Structural and electronic properties of phosphino(oligothiophene) gold(I) complexes

Article abstract of DOI:10.1021/ic0493200

A series of gold(I) complexes containing phosphino(oligothiophene) ligands of varying conjugation length has been prepared. Solid state crystal structures of (PT₃)AuCl (PT₃ = 5-diphenylphosphino-2,2′: 5′,2″-terthiophene) and AuCl(PTP

Full text of DOI:10.1021/ic0493200

Inorg. Chem. 2005, 44, 620−627
Structural and Electronic Properties of Phosphino(oligothiophene)
Gold(I) Complexes
Tracey L. Stott, Michael O. Wolf,* and Brian O. Patrick
Department of Chemistry, UniVersity of British Columbia,
VancouVer, British Columbia, Canada V6T 1Z1
Received May 25, 2004
A series of gold(I) complexes containing phosphino(oligothiophene) ligands of varying conjugation length has been
prepared. Solid state crystal structures of (PT3)AuCl (PT3 5-diphenylphosphino-2,2 :5 ,2′′-terthiophene) and AuCl-
(PTP)AuCl (PTP 2,5-diphenylphosphinothiophene) have been obtained. The complex AuCl(PTP)AuCl crystallizes
as a dimer with two intermolecular Au Au contacts. Variable temperature NMR spectroscopy is used to demonstrate
)
′ ′
)
−
the presence of aurophilic interactions in solution for AuI(PTP)AuI. Dual emission is observed for AuCl(PTP)AuCl
in solution and is attributed to emission from both monomer and dimer. In the solid state, dimer emission is dominant.
The iodo analogue, AuI(PTP)AuI, shows only low energy dimer emission in both solution and the solid state.
Compounds in which the ligands contain longer bridges (either bithienyl or terthienyl) show absorption and emission
bands due to the π−π* transition only, both in solution and the solid state.
Introduction
Interest in the coordination chemistry of gold has grown
in recent years with the discovery of novel electronic and
structural properties of gold complexes.12 Gold compounds
can exhibit “aurophilicity”, where the formation of weak
Au-Au interactions occurs,13-15 resulting in a variety of
structures, including dimeric16-18 and polymeric19-23 forms.
Conjugated oligomers and polymers are an important class
of materials that have generated much research interest in
recent years. Some possible applications of these materials
include energy and memory storage, sensors, and nanoelec-
tronics.1-3 Crystalline oligomers, whose structure may be
readily determined, have been used to better understand
structure-property relationships.4 Pendant metal groups
attached to conjugated oligomers may be used both to control
the structural interaction between oligomers and to modify
the electronic and optical properties of the oligomer.5 Metal
groups have been attached to conjugated oligomers using a
number of different coordinating groups.6 Our research group
has investigated the use of phosphine substituents as ligating
groups, as they allow coordination of a wide range of
transition metal complexes.7-11
(8) Clot, O.; Wolf, M. O.; Yap, G. P. A.; Patrick, B. O. J. Chem. Soc.,
Dalton Trans. 2000, 16, 2729-2737.
(9) Clot, O.; Wolf, M. O.; Patrick, B. O. J. Am. Chem. Soc. 2001, 123,
9963-9973.
(10) Clot, O.; Akahori, Y.; Moorlag, C.; Leznoff, D. B.; Wolf, M. O.;
Batchelor, R. J.; Patrick, B. O.; Ishii, M. Inorg. Chem. 2003, 42, 2704-
2713.
(11) Moorlag, C.; Clot, O.; Wolf, M. O.; Patrick, B. O. Chem. Commun.
2002, 24, 3028-3029.
(12) Forward, J. M.; Fackler, J. P., Jr.; Assefa, Z. In Optoelectronic
Properties of Inorganic Compounds; Roundhill, D. M., Fackler, J. P.,
Jr., Eds.; Plenum Press: New York, 1999; pp 195-229.
(13) Pyykko¨, P. Chem. ReV. 1997, 97, 597-636.
(14) Pyykko¨, P. Angew. Chem., Int. Ed. 2002, 41, 3573-3578.
(15) Schmidbaur, H. Gold Bull. 1990, 23, 11-21.
(16) Toronto, D. V.; Weissbart, B.; Tinti, D. S.; Balch, A. L. Inorg. Chem.
1996, 35, 2484-2489.
* To whom correspondence should be addressed. E-mail: mwolf@
chem.ubc.ca.
(1) Tour, J. M. Acc. Chem. Res. 2000, 33, 791-804.
(2) McQuade, D. T.; Pullen, A. E.; Swager, T. M. Chem. ReV. 2000, 100,
2537-2574.
(3) MacDiarmid, A. G. Angew. Chem., Int. Ed. 2001, 40, 2581-2590.
(4) Fichou, D.; Ziegler, C. In Handbook of Oligo- and Polythiophenes;
Fichou, D., Ed.; Wiley-VCH: Weinheim, 1999; pp 183-274.
(5) Wolf, M. O. AdV. Mater. 2001, 13, 545-553.
(6) Stott, T. L.; Wolf, M. O. Coord. Chem. ReV. 2003, 246, 89-101.
