Gold(I)-dithioether supramolecular polymers: Synthesis, characterization, and luminescence

Article abstract of DOI:10.1021/ic701275k

A series of discrete compounds and supramolecular polymers were synthesized by self-assembly of dithioether building blocks and HAuCl4·3H ₂O. In complexes 1 {[AuL^1-MeCl], where L^1-Me is bis(methylthio)methane} and 2 {[Au₂ L^2-PhCl₂], where L^2-Ph is 1,2-bis(phenylthio)ethane}, adjacent units are connected via aurophilic interactions. Complex 1, a one-dimensional (1D) supramolecular polymer, and complex 2, a two-dimensional supramolecular network, both feature nearly linear [Au-Au-]_∞ chains. Complexes 4a, 4b, and 4c, all of which contain 1,3-bis(phenylthio)propane (L^3-Ph), are polymorphs having the composition [Au₂L^3-PhCl ₂]. Complex 3 {[Au₂L^1-PhCl₂], where L^1-Ph is bis(phenylthio)methane}and complexes 4a and 4b consist of nearly identical 1D supramolecular polymers formed through Au-Au interactions. The third polymorph, 4c, is a molecular complex, as it does not have metal-metal interactions. Complex 5 {[Au₂L^4-PhCl₂], where L^4-Ph is 1,4-bis(phenylthio)butane} is also molecular. UV-vis spectra showed that the absorption bands of these complexes are allowed ligand-centered transitions between 230 and 260 nm. Complexes 1, 2, and 6 {[AuL ^3-MeCl], where L^3-Me is 1,3-bis(methylthio)propane} exhibited solid-state luminescence at 5 K with vibronic progressions and band maxima at approximately 570 nm. It is suggested that complex 6 contains [Au-Au-],*, chains.

Full text of DOI:10.1021/ic701275k

Inorg. Chem. 2008, 47, 2964-2974
Gold(I)-Dithioether Supramolecular Polymers: Synthesis,
Characterization, and Luminescence
Mohamed Osman Awaleh,† François Baril-Robert,‡ Christian Reber,‡
Antonella Badia,‡ and François Brisse*,‡
Institut des Sciences de la Terre, Centre d’Etudes et de Recherches Scientifiques de Djibouti
(CERD), B.P. 486, Djibouti, Republic of Djibouti, and Département de Chimie, UniVersité de
Montréal, C.P. 6128, Succursale Centre-Ville, Montréal, QC, Canada H3C 3J7
Received June 28, 2007
A series of discrete compounds and supramolecular polymers were synthesized by self-assembly of dithioether
building blocks and HAuCl4 ·3H2O. In complexes 1 {[AuL1-MeCl], where L1-Me is bis(methylthio)methane} and 2 {[Au2
L
2-PhCl2], where L2-Ph is 1,2-bis(phenylthio)ethane}, adjacent units are connected via aurophilic interactions. Complex
1, a one-dimensional (1D) supramolecular polymer, and complex 2, a two-dimensional supramolecular network,
both feature nearly linear [Au-Au-]∞ chains. Complexes 4a, 4b, and 4c, all of which contain 1,3-bis(phenyl-
thio)propane (L3-Ph), are polymorphs having the composition [Au2L3-PhCl2]. Complex 3 {[Au2L1-PhCl2], where L1-Ph is
bis(phenylthio)methane}and complexes 4a and 4b consist of nearly identical 1D supramolecular polymers formed
through Au-Au interactions. The third polymorph, 4c, is a molecular complex, as it does not have metal-metal
interactions. Complex 5 {[Au2L4-PhCl2], where L4-Ph is 1,4-bis(phenylthio)butane} is also molecular. UV–vis spectra
showed that the absorption bands of these complexes are allowed ligand-centered transitions between 230 and
260 nm. Complexes 1, 2, and 6 {[AuL3-MeCl], where L3-Me is 1,3-bis(methylthio)propane} exhibited solid-state
luminescence at 5 K with vibronic progressions and band maxima at approximately 570 nm. It is suggested that
complex 6 contains [Au-Au-]∞ chains.
Introduction
We were interested in studying structured inorganic–or-
ganic frameworks built up by self-assembly of dithioether
organic building blocks with Ag(I) and Au(I) in order to
explore properties of metal-organic supramolecular com-
pounds, such as anion exchange or luminescence. As
dithioether building blocks (denoted Ln-R), we chose dithio-
ethers RS(CH2)nSR having aliphatic chains between the
sulfur atoms, where n is the number of CH2 groups and R
is an aryl or an alkyl group. These were combined with Ag(I)
salts in order to form hybrid inorganic–organic supramo-
lecular architectures.6
The synthesis and characterization of self-assembled
supramolecular structures based on gold(I) building blocks
is an active research area because of the interesting structural
and spectroscopic properties of these materials.1,2 Further-
more, self-assembly of metal-organic supramolecular poly-
mers has attracted a great deal of attention because of the
potential applications of these polymers as functional materi-
als.3–5
* To whom correspondence should be addressed. E-mail: fsbrisse@
sympatico.ca. Fax: (+)(514) 343-7586.
The selection of these ligands was motivated by four
reasons: (1) according to the Pearson hard–soft acid–base
†
Centre d’Etudes et de Recherches de Djibouti.
Université de Montréal.
‡
(1) Yip, S. K.; Cheng, E. C. C.; Yuan, L. H.; Zhu, N.; Yam, V. W. W.
Angew. Chem., Int. Ed. 2004, 43, 4954.
(2) Schmidbaur, H. Chem. Soc. ReV. 1995, 391, 400.
(3) (a) Jung, O. K.; Kim, Y. J.; Lee, Y. A.; Park, J. K.; Chae, H. K. J. Am.
Chem. Soc. 2000, 122, 9921. (b) Jung, O. S.; Kim, Y. J.; Lee, Y. A.;
Park, K. M.; Lee, S. S. Inorg. Chem. 2003, 42, 844. (c) Yaghi, O. M.;
Li, H. J. Am. Chem. Soc. 1995, 117, 10401.
(5) Batten, S. R.; Murray, K. S. Coord. Chem. ReV. 2003, 246, 103.
(6) (a) Bu, X. H.; Chen, W.; Hou, W. F.; Du, M.; Zhang, R. H.; Brisse,
F. Inorg. Chem. 2002, 41, 3477. (b) Awaleh, M. O.; Badia, A.; Brisse,
F. Inorg. Chem. 2005, 44, 7833. (c) Awaleh, M. O.; Badia, A.; Brisse,
F.; Bu, X. H. Inorg. Chem. 2006, 45, 1560. (d) Awaleh, M. O.; Badia,
A.; Brisse, F. Cryst. Growth Des. 2005, 5, 1897. (e) Awaleh, M. O.;
Badia, A.; Brisse, F. Cryst. Growth Des. 2006, 6, 2674. (f) Awaleh,
M. O.; Badia, A.; Brisse, F. Inorg. Chem. 2007, 46, 3185.
(4) (a) Rowsell, J. L. C.; Eckert, J.; Yaghi, O. M. J. Am. Chem. Soc.
2005, 127, 14904. (b) Rowsell, J. L. C.; Yaghi, O. M. Angew. Chem.,
Int. Ed. 2005, 44, 4670.
