frozen
out at low temperature. The higher energy transitions also
show vibronic coupling with the thienyl rings, consistent
with an electronically delocalized system.
Figure 4. Solid state molecular structure of Au2(dppm)(A2T3). Hydro-
gens and occluded solvent have been omitted for clarity and thermal
ellipsoids are drawn at 50% probability.
The spectra of all the compounds exhibit a bathochro-
mic shift in the lowest energy band with decreasing tem-
perature. For A2T3, the absorption red-shifts by ∼900
cm-1 upon cooling to 85 K. The absorption band of
2,20:50,200-terthiophene is known to bathochromically
shift by ∼1600 cm-1 from room temperature to 77 K.38
This has been attributed to increased planarity of the
terthienyl group at low temperature resulting in increased
conjugation, and a similar effect is likely involved here. At
low temperature, the spectra of the Au(I) complexes are
considerably less red-shifted than the spectrum of A2T3.
At 85 K the lowest energy absorption bands are batho-
chromically shifted by ∼480 cm-1, ∼450 cm-1, and ∼360
cm-1 for [n-Bu4N]2[(AuCN)2A2T3], Au2(dppm)(A2T3),
and (AuPPh3)2A2T3, respectively. This suggests that the
presence of the Au(I) centers restrict rotation of the
thienyl units more than in free A2T3 which is not hindered
by the metal centers.
Figure 5. UV/vis absorption spectra of A2T3, (AuPPh3)2A2T3, [n-Bu4N]2-
[(AuCN)2A2T3], and Au2(dppm)(A2T3) in CH2Cl2 at 298 K.
πfπ* transition, as has been previously observed for
other Au(I)-acetylide complexes,39 and is most clearly
evident in [n-Bu4N]2[(AuCN)2A2T3] where λmax = 260
nm. In (AuPPh3)2A2T3 and Au2(dppm)(A2T3), the higher
energy transitions consist of a combination of the πfπ*
transitions of the phenyl rings of PPh3 and dppm as well
as A2T3 based πfπ* transitions. The lower energy bands
in the gold complexes are all red-shifted with respect to
the lower energy band in A2T3, as previously observed
in related complexes.29 The red-shift has previously been
attributed to electronic interactions of the acetylide
ligand with AuPPh3, and was found to depend on whether
one or two AuPPh3 groups are coordinated.29 By con-
trast, the compounds discussed here demonstrate that
changing the peripheral ligands on the Au2A2T3 moiety
changes the electronic interaction of the Au with the
A2T3. The larger red-shift of the lowest energy transition
of Au2(dppm)(A2T3) is not only an electronic effect due to
the presence of the dppm ligand but also a result of the
Emission Spectra. A2T3, (AuPPh3)2A2T3, and [n-Bu4N]2-
[(AuCN)2A2T3] are all emissive at room temperature. The
excitation and emission spectra of these compounds in
CH2Cl2 solution are shown in Figure 7. The excitation
spectra of the molecules match their respective electronic
absorption spectra, except <300nm where the low intensity
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1999, 578, 3–30.
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V. F. Khim. Geterotsikl. Soedin. (Engl. Transl.) 1967, 452–458.
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8806 Inorganic Chemistry, Vol. 49, No. 19, 2010
Kuchison et al.
Table 1. Absorption Data for Compounds at 298 K in CH2Cl2 Solutions and 85 K in MeOH/EtOH
compound
λ
max /nm (εmax/M-1 cm-1) at 298 K
λmax/nm at 85 K
A2T3
(AuPPh3)2A2T3
[n-Bu4N]2[(AuCN)2A2T3]
Au2(dppm)(A2T3)
274 (9 000), 385 (21 000)
271 (sh), 280, 295, 308, 379, 393 (sh), 401, 419 (sh), 427
262, 303, 323 (sh), 390, 412, 438
259, 310, 322, 393, 409, 414, 435, 441 (sh)
268, 275, 289, 312, 326, 400, 425, 454
267 (34 000), 307 (24 000), 411 (24 000)
260 (25 000), 320 (18 000), 404 (25 000)
301 (33 000), 326 (28 000), 421 (15 000)
Figure 6. Comparison of 298 and 85 K absorption spectra of A2T3, (AuPPh3)2A2T3, [n-Bu4N]2[(AuCN)2A2T3], and Au2(dppm)(A2T3) in MeOH/EtOH.
of the xenon lamp results in weak emission. The emission
spectrum of A2T3 is similar to that of 5,500-bis(acetylene)-
terthiophene (λem= 446 and 469 nm)29 and 2,20:50,200-
terthiophene (λem= 407 and 426 nm),38 with ring vibra-
tions coupled in all three cases. The emission bands of
(AuPPh3)2A2T3 and [n-Bu4N]2[(AuCN)2A2T3] are red-
shifted with respect to those of A2T3 (Figure 6, Table 2).
All of the compounds which are emissive at room tem-
perature had excited state lifetimes of <50 ps. Such short
lifetimes are typical of fluorescence of terthiophene deri-
vatives. For example, emission lifetimes of phosphonic
acid monoethyl ester and carboxylic acid derivatized
terthiophenes are ∼20 and 200 ps, respectively.46,47 Emis-
sion quantum yields (Φem) were measured where possible
(Table 2), and are generally low; however, the Au com-
plexes both have a smaller quantum yield than A2T3
possibly a result of the heavy-atom effect.48 The small
Stokes shift, similar band shape of the emission to that of
A2T3, and short emission lifetimes of the Au complexes
are consistent with ligand-based emission from a singlet
state.
