Syntheses, structures, and photophysical properties of mono- and dinuclear sulfur-rich gold(I) complexes

Article abstract of DOI:10.1021/ic7022067

The dinuclear gold complexes [{Au(PPh₃)}₂(μ-dmid)] (1) (dmid = 1,3-dithiole-2-one-4,5-dithiolate) and [{Au(PPh₃)} ₂(μ-dddt)] (2) (dddt = 5,6-dihydro-1,4-dithiine-2,3-dithiolate) were synthesized and characterized by X-ray crystallography. Both complexes exhibit intramolecular aurophilic interactions with Au...Au distances of 3.1984(10) A for 1 and 3.1295(11) A for 2. A self-assembly reaction between 4,5-bis(2-hydroxyethylthio)-1,3-dithiole-2-thione ((HOCH ₂CH₂)₂dmit) and [AuCl(tht)] affords the complex [AuCl{(HOCH₂CH₂)₂dmit}]₂ (4), which possesses an antiparallel dimeric arrangement resulting from a short aurophilic contact of 3.078(6) A. This motif is extended into two dimensions due to intra- and intermolecular hydrogen bonds via the hydroxyethyl groups, giving rise to a supramolecular network. Three compounds were investigated for their rich photophysical properties at 298 and 77 K in 2-MeTHF and in the solid state; [Au₂(μ-dmid)(PPh₃)₂] (1), [Au ₂(μ-dddt)(PPh₃)₂] (2), and [AuCl{(HOCH ₂CH₂)₂dmit}] (4). 1 exhibits relatively long-lived LMCT (ligand-to-metal charge transfer) emissions at 298 K in solution (370 nm; τ_e ～17 ns, where M is a single gold not interacting with the other gold atom; i.e., the fluxional C-SAuPPh₃ units are away from each other) and in the solid state (410 nm; τ_e ～70 μs). At 77 K, a new emission band is observed at 685 nm (τ_e = 132 μs) and assigned to a LMCT emission where M is representative for two gold atoms interacting together consistent with the presence of Au...Au contacts as found in the crystal structure. In solution at 77 K, the LMCT emission is also red-shifted to 550 nm (τ_e ～139 μs). It is believed to be associated to a given rotamer. 2 also exhibits LMCT emissions at 380 nm at 298 K in solution and at 470 nm in the solid state. 4 exhibits X/MLCT emission (halide/metal to ligand charge transfer) where M is a dimer in the solid state with obvious Au...Au interactions, resulting in red-shifted emission band, and is a monomer in solution in the 10^-5 M concentration (i.e., no Au...Au interactions) resulting in blue-shifted luminescence. Both fluorescence and phosphorescence are observed for 4.

Full text of DOI:10.1021/ic7022067

Inorg. Chem. 2008, 47, 7483-7492
Syntheses, Structures, and Photophysical Properties of Mono- and
Dinuclear Sulfur-Rich Gold(I) Complexes
Fabrice Guyon,*,† Aure´lien Hameau,† Abderrahim Khatyr,† Michael Knorr,† Hedi Amrouche,‡
Daniel Fortin,‡ Pierre D. Harvey,*,‡ Carsten Strohmann,§ Amadou L. Ndiaye,†,| Volker Huch,|
Michael Veith,|,⊥ and Narcis Avarvari#
Institut UTINAM, UMR CNRS 6213, UniVersite´ de Franche-Comte´, Faculte´ des Sciences et
Techniques, 16 route de Gray, 25030 Besanc¸on, France, De´partement de Chimie, UniVersite´ de
Sherbrooke, Sherbrooke, J1K 2R1 Que´bec, Canada, Institut fu¨r Anorganische Chemie der
UniVersita¨t Wu¨rzburg, Am Hubland, D-97074 Wu¨rzburg, Germany, INM-Leibniz Institute for New
Materials, Campus D2 2, Saarland UniVersity, Im Stadtwald, Geba¨ude D2 2, 66123 Saarbru¨cken,
Germany, Institute for Inorganic Chemistry, Saarland UniVersity, PO Box 15 11 50, 66041
Saarbruecken, Germany, and Laboratoire , Chimie Inge´nierie Mole´culaire et Mate´riaux .
(CIMMA), UMR 6200, 2 bouleVard LaVoisier, 49045 Angers, France
Received November 9, 2007
The dinuclear gold complexes [{Au(PPh3)}2(µ-dmid)] (1) (dmid ) 1,3-dithiole-2-one-4,5-dithiolate) and [{Au(PPh3)}2(µ-
dddt)] (2) (dddt ) 5,6-dihydro-1,4-dithiine-2,3-dithiolate) were synthesized and characterized by X-ray crystallography.
Both complexes exhibit intramolecular aurophilic interactions with Au · · · Au distances of 3.1984(10) Å for 1 and 3.1295(11)
Å for 2. A self-assembly reaction between 4,5-bis(2-hydroxyethylthio)-1,3-dithiole-2-thione ((HOCH2CH2)2dmit) and [AuCl(tht)]
affords the complex [AuCl{(HOCH2CH2)2dmit}]2 (4), which possesses an antiparallel dimeric arrangement resulting from
a short aurophilic contact of 3.078(6) Å. This motif is extended into two dimensions due to intra- and intermolecular
hydrogen bonds via the hydroxyethyl groups, giving rise to a supramolecular network. Three compounds were investigated
for their rich photophysical properties at 298 and 77 K in 2-MeTHF and in the solid state; [Au2(µ-dmid)(PPh3)2] (1),
[Au2(µ-dddt)(PPh3)2] (2), and [AuCl{(HOCH2CH2)2dmit}] (4). 1 exhibits relatively long-lived LMCT (ligand-to-metal charge
transfer) emissions at 298 K in solution (370 nm; τe ∼17 ns, where M is a single gold not interacting with the other gold
atom; i.e., the fluxional C-SAuPPh3 units are away from each other) and in the solid state (410 nm; τe ∼70 µs). At 77
K, a new emission band is observed at 685 nm (τe ) 132 µs) and assigned to a LMCT emission where M is representative
for two gold atoms interacting together consistent with the presence of Au · · · Au contacts as found in the crystal structure.
In solution at 77 K, the LMCT emission is also red-shifted to 550 nm (τe ∼139 µs). It is believed to be associated to a
given rotamer. 2 also exhibits LMCT emissions at 380 nm at 298 K in solution and at 470 nm in the solid state. 4 exhibits
X/MLCT emission (halide/metal to ligand charge transfer) where M is a dimer in the solid state with obvious Au · · · Au
interactions, resulting in red-shifted emission band, and is a monomer in solution in the 10-5 M concentration (i.e., no
Au · · · Au interactions) resulting in blue-shifted luminescence. Both fluorescence and phosphorescence are observed for 4.
Introduction
properties generally associated with these systems.1 It was
recognized that aurophilic Au · · · Au contacts may play a
central role in the photophysical properties of gold(I)
complexes.2 For example, Yam and colleagues have devel-
oped luminescence chemosensors based on the switching on
and off of weak Au · · ·Au interactions using dinuclear gold(I)
phosphine thiolate complexes.3 Numerous studies were
devoted to the synthesis of complexes which exhibit inter-
or intramolecular metal-metal interactions. Of particular
Di- and polynuclear gold complexes have attracted much
attention in the past two decades due to the rich luminescence
* To whom correspondence should be addressed. E-mail: fabrice.guyon@
univ-fcomte.fr.
†
Universite´ de Franche-Comte´, Faculte´ des Sciences et Techniques.
De´partement de Chimie, Universite´ de Sherbrooke.
Institut fu¨r Anorganische Chemie der Universita¨t Wu¨rzburg.
INM-Leibniz Institute for New Materials.
Institute for Inorganic Chemistry, Saarland University.