(7) Clot, O.; Wolf, M. O.; Patrick, B. O. J. Am. Chem. Soc. 2000, 122,
10456-10457.
(17) Bardaji, M.; Jones, P. G.; Laguna, A. J. Chem. Soc., Dalton Trans.
2002, 3624-3629.
(18) Balch, A. L.; Fung, E. Y.; Olmstead, M. M. J. Am. Chem. Soc. 1990,
112, 5181-5186.
(19) Brandys, M.-C.; Puddephatt, R. J. Chem. Commun. 2001, 1280-1281.
(20) Leznoff, D. B.; Xue, B.-Y.; Batchelor, R. J.; Einstein, F. W. B.; Patrick,
B. O. Inorg. Chem. 2001, 40, 6026-6034.
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Chem. Soc. 2002, 124, 10662-10663.
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Chem. 1997, 36, 2294-2300.
620 Inorganic Chemistry, Vol. 44, No. 3, 2005
10.1021/ic0493200 CCC: $30.25
© 2005 American Chemical Society
Published on Web 01/12/2005

Phosphino(oligothiophene) Gold(I) Complexes
Scheme 1
Figure 1. ORTEP view of (PT3)AuCl. The hydrogen atoms are omitted
for clarity, and thermal ellipsoids are drawn at 50% probability.
Scheme 2
Table 1. Selected Interatomic Distances (Å) and Angles (deg) for
(PT3)AuCl
Au(1)-Cl(1)
Au(1)-P(1)
P(1)-C(19)
P(1)-C(13)
P(1)-C(1)
C(1)-S(1)
C(4)-S(1)
2.2899(19)
2.2345(19)
1.824(8)
1.830(8)
1.776(7)
1.725(7)
1.725(7)
P(1)-Au(1)-Cl(1)
Au(1)-P(1)-C(19)
Au(1)-P(1)-C(13)
Au(1)-P(1)-C(1)
P(1)-C(1)-S(1)
C(1)-S(1)-C(4)
175.28(8)
114.6(2)
114.6(3)
109.6(3)
120.7(4)
93.0(4)
Many gold complexes have been shown to exhibit lumines-
cence in solution and in the solid state,17,24-26 and this has
resulted in the testing of some gold compounds as potential
light emitting materials27,28 and sensors.29 Our group has
recently prepared some Au(I) phosphine complexes that
exhibited intramolecular Au-Au interactions.10 Here we
report the preparation of a series of thiophene oligomers
coordinated to Au(I) via a terminal or R-phosphine substitu-
ent, and the systematic study of their absorption and emission
properties, both in solution and in the solid state, as a function
of conjugation length of the oligomer.
Table 2. Selected Crystallographic Data for (PT3)AuCl and
AuCl(PTP)AuCl
(PT3)AuCl
AuCl(PTP)AuCl
formula
habit
C24H17PS3ClAu
prism
C69H74P4S2Cl6Au4
tablet
dimension/mm3
T/K
0.30 × 0.20 × 0.20
0.50 × 0.40 × 0.15
173
173
cryst syst
space group
a/Å
b/Å
c/Å
monoclinic
P21/n
9.6606(6)
18.844(1)
13.0096(8)
90
103.84(1)
90
2299.6(2)
4
triclinic
P1h
11.339(1)
13.439(2)
13.935(2)
67.17(1)
69.44(1)
78.08(1)
1826.4(4)
1
Results and Discussion
R/deg
Syntheses. Gold complexes were prepared according to
the reactions shown in Scheme 1 and readily isolated by
precipitation from hexanes to yield analytically pure samples.
The iodo complex AuI(PTP)AuI was synthesized by halogen
exchange (Scheme 2), and purified by washing with water.
All of the gold complexes are stable in the solid state and in
solution.
â/deg
γ/deg
V/Å3
Z
D
calc/g cm-3
1.921
4683
68.66
0.044
1.902
8476
84.11
0.034
unique data
µ(Mo KR)/cm-1
R(F)a (I > 2σ(I))
Rw(F2)b (all data)
0.103
0.073
Solid State Crystal Structures. Single crystals of (PT)-
AuCl were grown by slow diffusion of hexanes into a
dichloromethane solution of the complex. The molecular
structure could not be completely refined, although it was
established that no gold-gold contacts exist in the solid state.
Single crystals of (PT3)AuCl were also grown by slow
diffusion of hexanes into a dichloromethane solution. The
molecular structure of (PT3)AuCl is shown in Figure 1, and
selected interatomic distances and angles are presented in
a R ) ∑||Fo| - |Fc||/∑|Fo|. b Rw ) (∑(F2o - Fc2)2/∑w(F2o)2)1/2
.