Unlike the other compounds, Au2(dppm)(A2T3) is
non-emissive at room temperature. This suggests that
either radiationless decay dominates the relaxation of
the excited state or any emission is too weak to be ob-
served. There are several Au(I) complexes known where
ligand phosphorescence is the dominant emission ob-
served in solution,42,49,50 and it is possible that this also
occurs in Au2(dppm)(A2T3). Since the terthienyl group in
Au2(dppm)(A2T3) is remarkably planar, the ligand-based
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(47) Anestopoulos, D.; Fakis, M.; Mousdis, G.; Giannetas, V.; Persephonis,
P. Synth. Met. 2007, 157, 30–34.
´

Article
Inorganic Chemistry, Vol. 49, No. 19, 2010 8807
Figure 8. Emission (right side) and excitation (left side) spectra of
Au2(dppm)(A2T3) as a function of temperature in MeOH/EtOH.
Figure 7. Emission and Excitation Spectra of A2T3, (AuPPh3)2A2T3,
and [n-Bu4N]2[(AuCN)2A2T3] in CH2Cl2 at 298 K.
spectra at low temperature in all cases. Unlike the absorp-
tion spectra, the emission bands do not shift with decreas-
ing temperature. This indicates that fluorescence is likely
occurring from a state localized on the planar oligo-
thiophene backbone as has previously been observed in
2,20:50,200-terthiophene.38 The intensity of the emission
also increased with decreasing temperature, consistent
with reduced nonradiative decay pathways at low tem-
perature.
Table 2. Emission Data for Compounds at 298 K in CH2Cl2 and 85 K in
MeOH/EtOH
λem/nm
at 298 K
Φem
(298 K)
compound
λem/nm at 85 K
A2T3
(AuPPh3)2A2T3
[n-Bu4N]2[(AuCN)2A2T3]
Au2(dppm)(A2T3)
438, 462
452, 479
447, 475
432, 461, 493, 529
451, 482, 517, 559
448, 478, 511, 553
465, 498, 536, 581
0.042
0.016
0.032
Photoinduced Electron Transfer. It has previously been
shown in separate studies that terthiophene derivatives,54,55
bis-Au(I) complexes,56 and Au(I) acetylide complexes39,42
are capable of undergoing photoinduced electron trans-
fer (PET) to methyl viologen (MV2þ). The presence of
several of these same structural features in the complexes
discussed here suggested the possibility of photoinduced
electron transfer occurring in these complexes. This type
of excited state reactivity is of interest for potential appli-
cations in solar energy harvesting and hydrogen photo-
generation.57
triplet state may be populated more readily than in
[n-Bu4N]2[(AuCN)2A2T3] or (AuPPh3)2A2T3. Sparging a
solution of Au2(dppm)(A2T3) with nitrogen gas did not
result in any observable emission. Phosphorescence from
2,20:50,200-terthiophene is difficult to observe, but has been
reported at 826 nm at 18 K51 and at 682 nm at 80 K using
nanosecond excitation with gated detection.52 Such ex-
perimental difficulties may complicate the observation of
a thiophene-based triplet emission from Au2(dppm)-
(A2T3). Alternatively, radiationless decay because of
Au(I)-Au(I) states may occur. Gold-based emission is
sensitive to the ligands present and these can result in
non-emissive interactions.53
Interestingly, Au2(dppm)(A2T3) is emissive at low tem-
perature. The emission bands are red-shifted with respect
to those seen in the other compounds (Table 2). As in
(AuPPh3)2A2T3 and [n-Bu4N]2[(AuCN)2A2T3], the small
Stokes shift between the excitation and emission bands of
Au2(dppm)(A2T3) is consistent with ligand-based emis-
sion. The strong emission from Au2(dppm)(A2T3) at 85 K
decreases with increasing temperature and is essentially
gone >185 K (Figure 8).
The excited state oxidation potentials (E(M/Mþ)*) of
(AuPPh3)2A2T3, [n-Bu4N]2[(AuCN)2A2T3], Au2(dppm)-
(A2T3), and A2T3 were calculated using eq 1 where E(M/
Mþ) is the first electrochemical oxidation potential and
E* is emission energy.58 The calculated singlet excited
state redox potentials are shown in Table 3.
EðM=MþÞꢀ ¼ EðM=MþÞ - Eꢀ
ð1Þ
Given that the reduction potential of (MV2þ/MVþ 3 ) is
-0.69 V versus SCE,59 it is predicted that the singlet states
of A2T3 and all of the gold complexes are thermodynam-
As observed in the absorption spectra, the low tem-
perature emission spectra show vibronic coupling with
the thiophene ring vibrations (Figure 8 and 9). The 85 K
emission spectra for A2T3, (AuPPh3)2A2T3, [n-Bu4N]2-
[(AuCN)2A2T3], and Au2(dppm)(A2T3) all have four
bands separated by ∼1400 cm-1. The low energy region
of the excitation spectra match the respective absorption
ically capable of photoreducing MV2þ
.
Irradiation of CH3CN solutions of A2T3 and MV2þ
with white or UV light results in a substantial decrease in
(54) Kim, Y. S.; McNiven, S.; Ikebukuro, K.; Karube, I. Photochem.
Photobiol. 1997, 66, 180–184.
(55) Evans, C. H.; Scaiano, J. C. J. Am. Chem. Soc. 1990, 112, 2694–2701.
(56) Che, C. M.; Kwong, H. L.; Yam, V. W. W.; Cho, K. C. J. Chem. Soc.,
Chem. Commun. 1989, 885–886.
(51) Xu, B.; Holdcroft, S. J. Am. Chem. Soc. 1993, 115, 8447–8448.