Laboratoire , Chimie Inge´nierie Mole´culaire et Mate´riaux ..
‡
§
|
⊥
#
10.1021/ic7022067 CCC: $40.75  2008 American Chemical Society
Inorganic Chemistry, Vol. 47, No. 17, 2008 7483
Published on Web 07/29/2008

Guyon et al.
interest are the dithiolene compounds for the following
reasons: (i) as soft Lewis bases, the electrochemically active
dithiolene ligands possess a high affinity toward gold, (ii)
because they may act as bridging ligands, they promote the
formation of dinuclear gold complexes with intramolecular
Au · · · Au separations shorter than the sum of the Van der
Waals radii of gold. Moreover, (iii) some of them may favor
intermolecular contacts via S · · · S interaction.4 The family
of 1,2 dithiolene ligands includes sulfur-rich dithiolenes, such
as 1,3-dithiole-2-thione-4,5-dithiolate (dmit), which was
successfully used for nickel, palladium, or platinum com-
plexes for the elaboration of conducting and superconducting
molecular materials.5 The remarkable properties of these
synthetic metals result mainly from the propensity of the
ligand to overlap with each other in the solid state due to
the presence of numerous sulfur atoms. Also, some [(AuL)2(µ-
dmit)] (L ) phosphane) complexes6 and related derivatives7
were reported and structurally characterized. However, there
are no thorough reports on their photophysical properties.
In continuation of our previous studies on dithiolene
complexes,8 we wish to report the synthesis, structural
characterization, and photophysical studies of two novel
sulfur-rich dithiolene gold(I) complexes based on the 1,3-
dithiole-2-one-4,5-dithiolate (dmid) and the more electron-
rich 5,6-dihydro-1,4-dithiine-2,3-dithiolate (dddt) ligands, as
well as the compounds resulting from the self-assembly
processes between 4,5-bis(methylthio)-1,3-dithiole-2-thione
(Me2dmit) or 4,5-bis(2-hydroxyethylthio)-1,3-dithiole-2-
thione ((HOCH2CH2)2dmit) ligands and the [AuCl] fragment.
This second approach was motivated by the recent syntheses
of the coordination polymers [HgX2(Me2dmit)]n (X ) Cl,
Br, I),9 [CuX(Me2dmit)]n,10 and [HgI2((HOCH2CH2)2dmit)].11
The polymeric structures encountered in these materials result
in part from a combination of π-π and S · · · S interactions
between the sulfur rich ligands, therefore these latters appear
also as excellent candidates to promote intermolecular
Au · · · Au interactions.
Experimental Section
Materials. [AuCl(PPh3)],12 [AuCl(tht)],13 Me2dmit,14 and
(HOCH2CH2)2dmit15 were prepared according to the literature
procedures. All manipulations were performed using Schlenk
techniques in an atmosphere of dry oxygen-free argon.
Synthesis of [Au2(µ-dmid)(PPh3)2] (1). A solution of 1,3,4,6-
tetrathiapentalene-2,5-dione16 (0.047 g; 0.225 mmol) in MeOH was
reacted with a solution of MeONa (0.45 mmol). After stirring for
1 h, solid [AuCl(PPh3)] (0.223 g; 0.45 mmol) was added. The
precipitate, which immediately appeared, was collected by filtration,
washed with MeOH, and dried to provide 1 as a yellow-green solid.
(0.200 g, 81% yield). Anal. found: C, 42.18; H, 2.80.
C39H30Au2OP2S4 calcd: C, 42.63; H, 2.75%. 31P{1H} NMR (CDCl3):
(1) (a) King, C.; Wang, J. C.; Khan, M. N. I.; Fackler, J. P. Inorg. Chem.
1989, 28, 2145. (b) Yam, V. W.-W.; Lo, K. K. W. Chem. Soc. ReV.
1999, 28, 323. (c) Puddephatt, R. J. Coord. Chem. ReV. 2001,
216-217, 313. (d) Lagunas, M. C.; Mendicute Fiero, C.; Pintado-
Alba, A.; de la Riva, H.; Betanzos-Lara, S. Gold Bull. 2007, 40, 135.
(2) (a) Assefa, Z.; McBurnett, B. G.; Staples, R. J.; Fackler, J. P., Jr.;
Assmann, B.; Angermaier, K.; Schmidbaur, H. Inorg. Chem. 1995,
34, 75. (b) Forward, J. M.; Bohmann, D.; Fackler, J. P., Jr.; Staples,
R. J. Inorg. Chem. 1995, 34, 6330. (c) Pintaldo-Alba, A.; de la Riva,
H.; Nieuwhuyzen, M.; Bautista, D.; Raithby, P. R.; Sparkes, H. A.;
Teat, S. J.; Lopez-de-Luzuriaga, J. M.; Lagunas, M. C. J. Chem. Soc.,
Dalton Trans. 2004, 3459. (d) Tzeng, B. C.; Chan, C. K.; Cheung,
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4970.
δ ) 37.0; 13C NMR (CDCl3): δ ) 193.5 (CdO); IR (KBr) ·/cm-1
:
1663 and 1613 (CdO). UV-vis (CH2Cl2) λabs (nm) (ꢀ, M-1cm-1):
231 (43200), 303 (7500).
Synthesis of [Au2(µ-dddt)(PPh3)2] (2). A solution of 5,6
dihydro-1,3dithiolo[4,5-b]-1,4-dithiine-2-one17 (0.049 g; 0.235
mmol) in MeOH was reacted with a solution of MeONa
(0.47 mmol). After stirring for 1 h, solid [AuCl(PPh3)] (0.232 g;
0.47 mmol) was added. The precipitate, which immediately
appeared, was collected by filtration, washed with MeOH, and dried
to provide 2 as a green solid. (0.215 g; 83% yield). Anal. found:
C, 43.52; H, 3.09. C40H34Au2P2S4 Calcd: C, 43.72; H, 3.12%.
31P{1H} NMR (CDCl3): δ ) 35.1. UV-vis (CH2Cl2) λabs (nm) (ꢀ,
M-1cm-1): 236 (36 800), 327 (7200).
(3) (a) Yam, V. W.-W.; Li, C.-K.; Chan, C. L. Angew. Chem., Int. Ed.
Engl. 1998, 37, 2857. (b) Yam, V. W.-W.; Chan, C. L.; Li, C.-K.;
Wong, K. M.-C. Coord. Chem. ReV. 2001, 216-217, 173.
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J. P., Jr. Inorg. Chem. 1993, 32, 1749. (b) Gimeno, M. C.; Jones,
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3932.
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Cassoux, P.; Valade, L.; Kobayashi, H.; Kobayashi, A.; Clark, R. A.;
Underhill, A. E. Coord. Chem. ReV. 1991, 110, 115.
(9) Hameau, A.; Guyon, F.; Knorr, M.; Enescu, M.; Strohmann, C.
Monatsh. Chem. 2006, 137, 545.
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1996, 35, 2995. (b) Cerrada, E.; Jones, P. G.; Laguna, A.; Laguna,
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E. J.; Jones, P. G.; Laguna, A.; Laguna, M.; Terroba, R. Organome-
tallics 1995, 14, 5537.
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2004, 23, 1447. (b) Hameau, A.; Guyon, F.; Knorr, M.; Khatyr, A.;
Strohmann, C. Manuscript in preparation.
(11) Ndiaye, A. L.; Guyon, F.; Knorr, M.; Huch, V.; Veith, M. Z. Anorg.
Allg. Chem. 2007, 633, 1959.
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Chim. Acta 2004, 357, 3532. (b) Cerrada, E.; Laguna, M.; Sorolla,
P. A. Polyhedron 1998, 17, 295.
(12) Uson, R.; Laguna, A. Organomet. Synth. 1985, 3, 325.