2964 Inorganic Chemistry, Vol. 47, No. 8, 2008
10.1021/ic701275k CCC: $40.75  2008 American Chemical Society
Published on Web 03/26/2008

Gold(I)-Dithioether Supramolecular Polymers
concept,7 silver(I) and gold(I) ions are soft Lewis acids and
hence have good ability to coordinate to thioether ligands
that are soft Lewis bases; (2) these symmetrical dithioether
building blocks afford two coordination sites to d10 metal
centers, expanding the coordination spheres of the metal
centers into extended solid-state networks; (3) lengthening
of the aliphatic segment between the S atoms increases the
degree of conformation of these ligands,8 allowing the effect
of flexibility of the organic building blocks on the resulting
coordination polymers to be studied; and (4) hindrance of
the coordination spheres of the d10 metal centers may be
affected by the bulk of the R substituent of the dithioether
ligands. Thus, variation of the bulk of R allowed us to study
its effect upon the topology of the resulting coordination
polymers.
In supramolecular metal-organic frameworks obtained by
the combination of these dithioether organic spacers and
silver(I) salts, the Ag(I) coordination sphere was expanded
by the dithioether ligands.6 On the other hand, the aurophilic
interaction between adjacent gold(I) atoms usually allows
the expansion of Au(I) complexes into hybrid inorganic–or-
ganic extended solid-state networks.2,9–13 This interaction has
an energy on the order of 5–10 kcal mol-1 for a Au(I)-Au(I)
distance of 3.05 Å, which is comparable to that of hydrogen
bonds.2,14 Individual Au(I)-Au(I) interactions may be
considered weak. However, these weak interactions can
cooperate in the solid state to form a stronger system, and
as a result, many gold(I)-thioether complexes were found
to be insoluble in common organic solvents.14 Because of
their insolubility, they could not be crystallized, making an
accurate determination of the structures of those gold(I)
coordination polymers difficult14 and justifying the synthesis
of soluble gold(I)-thioether compounds that can be crystal-
lized in order to establish their structures.14 To the best of
our knowledge, there is only one gold(I)-RS(CH2)nSR
complex {[Au2L2-PhCl2], where L2-Ph is 1,2-bis(phenylthio)-
ethane} whose structure has been characterized fully.15 This
structure was established at room temperature. One of
our goals was to transpose our previous studies6 of
Ag(I)-RS(CH2)nSR metal-organic frameworks (MOFs) to
gold(I) by preparing and characterizing supramolecular
gold(I)-Ln-R complexes. In addition, we were interested in
the photoluminescence properties of such gold(I)-dithioether
complexes.
Self-assembly of Ln-R dithioether molecules and gold
halides may lead to the formation of a neutral molecular
entity in which the sulfur atoms of Ln-R are coordinated to
one or two gold(I) ions. In turn, these compounds may
increase their dimensionalities via aurophilic interactions, as
depicted in Chart 1.
Au(I) · · · Au(I) interactions and other structural features
may be deduced from the interpretation of luminescence and
Raman spectra.16 In a recent report, Balch17 has demonstrated
the important influence of small structural variations on the
electronic properties of gold(I) complexes. Furthermore,
Fackler and co-workers18 determined that the nature of the
Au(I)-Au(I) interaction in the solid state has a profound
influenceontheopticalpropertiesofgold(I)-dithiophosphonate
complexes. The electronic properties of these complexes
strongly depend on the strength of the aurophilic interac-
tions18,19 and the number of Au(I)-Au(I) bonds.16 Therefore,
luminescence spectroscopy is now considered an important
tool in the study of these compounds.
Here we report on the synthesis, structural characterization,
and solid-state luminescence of several gold(I) complexes
obtained by self-assembly of gold chloride with each of
several dithioether building blocks. The organic building
blocks used in this study were bis(methylthio)methane
(L1-Me), bis(phenylthio)methane (L1-Ph), 1,2-bis(phenylthio)-
ethane (L2-Ph), 1,3-bis(phenylthio)propane (L3-Ph), 1,3-bis-
(methylthio)propane (L3-Me), and 1,4-bis(phenylthio)butane
(L4-Ph).
Experimental Section
Materials and General Methods. Except for the ligands, all of
the required reagents were commercially available and employed
without further purification. Elemental analyses were performed by
1
the Laboratoire d’analyse élémentaire (Université de Montréal). H
(300 MHz) NMR spectra in solution were recorded at 25 °C on a
Bruker AV300; 1H NMR chemical shifts (δ) are reported in parts per
million and referenced to residual solvent signals of the deuterated
solvents DMSO-d6 (δ1H ) 2.50) and acetone-d6 (δ1H ) 2.05).
Luminescence spectra were recorded using a single-channel spectrom-
eter, and the UV lines (333.6–363.8 nm) of an argon ion laser (Spectra-
Physics Stabilite 2017) were used to excite crystalline samples inside
a closed-cycle He cryostat (Sumitomo Heavy Industries SRDK-205).
Luminescence was collected and dispersed using a 0.5 m monochro-
mator (SPEX 500 M, 600 lines/mm) with a long-pass filter to remove
the excitation (Schott KV-418) lines. Emitted light was detected using
a photomultiplier tube (Hamamatsu R928) connected to a photon
counter (Stanford Instruments SR 400). All spectra were corrected for
instrument response using a tungsten lamp (Oriel 63350) according
(7) (a) Pearson, R. G. J. Am. Chem. Soc. 1963, 85, 3533. (b) Pearson,
R. G. J. Chem. Educ. 1968, 45, 581. (c) Pearson, R. G. J. Chem. Educ.
1968, 45, 643.
(8) (a) Awaleh, M. O.; Badia, A.; Brisse, F. Acta Crystallogr. 2005, E61,
o2479. (b) Chen, W.; Hou, B. H.; Zhou, L. N.; Wang, J. K.; Li, H.
Acta Crystallogr. 2005, E61, o1890. (c) Awaleh, M. O.; Badia, A.;
Brisse, F. Acta Crystallogr. 2005, E61, o2476. (d) Chen, W.; Yin,
Q.-X.; Xie, C.; Wang, J.-K.; Li, H. Acta Crystallogr. 2004, E60, o2147.
(e) Awaleh, M. O.; Badia, A.; Brisse, F. Acta Crystallogr. 2005, E61,
o2473.
(9) Leznoff, D. B.; Lefebvre, J. Gold Bull. 2005, 38, 47.
(10) Puddephatt, R. J. The Chemistry of Gold; Elsevier: Amsterdam, 1978.
(11) Tzeng, B. C.; Schier, A.; Schmidbaur, H. Inorg. Chem. 1999, 38, 3978.
(12) Hollatz, C.; Schier, A.; Schmidbaur, H. J. Am. Chem. Soc. 1997, 119,
8115.
(16) (a) Rawashdeh-Omary, M. A.; Omary, M. A.; Patterson, H. H.; Fackler,
J. P., Jr. J. Am. Chem. Soc. 2001, 123, 11237. (b) Rawashdeh-Omary,
M. A.; Omary, M. A.; Patterson, H. H. J. Am. Chem. Soc. 2000, 122,
10371.
(13) (a) Puddephatt, R. J. Coord. Chem. ReV. 2001, 216–217, 313. and
references therein. (b) Schmidbaur, H. Gold: Progress in Chemistry,
Biochemistry and Technology; Wiley: New York, 1999.