(52) Wasserberg, D.; Marsal, P.; Meskers, S. C. J.; Janssen, R. A. J.;
Beljonne, D. J. Phys. Chem. B 2005, 109, 4410–4415.
(53) Tiekink, E. R. T.; Kang, J. G. Coord. Chem. Rev. 2009, 253, 1627–
1648.
(57) Kalyanasundaram, K. Coord. Chem. Rev. 1982, 46, 159–244.
(58) Kalyanasundaram, K. Photochemistry of Polypyridine and Porphyrin
Complexes; Academic Press Limited: Toronto, 1992.
(59) Peon, J.; Tan, X.; Hoerner, J. D.; Xia, C.; Luk, Y. F.; Kohler, B.
J. Phys. Chem. A 2001, 105, 5768–5777.

8808 Inorganic Chemistry, Vol. 49, No. 19, 2010
Kuchison et al.
Figure 9. Comparison of room temperature excitation and emission spectra of A2T3, (AuPPh3)2A2T3, and [n-Bu4N]2[(AuCN)2A2T3] in EtOH-MeOH.
Table 3. Calculated Singlet Excited State Redox Potentials of Compounds
Scheme 3
compound
E(M/Mþ)* (V vs SCE)
A2T3
(AuPPh3)2A2T3
[n-Bu4N]2[(AuCN)2A2T3]
Au2(dppm)(A2T3)
-1.77
-1.40
-1.84
-1.90
the intensity of the A2T3 absorption band at 385 nm
(Supporting Information, Figure S1 and S2). The char-
acteristic blue color of the MVþ radical cation was not
3
observed after this irradiation. Irradiation of A2T3 in
the absence of MV2þ under the same conditions did not
result in a decrease in the absorption band intensity.
These results suggest some interaction between A2T3
and MV2þ occurs upon irradiation, possibly resulting in
decomposition of the A2T3; however, there is no evidence
for PET.
with UV light resulted in the observation of MVþ 3 , but
white light did not. This suggests that population of the
higher energy states is required for electron transfer.
These differences may be related to either the rigidity or
the aurophilic interaction of Au2(dppm)(A2T3).
None of the gold compounds show significant decom-
position with light irradiation in CH3CN. A shoulder
appears at 470 nm in the absorbance spectrum of
[n-Bu4N]2[(AuCN)2A2T3] when left in solution overnight.
Since this suggests possible thermal decomposition, solu-
tions of [n-Bu4N]2[(AuCN)2A2T3] were used immediately
after preparation. The spectra of (AuPPh3)2A2T3 or Au2-
(dppm)(A2T3) remained stable when solutions were left
overnight.
Electropolymerization. Oligothiophene complexes may
be electropolymerized, giving materials with longer con-
27
ꢀ
jugation lengths. Previously, Lardies et al. and Powell
et al.26 have electropolymerized Au(I)-thienyl com-
plexes. The presence of aurophilic interactions in digold-
phosphine complexes resulted in substantial interannular
twisting of the oligothiophene backbone which pre-
vents electropolymerization.22 (AuPPh3)2A2T3, [n-Bu4N]2-
[(AuCN)2A2T3], and Au2(dppm)(A2T3) have relatively
planar terthiophene ligands and thus are good candidates
for electropolymerization. The oxidative electropolymeri-
zation reaction of the Au complexes, and the proposed
structure of the products are shown in Scheme 3.
Irradiation of (AuPPh3)2A2T3/MV2þ solutions with
either UV or white light resulted in the appearance of
absorption bands due to MVþ 3 (Supporting Information,
Figure S3 and S4).60 The short emission lifetime for this
complex suggests that either intermolecular electron tran-
sfer from the singlet state is extremely rapid, or another,
non-emissive, excited state is involved in the electron
transfer.
Despite excited [n-Bu4N]2[(AuCN)2A2T3] being thermo-
dynamically a stronger reducing agent than (AuPPh3)2-
A2T3, UV and white light irradiation resulted in no
absorption due to MVþ 3 . It is possible that there is a
large activation barrier for electron transfer, or that
[(AuCN)2A2T3]2- and MV2þ form an ion-pair in solution
causing back-electron transfer to be rapid. [Au(CN)2]-
has been prepared with a MV2þ counterion;61 however,
The cyclic voltammogram (CV) of A2T3 has one oxida-
tion wave at 1.00 V versus SCE that increases in current
with increasing number of scans (Supporting Informa-
tion, Figure S6). This behavior is characteristic of the
electropolymerization of a conductive polymer on the
working electrode. Both acetylene and thiophene are
known to electropolymerize and have similar oxidation
potentials,62,63 so it is difficult to predict the structure of
the electropolymerized A2T3.
Cyclic voltammetry of (AuPPh3)A2T3 shows one irre-
versible oxidation wave at 1.16 V versus SCE. Repeated
scans resulted in increased current with each subsequent
oxidation wave (Figure 10a), thus showing evidence that
electropolymerization is occurring. As the number of
scans is increased, the oxidation wave also shifted to
there are no literature reports of electron transfer from
3
[Au(CN)2]- to MV2þ to yield MVþ
.
Interestingly, substituting PPh3 for dppm results in
different excited state properties. Photoexcitation of a
CH3CN solution of Au2(dppm)(A2T3)/MV2þ solution
~
(62) Garcıa-Canadas, J.; Rodrıguez, J. G.; Lafuente, A.; Marcos, M. L.;
´ ´
Velasco, J. G. J. Polym. Sci., Part A: Polym. Chem. 2005, 43, 2407–2416.