(13) Uson, R.; Laguna, A.; Laguna, M. Inorg. Synth. 1989, 26, 85.
(14) Steimecke, G.; Sieler, H. J.; Kirmse, R.; Hoyer, E. Phosphorus Sulfur
1979, 7, 49.
(8) (a) Guyon, F.; Lenoir, C.; Fourmigue´, M.; Larsen, J.; Amaudrut, J.
Bull. Soc. Chim. Fr. 1994, 465, 187. (b) Guyon, F.; Fourmigue´, M.;
Cle´rac, R.; Amaudrut, J. J. Chem. Soc., Dalton Trans. 1996, 4093.
(c) Jourdain, I.; Fourmigue´, M.; Guyon, F.; Amaudrut, J. Organome-
tallics 1999, 18, 1834. (d) Guyon, F.; Jourdain, I.; Knorr, M.; Lucas,
D.; Monzon, T.; Mugnier, Y.; Avarvari, N.; Fourmigue´, M. Eur.
J. Inorg. Chem. 2002, 2026. (e) Guyon, F.; Lucas, D.; Jourdain, I.;
Fourmigue´, M.; Mugnier, Y.; Cattey, H. Organometallics 2001, 20,
2421.
(15) Hansen, T. K.; Jorgensen, T.; Jensen, F.; Thygesen, P. H.; Christiansen,
K.; Hursthouse, M. B.; Harman, M. E.; Malik, M. A.; Girmay, B.;
Underhill, A. E.; Begtrup, M.; Kilburn, J. D.; Belmore, K.; Roepstorff,
P.; Becher, J. J. Org. Chem. 1993, 58, 1359.
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7484 Inorganic Chemistry, Vol. 47, No. 17, 2008

Mono- and Dinuclear Sulfur-Rich Gold(I) Complexes
Synthesis of [AuCl(Me2dmit)] (3). To a solution of Me2dmit
(0.120 g; 0.5 mmol) in 10 mL of CH2Cl2 was added 1 equiv of
[AuCl(tht)] (0.170 g; 0.5 mmol). The mixture was stirred at room
temperature for 18 h. The yellow precipitate was then filtered and
crystallized in hot CHCl3. Yellow needles were obtained by cooling
a CHCl3 solution at -20 °C (0.200 g; 82% yield). Anal. found: C,
13.36; H, 1.46. C5H6AuClS5 Calcd: C, 13.09; H, 1.32%. IR (KBr)
·/cm-1: 1015 (CdS). UV-vis (CH2Cl2) λabs (nm) (ꢀ, M-1cm-1):
243 (15300), 295 (6400), 433 (17 200).
absorption correction was employed using the FACEIT-program
in IPDS (Stoe & Cie, 1999). All structures were solved applying
direct and Fourier methods, using SHELXS-90 and SHELXL-97.24,25
For each structure, the non-hydrogen atoms were refined anisotro-
pically. All of the hydrogen atoms were placed in geometrically
calculated positions and each was assigned a fixed isotropic
displacement parameter based on a riding-model. Refinement of
the structures was carried out by full-matrix least-squares methods
2
based on Fo using SHELXL-97. All calculations were performed
Synthesis of [AuCl{(HOCH2CH2)2dmit}] (4). To a solution of
4,5-bis[(2′-hydroxyethyl)thio]1,3-dithiole-2-thione (0.100 g; 0.349
mmol) in acetone (8 mL) was added 1 equiv of [AuCl(tht)] (0.112
g; 0.349 mmol) dissolved in acetone (7 mL). The resulting clear
yellow-orange solution was stirred during 1 h at room temperature.
After filtration, the filtrate was reduced to ca. 7 mL and cooled to
allow formation of yellow crystals (0.105 g; 58% yield) suitable
for X-ray measurement. Anal. found: C, 16.15; H, 1.84.
using the WinGX crystallographic software package, using the
programs SHELXS-90 and SHELXL-97. The crystallographic data
for each complex are given in Table 1.
Results and Discussion
Synthesis of 1,2-Dithiolene Bridged Dinuclear Gold(I)
Complexes. The preparation of [{Au(PPh3)}2(µ-dmid)] (1)
and [{Au(PPh3)}2(µ-dddt)] (2) was performed by the reaction
of the dithiolene dianion with 2 equiv of [AuCl(PPh3)]. The
ligands dmid and dddt are obtained from the corresponding
1,3-dithiol-2-ones by treatment with sodium methanolate
(Scheme 1). The dinuclear 1 and 2 complexes are obtained
as green-yellow crystalline solids and are air-stable.
The 31P{1H} NMR spectra of both compounds exhibit a
broadened singlet at room temperature, indicating the pres-
ence of two magnetically equivalent phosphorus atoms in
solution. At 296 K, the proton NMR spectrum of the
ethylenic segment of 2 consists in a AA′BB′ pattern centered
at 3.27 ppm. This is indicative of a nonequivalence of the
two faces of the dithiolene core. The fluxional behavior in
solution of a similar system has been studied elsewhere by
means of temperature-dependent NMR spectroscopy.8b
Structural Analysis of 1 and 2. Suitable single crystals
of 1 and 2 were grown from CH2Cl2/hexane. 1 crystallizes
with one solvent molecule of CH2Cl2. Their molecular
structures shown in Figures 1 and 2 are very reminiscent to
those of the structurally characterized [{Au(PR3)}2(µ-dithi-
olene)] complexes. Selected bond lengths and angles are
listed in Table 2 and were compared with those of [{Au-
C14H20S10O4Au2Cl2 Calcd: C, 16.20; H, 1.92%. ATR-IR ·/cm-1
:
1
3252 (OH), 1008 (CdS). H NMR (DMSO-d6): δ ) 3.12 (4H, t,
J ) 6.2 Hz); 3.63 (4H, t, J ) 6.2 Hz); 5.12 (2H, s, OH).
Apparatus. IR spectra have been recorded on a Nicolet Nexus
470 spectrometer. Elemental C, H analyses were performed on a
Leco Elemental Analyzer CHN 900. The 31P{1H} NMR spectra
were recorded at 300.13 MHz on a Bruker DRX 300 spectrometer.
The chemical shifts are in ppm. The UV-vis spectra were recorded
on a Uvikon-XL spectrometer and on a Hewlett-Packard diode array
model 8452A. The emission and excitation spectra were obtained
using a double monochromator Fluorolog 2 instrument from Spex.
Phosphorescence time-resolved measurements were performed on
a PTI LS-100 using a 1 µs tungsten flash lamp. Fluorescence and
phosphorescence lifetimes were measured on a Timemaster Model
TM-3/2003 apparatus from PTI. The source was nitrogen laser with
high-resolution dye laser (fwhm ∼1300 ps) and the fluorescence
lifetimes were obtained from high quality decays and deconvolution
or distribution lifetimes analysis. The uncertainties were about (
40 ps based on multiple measurements.
Quantum Yield Measurements. For room temperature, all
samples were prepared under inert atmosphere (in a glovebox, PO2
< 20 ppm) by dissolution of the different compounds in 2-MeTHF
using 1 mL quartz cells with septum (298 K) or quartz NMR tubes
in liquid nitrogen for 77 K measurements. Two different measure-
ments (i.e., different solutions) were performed for each photo-
physical data (quantum yields and Φ). The sample concentrations
were chosen to correspond to an absorbance of 0.05 at the excitation
wavelength. Each absorbance value was measured five times for
better accuracy in the measurements of Φe. The reference for Φe
was 9,10-diphenylanthracene (ΦF ) 1.0).18
Theoretical Computations. Calculations using the density
functional theory (DFT) approximation were performed using the
commercially available Gaussian 03 software.19 The hybrid B3LYP
exchange-correlation function has been considered due to the high
accuracy of the ensued results,20–22 with the 3-21G* as the basis
set for P, 6-31G(d) for carbon, hydrogen, and sulfur and
LANL2DZ for gold.23 All computations were performed without
symmetry constraint.