(14) Corbierre, M. K.; Lennox, R. B. Chem. Mater. 2005, 17, 5691. and
references therein.
(17) Balch, A. L. Gold Bull. 2004, 37, 45.
(18) Zyl, W. E. V.; Lopez-de-Luzuriaga, J. M.; Mohamed, A. A.; Staples,
R. J.; Fackler, J. P., Jr. Inorg. Chem. 2002, 41, 4579.
(19) King, C.; Wang, J. C.; Khan, M. N. I.; Fackler, J. P., Jr. Inorg. Chem.
1989, 28, 2145.
(15) Drew, M. G. B.; Riedl, M. J. J. Chem. Soc., Dalton Trans. 1973, 52.
Inorganic Chemistry, Vol. 47, No. 8, 2008 2965

Awaleh et al.
Chart 1. Discrete Molecules May Be Associated into One- or Two-Dimensional Networks via Aurophilic Interactionsa
a
X ) Cl; Y ) (CH2)n.
to a literature procedure.20 Raman spectra were recorded with a Raman
microscope (Renishaw System 3000). UV–vis spectroscopy was
performed using a Cary 500i spectrometer.
a yellow solution that turned orange upon the addition of L2-Ph (150
mg, 0.608 mmol). Dropwise addition of diethyl ether (10 mL) over
the course of 1 h caused the solution to change from orange to
colorless. The solution was left to stand at room temperature.
Colorless crystals suitable for X-ray analysis appeared after a few
weeks. Yield: 79% based on HAuCl4 ·3H2O. Anal. Calcd for
Syntheses. The ligands (L1-Me, L1-Ph, L2-Ph, L3-Ph, L3-Me, and L4-Ph
)
were synthesized according to a published report,21 and details of
their characterization are provided in the Supporting Information.
[AuL1-MeCl]∞ (1). HAuCl4 ·3H2O (65 mg, 0.165 mmol) was
dissolved in 10 mL of anhydrous ethanol at room temperature,
forming a yellow solution. Upon the addition of L1-Me (0.30 mL,
2.935 mmol), the solution first turned orange and then became
colorless within 20 min. Hairlike crystals suitable for X-ray analysis
grew from this solution within minutes. Yield: 90% based on
HAuCl4 ·3H2O. Anal. Calcd for C3H8S2AuCl: C, 10.58; H, 2.37.
Found: C, 10.09; H, 2.05. 1H NMR (DMSO-d6, 300 MHz): δ 2.089
(s, 6H, CH3-S-CH2-S-CH3), 3.705 (s, 2H, CH3-S-CH2-
1
C14H14S2Au2Cl2: C, 23.64; H, 1.98. Found: C, 23.34; H, 2.11. H
NMR (DMSO-d6, 300 MHz): δ 3.154 (s, 4H, -S-(CH2)2-S-),
7.218–7.431 (m, 10H, C6H5-). Raman: ν(Au-S), 273.3 cm-1
;
ν(Au-Cl), 375.3 cm-1
.
[Au2L1-PhCl2]∞ (3). This complex was synthesized in the same
manner as 2, using HAuCl4 ·3H2O (128 mg, 0.325 mmol) and L1-Ph
(498 mg, 2.146 mmol). Colorless crystals were obtained after a
few weeks. Yield: 54% based on HAuCl4 ·3H2O. Anal. Calcd for
1
C13H12S2Au2Cl2: C, 22.40; H, 1.73. Found: C, 22.71; H, 1.77. H
S-CH3). Raman: ν(Au-S), 264.4 cm-1; ν(Au-Cl), 387.6 cm-1
.
NMR (DMSO-d6, 300 MHz): δ 4.662 (s, 2H, -S-CH2-S-),
[Au2L2-PhCl2]∞ (2). Dissolution of HAuCl4 ·3H2O (132 mg, 0.335
7.219–7.431 (m, 10H, C6H5-). Raman: ν(Au-S), 257.7 cm-1
;
mmol) in 10 mL of anhydrous ethanol at room temperature yielded
ν(Au-Cl), 366.6 cm-1
.
[Au2L3-PhCl2]∞ (4a). This complex was synthesized in the same
manner as 2, using HAuCl4 · 3H2O (133 mg, 0.338 mmol) and
L3-Ph (0.30 mL, 1.305 mmol). After about 3 weeks, crystals
suitable for X-ray analysis were deposited. Yield: 76% based
on HAuCl4 · 3H2O. Anal. Calcd for C15H16S2Au2Cl2: C, 24.84;
(20) Davis, M. J.; Reber, C. Inorg. Chem. 1995, 34, 4585.
(21) Hartley, F. R.; Murray, S. G.; Levason, W.; Soutter, H. E.; McAuliffe,
C. A. Inorg. Chim. Acta 1979, 35, 265.
(22) SAINT Release 6.06, Integration Software for Single Crystal Data;
Bruker AXS Inc.: Madison, WI, 1999.
(23) Sheldrick, G. M. SADABS Bruker Area Detector Absorption Correc-
tions; Bruker AXS Inc.: Madison, WI, 1996.
1
H, 2.22. Found: C, 24.74; H, 2.36. H NMR (DMSO-d6, 300
2966 Inorganic Chemistry, Vol. 47, No. 8, 2008

Gold(I)-Dithioether Supramolecular Polymers
MHz): δ 1.846 (qt, 2H, -S-CH2-CH2-CH2-S-), 3.06 (t, 4H,
-S-CH2-CH2-CH2-S-), 7.145–7.328 (m, 10H, C6H5-).
dimensions were refined using CAD-4 software,24 while NRC-2
and NRC-2A were used for data reduction.25 An absorption
correction based on the crystal geometry was applied.25
Raman: ν(Au-S), 264.2 cm-1; ν(Au-Cl), 341.7 cm-1
.
Space groups were confirmed using the XPREP26 routine in the
program SHELXTL.27 The structures of 1-3 and 4a-4c were
solved using the Patterson method and difference Fourier techniques
with SHELXS-97.28 Refinements were performed on F2 using full-
matrix least-squares analysis. On the other hand, the structure of 5
was solved using direct methods and refined using full-matrix least-
squares on F2 with the SHELXTL program.27 For complex 4b,
XPREP gave three possible space groups: C2, Cm, and C2/m. Since
our starting materials were not chiral, we first tried to solve this
structure in space groups Cm and C2/m, but neither gave a
reasonable structure. On this basis, we finally solved 4b in space
group C2. The Flack parameter,29 which had a value of 0.01(5)
for 4b, confirmed that the reported structure had the correct
handedness. All non-hydrogen atoms were refined anisotropically,
while the hydrogen atoms were introduced at calculated positions
and included in the refinement using the riding-model approxima-
tion, with Uiso(H) ) 1.5Ueq(C) for methyl groups and Uiso(H) )
1.2Ueq(C) otherwise. A very small piece of 6 was mounted on a
Smart 6K diffractometer equipped with a rotating anode (Cu KR).
Unfortunately, the data were not of sufficiently good quality, and
the structure could not be solved. Crystal data, data collection, and
refinement parameters are listed in Table 1. Selected bond distances
and angles for complexes 1-5 are listed in Table S1 in the
Supporting Information.
[Au2L3-PhCl2]∞ (4b). HAuCl4 ·3H2O (121 mg, 0.307 mmol) was
added to 10 mL of anhydrous ethanol, producing a yellow solution.