(63) Roncali, J.; Garreau, R.; Yassar, A.; Marque, P.; Gamier, F.;
Lemaire, M. J. Phys. Chem. 1987, 91, 6706–6714.
(60) Kosower, E. M.; Cotter, J. L. J. Am. Chem. Soc. 1964, 86, 5524–5527.
(61) Kunkely, H.; Vogler, A. Inorg. Chem. Commun. 2000, 3, 205–207.

Article
Inorganic Chemistry, Vol. 49, No. 19, 2010 8809
Figure 10. Electropolymerization of (a) (AuPPh3)2A2T3 on an ITO electrode and (b) electropolymerization of [n-Bu4N]2[(AuCN)2A2T3] on a Pt disk
electrode. Scan rate = 100 mV/s. Solvent = CH2Cl2. Electrolyte = 0.1 M [n-Bu4N][PF6].
Table 4. XPS Analysis Data of Electropolymerized Films
compound
sample no.
%Au
%S
%P
%N
3.79
Au:S
Au:N
1:0.6
Au:P
poly-(AuPPh3)2A2T3
1
2
3
1
1
2
3
0.27
0.51
0.44
5.50
1.75
2.18
0.77
8.50
8.72
9.68
10.07
6.87
5.81
6.23
1:31
1:17
1:22
1:1.8
1:3.9
1:2.6
1:8.1
0.98
0.59
1:1.9
1:1.3
poly-[n-Bu4N]2[(AuCN)2A2T3]
poly-Au2(dppm)(A2T3)
2.67
3.13
0.61
1:1.5
1:1.4
1:0.8
higher potential. This shift suggests that either the con-
jugation in the electropolymerized material is less than in
the monomer, or that a poorly conductive material forms
as a consequence of the electropolymerization. With two
large AuPPh3 groups close together, steric interactions
may cause twisting along the oligo/polythiophene back-
the [n-Bu4N]2[(AuCN)2A2T3] monomer supporting the
conclusion that the Au-acetylide complex remains intact.
The lower nitrogen content suggests less counterion may
be present in the polymer than in the monomer and could
indicate some p-doping of the resulting polythiophene.
Doped polymer would carry a positive charge on the
backbone balancing the negative charge at the metal, thus
no longer requiring counterions for charge balance.
Similarly, the growth in the oxidation wave of an Au2-
(dppm)(A2T3) solution with increasing scans indicates
electropolymerization of this complex (Figure 11a). The
CV of Au2(dppm)(A2T3) has two oxidation waves, one at
0.76 V and another at 1.51 V versus SCE. Metal-metal
interactions are known to stabilize Au2þ centers.66 For
example, [(Au2{μ-(CH2)2PPh2}(μ-dppa)][ClO4] (dppa =
Ph2PNHPPh2) has an irreversible oxidation wave at
0.92 V67 while [Au2(μ-CH2PPh2CH2)2] oxidizes at 0.11 V.68
Repetitive scanning past the first oxidation wave of Au2-
(dppm)(A2T3) resulted in no increase in current, which
suggests the oxidation wave at 0.76 V is from a Auþ/2þ
oxidation process. Scanning to higher potential resulted
in increased conductivity and therefore polymer forma-
tion, which suggests the oxidation wave at 1.51 V is from a
terthiophene-based oxidation. A reduction wave, similar
to that found in the CV of (AuPPh3)2A2T3, appears at
-0.35 V and increases with repetitive scans. Repetitive
scans resulted in a shiny yellow-gold film on the working
electrode. The XPS analysis on the poly-Au2(dppm)-
(A2T3) film indicates slightly less Au than expected from
ꢀ
bone. Lardies et al. also observed an increase in oxidation
potential with increasing scans during electropolymeri-
zation.27 X-ray photoelectron spectroscopy (XPS) anal-
ysis of the films prepared here revealed a lower Au con-
tent than would be expected from the monomer formula,
despite analytically pure monomer being used (Table 4).
Metal-acetylide bonds are stablilized by ionic character,64
and it is possible that oxidative electropolymerization
decreases the Au-C bond strength allowing [AuPPh3]þ
to dissociate from the polymer. A reduction wave is ob-
served at 0.5 V. Waves at similar potentials are observed
for Au nanoparticles and are attributed to reduction of
Au oxide.65 It is possible that Au(0) particles are formed
by loss and reduction of Au from the polymer. Alterna-
tively, this could indicate poly-A2T3 formation since a
similar reduction wave is observed during electropoly-
merization of A2T3 (Supporting Information, Figure S6).
The presence of this wave with repetitive scanning may
indicate loss of Au from the polymer is occurring.
The complex [n-Bu4N]2[(AuCN)2A2T3] also has one irre-
versible oxidation wave at 1.08 V versus SCE (Figure 10b).
With increasing scans, the oxidation wave became qua-
sireversible, and the current increases, as expected for
electropolymerization on the working electrode surface.
XPS data shows the same Au/S elemental composition as
(66) Laguna, A.; Laguna, M. Coord. Chem. Rev. 1999, 193-195, 837–856.
(67) Bardaji, M.; Connelly, N. G.; Gimeno, M. C.; Jimenez, J.; Jones,
P. G.; Laguna, A.; Laguna, M. J. Chem. Soc., Dalton Trans. 1994, 1163–
1167.
(68) Bardaji, M.; Jones, P. G.; Laguna, A.; Laguna, M. Organometallics
1995, 14, 1310–1315.
(64) Kaharu, T.; Ishii, R.; Adachi, T.; Yoshida, T.; Takahashi, S.
J. Mater. Chem. 1995, 5, 687–692.
(65) Kumar, S.; Zou, S. Langmuir 2009, 25, 574–581.