(19) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb,
M. A.; Cheeseman, J. R.; Montgomery, J. A.; Vreven, J. T.; Kudin,
K. N.; Burant, J. C.; Millam, J. M.; Iyengar, S. S.; Tomasi, J.; Barone,
V.; Mennucci, B.; Cossi, M.; Scalmani, G.; Rega, N.; Petersson, G. A.;
Nakatsuji, H.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa,
J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Klene,
M.; Li, X.; Knox, J. E.; Hratchian, H. P.; Cross, J. B.; Adamo, C.;
Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin,
A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Ayala, P. Y.;
Morokuma, K.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.;
Zakrzewski, V. G.; Dapprich, S.; Daniels, A. D.; Strain, M. C.; Farkas,
O.; Malick, D. K.; Rabuck, A. D.; Raghavachari, K.; Foresman, J. B.;
Ortiz, J. V.; Cui, Q.; Baboul, A. G.; Clifford, S.; Cioslowski, J.;
Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz, P.; Komaromi, I.;
Martin, R. L.; Fox, D. J.; Keith, T.; Al-Laham, M. A.; Peng, C. Y.;
Nanayakkara, A.; Challacombe, M.; Gill, P. M. W.; Johnson, B.; Chen,
W.; Wong, M. W.; Gonzalez, C.; Pople, J. A. Gaussian 03, RC, Ed.;
Gaussian, Inc.: Wallingford, CT, 2004.
Crystal-Structure Determinations. A suitable crystal of each
complex was mounted in an inert oil (perfluoropolyalkylether) and
used for X-ray crystal structure determinations. Data were collected
on a Stoe IPDS diffractometer at 173(2) K for 1 and 2 and at 293
K for 4. The intensities were determined and corrected by the
program INTEGRATE in IPDS (Stoe & Cie, 1999). An empirical
(20) Becke, A. D. J. Chem. Phys. 1993, 98, 5648.
(21) Lee, C.; Yang, W.; Parr, R. G. Phys. ReV. B, Condens. Matter 1988,
37, 785.
(22) Miehlich, B.; Savin, A.; Stoll, H.; Preuss, H. Chem. Phys. Lett. 1989,
157, 200.
(23) (a) Dobbs, K. D.; Hehre, W. J. J. Comput. Chem. 1986, 7, 359. (b)
Dobbs, K. D.; Hehre, W. J. J. Comput. Chem. 1987, 8, 861. (c) Dobbs,
K. D.; Hehre, W. J. J. Comput. Chem. 1987, 8, 880.
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80, 969.
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Germany, 1990.
Inorganic Chemistry, Vol. 47, No. 17, 2008 7485

Guyon et al.
Table 1. Crystallographic data for 1, 2, and 4
identification code
1·CH2Cl2
2
4
empirical formula
fw
C40H32Au2Cl2OP2S4
1183.67
C40H34Au2P2S4
1098.79
C14H20Au2Cl2O4S10
1037.73
wavelength
cryst syst
space group
unit cell dimensions
0.71073 Å
monoclinic
P2(1)/n
0.71073 Å
monoclinic
P2(1)
0.71073 Å
monoclinic
P2(1)/n
a ) 5.4398(11) Å R) 90°.
b ) 30.511(6) Å ꢀ) 105.49(3)°.
c ) 8.6704(17) Å
ꢀ ) 105.49(3)°
1386.8 (5) Å3
a ) 10.928(2) Å,
b ) 10.726(2) Å,
c ) 34.297(7) Å,
ꢀ ) 95.18(3)°
4003.6(14) Å3
4
a ) 10.528(2) Å,
b ) 10.691(2) Å,
c ) 16.689(3) Å,
ꢀ ) 98.94(3)°
1855.7(6) Å3
2
V
Z
Dcalcd
2
1.964 mg/m3
1.996 mg/m3
8.237 mm-1
1052
2.485 mg/m3
absorption coefficient
F(000)
cryst size
θ range for data collection
index ranges
7.775 mm-1
11.535 mm-1
2264
976
0.30 × 0.20 × 0.20 mm3
2.24 to 26.00°
-13 e h e13,
-13 e k e 13,
-42 e l e 42
7829
? × ? × ? mm3
2.15 to 27.00°
-13 e h e13,
-13 e k e 13,
-21 e l e 21
15925
0.7 × 0.1 × 0.05 mm3
2.53 to 27.98°
-6 e h e6,
-40 e k e 39,
-11 e l e 11
reflns collected
12410
independent reflns
6429
8019
3107
[R(int) ) 0.0591]
Full-matrix least squares on F2
7828/0/460
[R(int) ) 0.0505]
Full-matrix least squares on F2
8019/1/433
[R(int) ) 0.0798]
Full-matrix least squares on F2
3107/0/148
refinement method
data/restraints/params
GOF on F2
1.061
1.010
1.034
final R indices [I > 2σ(I)]
R indices (all data)
largest diff. peak and hole
R1 ) 0.0368, wR2 ) 0.0923
R1 ) 0.0461, wR2 ) 0.0959
1.392 and -1.141 e ·Å-3
R1 ) 0.0442, wR2 ) 0.1092
R1 ) 0.0492, wR2 ) 0.1143
1.625 and -2.012 e ·Å-3
R1 ) 0.0270, wR2 ) 0.0629
R1 ) 0.0396 wR2 ) 0.0674
1.074 and -1.219 e ·Å-3
Scheme 1. (i) 2 equiv NaOMe in MeOH, (ii) 2 equiv [AuCl(PPh3)2]
(PPh3)}2(µ-dmit)]6a and [{Au(PPh3)}2(µ-mnt)] (mnt ) 1,2-
dicyanoethene-1,2-dithiolate).4a In 1 and 2, the two gold
atoms are bridged by the 1,2-dithiolene, and each one is
coordinated to a PPh3 with typical Au-S and Au-P
distances (in the range 2.311(2)-2.344(2) and 2.254-
(2)-2.274(2) Å, respectively). The geometry about one gold
atom is approximately linear (S(2)-Au(2)-P(2) ) 172.47(5)°
for 1 and 173.41(9)° for 2), but the coordination of the second
Figure 2. Thermal ellipsoid plot of 2 (50% level). Hydrogen atoms are
omitted for clarity.
gold deviates more significantly from linearity [S(1)-Au(1)-
P(1) ) 165.16(5)° for 1 and 163.40(8)° for 2] due to the
existence of an additional Au · · · S interaction [Au(1)-S(2)
) 2.720(2) Å for 1 and 2.830(2) Å for 2]. This unsym-
metrical coordination around the gold(I) centers is a common
feature for the 1,2-dithiolene ligands. Fackler et al. have
shown that electronic rather than steric factors are responsi-
ble for the irregular geometries observed.26 Only one of the
atoms of gold is almost coplanar to the 1,3-dithiole-2-thione
skeleton. Both complexes exhibit Au · · · Au intramolecular
(25) G. M. Sheldrick SHELXL-97; University of Go¨ttingen: Go¨ttingen,
Germany, 1997.
(26) Davila, R. M.; Staples, R. J.; Elduque, A.; Harlass, M. M.; Kyle, L.;
Fackler, J. P., Jr. Inorg. Chem. 1994, 33, 5940.
Figure 1. Thermal ellipsoid plot of 1 (50% level). Hydrogen atoms and
solvated CH2Cl2 are omitted for clarity.