Table 1. Table 2 contains crystallographic data for this
structure. The complex crystallizes as a monomer, with no
gold-gold interactions present. No Au-S interactions are
observed, with the shortest Au-S distance in the structure
being 3.707 Å. The Au-Cl and Au-P bond lengths are very
similar to those in (PPh3)AuCl (Au-Cl 2.279 Å and Au-P
2.235 Å).30 The P-Au-Cl bond is somewhat less linear than
that in (PPh3)AuCl (179.63°). The P-C bond lengths to the
phenyl groups are slightly longer than the corresponding
bond to the terthienyl group and are similar to the P-C bond
lengths of (PPh3)AuCl. The first two rings of the terthienyl
moiety are essentially coplanar, with an interannular torsion
angle ( S-C-C-S) of 176°, whereas the ring furthest from
the phosphine substituent is twisted slightly more with an
interannular torsion angle between the second and third rings
of -162°.
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1999, 74, 1361-1363.
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1976, B32, 962-963.
Inorganic Chemistry, Vol. 44, No. 3, 2005 621

Stott et al.
Figure 2. ORTEP view of AuCl(PTP)AuCl. The hydrogen atoms are
omitted for clarity, and thermal ellipsoids are drawn at 50% probability.
Figure 3. Variable temperature (a) 1H NMR and (b) 31P{1H} NMR spectra
of AuI(PTP)AuI in CD2Cl2.
Table 3. Selected Interatomic Distances (Å) and Angles (deg) for
AuCl(PTP)AuCl
Au(1)-Au(2)
Au(1)-Cl(1)
Au(2)-Cl(2)
Au(1)-P(1)
Au(2)-P(2)
P(1)-C(1)
3.0966(5)
2.3041(10)
2.2997(12)
2.2346(10)
2.2404(11)
1.813(4)
1.813(4)
1.803(4)
1.802(4)
1.812(5)
P(1)-Au(1)-Cl(1)
P(2)-Au(2)-Cl(2)
P(1)-Au(1)-Au(2)
P(2)-Au(2)-Au(1)
Cl(1)-Au(1)-Au(2)
Cl(2)-Au(2)-Au(1)
C(7)-P(1)-Au(1)
C(13)-P(1)-Au(1)
C(17)-P(2)-Au(2)
C(23)-P(2)-Au(2)
173.07(4)
175.75(4)
103.45(3)
96.54(3)
83.00(3)
87.67(4)
109.70(13)
115.68(13)
116.07(17)
114.16(14)
Scheme 3
P(1)-C(7)
P(1)-C(13)
P(2)-C(16)
P(2)-C(17)
broadening in the 1H spectrum. These minor changes, similar
to those seen in other complexes,35-37 suggest that aurophilic
interactions, as in the solid state, are absent in this temper-
ature range. Some changes were observed in the NMR
spectra of AuCl(PTP)AuCl as the temperature was decreased
The X-ray crystal structure of AuCl(PTP)AuCl is shown
in Figure 2, along with a table of selected interatomic
distances and angles (Table 3). This complex, in contrast to
(PT3)AuCl, crystallizes as a dimer with inversion symmetry,
which has two gold-gold interactions (3.0966(5) Å). Related
structures have been previously observed,18,31,32 with com-
parable Au-Au distances. The Au-P and Au-Cl bond
lengths and the P-Au-Cl bond angles are similar to those
in (PT3)AuCl. The shortest Au-S distance in the structure,
3.504 Å for Au(2)-S(1), is beyond the sum of the van der
Waals radii of these elements. A structural determination of
AuI(PTP)AuI was attempted; however, the crystallographic
data was only of sufficient quality to determine that the
connectivity is the same as in AuCl(PTP)AuCl and that the
Au-Au distance is 3.0210(9) Å. Anisotropic refinements of
the structure were unsatisfactory. As predicted,16,33,34 the
gold-gold contacts are shorter than in AuCl(PTP)AuCl.
1
from 300 to 191 K.38 In the H NMR spectrum, the peaks
broaden and separate. The 31P NMR spectrum consists of a
singlet at room temperature that begins to broaden below
210 K. It is very broad at the lowest accessible temperature
(191 K) but does not split into two peaks. This may indicate
that an equilibrium between monomer and dimer exists
(Scheme 3), but it is still too rapid to allow observation of
separate resonances on the NMR time scale.
The same experiment on the iodo analogue (AuI(PTP)-
AuI) was carried out to determine if the shorter gold-gold
distance in this complex results in the observation of separate
resonances for monomer and dimer at a higher temperature.
The spectra, shown in Figure 3, indicate that this does occur.
1
VT-NMR Spectroscopy. Variable temperature (VT) H
1
Broadening is observed in the H NMR spectrum with
and 31P NMR experiments were performed on (PT)AuCl,
AuCl(PTP)AuCl, and AuI(PTP)AuI. The 31P resonance for
(PT)AuCl shifts slightly with temperature, and there is some
decreasing temperature, and some peaks begin to separate
out at low temperature. In the 31P NMR spectrum, coales-
cence occurs at 200 K, and two peaks are observed at 191
K, with a separation of 1150 Hz (kc ) 2500). ∆Gq was
(31) Eggleston, D. S.; Chodosh, D. F.; Girard, G. R.; Hill, D. T. Inorg.
Chim. Acta 1985, 108, 221-226.
(32) Bates, P. A.; Waters, J. M. Inorg. Chim. Acta 1985, 98, 125-129.