8810 Inorganic Chemistry, Vol. 49, No. 19, 2010
Kuchison et al.
Figure 11. (a)ElectropolymerizationofAu2(dppm)(A2T3) ona Ptdiskelectrode(Scan rate=100mV/s) and (b) CVofpoly-Au2(dppm)(A2T3) at aPtdisk
electrode in monomer-free solution. Electrolyte = 0.1 M [n-Bu4N][PF6]. Solvent = CH2Cl2.
the monomer formula is present, but does not show the
same dramatic loss of Au as in poly-(AuPPh3)2A2T3. The
bridging dppm and the lower steric bulk of this ligand
relative to PPh3 may inhibit [Au2dppm]2þ dissociation
during electropolymerization. Interestingly, a poly-Au2-
(dppm)(A2T3) film in monomer free solution showed a
Auþ/2þ oxidation wave in addition to the polythiophene
oxidation wave as shown in Figure 11b which suggests
that the Au-Au interaction persists in the polymerized
material.
photoinduced electron transfer with MV2þ with broadband
white light. These differences are attributed to electronic
effects, possibly related to either the rigidity or aurophilic
interaction of Au2(dppm)(A2T3), allowing PET in the case of
(AuPPh3)2A2T3 but not for Au2(dppm)(A2T3).
All of the complexes exhibited a terthiophene-based oxi-
dation wave in the CV, and Au2(dppm)(A2T3) also has a
Auþ/2þ oxidation wave. All of the Au complexes electro-
polymerize, and the presence of the aurophilic interaction in
Au2(dppm)(A2T3) does not inhibit electropolymerization;
thus, this is the first example of a complex with an intramolec-
ular Au-Au interaction which electropolymerizes.
Conclusions
The new conjugated diacetylene A2T3 and the three gold
complexes containing this ligand reported here reveal some
interesting aspects of the electronic properties of metal-
containing oligothiophenes. Two structural aspects of the
gold complexes: the presence or absence of aurophilic inter-
actions and the conjugation in the oligothiophene backbone,
are relevant in understanding the electronic behavior of
the complexes. It is apparent that steric constraints prevent
aurophilic interactions from occurring in (AuPPh3)2A2T3.
Removing these constraints in [n-Bu4N]2[(AuCN)2A2T3] still
does not give aurophilic interactions, presumably because of
intercalation of the cation betweenthe Au centers. It isonlyin
Au2(dppm)(A2T3), with the bridging dppm and no cations
present, that an aurophilic interaction is observed. This reluc-
tance to form aurophilic interactions suggests that these are
weak here and observed only with forcing conditions. The
conjugation in the terthiophene backbone is also found to
depend on steric influences. In the solid state, the greatest
conjugation (as assessed by the interannular torsion angles
and the visible absorption spectra) is found in Au2(dppm)-
(A2T3). Interestingly, this compound is the only one which
does not emit at room temperature, an effect attributed to
either the presence of a low-lying triplet state because of the
highly conjugated terthiophene or to a deactivating pathway
resulting from the aurophilic interaction.
Experimental Section
General Procedures. 3,300-Dibromo-2,20:50,200-terthiophene
(Br2T3),31 AuCl(tht)69 (tht = tetrahydrothiophene), and methyl
viologen hexafluorophosphate (MV2þ 70
) were prepared accord-
ing to slightly modified literature procedures. Au(PPh3)Cl was
prepared by addition of triphenylphosphine to AuCl(tht).71
[n-Bu4N]CN, triphenylphosphine (PPh3), bis(diphenylphos-
phino)methane (dppm), methyl viologen chloride and CuI were
purchased from Sigma-Aldrich, HAuCl4 and Pd(PPh3)4 were
purchased from Strem Chemicals, [n-Bu4N][PF6] was purchased
from Fluka Chemicals, and trimethylsilylacetylene was pur-
chased from Acros Chemicals.
1H, 13C{1H}, and 31P{1H} NMR spectra were collected on
either a Bruker AV-300 spectrometer or a Bruker AV-400 spec-
trometer. 1H and 13C{1H} NMR spectra were referenced to resi-
dual solvent, and 31P{1H} NMR spectra referenced to external
85% H3PO4. Infrared spectra were obtained on a Nicolet 6700
FTIR with a Smart Orbit accessory. Solution and solid-state
UV-vis absorption spectra were obtained on a Varian Cary
5000 UV-vis-near-IR spectrophotometer. Solution excitation
and emission spectra were obtained on a Photon Technology
International QuantaMaster fluorimeter and were uncorrected
for lamp intensity. Low temperature absorption and emission
spectra were obtained from 4:1 ethanol/methanol solutions
using an Oxford OptistatDN cryostat. The limited solubility
of (AuPPh3)2A2T3, Au2(dppm)(A2T3), and A2T3 in the alcohol
mixture required dissolving them in a small amount of DMF
prior to addition to the ethanol/methanol. Quantum yields were
measured using a Labsphere general purpose integrating sphere.
Photoinduced electron transfer was explored by irradia-
tion of the complexes in the presence of an electron acceptor,
MV2þ. [n-Bu4N]2[(AuCN)2A2T3] did not undergo PET to
MV2þ, possibly because of the formation of an ion pair in
which rapid back electron transfer can occur. (AuPPh3)2-
A2T3 and Au2(dppm)(A2T3) both undergo PET to MV2þ
with UV light excitation, but only (AuPPh3)2A2T3 undergoes
(69) Uson, R.; Laguna, A.; Vicente, J. J. Organomet. Chem. 1977, 131,
471–475.
(70) Manjula, A.; Nagarajan, M. ARKIVOC 2001, 165–183.