Upon the addition of L3-Ph (0.30 mL, 1.305 mmol), the solution
turned orange. Dropwise addition of diethyl ether (10 mL) caused
the solution to become colorless. This solution yielded crystals by
diffusion into petroleum ether. After 2–3 weeks, colorless crystals
suitable for X-ray analysis were deposited. Yield: 62% based on
HAuCl4 ·3H2O. Anal. Calcd for C15H16S2Au2Cl2: C, 24.84; H, 2.22.
Found: C, 24.61; H, 2.32. 1H NMR (DMSO-d6, 300 MHz): δ 1.853
(qt, 2H, -S-CH2-CH2-CH2-S-), 3.047 (t, 4H, -S-CH2-CH2-
CH2-S-), 7.135–7.323 (m, 10H, C6H5-). Raman: ν(Au-S), 265.4
cm-1; ν(Au-Cl), 344.1 cm-1
.
[Au2L3-PhCl2] (4c). This complex was synthesized as follows:
HAuCl4 ·3H2O (135 mg, 0.343 mmol) was dissolved in 10 mL of
anhydrous ethanol at room temperature. The yellow solution turned
orange upon the addition of L3-Ph (0.30 mL, 1.305 mmol). The
solution was left to stand at room temperature for a few weeks,
during which light-orange prismatic crystals suitable for X-ray
analysis appeared. Yield: 68% based on HAuCl4 ·3H2O. Anal. Calcd
for C15H16S2Au2Cl2: C, 24.84; H, 2.22. Found: C, 24.67; H, 2.24.
1H NMR (DMSO-d6, 300 MHz):
-S-CH2-CH2-CH2-S-), 3.093 (t, 4H, -S-CH2-CH2-CH2-
S-), 7.142–7.453 (m, 10H, C6H5-). Raman: ν(Au-S), 266.3 cm-1
δ
2.016 (qt, 2H,
;
ν(Au-Cl), 342.4 cm-1
.
[Au2L4-PhCl2] (5). The complex was synthesized in the same
manner as 2, using HAuCl4 · 3H2O (123 mg, 0.312 mmol) and
Results
L
4-Ph (209 mg, 0.761 mmol). After a few weeks, colorless crystals
suitable for X-ray analysis were deposited. Yield: 85% based on
HAuCl4 ·3H2O. Anal. Calcd for C8H9S1Au1Cl1: C, 25.99; H, 2.45.
Found: C, 25.76; H, 2.24. 1H NMR (acetone-d6, 300 MHz):
δ 1.823 (qt, 4H, -S-CH2-(CH2)2-CH2-S-), 3.025 (t, 4H,
-S-CH2-(CH2)2-CH2-S-), 7.183-7.462 (m, 10H, C6H5-).
Synthesis of the Complexes. All of the syntheses started
from Au(III) salts. These were reduced to the Au(I) oxidation
state by the ligand, which was used in a slight excess. The
reactions that took place are given in Chart S1 in the
Supporting Information. The yellow solution of HAuCl4 ·
3H2O in anhydrous ethanol turned to orange and then quickly
changed to colorless as the ligand was added to the solution.
The stoichiometry of the resulting complexes confirmed that
gold was in the Au(I) oxidation state.
Raman: ν(Au-S), 262.2 cm-1; ν(Au-Cl), 337.4 cm-1
.
[AuL3-MeCl] (6). HAuCl4 ·3H2O (127 mg, 0.322 mmol) was
added to 10 mL of anhydrous ethanol at room temperature, yielding
a yellow mixture. Upon the addition of L3-Me (0.30 mL, 1.305
mmol), an orange precipitate formed, and after a few minutes, a
colorless microcrystalline powder was deposited. Yield: 82% based
on HAuCl4 ·3H2O. Anal. Calcd for C5H12S2AuCl: C, 16.29; H, 3.28.
Found: C, 16.34; H, 3.07. No NMR spectra were obtained for 6
because the complex could not be solubilized. Raman: ν(Au-S),
Al-Sa’ady et al.30 reported that for the synthesis of
gold(I)-thioether complexes, it was usually better to start
from a gold(III) halide salt, allowing the thiodiglycol ligand
to reduce gold(III) to gold(I). On the other hand, it has also
been reported in the literature that spontaneous reduction of
square planar Au(III) to linear Au(I) by various thiols is a
favorable reaction.31
260.1 cm-1; ν(Au-Cl), 370.1 cm-1
.
Structure Determination. X-ray intensity data for complexes
1 and 2 were obtained using a SMART 6K CCD instrument
equipped with a rotating anode (Cu KR, λ ) 1.54178 Å) and a
Mirror Montel 200 Optics monochromator. X-ray data for 3, 4a,
4b, 5, and 6 were obtained using a Brucker AXS Platform
diffractometer equipped with a SMART 2K CCD area detector and
graphite-monochromatized Cu KR radiation. The program SAINT22
was used for unit cell refinements and data reduction processing
for 1-3, 4b, 5, and 6. An empirical absorption correction based
on multiple measurements of equivalent reflections was applied
using the program SADABS.23
(25) Gabe, E. J.; Le Page, Y.; Charland, J. P.; Lee, F. L.; White, P. S.
J. Appl. Crystallogr. 1989, 22, 384.
(26) XPREP Release 5.10, X-ray Data Preparation and Reciprocal Space
Exploration Program; Bruker AXS Inc.: Madison, WI, 1997.
(27) SHELXTL Release 5.10, The Complete Software Package for Single-
Crystal Structure Determination; Bruker AXS Inc.: Madison, WI,
1997.
(28) (a) Sheldrick, G. M. SHELXS97, Program for the Solution of Crystal
Structures; University of Göttingen: Göttingen, Germany, 1997. (b)
Sheldrick, G. M. SHELXL97, Program for the Refinement of Crystal
Structures; University of Göttingen: Göttingen, Germany, 1997.
(29) Flack, H. D.; Schwarzenbach, D. Acta Crystallogr. 1988, A44, 499.
(30) Al-Sa’ady, A. K.; McAuliffe, C. A.; Parish, R. V.; Sandbank, J. A.
Inorg. Synth. 1985, 23, 191.
Diffraction data for 4c were collected on an Enraf-Nonius CAD-4
diffractometer using the ω-scan technique with graphite-mono-
chromatized Mo KR radiation (λ ) 0.71073 Å). The unit cell
(31) (a) Canumalla, A. J.; Al-Zamil, N.; Phillips, M.; Isab, A. A.; Shaw,
C. F., III. J. Inorg. Biochem. 2001, 85, 67. (b) Nakamoto, M.;
Kashigawa, Y.; Yamamoto, M. Inorg. Chim. Acta 2005, 358, 4229.
(24) Enraf-Nonius CAD-4 Software, version 5.0; Enraf-Nonius: Delft, The
Netherlands, 1989.
Inorganic Chemistry, Vol. 47, No. 8, 2008 2967

Awaleh et al.