7486 Inorganic Chemistry, Vol. 47, No. 17, 2008

Mono- and Dinuclear Sulfur-Rich Gold(I) Complexes
Table 2. Selected Bonds (Angstroms) and Angles (Degrees) of
[(AuL)2(µ-dithiolene)] (L ) PPh3)
Scheme 3
[(AuL)2
[(AuL)2
1
2
(µ-dmit)]6a (µ-mnt)]4a
Au(1)-S(1)
Au(2)-S(2)
Au(1)-S(2)
Au(1)-Au(2)
Au(1)-P(1)
Au(2)-P(2)
C(1)-S(1)
2.3441(17) 2.321(2)
2.3366(15) 2.311(2)
2.7203(16) 2.830(2)
3.1985(10) 3.1295(11) 3.0681(8)
2.2709(16) 2.274(2)
2.2652(15) 2.254(2)
2.3435(12) 2.323(4)
2.3474(11) 2.321(4)
2.8226(14) 2.811(5)
3.115(3)
2.2569(12) 2.273(4)
2.2779(11) 2.269(4)
the ligand at 394 nm is shifted toward lower energy to appear
at 433 nm in 3. With reference to earlier spectroscopic studies
of gold thione complexes,27 this lowest energy band can be
assigned to electronic transition from a sulfur n lone pair to
the (CdS) π* orbital (n f π*). Although the poor quality
of the crystals of 3 does not allow a detailed discussion of
the crystal structure,28 the coordination mode of Me2dmit
on [AuCl] fragment could be described as outlined in Scheme
3. The complexation on gold occurs via the thiocarbonyl
function as observed in the case of CuI and HgX2 adducts.9,10
Both the length of the Au-S bond of about 2.213 Å and the
Cl-Au-S bond angle of 174.2° lie in a similar range found
for thione 4 (below). An additional weak contact of 3.21 Å
is also identified between a thioether function and a second
AuCl fragment. By this manner, Me2dmit acts as a bridging
ligand between AuCl fragments, leading to the formation of
a 1D coordination polymer (Scheme 3). The coordination
mode via the sulfur of the thioketone group is also confirmed
by the IR spectra because the CdS vibration appears at lower
position in 3 than in the free ligand (1015 vs 1057 cm-1). A
comparable shift to lower wavenumbers is also observed for
the CdS vibration measured in 4 (1008 cm-1) and that
recorded for (HOCH2CH2)2dmit (1070 cm-1). Furthermore,
the ATR-IR spectrum of 4 indicates the presence of hydrogen
bonds because broad OH vibrations were observed at 3252
cm-1.
Structural analysis of 4. Compared to 3, complex 4
displays a very different architecture, which consists of a
dimeric structural motif. It results from a surprisingly close
aurophilic contact of 3.078(6) Å between the two metal
centers as depicted in Figure 3. A similar arrangement in
antiparallel pairs was reported for the thione complex
[AuCl(C3H4S3)] (C3H4S3 ) ethylenthiocarbonate) with a
Au · · · Au separation of 3.366 Å.27 More recently, an
Au · · · Au contact of 3.1488(7) Å was established in the
dimeric association of two gold(I) macrocycles.29 The
intermolecular Au · · · Au distance in 4 is also significantly
shorter than the intramolecular semi-supported interactions
observed for 1 and 2 (Table 2), in which the two gold atoms
are held in close proximity by the clamping effect of the
two bridging ligands. The close contact in 4 may better be
compared with the distances of 3.023(1) and 3.0038(6) Å
reported for semi-supported [ClAu(µ-dppdiene)AuCl] (dp-
pdiene ) 2,3-(bisphenylphosphino)-1,3-butadiene) and
[ClAu(µ-dpephos)AuCl] (dpephos ) bis(2-diphenylphos-
phino)phenylether), respectively.30a,b This value is not so
1.761(6)
1.761(7)
1.340(9)
165.16(5)
172.47(5)
1.747(9)
1.769(10)
1.349(14)
163.40(8)
173.41(9)
96.34(6)
98.57(6)
107.8(3)
97.4(3)
1.740(4)
1.749(4)
1.362(5)
159.32(4)
174.86(3)
92.54(3)
103.10(3)
1.729(18)
1.751(15)
1.372(24)
158.9(2)
174.7(1)
C(2)-S(2)
C(1)-C(2)
S(1)-Au(1)-P(1)
S(2)-Au(2)-P(2)
S(1)-Au(1)-Au(2) 95.30(4)
P(1)-Au(1)-Au(2) 97.26(4)
Au(1)-S(1)-C(1)
Au(2)-S(2)-C(2)
102.6(2)
96.0(2)
104.15(14) 106.4(5)
102.39(13) 103.9(5)
Scheme 2. (i) Toluene reflux for 15 h
interactions. The Au(1)-Au(2) distance of 1 [3.1984(10) Å]
is longer than the one of 2 [3.1295(11) Å], which is typical
of this type of complex. No S · · · S short contacts are noted
in the solid state.
Recently, we reported on a novel efficient method for the
preparation of dimetallic cyclopentadienyl cobalt complexes
bridged by the ethylenetetrathiolate C2S4 ligand.8d The
4-
reaction consists of the oxidative addition of 1,3-dithiol-2-
one across [Cp*Co(CO)2] (Cp* ) η5-C5Me5). With the aim
to obtain the first heterodimetallic complex bridged by the
ethylenetetrathiolate ligand, we react 1 with 1 equiv of
[Cp*Co(CO)2] in refluxing toluene. Unfortunately, all at-
tempts to isolate the desired product were unsuccessful.
Instead, we observed the deposition of a gold mirror inside
the Schlenk tube together with the formation of diamagnetic
[Cp*Co(dmid)] (Scheme 2), which was identified by its
intense deep-green color and comparison of its NMR
spectrum.8d In summary, the [CoI] fragment reduces the
gold(I) atoms rather than the 1,3-dithiol-2-one function.
Synthesis of [AuCl(Me2dmit)] (3) and [AuCl-
{(HOCH2CH2)2dmit}] (4). The commonly used gold precur-
sor [AuCl(tht)] (tht ) tetrahydrothiophene) is known for the
lability of the sulfide ligand, facilitating its substitution by
other neutral or anionic ligands.13 Thus, Me2dmit and
(HOCH2CH2)2dmit react with [AuCl(tht)] in a 1:1 metal-to-
ligand ratio at room temperature to afford yellow crystals
of [AuCl(Me2dmit)] (3) and [AuCl{(HOCH2CH2)2dmit}] (4)
in 82% and 58% yield, respectively. The compositions of
the air stable isolated products were established by elemental
analysis and single crystal X-ray diffraction studies (below).
The UV-vis absorption spectra of 3 and the Me2dmit ligand
measured in CH2Cl2 at room temperature are dominated by
an intraligand charge transfer (π f π*) between 230 and
340 nm centered on the CdC and CdS groups (Supporting
Information). Upon coordination, the lowest energy band of
(27) Raubenheimer, H. G.; Otte, R.; Linford, L.; Van Zyl, W. E.; Lombard,
A.; Kruger, G. J. Polyhedron 1992, 11, 893.
(28) Crystal data for 3 (at 293 K): monoclinic, P21, a ) 7.3521, b ) 9.4866,
c ) 8.0530 Å, ꢀ ) 94.171°, V ) 560.2(2) Å3, Z ) 2.
(29) (a) Mohr, F.; Jennings, M. C.; Puddephatt, R. J. Eur. J. Inorg. Chem.
2003, 217.
Inorganic Chemistry, Vol. 47, No. 17, 2008 7487

Guyon et al.
The O · · · O distance of the intermolecular interaction is
similar to that of the intramolecular one (2.814(7) vs 2.801(6)
Å). The intermolecular O-H· · ·O angle is less deviated from
linearity than the intramolecular one (177.70° vs 165.83°).