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(34) Xiao, H.; Weng, Y.-X.; Wong, W.-T.; Mak, T. C. W.; Che, C.-M. J.
Chem. Soc., Dalton Trans. 1997, 221-226.
(35) Dickert, F. L.; Hellmann, S. W. Anal. Chem. 1980, 52, 996-998.
(36) Hunt, C. T.; Balch, A. L. Inorg. Chem. 1982, 21, 1641-1644.
(37) Cyr, P. W.; Patrick, B. O.; James, B. R. Chem. Commun. 2001, 1570-
1571.
(38) See Supporting Information.
622 Inorganic Chemistry, Vol. 44, No. 3, 2005

Phosphino(oligothiophene) Gold(I) Complexes
Figure 5. Comparison of UV-vis spectra of PTP, OPTPO, and complexes.
corresponding ligands,43 and the n-π* transitions disappear
in the spectra. The hypsochromic shifts decrease with
increasing chain length. The π-π* transitions in the
complexes are of lower energy than in the corresponding
unsubstituted oligomers (thiophene (231 nm), 2,2′-bithiophene
(303 nm), 2,2′:5′,2′′-terthiophene (354 nm)).44 It is possible
that the red shifts observed in the complexes relative to the
unsubstituted oligomers are due to stabilization of the bridge-
centered π* LUMO by interaction with an unoccupied orbital
on the phosphorus.43 Several bands appear in the region
between 260 and 280 nm that are assigned as vibrational
structure of the phenyl group.45 The spectra of (PT3)AuCl,
AuCl(PT3P)AuCl, and (PT2)AuCl all exhibit shoulders, and
the bands are broad, likely due to the presence of multiple
conformations in solution.46,47 The molar absorptivities
increase with increasing conjugation length.
Figure 4. UV-vis spectra of gold complexes.
Table 4. Solution Absorption Data for Gold Complexes
complex
(PT)AuCl
λ )
max/nm (ꢀmax/M-1 cm-1
245 (sh) (1.7 × 104), 263(sh) (9.9 × 103),
269 (sh) (7.9 × 103), 275 (sh) (4.4 × 103)
268 (sh) (5.9 × 103), 276 (4.8 × 103), 329 (1.9 × 104)
263 (sh) (1.1 × 104), 279 (sh) (7.1 × 103),
377 (3.2 × 104)
(PT2)AuCl
(PT3)AuCl
AuCl(PTP)AuCl 269 (2.0 × 104), 277 (2.1 × 104)
AuCl(PT2P)AuCl 263 (sh) (1.2 × 104), 267 (sh) (1.1 × 104),
275 (sh) (9.2 × 104), 334 (sh) (3.2 × 104),
342 (sh) (3.12 × 104)
AuCl(PT3P)AuCl 263 (sh) (1.2 × 104), 267 (sh) (1.2 × 104),
276 (sh) (9.2 × 103), 386 (3.9 × 104)
AuI(PTP)AuI
251(sh) (2.8 × 104), 269 (sh) (2.0 × 104),
276 (sh) (1.8 × 104), 285 (sh) (1.7 × 104).
A comparison of the absorbance spectra of PTP, its
complexes, and the diphosphine oxide OPTPO43 is shown
in Figure 5. OPTPO is more hypsochromically shifted
relative to PTP than either of the gold complexes, possibly
due to the greater electronegativity of O versus Au. The
spectra of the two complexes show similar spectral features
to those described above, that is, a blue shift relative to the
ligand and the appearance of phenyl vibrational bands.
However, the spectrum of the iodo complex is less blue
shifted than that of the chloro complex. This effect has been
previously explained for related complexes as a change in
the HOMO from mainly Au 5d character in the chloro
complex to a combination of Au 5d and I filled π orbital
character in the iodo complex.16,34,48 Though other groups
have reported seeing new absorption bands at high concen-
trations for complexes exhibiting gold-gold interactions in
calculated to be 9 kJ/mol.39 This is close to previously
reported energies for gold-gold interactions;22,40-42 accord-
ingly, the dynamic process is assigned to the monomer-
dimer equilibrium in solution. The presence of a monomer-
dimer equilibrium is also supported by molecular weight
values determined by vapor pressure osmometry, which were
found to be higher in both cases than would be expected for
a pure monomer (1228 for AuCl(PTP)AuCl and 1415 for
AuI(PTP)AuI in CH2Cl2).
Solution Absorption Spectra. The solution electronic
absorption spectra for the gold complexes in CH2Cl2 are
shown in Figure 4 and the data summarized in Table 4,
including the molar absorptivities (ꢀ). The spectra are
dominated by the thiophene π-π* transitions, which show
the expected bathochromic shift with increasing conjugation
length. Upon coordination of the gold centers, the π-π*
transitions undergo a hypsochromic shift relative to the
(43) Stott, T. L.; Wolf, M. O. J. Phys. Chem. B 2004, 108, 18815-18819.
(44) Becker, R. S.; Seixas de Melo, J.; Macanita, A. L.; Elisei, F. J. Phys.
Chem. 1996, 100, 18683-18695.
(45) Jaffe´, H. H.; Freedman, L. D. J. Am. Chem. Soc. 1952, 74, 1069-
1071.