Table 1. Crystal Data and X-ray Data Collection Parameters
1
2
3
4a
4b
4c
5
formula
mol wt
C3H8S2AuCl
340.63
C
14H14S2Au2Cl2
C
6.5H6SAuCl
C
15H16S2Au2Cl2
C
7.5H8SAuCl
C
7.5H8SAuCl
C8H9SAuCl
369.63
711.21
348.60
725.23
362.615
362.615
crystal size
(mm)
0.06 × 0.04 × 0.02 0.08 × 0.05 × 0.03 0.07 × 0.05 × 0.03 0.12 × 0.07 × 0.05 0.10 × 0.07 × 0.044 0.25 × 0.17 × 0.12 0.10 × 0.07 × 0.04
crystal system monoclinic
triclinic
1.54178
monoclinic
1.54178
C2/c
monoclinic
1.54178
P21/c
monoclinic
1.54178
C2
monoclinic
0.71073
C2/c
monoclinic
1.54178
P21/c
λ (Å)
1.54178
P21/c
j
space group
a (Å)
P1
5.9972(2)
20.3108(5)
6.3029(1)
90
6.2629(2)
8.9090(2)
14.7547(4)
93.667(1)
92.614(1)
100.891(1)
805.37(4)
2
19.7419(4)
10.5996(2)
7.4895(2)
90
11.6093(3)
8.5159(2)
19.0202(5)
90
21.4504(6)
5.6699(2)
7.7774(2)
90
21.353(9)
10.049(7)
8.346(3)
90
11.9960(6)
9.7548(5)
8.5660(5)
90
b (Å)
c (Å)
R (deg)
ꢀ (deg)
γ (deg)
V (Å3)
Z
97.706(1)
90
98.275(2)
90
102.788(2)
90
106.423(1)
90
91.04(3)
90
107.620(3)
90
760.81(3)
4
1550.91(6)
8
1833.74(8)
4
907.31(5)
4
1790.6(1.6)
8
955.35(9)
4
Dcalc (g cm-3
F(000)
T (K)
)
2.974
2.933
2.986
2.627
2.665
2.690
2.570
616
644
1256
1320
660
1320
676
150
100
200
220
220
100
220
µ (mm-1
)
43.824
68.28
39.109
68.91
40.595
72.75
34.373
72.90
34.736
72.01
16.889
26.49
33.008
72.02
θmax (deg)
Ra [I g 2σ(I)] 0.0337
0.0618
0.1463
0.0707
0.1567
1.037
0.0492
0.1234
0.0497
0.1245
1.105
0.0419
0.0960
0.0460
0.0982
1.015
0.1014
0.2372
0.1019
0.2379
1.195
0.0363
0.0809
0.0747
0.0843
0.974
0.0538
0.1338
0.0561
0.1371
1.021
b
Rw [I g 2σ(I)] 0.0885
Ra (all data)
0.0359
0.0896
1.110
b
Rw (all data)
Sc
a R ) ∑|Fo| - |Fc|/∑|Fo|. b Rw ) [∑w(Fo2 - Fc )2/∑w(Fo )2]1/2
.
c S ) [∑w(Fo2 - Fc )2/(m - n)]1/2, where m is the number of reflections and n the number
2
2
2
of parameters.
Figure 1. Complex 1. (a) The chemical unit. (b) Side view of the chains in the unit cell. (c) Projection down the chain axis. Color code: C, gray; Cl, green;
S, yellow; Au, orange. The hydrogen atoms are omitted for clarity.
Crystals of complexes 1 and 6 (containing L1-Me and L3-Me
respectively) were formed within 20 min, while crystals of
the other complexes suitable for crystal structure determina-
tions were obtained after a few weeks.
,
complexes containing bromide, nitrate, or acetate anions
would crystallize. This inability to obtain crystals was
attributed to the possibility of cooperative aurophilic interac-
tions.14
When methanol or propanol was used instead of anhydrous
ethanol to dissolve the gold salts, only complexes 1 and 6
were formed; the other complexes were not produced.
Attempts to obtain complexes with different stoichiometries
always failed, since the resulting complexes always had the
same unit cell parameters regardless of the metal-to-ligand
ratios of the starting materials. Except for 4c, which was
light orange, all of the crystalline complexes were colorless.
All of the complexes were soluble in common solvents
except for 6, which was found to be insoluble in any organic
solvent. The metal-to-ligand ratio was 1:1 for both complexes
in which R was a methyl group (1 and 6) and 2:1 for all of
the other complexes (2-5), in which R was a phenyl group.
Out of 20 planned complexes, only eight provided material
that could be used for crystal structure determination and/or
luminescence studies. In many cases, the product we at-
tempted to synthesize did not materialize, would not crystal-
lize, or could not be recrystallized for lack of a suitable
solvent. This was especially true when we attempted to study
the influence of the anion. For example, none of the
Description of the Crystal Structures. A schematic
description of the connectivities of the compounds reported
here is shown in Chart S2 in the Supporting Information.
Complexes 1, 3, 4a, and 4b form one-dimensional (1D)
supramolecular polymers, of which 3, 4a, and 4b are
topologically identical. Complex 2 is a two-dimensional (2D)
supramolecular network. On the other hand, complexes 4c
and 5 are discrete molecules. When Au-Au interactions are
taken into account in the description of the Au(I) coordi-
nation, the metal environment is square planar in 1 and 2,
T-shaped in 3, 4a, and 4b, and linear in 4c and 5. Finally,
the polymorphism observed for complexes 4a-4c formed
from self-assembly of L3-Ph and HAuCl4 · 3H2O is worth
noting.
[AuL1-MeCl]∞ (1). Self-assembly of the bis(methylthio)-
methane building block, L1-Me, with the gold salt led to the
formation of a 1D supramolecular polymer, [AuL1-MeCl]∞,
having a metal-to-ligand ratio of 1:1 (Figure 1). The
backbone of the polymer is an infinite chain of gold atoms.
2968 Inorganic Chemistry, Vol. 47, No. 8, 2008

Gold(I)-Dithioether Supramolecular Polymers
Figure 2. Complex 2. (a) Projection showing (Au-Au-)∞ chains of 2 linked by the ligands, generating the 2D coordination network. (b) A Au6L2 macrocycle
(the phenyl rings have been removed for clarity). (c) Side view of sheets of the 2D coordination network, parallel to the ac plane. Color code: C, gray; Cl,
green; S, yellow; Au, orange.
A ligand molecule and a chlorine anion are coordinated to
each gold atom. Each gold atom is surrounded by four
neighbors (one Cl, one S, and two Au atoms) in a slightly
distorted square planar coordination (Figure 1b and Figure
S1a,b in the Supporting Information). In this complex, only
one sulfur atom of the building block is coordinated to the
gold center, while the second sulfur atom of the ligand and
its methyl group lie between polymeric chains in layers parallel
to the ac plane at intervals of b/2 (Figure 1b). The Au(I)-Au(I)
distance between adjacent units is 3.1658(4) Å. This distance
is in the normal range of 2.7690(7)–3.341(2) Å for aurophilic
interactions,32–40 indicating that some aurophilic interactions
between adjacent [AuL1-MeCl] units exist. There are no
interactions between the S atoms, since the S · · · S distance
is 3.715 Å, which is larger than the sum of the van der Waals
radii (3.60 Å)41 for the sulfur atoms.