Other literature-known gold compounds combining strong
hydrogen bonding and aurophilic attraction exist. For ex-
ample, the cooperative force of aurophilic and hydrogen
bonding were recently used to self-assemble supramolecular
networks, exploiting the propensity of thiobarbituric deriva-
tives, which strongly interact both with both Au(I), to form
NH · · · O and OH · · · H bonds.32
Electronic Structure and Photophysics. The X-ray
structures of 1 and 2 reveal the presence of two nonequivalent
Au(PPh3) units due to their relative orientations with the
π-system-containing electron rich residue dithiolene. There-
fore, two possible chromophores (and lumophores) sites are
available. In addition, close intramolecular Au · · ·S and
Au · · · Au contacts are also evident, thus creating the pos-
sibility of other low-lying excited states such Au · · ·Au
centered dσ*pσ. It is known from the literature that gold(I)
thiolate complexes such as (Ph3P)AuSPh and (Ph3P)AuS(C6H4-
o-OMe) exhibit room temperature luminescence at 413 and
429 nm when excited at 360 and 350 nm, with emission
lifetimes (τe) of 17 and 75 µs, respectively.2b These emissions
are assigned to a ligand-to-metal-charge-transfer (LMCT)
from a thiolate residue to the gold center. The authors also
clearly demonstrated the electronic behavior when Au · · ·Au
contacts are close enough to split the orbitals Au (6pz) and
S(pπ), thus creating an intramolecular dσ*pσ excited-state
that generates a red-shifted emission. On the basis of the
crystallographic results, 1, 2, and 4 are good candidates to
exhibit such excited states, and their emitting properties
should also depend on the Au · · ·Au interactions. To describe
and assign the electronic transitions and MOs, DFT, and
TDTFT calculations were performed. All of the spectroscopic
and photophysical data are presented in Table 3.
Complex 1. Using the X-ray data for 1, the nature of the
HSOMO (triplet-state highest singly occupied molecular
orbital) and HOMO (singlet state highest occupied molecular
orbital) are computed, as well as the energy difference, to
address the nature of the observed long-lived emission. These
two MOs involved in the transition are presented in Figure
4. The triplet state is primarily located onto the Au · · ·Au
units, whereas the HOMO is mainly composed of the
dithiolene π system. The calculated emission wavelength is
436 nm for the crystal geometry at 173 K, comparing
favorably to that experimentally found (410 nm at 298 K,
Figure 5). This comparison is considered fair and we assign
the emission to a LMCT excited state where M is the two
interacting gold units and L is the dithiolene. These
computations and conclusions agree with those of Forward
et al.2b on a similar system.
Figure 3. Thermal ellipsoid plot of 4 (50% level). Selected bond lengths
(Å) and angles (°): Au-S(1) 2.293(2), Au-Cl 2.293 (2), Au-Au# 3.078(6),
S(1)-C(1) 1.702(5), S(2)-C(1) 1.714(5), S(1)-C(1) 1.702(5), S(2)-C(1)
1.714(5), S(2)-C(3) 1.752(6), S(3)-C(1) 1.714(6), S(3)-C(2) 1.758(5),
S(4)-C(3) 1.768(5), S(4)-C(4) 1.818(7), S(5)-C(2) 1.767(6), S(5)-C(6)
1.840(6), C(3)-C(2) 1.353(8), C(4)-C(5) 1.523(8), C(6)-C(7) 1.513(8),
C(5)-O(1) 1.419(8), C(7)-O(2) 1.427(6), S(1)-Au-Cl 173.59(5),
S(1)-Au-Au#1 102.27(4), Cl-Au-Au#1 84.00(4), C(1)-S(1)-Au
100.30(19), C(1)-S(2)-C(3) 96.7(3), C(1)-S(3)-C(2) 96.3(3), C(3)-
S(4)-C(4) 100.4(3). # denotes symmetry related atoms.
different from those found for the fully supported dppm-
spanned dinuclear complexes [ClAu(µ-dppm)2AuCl] (2.96-
(1) Å), [(Au(µ-dppm)2Au][BF4]2 (2.931(1) Å), [(Au(µ-
dppm)2Au][PF6]2 (2.9792(10) Å), or the tetranuclear
compound [(OC)3Fe{Si(OMe)3}(µ-dppm)Au]2 (2.9622(1)
Å).30c–g The 1,3-dithiole-2-thione-4,5-dithiolate skeleton and
the AuCl fragment are almost coplanar. Due to the torsion
angle Cl-Au-Au-Cl of 180°, the Au · · · Cl# and Cl# · · · S1
distances are quite short and amount to 3.641(7) and 3.326(5)
Å, respectively. The hydroxyethyl side-chains adopt a syn-
orientation relatively to this plane and allow the formation
of intramolecular hydrogen bonds. The O(1) · · ·O(2) separa-
tion in the resulting eleven-membered ring is similar to that
determined recently by us for the free ligand (2.801(6) vs
2.790(3) Å).11 The Cl-Au-S bond angle of 173.59° deviates
slightly from linearity.
The CdS bond length of 1.702(5) Å is elongated with
respect to that reported for ligand (HOCH2CH2)2dmit (1.644(2)
Å),11 suggesting a strong coordination of this sulfur rich
ligand to the gold(I) atom. The Au-S bond distance
corroborates this observation because its value of 2.293(2)
Å is similar to that reported in gold(I) thiolate complexes
[Au(PPh3)(SPh)] (2.30(1) and 2.32(1) Å)31 and [Au(PPh3)-
{SPh(o-Cl)}] (2.292(2) Å).2b In contrast with the coordina-
tion polymer 3, the thioether groups of 4 are not involved in
any bonding interactions. In addition to the intramolecular
hydrogen bonds, O(1) is connected to O(2) of an adjacent
dimeric unit via intermolecular hydrogen bonds, thus gen-
erating a supramolecular network (Supporting Information).
(30) (a) Schmidbaur, H.; Dziwok, K.; Grohmann, A.; Mu¨ller, G. Chem.
Ber. 1989, 122, 893. (b) de la Riva, H.; Pintado-Alba, A.; Nieuwen-
huyzen, M.; Hardacre, C.; Lagunas, M. C. Chem. Commun. 2005,
4970. (c) Schmidbaur, H.; Wohlleben, A.; Schubert, U.; Frank, A.;
Huttner, G. Chem. Ber. 1977, 110, 2751. (d) The Au · · ·Au separation
of 3.351(2) Å in [ClAu(µ-dppm)AuCl] is considered as short, but non-
bonding. Schmidbaur, H.; Wohlleben, A.; Wagner, F. E.; Orama, O.;
Huttner, G. Chem. Ber. 1977, 110, 1748. (e) Porter, L. C.; Khan, Md.
N. I.; King, C.; Fackler, J. P. Acta Crystallogr. 1989, C45, 947. (f)
Wu, M.; Zhang, L.; Chen, Z. Acta Crystallogr. 2003, E59, m72. (g)
Braunstein, P.; Knorr, M.; Tiripicchio, A.; Tiripicchio Camellini, M.
Inorg. Chem. 1992, 31, 3685.
(32) (a) Hollatz, C.; Schier, A.; Schmidbaur, H. J. Am. Chem. Soc. 1997,
119, 8115. (b) Hunks, W. J.; Jennings, M. C.; Puddephatt, R. J. Inorg.
Chem. 2002, 41, 4590. (c) Supramolecular structures may also result
from the combination of aurophilic and π-π interactions Nunokawa,
K.; Okazaki, K.; Onaka, S.; Ito, M.; Sunahara, T.; Ozeki, T.; Imai,
H.; Inoue, K. J. Organomet. Chem. 2005, 690, 1332.