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Verlagagesellschaft: Weinheim, 1993.
(40) Narayanaswamy, R.; Young, M. A.; Parkhurst, E.; Ouellette, M.; Kerr,
M. E.; Ho, D. M.; Elder, R. C.; Bruce, A. E.; Bruce, M. R. M. Inorg.
Chem. 1993, 32, 2506-2517.
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Hawthorne, M. F. J. Am. Chem. Soc. 1996, 118, 2679-2685.
(42) Wang, S.-G.; Schwarz, W. H. E. J. Am. Chem. Soc. 2004, 126, 1266-
1276.
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J. Phys. Chem. A 1998, 102, 5142-5149.
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J. Phys. Chem. A 1999, 103, 795-802.
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1996, 35, 2490-2496.
Inorganic Chemistry, Vol. 44, No. 3, 2005 623

Stott et al.
Figure 7. Solution excitation and emission spectra of AuCl(PTP)AuCl
and AuI(PTP)AuI.
band is due either to emission from a metal-based state of
dimer present in solution or to an excimer. The large Stokes
shift of this emission is typical of metal-based states in
similar compounds.12 Metal-metal bonded exciplexes have
been previously observed, including examples resulting from
Au-Au interactions, and typically show enhanced emission
at higher concentrations relative to monomer.50 Here only a
small range of concentrations could be studied due to the
weak emission; however, in dilute solutions the LE band is
present, suggesting that this is due to ground state dimer-
ization rather than excimer. In AuI(PTP)AuI, only LE
emission is observed. Both VT-NMR and vapor pressure
osmometry support the conclusion that both monomer and
dimer are present in solution so the absence of the HE band
in the spectrum of this complex is best attributed to
quenching of this emission due to the iodo ligands.
The complexes (PT2)AuCl and AuCl(PT2P)AuCl (Figure
8) do not exhibit dual emission. The spectra for these
complexes consist of a single band at 392 and 400 nm,
respectively. The emission is assigned as the π-π* transition
of the bithienyl moiety and is bathochromically shifted
relative to unsubstituted bithiophene (362 nm).44 The emis-
sion spectra of the terthienyl complexes (PT3)AuCl and
AuCl(PT3)AuCl (Figure 8) have maxima at 459 and 465 nm,
respectively. Similar to the absorption spectra, these bands
are blue-shifted relative to the free ligand43 but occur at lower
energy than the emission of unsubstituted 2,2′:5′,2′′-ter-
thiophene (426 nm).44
Figure 6. Solid state UV-vis spectra of selected gold complexes.
Table 5. Solid State Electronic Absorption Data for Gold Complexes
complex
(PT)AuCl
λmax/nm
no clear peak
(PT2)AuCl
(PT3)AuCl
AuCl(PTP)AuCl
AuCl(PT2P)AuCl
AuCl(PT3P)AuCl
AuI(PTP)AuI
270 (sh), 335, 360 (sh)
270, 382, 420 (sh), 420 (sh)
no clear peak
275 (sh), 345, 375 (sh)
275 (sh), 395, 431 (sh)
no clear peak
the solid state and in VT-NMR,16,22,49 new bands were not
observed for either AuCl(PTP)AuCl or AuI(PTP)AuI.
Solid State Absorption Spectra. Solid state UV-vis
spectra of selected complexes are shown in Figure 6, and
the results for all the compounds are summarized in Table
5. The data generally show the same trends observed in the
solution spectra; for example, a red shift in the π-π*
transition occurs with increasing chain length, and decreases
in magnitude as the chain length is increased. The wavelength
of maximum absorption is slightly red-shifted relative to
solution, which may be due to increased planarity in the solid
state. Somewhat suprisingly, as AuCl(PTP)AuCl has gold-
gold contacts in the solid state, no new absorption bands
were observed in the spectrum of this compound.
Solution Emission Spectra. The gold complex (PT)AuCl
is very weakly emissive in solution, while both AuCl(PTP)-
AuCl and AuI(PTP)AuI emit more strongly. AuCl(PTP)AuCl
shows two emission bands, a high energy (HE) band at 345
nm and a low energy (LE) band at 485 nm (Figure 7). Both
bands show similar excitation spectra, which match the
absorbance spectrum of the complex. The iodo complex AuI-
(PTP)AuI shows only a single emission band at 490 nm,
also with an excitation spectrum matching the absorbance
spectrum.
Solid State Emission Spectroscopy. Emission from (PT)-
AuCl, which is very weak in solution, occurs at 390 nm in
the solid state (Figure 9, Table 6). The excitation spectrum,
with a peak at 350 nm, differs from the absorption spectrum
of this compound. AuCl(PTP)AuCl has a similar emission
band at 402 nm, with excitation at 360 nm, which also does
not match the absorption spectrum. Several explanations for
this phenomenon are possible, on the basis of literature
observations of similar results. One is phenyl triplet emission,
The HE band in the spectrum of AuCl(PTP)AuCl is
assigned to ligand-based (PTP) monomer emission. The LE
(49) Feng, D.-F.; Tang, S. S.; Liu, C. W.; Lin, I. J. B.; Wen, Y.-S.; Liu,
(50) Rawashdeh-Omary, M. A.; Omary, M. A.; Patterson, H. H.; Fackler,
L.-K. Organometallics 1997, 16, 901-909.