[Au2L2-PhCl2]∞ (2). Complex 2 was obtained by the reaction
of the 1,2-bis(phenylthio)ethane building block, L2-Ph, and the
gold salt. Each ligand molecule is linked to two Au(I) metal
centers to form a [Au2L2-PhCl2] entity (Figure 2). Gold atoms
of neighboring entities are linked to one another via aurophilic
interactions, forming [Au-Au-]∞ infinite chains parallel to the
a axis (Figure 2a). The resulting system is the 2D supramo-
lecular network [Au2L2-PhCl2]∞. The Au(I) · · ·Au(I) separations
have values of 3.1204(5) and 3.1499(5) Å, which are in the
normal range for aurophilic interactions.32–40 The Au(I)-Au(I)
chains are interlinked by ligand molecules, thus forming Au6L2
macrocycles (Figure 2b). In this complex, the two crystallo-
graphically independent Au(I) metal centers are surrounded by
four neighbors in a slightly distorted square planar coordination
(Figure S1c,d in the Supporting Information). As Drew and
Riedl15 established this structure from room temperature X-ray
data, it is of interest to compare our results with theirs. The
relative shrinkage of the unit cell volume, ∆V/V, was -0.033
over a temperature interval of 173 °C. This effect was unevenly
spread over the three crystallographic directions. In the b and
c directions, ∆b/band ∆c/c were only -0.007 and -0.008,
respectively. It was not surprising to observe that the most
prominent shrinkage took place along the a direction, with ∆a/a
) -0.026, as the [Au-Au-]∞ chains lie in this direction.
Because of the shrinkage of the unit cell, the Au-Au distances
at 100 K [3.1204(5) and 3.1499(5) Å] were significantly shorter
(32) Sladek, A.; Schmidbaur, H. Inorg. Chem. 1996, 35, 3268. and
references therein.
(33) Schmidbaur, H. Pure Appl. Chem. 1993, 65, 691.
(34) Li, J.; Pyykkö, P. Inorg. Chem. 1993, 32, 2630.
(35) Chen, J.; Mohamed, A. A.; Abdou, H. E.; Krause Bauer, J. A.; Fackler,
J. P., Jr.; Bruce, A. E.; Bruce, M. R. M. Chem. Commun. 2005, 1575.
(36) Tzeng, B. C.; Liao, J. H.; Lee, G. H.; Peng, S. M. Inorg. Chim. Acta
2004, 357, 1405.
(37) Mansour, M. A.; Connick, W. B.; Lachicotte, R. J.; Gysling, H. J.;
Eisenberg, R. J. Am. Chem. Soc. 1998, 120, 1329.
(38) Tzeng, B. C.; Yeh, H. T.; Huang, Y. C.; Chao, H. Y.; Lee, G. H.;
Peng, S. M. Inorg. Chem. 2003, 42, 6008.
(39) Forward, J. M.; Bohmann, D.; Fackler, J. P., Jr.; Staples, R. J. Inorg.
Chem. 1995, 34, 6330.
(40) Pyykkö, P. Chem. ReV. 1997, 97, 597.
(41) Porterfield, W. W. Inorganic Chemistry: A Unified Approach; Addison-
Wesley: Reading, MA, 1984; p 168.
(42) Simonov, Y.; Bologa, O.; Bourosh, P.; Gerbeleu, N.; Lipkowski, J.;
Gdaniec, M. Inorg. Chim. Acta 2006, 359, 721.
(43) Allen, F. H.; Kennard, O. Chem. Des. Autom. News 1993, 8, 31.
Inorganic Chemistry, Vol. 47, No. 8, 2008 2969

Awaleh et al.
Figure 3. Comparison of the chemical repeat units in (a) complex 3, (b) complex 4a, and (c) complex 4b.
Figure 4. 1D coordination polymer chains in 3, 4a, and 4b. (a) The single chain of 3. (b) Formation of a double chain in 3 through weak Au · · ·Cl
interactions. (c) The single chain in 4a. (d) The single chain in 4b. Color code: C, gray; Cl, green; S, yellow; Au, orange.
than the corresponding quantities obtained at room temperature
[3.187(2) and 3.209(2) Å] with relative ∆d/d values of -0.021
and -0.018, respectively.
Au-Cl separation was 3.323(4) Å.42 According to Simonov
et al.42 and Allen et al.,43 17 gold complexes listed in the
Cambridge Structural Database (CSD) exhibit weak Au· · ·Cl
interactions characterized by a separation of 3.281-3.526
Å. It should be pointed out that since this interaction was
observed only in 3, it may be associated with the size of the
ligand: L1-Ph is the shortest ligand, which presumably allows
for a closer approach of the chains.
The ligand torsion angles in 3, 4a, and 4b (Figure 3a-c
and Table 2) differ significantly from one another. The
packing of the chains in these complexes is shown by
projections on their ab or ac planes (Figure 5a–c).
[Au2L1-PhCl2]∞ (3) and [Au2L3-PhCl2]∞ (4a and 4b). Com-
plexes 3, 4a, and 4b have the same metal-to-ligand stoichi-
ometry (2:1) and adopt very similar structures. Each gold
atom has two neighbors (one S and one Cl), as shown in
Figure 3a-c. A third neighbor, a gold atom, links the
Au(Cl)-L-Au(Cl) molecule to another through aurophilic
interactions, forming 1D supramolecular polymers in which
the chemical repeat unit is [Au(Cl)-L-Au(Cl)-]. These
linear chains are illustrated in Figure 4a,c,d. The Au-Au
distances of 3.0347(4), 3.2997(4), and 3.1918(9) Å for 3,
4a, and 4b, respectively, fall in the normal range indicating
Au-Au aurophilic interactions, 2.7690(7)-3.341(2) Å.32–40
Complex 3 has weak Au-Cl interactions between neigh-
boring polymer chains, since the Au-Cl distance [3.284(1)
Å] is shorter than the sum of the Au and Cl van der Waals
radii (3.41 Å).41 Thus, this complex may best be described
as a columnar supramolecular polymer (Figures 4b and 5d).
Such secondary interactions were observed in the self-
assembly of a gold salt with dimethylglyoxime, where the
Molecular Complexes [Au2L3-PhCl2] (4c) and [Au2L4-Ph
-
Cl2] (5). Complexes 4c and 5 were obtained by the combi-
nation of gold(I) with L3-Ph and L4-Ph, respectively. The
distances between Au atoms in adjacent [Au2L3-PhCl2]
components in complex 4c and neighboring [Au2L4-PhCl2]
molecules in 5 (3.615 and 4.555 Å, respectively) are greater
than 3.32 Å, which is twice the van der Waals radius of
Au,41 indicating that aurophilic interactions are absent in
these complexes. In both 4c and 5, the gold atoms have a
linear coordination (Figure 6a,b). Projections of the molecular
2970 Inorganic Chemistry, Vol. 47, No. 8, 2008

Gold(I)-Dithioether Supramolecular Polymers
Table 2. Torsion Angles of Interest (deg) for the Complexes
group. Each gold atom is bound to only one other gold atom.
Since a given chemical unit, [Au2L1-PhCl2] or [Au2L3-PhCl2],
possesses two gold atoms, each unit is connected to two others
via aurophilic interactions, generating topologically comparable
1D supramolecular polymers (Figure 4).
4a
4b
4c
Au-S-C-C
S-C-C-C
C-C-C-S
C-C-S-Au
-173.7(1)
67.5(1)
178.4(1)
-49.5(1)
-170.5(1)
-51.2(1)
-51.2(1)
-170.5(1)
-176.2(1)
-178.9(1)
-178.9(1)
-176.2(1)
Class 3. The absence of short Au · · · Au contacts between
adjacent [Au2L3-PhCl2] units in 4c and [Au2L4-PhCl2] units
in 5 results in molecular structures. It is suggested that
Au· · ·Au interactions are absent in these complexes because
the aliphatic segments within the ligands are parallel to one
another and the phenyl groups are disposed in opposite
directions. Furthermore, the lengths of the aliphatic chains
in these complexes are such that the Au atoms of neighboring
molecules cannot face one another (Figure 7a,b).