(31) Onaka, S.; Katsukawa, Y.; Shiotsuka, M.; Kanegawa, O.; Yamashita,
M. Inorg. Chim. Acta 2001, 312, 100.
7488 Inorganic Chemistry, Vol. 47, No. 17, 2008

Mono- and Dinuclear Sulfur-Rich Gold(I) Complexes
Table 3. Spectroscopic and Photophysical Data of 1, 2, and 4
b
compounds
λabs (nm) (ꢀ, M-1 cm-1
)
λem (nm)
τe
Φb
1
238 (45 100)
318 (6900)
400 and 550a
phosphorescence (µs):
37 ( 5 at 450 nma
250 ( 7 at 570 nma
0.017 ( 0.002 at 400 nma
78 ( 14 at 400 nmc
139 ( 20 at 650 nmc
70 ( 4 at 400 nmd
phosphorescence (µs):
72 ( 16 at 440 nma
248 ( 10 at 600 nma
2 at 320 nmb
0.6%
370b
450 and 685c
410d
2
4
241 (38 750)
327 (7800)
450 and 600a
380b
0.5%
405 and 480c
405 and 480d
95 ( 4 at 400 nmc
65 ( 20 at 400 nmd
fluorescence (ns):
244 (18 800)
424 (12 750)
510 and 610a
670c
2.6%e
1.38 ( 0.02 at 510 nma
phosphorescence (µs):
676 ( 13 at 580 nma
191 ( 7 at 510 nma
615d
a In 2-MeTHF at 77 K. b In 2-MeTHF at 298 K. c In solid state at 77 K. d In solid state at 298 K. e Sum of ΦF and ΦP.
Figure 4. MO representations of the HOMO and HSOMO involved in the triplet emission for 1. The calculated emission is found at 436 nm in the solid
state at 173 K. The observed maxima are at 410 nm at 298 K and 685 nm at 77 K in the solid state.
the solid state at 77 K (Figure 5). Conversely, in solution at
298 K where there is no constraint to rotation about the C-S
single bonds, the complex should adopt one or many flexible
configurations (rotamers) where the intramolecular steric
interactions between the AuPPh3 fragments are minimized.
As a consequence a blue-shifted emission is anticipated.
Indeed, this band is observed at 370 nm (Figure 5). In such
a case, the emission is also assigned to a LMCT, but the
two gold units are not interacting and the assignment is an
LMCT where M is a single metal center. A broadband
centered at 550 nm for 1 in a 77 K frozen solution is also
observed. It is believed that the broad envelope includes a
series of emission bands arising from frozen different
rotamers between the two extreme cases, close Au · · ·Au
contacts (685 nm), and open conformation (370 nm) de-
scribed above.
TDDFT calculations were performed in an attempt to
describe the absorption spectra. The results are difficult to
interpret because no simple HOMO-LUMO transition is
computed. Instead, the TDDFT computations indicate the
presence of many small absorption transition vectors in
the 321-342 nm window. The knowledge of the nature of
Figure 5. Emission (blue), excitation (red), and absorption spectra (black)
of 1 in the solid state and in 2-MeTHF solution at 77 and 298 K. The
absorption spectra indicated in the solid-state spectra are those of the solution
the T1 state can now be tentatively used as a landmark to
find out what the most probable transition in the absorption
may be. However, knowing that we must have an absorption
band around 318 nm (Figure 5), and that the S1 excited-
state must be closely related to the T1 excited state, the
TDDFT computations indicate only the presence of a single
logical candidate for a possible MO with a singlet transition
for comparison purposes. The sharp peak at 395 nm is an artifact.
Upon cooling the samples, the close Au · · · Au contacts
shorten because of the flexibility of the two dangling AuPPh3
branches. The strengthening (i.e., shortening) of the Au · · ·Au
interactions induces a red-shift of the emission band. Indeed,
the new emission maximum is now observed at 685 nm for
Inorganic Chemistry, Vol. 47, No. 17, 2008 7489

Guyon et al.
Figure 6. Calculated MOs for 1 for the MOs involved in the absorption
and emission spectra.
Figure 8. Emission (blue), excitation (red), and absorption spectra (black)
of 2 in the solid state and in 2-MeTHF solution at 77 and 298 K. The
absorption spectra indicated in the solid-state spectra are those of the solution
for comparison purposes. The sharp peak (x) at 395 nm is an artifact.
∼480 nm (Figure 8). On the basis of the TDDFT computa-
tions, which place this emission at 508 nm (Figure 7), the
assignment for this phosphorescence is the same (i.e., LMCT
where M is the two Au units and L is still the electron rich
dithiolene).
However, on the high-energy side of the solid-state spectra
at 77 and 298 K, a structureless emission centered at 405
nm is observed. This emission exhibits an excitation spectrum
that matches the absorption (in solution) and reminds that
found in 1 in the same range. We would like to propose that
this emission is also LMCT but for a rotamer where the
Au · · · Au interactions are not as pronounced as the former.
In other words, the powder is not homogeneous, whereas
crystals for structure determination were obtained only for
one of them. This proposal is supported by the observation
of one and two emission bands for 2 in 2-MeTHF at 298
and 77 K, respectively (Figure 8). At 298 K, the 370 nm
band is associated with a rotamer, where the intramolecular
Au · · · Au interactions are minimal for steric reasons. As the
temperature is decreased to 77 K, two bands are depicted at
∼450 and ∼600 nm. These trapped species exhibit different
emission lifetimes as demonstrated by time-resolved spec-
troscopy (Figure 9). These two species do not exhibit the
same lifetime. These are assigned to two different conformers
depending on the relative amplitude of Au · · ·Au interactions.
The TDDFT computation analysis applied for the absorp-
tion spectra are also very similar to 1, giving a predicted
LMCT absorption around 322-370 nm based on the multiple
possible calculated lower-energy transitions. Again, the
electronic transition HOMO to LUMO +12, the first MO
based on the gold centers, exhibits the largest computed
oscillator strength. Experimentally, a band at 327 nm is
observed in solution.
Figure 7. Calculated MOs for 2 for the MOs involved in the absorption
and emission spectra.
in the 321 to 342 nm range. This MO is LUMO+12, which
also exhibits the largest oscillator strength. It also bears close
resemblance to HSOMO (Figure 6), and is the first empty
gold-based orbital. It is located at 0.063 a.u. higher in energy
than the HSOMO. All in all, the absorption spectrum is
probably governed by an LMCT (where M is a single gold
unit) as presented in Figure 6, and intersystem crossing
populates a triplet state where the MOs include both gold
metals.
Complex 2. The crystal structure and luminescence
properties are very similar to 1, so the electronic spectra and
computational results are found unsurprisingly similar. The
HOMO and HSOMO (triplet) are computed by DFT using
the X-ray structure data for 2 as well as TDDFT is used for
assignment purposes. The same conclusions are drawn below
(Figure 7).
The emission spectra of 2 at 298 K in the solid exhibit a
structured emission on the low-energy side of the spectra at
7490 Inorganic Chemistry, Vol. 47, No. 17, 2008

Mono- and Dinuclear Sulfur-Rich Gold(I) Complexes
Figure 9. Time-resolved emission (low-resolution) spectra of 2 in 2-MeTHF
at 77 K, demonstrating evidence for two emitting species.
In summary, the solid-state spectra of structurally quite
similar 1 and 2 exhibit at 298 K emission maxima at ∼410
and ∼480 nm, respectively. These results are consistent with
the shorter Au · · · Au separation in 2 (3.20 Å for 1 and 3.13
Å for 2). In solution at 298 K, the emission maxima are
closer (370 nm for 1 and 380 nm for 2), which is consistent
with free rotations about the C-S bond that may lead to
conformation where no Au · · ·Au interaction exists or is very
weak. So, the emission arises from a LMCT excited-state
involving a noninteracting SAuPPh3. At 77 K, the solid-state
spectra exhibit emission maxima at ∼685 and ∼480 nm for
1 and 2, respectively. These LMCT emissions are obviously
different. The explanation stems from the different crystal
systems (above). Upon cooling, the contraction of the unit-
cell dimensions may be different. Unfortunately, we do not
have the X-ray structures of these compounds at 77 K to
confirm this hypothesis.