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Article
Inorganic Chemistry, Vol. 49, No. 19, 2010 8811
Fluorescence lifetime measurements were carried out on a
Princeton Instruments Spectra Pro 2300i Imaging Triple Grat-
ing Monochromator/Spectrograph with a Hamamatsu Dyna-
mic Range Streak Camera (excitation source: EKSPLA Nd:
YAG laser, λ = 355 nm). Samples were prepared with an optical
density of 0.1 at the maximum of the lowest energy absorption
band. Cyclic voltammetry was carried out using an Autolab
potentiostat. Either a platinum disk or indium tin oxide (ITO)
on a glass slide was used as the working electrode. The reference
electrode was a silver wire, and the counterelectrode was plati-
num mesh. Decamethylferrocene was used as an internal refer-
ence to correct the potentials to the saturated calomel electrode
(SCE). The electrolyte, [n-Bu4N][PF6], was recrystallized three
times from ethanol and heated to 90 °C under vacuum for 3 days
prior to use. Cyclic voltammetry was carried out in CH2Cl2
dried over an activated alumina column. Solutions contained
0.1 M [n-Bu4N][PF6] and 1ꢁ10-3 M of the appropriate com-
pound. EI mass spectra were obtained using a Kratos MS-50
double focusing mass spectrometer coupled to a MASPEC data
system. The samples were introduced using direct insertion
probe. ESI mass spectra were recorded on Bruker Esquire-LC
ion trap mass spectrometer equipped with an electrospray ion
source. The solvent for the ESI-MS experiments was methanol,
and the concentration of the compound was ∼10 μM. MALDI
mass spectra were obtained on a Bruker Biflex IV MALDI-TOF
instrument equipped with a nitrogen laser. The samples were
dissolved in methanol or chloroform, and the MALDI mass
spectra acquired in positive reflectron mode with delay extrac-
tion. Spectra were obtained by averaging 100 laser shots.
Calibration of the MALDI-TOF spectra was performed exter-
nally using peptide standards. The CHN elemental analysis was
performed using an EA1108 elemental analyzer, using calibra-
tion factors. The calibration factor was determined by analyzing
a suitable certified organic standard (OAS) of a known elemen-
tal composition. X-ray photoelectron spectroscopy (XPS) anal-
ysis was performed using a Leybold MAX200 spectrometer
equipped with an Al KR source with a pass energy of 192 eV
and the sampling area was 2 ꢁ 4 mm.
solution (50 mL) of 3,300-di(trimethylsilylethynyl)-2,20:50,200-
terthiophene (1.18 g, 2.68 mmol). The solution immediately
changed from yellow to dark brown and was stirred overnight.
The THF was then removed in vacuo, and the subsequent
residue was dry loaded on a silica column and purified with an
acetone/hexanes (1:2) eluent. A2T3 was collected as a yellow
solid. Yield: 512 mg (65%). Crystals suitable for X-ray diffrac-
tion were grown from CH2Cl2/hexanes solution. 1H NMR (300
MHz, CDCl3); δ 7.51 (2, 2H), 7.11 (q, 4H, J = 5.1 Hz), 3.43 (s,
2H). 13C{1H} NMR (100 MHz, CDCl3) δ 140, 136, 132, 126,
123, 117, 82, 79. IR 2100 cm-1 (ν(CtC)). EI-MS m/z 296 (100%,
[M]þ). Anal. Calcd for C16H8S3: C, 64.83; H, 2.72. Found: C,
64.54; H, 2.75.
(AuPPh3)2A2T3. To a stirred CHCl3 solution (50 mL) of
AuCl(PPh3) (245 mg, 0.495 mmol) and A2T3 (73 mg, 0.247
mmol), NEt3 (3 mL) was added. The solution was left stirring
at room temperature for 48 h. The CHCl3 was then removed
in vacuo, and the residue was washed several times with 5 mL
aliquots of water. The residue was washed with acetone and
subsequently dissolved in minimal CHCl3 and hexanes was
added. The solution was cooled to 4 °C, and a yellow crystalline
precipitate formed. The precipitate was vacuum filtered to
obtain 267 mg (0.220 mmol, 89% yield) of (AuPPh3)2A2T3.
Crystals suitable for X-ray diffraction were grown from CHCl3/
hexanes solution. 1H NMR (400 MHz, CDCl3): δ 7.67 (s, 2H),
7.56 (m, 10H), 7.40 (m, 20H), 7.02 (d, 2H, J = 5.1 Hz), 6.98 (d,
2H, J = 5.1 Hz). 31P{1H} NMR (121 MHz, CDCl3): δ 42.05.
MALDI-TOF-MS m/z 1212 ([M]þ). Anal. Calcd for C52H36-
Au2P2S3 CHCl3: C, 47.78; H, 2.79. Found: C, 47.93; H, 2.89. IR
3
2226 cm-1 (ν(CtC)).
[n-Bu4N]2[(AuCN)2A2T3]. A CH2Cl2 solution (10 mL) con-
taining (AuPPh3)2A2T3 (100 mg, 0.0824 mmol) and n-Bu4NCN
(46.4 mg, 0.173 mmol) was sonicated at room temperature for 9
min. Immediately, hexanes (20 mL) were added, and the solu-
tion sonicated for another 9 min during which time a precipitate
formed. The mixture was left undisturbed for 1 h, and then the
hexanes/CH2Cl2 solution was decanted from the solid residue.