1
2
Au-Au-Au-Au
180
Au-S-C-C
S-C-C-S
-179.0(1)
180
180
Au-Au-Au-Au
3
5
Au-S-C-S
S-C-S-Au
178.9(1)
178.9(1)
Au-S-C-C
S-C-C-C
C-C-C-C
176.5(1)
175.6(1)
180
packing on the ac plane (Figure 7a,b) show the respective
dispositions of the molecules in crystals of these complexes.
The L4-Ph ligand in complex 5 and the L2-Ph ligand in
complex 2, which have an even number of CH2 groups in
the aliphatic chain, are in the fully extended conformation
(Table 2). This situation is common for symmetry-related
molecules having an even number of methylene groups in
Discussion
Structural Aspects. One can see the effect of the bulk of
the R substituent on the stoichiometry by comparing the
structures of complexes 1 and 3 (Figures 1a and 3a). Indeed,
for R ) Ph (i.e., for complex 3 with ligand L1-Ph), the two
sulfur atoms of the ligand are coordinated to two different
gold centers to form a [Au2L1-PhCl2] unit, while for R ) Me
(i.e., for complex 1 with ligand L1-Me), only one sulfur atom
of the ligand is bonded to a metal center to give [AuL1-Me
Cl]. In fact, all of the complexes involving phenyl-substituted
ligands (R ) Ph) contain the [Au2Ln-PhCl2] unit and have a
metal-to-ligand ratio of 2:1, regardless of the aliphatic chain
length in the ligand (n ) 1, 2, 3, or 4) . In contrast, the
ligands containing the less-bulky methyl group [in complexes
1 and 6 (n ) 1 and 3, respectively)] seem to favor the [Au
their aliphatic chains. For example, the free ligands L2-Ph
L
,
4-Ph, L6-Ph, L8-Ph, and L10-Ph, each of which contains a
crystallographic center of symmetry at the midpoint of its
central CH2-CH2 bond, all adopt the all-trans conformation.8
Polymorphism was observed in complexes containing the
1,3-bis(phenylthio)propane ligand, L3-Ph. The three poly-
morphs 4a-4c have identical [Au2L3-PhCl2] chemical units.
Nevertheless, they have distinct Au· · ·Au separations. Com-
plexes 4a and 4b, in which the Au(I)-Au(I) distances are
3.2997(4) and 3.1918(9) Å, respectively, form 1D supramo-
lecular polymers, while 4c, with a Au(I) · · ·Au (I) separation
of 3.615 Å, is composed of discrete molecules (Figures 4
and 6). As shown by the torsion angles in the Au-S(Ph)-
(CH2)3-S(Ph)-Au segment (Table 2), the polymorphs adopt
clearly different conformations. In 4a and 4b, the phenyl
groups of a given L3-Ph ligand lie on the same side of the
aliphatic chain, while in 4c, the phenyl groups are located
on opposite sides of the aliphatic chain (Figures 3b,c and
6a). Complex 4a has a trans-gauche-trans-gauche con-
formation, while the conformations of 4c and 4b are all-
trans and trans-gauche-gauche-trans, respectively. Con-
sequently, the dispositions of these three complexes in the
solid state differ from one another (Figures 5b,c and 7a).
Although one is a molecule and the other a 1D supramo-
lecular polymer, complex 4c containing L3-Ph and complex
3 containing L1-Ph adopt very similar packing modes, as
shown by their ab-plane projections (Figure S2 in the
Supporting Information).
L
n-MeCl] stoichiometry and a metal-to-ligand ratio of 1:1. A
steric effect thus seems to control the stoichiometry of the
resulting complexes.
The compounds synthesized here may be grouped into
three different classes on the basis of the presence or absence
and the type of aurophilic interactions:
Class 1. Complexes 1, 2, and possibly 6 (see Lumines-
cence, below) possess cooperative aurophilic interactions.
That is, their structures are based on the presence of infinite
chains of gold atoms (Figures 1b and 2a).
Self-assembly of L3-Me and gold chloride led to the formation
of complex 6, which has a metal-to-ligand ratio of 1:1. However,
good single crystals were not available for the determination
of its structure.44 The existence of a single gold atom per
molecule of 1 allows for linear [Au-Au-]∞ chains through
aurophilic interactions. Hence, the structure is that of a 1D
supramolecular polymer. On the other hand, because of its
stoichiometry, each molecule of 2 is involved in two sets of
aurophilic interactions, resulting in a 2D supramolecular
polymer. The structure of 2 may be seen as consisting of
adjacent [Au-Au-]∞ chains linked by L2-Ph ligands.
UV–Vis Spectroscopy. Electronic absorption data for
complexes 1-5 in CH3CN are listed in Table 3. Since
complex 6 was insoluble in common organic solvents, its
absorption spectrum could not be reported. All of the
complexes displayed moderately intense absorption bands
in the 234–256 nm range. The UV–vis spectra of the
complexes were similar to those of the corresponding free
ligands (as shown in Figures S3–S7 in the Supporting
Information), and the main absorption bands of the com-
Class 2. Complex 3, containing the ligand L1-Ph, and comp-
lexes 4a and 4b, containing the ligand L3-Ph, belong to this
(44) Crystal data for complex 6: formula, C25H60S10Au5Cl5; fw ) 1843.58;
space group, P21/c; a ) 23.774(3) Å; b ) 9.244(1) Å; c ) 11.851(1)
Å; ꢀ ) 119.415(5)o; V ) 2268.55 Å3; Z ) 2; Dcalc ) 2.699 g cm-3.
Inorganic Chemistry, Vol. 47, No. 8, 2008 2971

Awaleh et al.
Figure 5. Packing in complexes 3, 4a, and 4b. (a) Projection of 3 along the a axis. Dotted lines indicate Au · · ·Cl interactions. (b) Projection of 4a along
the c axis. (c) Projection of 4b along the c axis. (d) Channel formation in 3, as seen in a projection down the c axis. Color code: C, gray; Cl, green; S, yellow;
Au, orange.
Figure 6. Molecular complexes (a) 4c and (b) 5, both shown in the fully extended conformation. Color code: C, gray; Cl, green; S, yellow; Au, orange.
plexes could therefore be assigned to ligand-centered transi-
tions.
Luminescence. To the best of our knowledge, no lumi-
nescence spectra with somewhat resolved vibronic structures
(long progressions) have been reported for gold(I)-thioether
complexes.
Solid-state emission spectra for complexes 1, 2, and 6 at
5 K are shown in Figure 8, and their characteristics are
compared in Table 4. Luminescence energies and spectro-
scopic characteristics for many Au(I) compounds have been
observed and shown to vary widely, from the ultraviolet to
the orange spectral regions.45 Luminescence intensities
decrease with increasing temperature, and the compounds
do not emit at room temperature. The emitting compounds
1 and 2 (which include ligands L1-Me and L2-Ph, respectively)
contain 1D-polymeric chains. Many different interpretations
of the luminescence of gold(I) compounds have been
proposed, including ligand-centered (LC),46 metal-to-ligand
charge-transfer (MLCT),47 ligand-to-metal charge-transfer
(LMCT),39 metal-centered (MC),48 or a combination of these
categories.49 Ab initio calculations (MP2 and CIS) on gold(I)
cationic dimers containing thioether ligands50 assigned the
(45) 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; p 195.