Figure 10. Emission (blue), excitation (red), and absorption spectra (black)
of 4 in the solid state and in 2-MeTHF solution at 77 and 298 K. No
luminescence was observed in solution at 298 K. The weak features at ∼
520 nm may be S0-T1 absorptions visible due to the large concentration
(i.e., solid state) and the violation of the Beer-Lambert law.
Complex 4. This case turns out to be much simpler than
that for 1 and 2. The emission spectra of 4 are presented in
Figure 10. The spectra are characterized by an emission band
centered at ∼615 nm at 298 K, which is red-shifted at 77 K
to 670 nm. Again, DFT and TDDFT computations are used
to assign the electronic spectra. For the interpretation of the
solid-state properties, the two interacting 4 in the unit cell
are used for the calculations (Figure 11).
The HOMO is composed primarily of the chlorine lone
pair, Au dxy and p orbital of the sulfur atom of the CdS
bond (Figure 11). Some minor contributions of the remainder
of the π system of the dithiolene ligand are also noted. The
LUMO is now mainly composed of the π system of the
trithiocarbonate part of the dithiolene. All in all, these
computations indicate that the lowest energy transition is
X/MLCT (i.e., halide/metal-to-ligand charge transfer). Such
assignment is not unusual.33 The computed transition wave-
length is 425 nm, which compares favorably to that observed
in the spectra (i.e., about 480 nm in the solid and 420 nm in
solution; Figure 10). The fact that the emission maximum is
red-shifted in the solid with respect to the solution is due to
Au · · ·Au interactions, generating sets of Au2-centered bond-
ing and antibonding orbitals as depicted by Forward and
collaborators2b mixed with the MLCT manifolds. Indeed, the
gold dxy orbital calculated in the HOMO combines in the
Figure 11. Calculated MOs involved in the absorption and emission spectra
of two interacting complexes 4.
dimer to form the dδ* contribution to the overall MO. So,
we assign the MLCT transition for 4 in solution to an isolated
complex, and for 4 in the solid state to a dimer-like,
reminding the rotamers discussed for 1 and 2. In the isolated
state, 4 exhibits the HOMO and LUMO described in Figure
12.
The diradical nature of the triplet state consists of one
electron of the LUMO on one complex 4 (-0.156 au) of
the Au · · · Au interacting dimer and one electron located on
the HOMO (-0.232 au) of the other complex 4. The
computed emission wavelength is 616 nm, which fits nicely
with that observed at room temperature. Evidence for
Au · · · Au interactions comes from the red-shift of the
emission band which is expected upon contraction of the
(33) Piche´, D.; Harvey, P. D. Can. J. Chem. 1994, 72, 705.
Inorganic Chemistry, Vol. 47, No. 17, 2008 7491

Guyon et al.
1,2-dithiolene}]. The structural characterization reveals that
the variation of the dithiolene residue has no major impact
on the structural features compared with other literature-
known examples, notably the Au · · · Au contacts remain in
the range of about 3.1 Å. In contrast, upon treatment of
AuCl(tht) with neutral five-membered thiones, the structural
arrangement depends strongly on the nature of the organic
ligands. In the case of the Me2dmit ligand, no short gold
contacts are encountered, whereas a surprisingly short
unsupported aurophilic interaction is present in the dimeric
[AuCl{(HOCH2CH2)2dmit}]2 complex. The presence of
hydrogen bonding probably does not contribute to the
dimerization (a similar dimeric motif has been observed using
ethylene trithiocarbonate27), and the origin of the structural
diversity remains to be explored. With this in mind, we are
currently extending the reactivity of AuCl(tht) toward other
sulfur-rich thiones. The photophysical studies revealed that
the participation of intra- and intermolecular Au· · ·Au
interactions are relevant to the rich luminescent properties
of these species. The nature of the excited states are
essentially LMCT for the dithiolene derivatives 1 and 2 and
X/MLCT for the thione compound 4, where M could be an
isolated Au unit or interacting Au · · · Au-containing species.
In consequence, the emission spectra are strongly tempera-
ture-dependent. This phenomenon may be rationalized by a
strengthening of the Au · · ·Au interactions upon lowering the
recording temperature.
Figure 12. HOMO (left) and LUMO (right) of 4. The calculations were
performed on an optimized geometry of an isolated complex of
[AuCl{(HOCH2CH2)2dmit}].
Figure 13. Left: Steady-state emission spectra of 4 at various concentrations
showing no change in emission maximum nor the apparition of a new band.
Right: Time-resolved emission spectra of 4 at two different delay times stressing
evidence for two different species (fluorescence and phosphorescence).
unit cell (the crystal structure of 4 exhibits a Au · · · Au
separation of 3.077 Å). 4 is not luminescent at 298 K. At 77
K, a strong emission band is observed with a maximum at
∼ 610 nm, which is blue-shifted with respect to the solid-
state emission spectrum (680 nm) at this temperature and to
the one at 298 K (615). On the basis of this blue shift and
the assignment made for the absorption band in solution, a
MLCT assignment for an isolated molecule is also suggested.
A study of the emission spectra as a function of the
concentration was made (Figure 13). There was no change
in emission maximum, illustrating that within the concentra-
tions used in this work, the emission arises from an isolated
molecule. A shoulder for which the relative intensity did not
vary, exhibiting a different emission lifetime, was also noted
for 4 in solution. From time-resolved spectroscopy on the
nanosecond time scale (SI), the blue-shifted band decays in
this same time frame. Because the excitation spectra are same
for the red-shifted emission (i.e., phosphorescence), we
assigned this blue-shifted band to fluorescence. The Stoke
shift (i.e., energy gap between absorption and fluorescence)
is indeed reasonable for this assignment (i.e., 3500 cm-1).
The emission lifetime is 1.38 ( 0.02 ns. This phenomenon
was also reported by Eisenberg and his collaborators for other
gold-containing materials.34
Acknowledgment. Shawkat Mohammed Aly is thanked
for the recording of emission and time-resolved spectra of 4
and (HOCH2CH2)2dmit. The Besanc¸on group thanks the
regional council of the Region de Franche-Comte´ for funding
of a spectrofluorimeter and the French Research Ministry
for a Ph.D. grant for A. Hameau. The authors thank R.
Eisenberg (University of Rochester) for fruitful discussion.
The Natural Sciences and Engineering Research Council of
Canada (NSERC) is acknowledged for funding. The work
on compound 4 has been supported by the DFG (Deutsche
Forschungsgemeinschaft) in the framework of SPP 1166.
Supporting Information Available: Representation of the
supramolecular 2D network of 4 generated through intermolecular
O-H· · · O bonding, the UV-vis spectra of Me2dmit and 3, time-
resolved spectra of 4 in 2MeTHF at 77 K, and tables of selected
computed transition energies by TDDFT. This material is available
free of charge via the Internet at http://pubs.acs.org. Structures have
been deposited with the Cambridge Crystallographic Data Centre
(http://www.ccdc.cam.ac.uk; CCDC numbers: 663032 (1), 663031
(2), 663196 (4).
IC7022067
Conclusion
We synthesized two new members of dinuclear gold
dithiolene complexes belonging to the type [{Au(PR3)}2(µ-
(34) Lee, Y.-A.; McGarrah, J. E.; Lachicotte, R. J.; Eisenberg, R. J. Am.
Chem. Soc. 2002, 124, 10662.
7492 Inorganic Chemistry, Vol. 47, No. 17, 2008