The residue was rinsed twice with hexanes (5 mL), then dissolved
in 5 mL of a 1:1 mixture of acetone and diethyl ether. The
acetone/ether solution was left at 4 °C overnight, during which
time bright yellow crystals of [n-Bu4N]2[(AuCN)2A2T3] formed
and were collected by vacuum filtration (60 mg, 0.049 mmol,
59%). The crystals were suitable for X-ray diffraction. 1H NMR
(400 MHz, CDCl3): δ 7.95 (s, 2H), 7.00 (s, 4H), 3.18 (t, 16 H, J =
8.4 Hz), 1.64 (m, 16 H), 1.43 (m, 16 H), 0.99 (m, 24 H). Negative
ESI-MS m/z 982 (100%, [M-n-Bu4N]-). Anal. Calcd for
C50H78Au2N4S3: C, 49.01; H, 6.42; N, 4.57. Found: C, 49.41;
H, 6.43; N, 4.91. IR 2138 cm-1 (ν(CtN)); 2105 cm-1 (ν(CtC)).
Au2(dppm)(A2T3). A CH2Cl2 (20 mL) solution of (AuPPh3)2-
A2T3 (121 mg, 0.0998 mmol) and dppm (38 mg, 0.0998 mmol)
was sonicated at room temperature for 30 min. Immediately,
hexanes (20 mL) were added to the solution and sonicated for 9
min during which time a solid precipitate formed. The solid was
washed twice with hexanes (20 mL), and the residue dissolved in
5 mL of a 1:0.25:1 CHCl3/CH2Cl2/acetone solution and left to
crystallize. Dark orange crystals of Au2(dppm)(A2T3) formed
overnight and were washed three times with acetone. Yield:
51 mg (48%). Crystals suitable for single crystal X-ray diffrac-
Synthesis. Caution! Although no explosions were encountered
here, Au acetylide complexes have previously been shown to be
explosive64,72,73 and care must be exercised when working with
them.
3,300-Di(trimethylsilylethynyl)-2,20:50,200-terthiophene. A de-
gassed piperidine solution (50 mL) of Br2T3 (1.160 g, 2.86
mmol), trimethylsilylacetylene (10.1 g, 102.8 mmol), Pd(PPh3)4
(330 mg, 0.29 mmol) and CuI (59.8 mg, 0.314 mmol) was heated
to reflux in the dark for 5 days. After cooling the reaction to
room temperature, 50 mL of Et2O was added, and the mixture
was washed five times with 50 mL of H2O. The Et2O was then
removed in vacuo leaving a brown oil. The oil was partially
purified via column chromotography on silica with hexanes
as the eluent. The resulting red oil (1.18 g) contained some
trimethylsilyl impurities which were difficult to remove, and the
compound was used without further purification in the subse-
quent reaction. When a sample of the oil was left dissolved
in hexanes at -4 °C for 3 months, pure yellow 3,300-di(tri-
methylsilylethynyl)-2,20:50,200-terthiophene precipitated from
the solution. 1H NMR (300 MHz, CDCl3); δ 7.61 (s, 2H), 7.08
(d, 2H, J = 5.1 Hz), 7.06 (d, 2H, J = 5.4 Hz), 0.31 (s, 18H).
13C{1H} NMR (75 MHz, CDCl3); δ 135.7, 131.7, 125.9, 117.7,
100.7, -0.14, (no resonances attributed to the acetylenic car-
bons were observed). EI-MS m/z 440 (100%, [M]þ). Anal. Calcd
for C22H24Si2S3: C, 59.95; H, 5.49. Found: C, 59.66; H, 5.73.
3,300-Diethynyl-2,20:50,200-terthiophene (A2T3). A THF solu-
tion of n-Bu4NF (1 M, 5.9 mL) was added to a stirring THF
1
tion were grown from a CHCl3/CH2Cl2/acetone solution. H
NMR (300 MHz, CDCl3): δ 7.65 (m, 8H), 7.44 (m, 4H), 7.35 (m,
8H), 7.19 (s, 2H), 7.08 (d, 2H, JHH = 5.4 Hz), 7.00 (d, 2H, JHH =
5.4 Hz), 3.68 (t, 2H, JPH =10.7 Hz). 31P{1H} NMR (121 MHz,
CDCl3): δ 32.3 (s). TOF m/z 1073 ([M]þ). Anal. Calcd for
C41H28Au2P2S3 (CH3)2CO: C, 46.73; H, 3.03. Found: C,
3
46.64; H, 3.12. IR 2107 cm-1 (ν(CtC)).
X-ray Crystallography. All crystals were mounted on glass
fibers. All measurements were made on a Bruker X8 APEX II
diffractometer with graphite monochromated Mo-KR radia-
tion. Data were collected and integrated using the Bruker
(72) Mathews, J. A.; Watters, L. L. J. Am. Chem. Soc. 1900, 22, 108–111.
(73) McArdle, C. P.; Jennings, M. C.; Vittal, J. J.; Puddephatt, R. J.
Chem.;Eur. J. 2001, 7, 3572–3583.

8812 Inorganic Chemistry, Vol. 49, No. 19, 2010
Kuchison et al.
SAINT74 software package. Data were corrected for absorption
effects using the multiscan technique (SADABS75). The data
were corrected for Lorentz and polarization effects. The struc-
tures were solved by direct methods.76
0.204 and 0.501, respectively. All non-hydrogen atoms were
refined anisotropically. All hydrogen atoms were placed in
calculated positions but were not refined. The material crystal-
lizes with a small amount of disorder in one thiophene along
with its C-C-Au-C-N substituent. The minor disordered
fragment was refined using geometric restraints, as well as
restraints on anisotropic displacement parameters. The final
cycle of full-matrix least-squares refinement on F2 was based on
12644 reflections and 571 variable parameters.