J. P., Jr. J. Am. Chem. Soc. 2001, 123, 11237-11247.
624 Inorganic Chemistry, Vol. 44, No. 3, 2005

Phosphino(oligothiophene) Gold(I) Complexes
Figure 10. Solid state excitation and emission spectra of AuCl(PT2P)-
AuCl and AuCl(PT3P)AuCl.
Figure 8. Solution excitation and emission spectra of AuCl(PT2P)AuCl
and AuCl(PT3P)AuCl.
nm.51 A second is a ligand-to-metal charge transfer (LMCT),
similar to that reported by Fackler and co-workers.52 A third
explanation is that the band is due to an emissive impurity,
although the emission and excitation spectra do not cor-
respond to ligand43 and it is not clear what this impurity
might otherwise be. The analogous emission in (PT)AuCl
is presumably also from a similar source. AuCl(PTP)AuCl
also has a band at 470 nm, very similar to the solution
spectrum, with an excitation spectrum that corresponds to
the absorption spectrum. This band is assigned as arising
from a Au-Au state, on the basis of the lack of a
corresponding band in (PT)AuCl, and the large Stokes shift.
AuI(PTP)AuI has a similar band at 486 nm, which is similar
to that in solution, again pointing to emission from a Au-
Au state.
(PT2)AuCl and AuCl(PT2P)AuCl exhibit solid state emis-
sion spectra that are red shifted relative to solution by about
10 nm, and blue shifted relative to the free ligands43 by 65
nm (Figure 10). The terthienyl complexes exhibit a small
bathochromic shift (8 nm) upon coordination. The large
bathochromic shift compared to the solution data for these
complexes (29 nm for (PT3)AuCl and 50 nm for AuCl(PT3P)-
AuCl) and the bithienyl complexes may be attributed to
increased planarity in the solid state. No lower energy, gold-
based emission was observed in these complexes.
Figure 9. Solid state excitation and emission spectra of (PT)AuCl, AuCl-
(PTP)AuCl, and AuI(PTP)AuI.
Conclusions
Table 6. Emission Data for Gold Complexes
The structural data and absorption and emission spectra
of the series of Au compounds described here demonstrate
interesting trends that shed light on the behavior of this class
of metal-containing thiophene oligomers. Both AuCl(PTP)-
AuCl and AuI(PTP)AuI crystallize as dimers with intermo-
lecular Au-Au interactions. Although VT NMR experiments
on AuCl(PTP)AuCl do not show the emergence of separate
resonances due to monomer and dimer, the spectra broaden
significantly at low temperature, consistent with a dynamic
solution emission
solid emission
complex
(PT)AuCl
λ/nm
λ/nm
no emission
392
403
406
488
402, 470
408
(PT2)AuCl
(PT3) AuCl
442 (sh), 459
345, 485
388 (sh), 400
439, 465
490
AuCl(PTP)AuCl
AuCl(PT2P)AuCl
AuCl(PT3P)AuCl
AuI(PTP)AuI
515
486
as others have noted a weak (ꢀ ) 2 M-1 cm-1) absorption
band for Ph3PAuCl between 300 and 365 nm, which also
appears in the excitation spectrum of the emission band that
originates from the phenyl π-π* triplet state at about 360
(51) Larson, L. J.; McCauley, E. M.; Weissbart, B.; Tinti, D. S. J. Phys.
Chem. 1995, 99, 7218-7226.
(52) Assefa, Z.; McBurnett, B. G.; Staples, R. J.; Fackler, J. P., Jr. Inorg.
Chem. 1995, 34, 4965-4972.
Inorganic Chemistry, Vol. 44, No. 3, 2005 625

Stott et al.
(CDCl3): δ 7.61-7.42 (m, 10H), δ 7.36 (dd, J ) 8.9, 3.9 Hz, 1H),
δ 7.23 (dd, J ) 3.9, 1.2 Hz, 1H), δ 7.09 (s, 1H). 31P{1H} NMR
(CDCl3) δ 20.6 (s).
process. The VT NMR spectra of AuI(PTP)AuI also show
dynamic behavior with a higher coalescence temperature than
for AuCl(PTP)AuCl. This is indicative of a stronger Au-
Au interaction in the iodo complex and is consistent with
the observed shorter Au-Au contact in the solid state of
this complex.
(PT)AuCl. Yield: 67%. Anal. C16H13AuClPS requires: C, 38.38;
H, 2.62. Found: C, 38.74; H, 2.60. 1H NMR (CDCl3): δ 7.79 (ddd,
J ) 4.6, 1.2, 3.1 Hz, 1H), δ 7.62-7.40 (m, 11H), δ 7.22 (ddd, 5.0,
3.9, 1.5 Hz, 1H). 31P{1H} NMR (CDCl3) δ 20.5 (s).