(46) Watase, S.; Nakamoto, M.; Kitamura, T.; Kanehisa, N.; Kai, Y.;
Yanagida, S. J. Chem. Soc., Dalton Trans. 2000, 3585.
(47) Flamigni, L.; Talarico, A. M.; Chambron, J. C.; Heitz, V.; Linke, M.;
Fijita, N.; Sauvage, J. P. Chem.sEur. J. 2004, 10, 2689.
2972 Inorganic Chemistry, Vol. 47, No. 8, 2008

Gold(I)-Dithioether Supramolecular Polymers
Figure 7. Projections showing the packing of (a) 4c and (b) 5. Color code: C, gray; Cl, green; S, yellow; Au, orange.
Table 3. Values of λmax and ꢀ for Complexes 1-5
1
2
3
4a
4b
4c
5
λmax (nm)
234
255
256
254
255
256
254
ꢀ (dm3 mol-1 cm-1) 10216 12072 15276 14308 14588 15783 13018
luminescence to a predominantly metal-centered transition
that also involved other excited states with similar energies.
Metal-centered transitions are expected to shift to lower
energies as the Au(I)-Au(I) distances decrease.51 In contrast,
the luminescence band maximum (Emax) for complex 2
(17900 cm-1) was slightly higher in energy than that of 1
(17250 cm-1), even though the Au–Au distance in 2 is
shorter. The assignment from the computational study
therefore cannot be applied to the compounds in the present
work. Recent spectroscopic studies on molecular Au(I)
thiolate phosphine mixed-ligand complexes with two and
three Au(I) centers52,53 have led to an assignment of the
lowest-energy transition as a thiolate-to-Au(I) charge-transfer
transition. The luminescence maxima of the literature
complexes were located at wavenumbers on the order of
19000 cm-1, a value which is somewhat greater than those
observed for our complexes. The luminescence bands of
some of these model complexes exhibited width at half-
height (W1/2) values comparable to those of the title
compounds as well as barely resolved vibronic structure
involving modes in the 400-800 cm-1 range that also
resembled structure displayed by our complexes. These
comparisons indicate that an LMCT assignment52,53 appears
reasonable.
Figure 8. Solid-state luminescence spectra of (a) complex 1, (b) complex
2, and (c) complex 6 (black lines are experimental spectra, and red lines
are luminescence fits).
Table 4. Luminescence Parameters for Complexes 1, 2, and 6
1
2
6
Emax (cm-1
W1/2 (cm-1
)
)
17250
2400
17900
2300
17000
2800
indicating that emitting-state distortions occurred along
normal coordinates other than the low-frequency metal-metal
modes, leading to the large luminescence bands. Metal-
centered luminescence has been reported for gold(I) com-
pounds with sulfur ligands (dithiocarbonates), with spectra
characterized by band widths of 1000 cm-1.19 Thus, those
bands were narrower than the luminescence bands reported
here (Table 4) by a factor of at least 2. The assignment as a
purely metal-centered transition is therefore too simplistic,
as the vibrational progressions revealed a contribution from
the ligands (Figures S8 and S9 in the Supporting Informa-
tion). Luminescence spectra can be calculated,52,54 and such
calculations gave satisfactory agreement with the experi-
mental spectra in the present case, as illustrated in Figure 8.
The calculated spectra were obtained with electronic origins
set to 18950 and 19300 cm-1, vibrational frequencies of 610
and 610 cm-1, and dimensionless excited-state distortions
The luminescence spectra of the compounds exhibited
vibronic progressions (shoulders), as shown in Figure 8. The
average progression interval was on the order of 600 cm-1,
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A. Inorg. Chem. 1997, 36, 2751. (b) Yersin, H.; Riedl, U. Inorg. Chem.
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and Spectroscopy; Salomon, E. I., Lever, A. B. P., Eds.; Wiley: New
York, 1999; Vol. I, pp 259–306. (b) Zink, J. I. Coord. Chem. ReV.
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Inorganic Chemistry, Vol. 47, No. 8, 2008 2973

Awaleh et al.
of 2.22 and 2.52 for complexes 1 and 2, respectively. The
differing values obtained for the excited-state distortion
reveal small but significant differences in the characteristics
of the emitting states in the two complexes and quantitatively
demonstrate the influence of differences in ligand structure
on solid-state luminescence properties. The experimental
luminescence spectrum of complex 6 was similar to those
of 1 and 2 (Figure 8c). The spectrum was calculated with
the electronic origin set at 18800 cm-1, a vibrational
frequency of 610 cm-1, and a dimensionless excited-state
distortion of 2.75. Although its crystal structure could not
be established, we propose that complex 6 contains
[Au-Au-]∞ chains similar to those in 1 and 2 (Table 4),
on the basis of the fact that these three complexes produced
nearly identical luminscence spectra. Despite the highly
sensitive instrumentation used, the luminescence of com-
pounds 3-5 was too weak to be measured, even at the lowest
temperatures.55
T-shaped in 1 and 2 and linear in all of the other complexes.
If Au-Au interactions are considered, the Au(I) coordination
is square planar in 1 and 2 and T-shaped in the others.
The chemical repeat units in complexes 1-3, 4a, and 4b
are linked to one another via aurophilic interactions, giving
rise to 1D and 2D supramolecular compounds, while 4c and
5 are molecular complexes. The Au-Au distances in 1-3
and 4b are 3.0347(4)-3.1918(5) Å and 3.2997(4) Å in 4a.
The polymeric compounds 1 and 2, which contain Au(I)
chains, [Au-Au-]∞, exhibited solid-state luminescence with
vibronic progressions at 5 K. The luminescence spectrum
of 6 led us to conclude that this complex also contains
[Au-Au-]∞ chains. Polymorphism was observed for com-
plexes 4a-4c formed using 1,3-bis(phenylthio)propane as
the dithioether ligand.
Acknowledgment. The authors would like to thank the
Natural Sciences and Engineering Research Council of
Canada. M.O.A. thanks the Organisation Internationale de
la Francophonie and the Programme Canadien de Bourse
de la Francophonie for a graduate scholarship and also thanks
the Djibouti Presidency, the General Secretary of the Djibouti
Government, and the CERD for a research grant.
Concluding Remarks
In this study, we investigated the coordination chemistry
of Au(I) complexes with dithioether ligands of the form
RS(CH2)nSR, containing a short aliphatic segment (n ) 1-4)
and having R ) methyl or phenyl. The metal-to-ligand ratios
are 1:1 and 2:1 in complexes containing ligands with R )
methyl and phenyl, respectively. The Au(I) coordination is
Supporting Information Available: X-ray crystallographic
information files in CIF format for compounds 1-5, details of the
characterization of the ligands, a table of bond distances and angles,
and Figures S1-S9. This material is available free of charge via
the Internet at http://pubs.acs.org.
(55) Bussière, G.; Beaulac, R.; Cardinal-David, B.; Reber, C. Coord. Chem.
ReV. 2001, 219–221, 509.
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