A2T3. All data were collected to a maximum 2θ value of 55.0°.
Data were collected in a series of φ and ω scans in 0.50°
oscillations with 10.0 s exposures. The crystal-to-detector dis-
tance was 36.00 mm. Of the 18307 reflections that were col-
lected, 3066 were unique (Rint = 0.040); equivalent reflections
were merged. The linear absorption coefficient, μ, for Mo-KR
radiation is 5.16 cm-1. The minimum and maximum transmis-
sion coefficients were 0.812 and 0.975, respectively. All non-
hydrogen atoms were refined anisotropically. All hydrogen
atoms were placed in calculated positions but were not refined.
The final cycle of full-matrix least-squares refinement on F2 was
based on 3066 reflections and 172 variable parameters and
converged.
Au2(dppm)(A2T3). The data were collected to a maximum 2θ
value of 56.2°. Data were collected in a series of φ and ω scans in
0.50° oscillations with 5.0 s exposures. The crystal-to-detector
distance was 40.00 mm. Of the 57624 reflections that were
collected, 9505 were unique (Rint = 0.053); equivalent reflec-
tions were merged. The linear absorption coefficient, μ, for
Mo-KR radiation is 77.64 cm-1. The minimum and maximum
transmission coefficients were 0.190 and 0.537, respectively. All
non-hydrogen atoms were refined anisotropically. All C-H
hydrogen atoms were placed in calculated positions but were
not refined. The final cycle of full-matrix least-squares refine-
ment on F2 was based on 9505 reflections and 469 variable
parameters and converged (largest parameter shift was 0.00
times its esd) with unweighted and weighted agreement factors.
Photoinduced Electron Transfer to MV2þ. A solution of 4 ꢁ
10-3 M of either methyl viologen chloride or methyl viologen
hexafluorophosphate was degassed via three freeze-pump-
thaw cycles. Solutions (10-5 M) of the respective Au complexes
and A2T3 were prepared and degassed. Approximately 1.5 mL
of the methyl viologen solution and 1.5 mL of the acetylide
compound solution were added to a cuvette under N2(g). An
absorption spectrum was collected to ensure no decomposition
of any reactants occurred. This solution was then irradiated with
a hand-held lamp (λmax= 365 nm, intensity ∼0.5 mW) or a white
lamp (400-800 nm broadband light, intensity ∼50 mW) for
15-16 min. Lamp intensity powers were measured with an
Ophir power meter thermal sensor. After irradiation, the ab-
sorption spectrum of the solution was collected again.
(AuPPh3)2A2T3.. Data were collected in a series of φ and ω
scans in 0.50° oscillations with 20.0 s exposures. The crystal-to-
detector distance was 36.00 mm. The data were collected to a
maximum 2θ value of 56.0°. Of the 32338 reflections that were
collected, 5733 were unique (Rint = 0.034); equivalent reflec-
tions were merged. The linear absorption coefficient, μ, for
Mo-KR radiation is 64.02 cm-1. Data were corrected for
absorption effects using the multiscan technique (SADABS),75
with minimum and maximum transmission coefficients of 0.530
and 0.726, respectively. The material crystallizes with one-half-
molecule in the asymmetric unit, residing on a 2-fold axis of
rotation. All non-hydrogen atoms were refined anisotropically.
All hydrogen atoms were placed in calculated positions but were
not refined. There was unresolvable solvent (CHCl3, CH2Cl2 or
hexanes) in the lattice. As a result the PLATON/SQUEEZE77
program was used to generate a “solvent-free” data set. The final
cycle of full-matrix least-squares refinement on F2 was based on
5733 reflections and 267 variable parameters and converged
(largest parameter shift was 0.00 times its esd).
[n-Bu4N]2[(AuCN)2A2T3]. The data were collected to a maxi-
mum 2θ value of 56.2°. Data were collected in a series of φ and ω
scans in 0.50° oscillations with 10.0 s exposures. The crystal-to-
detector distance was 36.00 mm. Of the 61962 reflections that
were collected, 12644 were unique (Rint = 0.055); equivalent
reflections were merged. The linear absorption coefficient, μ, for
Mo-KR radiation is 64.02 cm-1. Data were corrected for
absorption effects using the multiscan technique (SADABS),75
with minimum and maximum transmission coefficients of
Acknowledgment. We thank the Natural Sciences and Engi-
neering Research Council of Canada for funding, the Labora-
tory for Advanced Spectroscopy and Imaging Research
(LASIR) for access to spectroscopic equipment, Dr. Saeid
Kamal for assistance with the lifetime measurements, and Dr.
Ken Wong for XPS data. A.M.K. thanks UBC and Mountain
Equipment Coop (MEC) for graduate fellowships.
(74) SAINT, Version 7.53A; Bruker AXS Inc.: Madison, WI, 1997-2008.
(75) SADABS, Bruker Nonius area detector scaling and absorption correc-
tion, V2008/1; Bruker AXS Inc.: Madison WI, 2008.
Supporting Information Available: X-ray crystallographic
data for A2T3, (AuPPh3)2A2T3, [n-Bu4N]2[(AuCN)2A2T3], and
Au2(dppm)(A2T3) in CIF format. Spectra of irradiated solu-
tions of complexes and MV2þ, cyclic voltammogram of A2T3.
This material is available free of charge via the Internet at http://
pubs.acs.org.
(76) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G. L.;
Giacovazzo, C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.; Spagna,
R. J. Appl. Crystallogr. 1999, 32, 115–119.
(77) Sluis, P. v. d.; Spek, A. L. Acta Crystallogr., Sect. A 1990, 46, 194–201.