(PT2)AuCl. Yield: 75%. Anal. C20H15AuClPS2 requires: C,
The solution absorption and emission spectra of AuCl-
(PTP)AuCl and AuI(PTP)AuI may then be interpreted in
terms of a monomer-dimer equilibrium. Emission from the
Au-Au dimer occurs in both compounds at low energy;
however, AuCl(PTP)AuCl also has a higher energy emission
assigned to ligand-based emission from the monomer. In the
solid state only the low energy (dimer) emission occurs, with
a higher energy emission also present in the spectrum of
AuCl(PTP)AuCl, which cannot be definitively assigned. This
unassigned band also occurs in (PT)AuCl in the solid state.
Both solution and solid state absorption and emission spectra
of the compounds containing either bithienyl or terthienyl
groups are dominated primarily by the π-π* transition of
the thienyl moiety. These compounds do not show any
evidence for low energy emission from a Au-Au state.
1
41.21; H, 2.59. Found: C, 41.20; H, 2.57. H NMR (CDCl3): δ
7.61-7.44 (m, 10H), δ 7.41 (dd, J ) 9.1, 3.7 Hz, 1H), δ 7.28 (dd,
J ) 4.9, 0.91 Hz, 1H), δ 7.24 (m, incl CD3Cl, 2H), δ 7.20 (dd, J
) 3.7, 0.91 Hz, 1H), δ 7.01 (dd, J ) 4.9, 3.7 Hz, 1H). 31P{1H}
NMR (CDCl3) δ 19.9 (s).
(PT3)AuCl. Yield: 93%. Anal. C24H17AuClPS3 requires: C,
1
43.35; H, 2.58. Found: C, 43.61; H, 2.50. H NMR (CDCl3): δ
7.64-7.44 (m, 10H), δ 7.41 (dd, J ) 8.9, 3.9 Hz, 1H), δ 7.23 (dd,
J ) 3.9, 1.2 Hz, 1H), δ 7.09 (s, 1H). 31P{1H} NMR (CDCl3) δ
20.0 (s).
AuI(PTP)AuI. This complex was synthesized by a modification
of the literature method.34 A mixture of AuCl(PTP)AuCl (0.05
mmol) and KI (1 mmol) was heated to reflux for 1 h in a 1:1 (vol/
vol) degassed mixture of acetone and CH2Cl2 under N2. The solution
was then stirred for 24 h. The solvent was removed by rotary
evaporation, and the resulting solid was washed with H2O. Yield:
75%. Anal. C28H22Au2I2P2S requires: C, 30.57; H, 2.02. Found:
Experimental
1
C, 30.17; H, 2.14. H NMR (CDCl3): δ 7.62-7.45 (m). 31P{1H}
General. The following compounds were made by literature
methods: 2,2′-bithiophene,53 2,2′:5′,2′′-terthiophene,53 PT,43 PTP,43
OPTPO,43 PT2,54 PT2P,55 PT3,9,54 PT3P,54 and Au(tht)Cl (tht )
tetrahydrothiophene).56 1H and 31P{1H} NMR experiments were
performed on either a Bruker AV-300 or a Bruker AV-400
spectrometer. Spectra were referenced to residual solvent (1H) or
external 85% H3PO4 (31P). Electronic spectra were obtained on a
Cary 5000 in HPLC grade CH2Cl2. Emission spectra were obtained
on a Cary Eclipse, also in HPLC grade CH2Cl2. Solid state
absorption and emission spectra were obtained by drop casting the
compound from a CH2Cl2 solution onto a quartz slide. Some spectra
contain peaks from overtones; these are indicated with an asterisk.
Microanalyses were performed at UBC. Vapor pressure osmometry
measurements were performed by Galbraith Laboratories, Tennes-
see.
General Synthesis of Au(I) Complexes. Au(tht)Cl and the
appropriate ligand were stirred together for 1 h in CH2Cl2. The
solvent was removed, and the resulting powder was dissolved in a
minimum amount of CH2Cl2, and precipitated in 100 mL of
hexanes. The precipitate was collected by filtration, washed with
hexanes, and dried under vacuum, yielding analytically pure
samples.
NMR (CDCl3) δ 26.8 (s).
X-ray Crystallographic Analyses. Suitable crystals of (PT3)-
AuCl and AuCl(PTP)AuCl were each mounted in oil on a glass
fiber with data collected at 173(1) K. Their structures were solved
using a direct methods structure solution57 and refined using Shelxl-
97.58
Data for (PT3)AuCl were collected to a maximum 2θ of 55.8°
on a Rigaku/ADSC CCD diffractometer in a series of two scan
sets. Scans were carried out using 0.50° oscillations with 35.0 s
exposures. Data were collected using the d*TREK program59 and
processed (integrated and corrected for absorption) using the
TwinSolve function of CrystalClear.60
The structure of (PT3)AuCl was determined by first indexing
the unit cell as a two-component “split crystal” wherein the major
and minor components are related by a rotation of 8.5° about an
axis normal to an imaginary (-1.74, -9.14, 1.00) plane. Data for
both components were then integrated, and the solution and
subsequent refinements were carried out using an HKLF4 format
data set containing only non-overlapped reflections. All non-
hydrogen atoms were refined anisotropically, while all hydrogen
atoms were included in calculated positions.
Data for AuCl(PTP)AuCl were collected to a maximum 2θ of
56.4° on a Bruker X8 APEX diffractometer in a series of 10 scan
sets. Scans were carried out using 0.50° oscillations with 7.0 s
exposures. Data were collected and integrated using the SAINT
suite of software61 and corrected for absorption using SADABS.62
The material crystallizes with one-half-molecule residing on an
AuCl(PTP)AuCl. Yield: 78%. Anal. C28H22Au2Cl2P2S re-
1
quires: C, 36.66; H, 2.42. Found: C, 36.99; H, 2.41. H NMR
(CDCl3): δ 7.60-7.45 (m). 31P{1H} NMR (CDCl3) δ 19.9 (s).
AuCl(PT2P)AuCl. Yield: 62%. Anal. C32H24Au2Cl2P2S2 re-
1
quires: C, 38.46; H, 2.42. Found: C, 38.85; H, 2.36. H NMR
(CDCl3): δ 7.62-7.44 (m, 10H), δ 7.39 (dd, J ) 8.9, 3.9 Hz, 1H),
δ 7.28 (dd, J ) 3.8, 1 Hz, 1H). 31P{1H} NMR (CDCl3) δ 20.8 (s).
AuCl(PT3P)AuCl. Yield: 57%. Anal. C36H26Au2Cl2P2S3 re-
(57) Altomare, A.; Burla, M. C.; Cammalli, G.; Cascarano, M.; Giacovazzo,
C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.; Spagna, A. J.
Appl. Crystallogr. 1999, 32, 115-119.
(58) Sheldrick, G. M. Shelxl-97; University of Go¨ttingen: Go¨ttingen,
Germany, 1997.
(59) d*TREK: Area Detector Software, Version 7.1; Molecular Structure
Corporation: The Woodlands, TX, 2001.
(60) CrystalClear: Version 1.2.5b20; Molecular Structure Corporation: The
Woodlands, TX, 2002.
1
quires: C, 39.98; H, 2.42. Found: C, 40.28; H, 2.34. H NMR
(53) Van Pham, C.; Burkhardt, A.; Shabana, R.; Cunningham, D. D.; Mark,
H. A.; Zimmer, H. Phosphorus, Sulfur Silicon Relat. Elem. 1989, 46,
153-168.
(54) Field, J. S.; Haines, R. J.; Lakoba, E. I.; Sosabowski, M. H. J. Chem.
Soc., Perkin Trans. 1 2001, 3352-3360.
(55) Myrex, R. D.; Colbert, C. S.; Gray, G. M.; Duffey, C. H. Organo-
metallics 2004, 23, 409-415.
(61) SAINT: Version 6.0.2; Bruker AXS Inc.: Madison, WI, 1999.
(62) SADABS: Version 2.0.5; Bruker AXS Inc.: Madison, WI, 2001.
(56) Uson, R.; Laguna, A. Organomet. Synth. 1986, 3, 322-342.
626 Inorganic Chemistry, Vol. 44, No. 3, 2005

Phosphino(oligothiophene) Gold(I) Complexes
inversion center. In addition, one-half-molecule of methylene
chloride, disordered about an inversion center, and one whole
molecule of hexane solvent are found in the asymmetric unit. All
non-hydrogen atoms were refined anisotropically, while all hydro-
gen atoms were included in calculated positions.
residuals are likely a result of reasonable modeling of the positions
and ADPs of the majority of the electron density contained in the
Au and I atoms. The distorted carbon atoms may arise from an
incomplete description of the twinning, or an inadequate absorption
correction.
Data for AuI(PTP)AuI were collected to a maximum 2θ value
of 50.0°. Data were collected in a series of scans in 0.50° oscillations
with 30.0 s exposures. Data were integrated using the SAINT suite
of software,61 corrected for absorption using SADABS,62 and
corrected for Lorentz and polarization effects. The material crystal-
lizes as a two-component twin, with the second component related
to the first by a 180° rotation about the reciprocal 1,0,0 axis. The
material crystallizes with one-half-molecule of hexane and one-
half-molecule of methylene chloride in the asymmetric unit. While
the final residuals (R1 (I g 2σ(I))) 0.040, wR2 (all data) ) 0.126)
are acceptable, the final anisotropic displacement parameters (ADPs)
for the phenyl and thiophene carbons are unacceptably distorted in
a manner inconsistent with disordered fragments. The acceptable
Acknowledgment. We thank the Natural Sciences and
Engineering Council of Canada for funding of this work.
T.L.S. thanks the University of British Columbia for a Laird
fellowship.
Supporting Information Available: CIF files for (PT3)AuCl
and AuCl(PTP)AuCl. Absorption and emission spectra for all
1
compounds, H and 31P NMR VT spectra for AuCl(PTP)AuCl,
crystallographic data for AuI(PTP)AuI. This material is available
free of charge via the Internet at http://pubs.acs.org.
IC0493200
Inorganic Chemistry, Vol. 44, No. 3, 2005 627