Luminescent phosphine gold(I) thiolates: Correlation between crystal structure and photoluminescent properties in [R3PAu{SC(OMe)=NC 6H4NO2-4}] (R = Et, Cy, Ph) and [(Ph 2P-R-PPh2){AuSC(OMe)

Article abstract of DOI:10.1021/ic0608243

Full title. Luminescent phosphine gold(I) thiolates: Correlation between crystal structure and photoluminescent properties in [R₃PAu{SC(OMe)=NC ₆H₄NO₂-4}] (R = Et, Cy, Ph) and [(Ph ₂P-R-PPh₂

Full text of DOI:10.1021/ic0608243

Inorg. Chem. 2006, 45, 8165−8174
Luminescent Phosphine Gold(I) Thiolates: Correlation between Crystal
Structure and Photoluminescent Properties in
[R3PAu SC(OMe) NC6H4NO2-4 ] (R Et, Cy, Ph) and
AuSC(OMe) NC6H4NO2-4 2] (R CH2, (CH2)2, (CH2)3,
{
d
}
)
[(Ph2P-R-PPh2)
{
d
}
)
(CH2)4, Fc)
Soo Yei Ho,† Eddie Chung-Chin Cheng,‡ Edward R. T. Tiekink,*,§ and Vivian Wing-Wah Yam*,‡
Department of Chemistry, National UniVersity of Singapore, Singapore 117543, Centre for
Carbon-Rich and Nano-Scale Metal-Based Materials Research and Department of Chemistry, The
UniVersity of Hong Kong, Pokfulam Road, Hong Kong SAR, PR China, and The UniVersity of
Texas, One UTSA Circle, San Antonio, Texas 78249-0698
Received May 14, 2006
X-ray crystallography shows the gold atoms in [R3PAu{SC(OMe)dNC6H4NO2-4}] (R
)
Et, Cy, Ph; 1−3, respectively)
and [(Ph2P-R-PPh2) AuSC(OMe) NC6H4NO2-4 2] (R
{
d
}
)
CH2, (CH2)2, (CH2)3, (CH2)4, Fc; 4−8, respectively) are
linearly coordinated by phosphorus and thiolate-sulfur; weak intramolecular Au‚‚‚O interactions are featured in all
structures. The smaller ethyl substituents in 1 allow for supramolecular association via Au‚‚‚S and Au‚‚‚Au interactions
that are not found in 2 and 3, which contain larger phosphorus-bound Cy and Ph groups, respectively. Intramolecular
Au‚‚‚Au interactions are found in the dppm, dppe, dppp, and Fc structures but not in the dppp analogue, for which
an anti conformation was found. The structures have been correlated with the results from photophysical study
conducted in the solid state. Thus, photoexcitation of 1
green and blue luminescence, respectively. The spectra in each medium are remarkably similar to each other, and
so the emission energy and excitation maxima observed for 1 7 appear to be independent of the nature of the
−7 with λ > 350 in the solid state and in solution produces
−
ancillary phosphines, as well as the presence or absence of Au‚‚‚Au interactions, either intermolecularly or
intramolecularly.
Introduction
electronic devices, as well as for gold thin films.3 They also
display interesting luminescence characteristics. While a
range of gold complexes exhibit luminescence, such as gold
thiolates,4 nanosized gold,5 anionic species,6 oligomers7 and
Gold and gold complexes exhibit a range of applications
in contemporary society. Nanosized gold has generated
enormous excitement in terms of catalytic applications,1 and
gold complexes have proven to be useful as drugs for the
treatment of rheumatoid arthritis and bronchial asthma2 and
may be precursors for the gold plating of ceramics and
(2) Ho, S. Y.; Tiekink, E. R. T. In Metallotherapeutic Drugs and Metal-
Based Diagnostic Agents: The Use of Metals in Medicine; Gielen,
M., Tiekink, E. R. T., Eds.; John Wiley & Sons Ltd.: Chischester, U.
K., 2005; Chapter 26, pp 507-527.
(3) (a) Aizenberg, J.; Black, A. J.; Whitesides, G. M. Nature 1998, 394,
868. (b) Schoenfisch, M. H.; Pemberton, J. E. J. Am. Chem. Soc. 1998,
120, 4502. (c) Aizenberg, J.; Black, A. J.; Whitesides, G. M. J. Am.
Chem. Soc. 1999, 121, 4500. (d) Rapson, W. S.; Groenewald, T. In
Gold Usage; Academic Press: London, 1978. (e) Okinaka, Y.;
Hoshino, M. Gold Bull. 1998, 31, 3.
* To whom correspondence should be addressed. Phone: +1-210-458-
5774. Fax: +1-210-458-7428. E-mail: edward.tiekink@utsa.edu (E.R.T.T.).
Phone: +852-28592153. Fax: +852-28571586. E-mail: wwyam@hku.hk
(V.W.-W.Y.).
† National University of Singapore.
(4) Lee, Y.-A.; Eisenberg, R. J. Am. Chem. Soc. 2003, 125, 7778.
(5) Yamamoto, Y.; Shiotsuka, M.; Okuno, S.; Onaka, S. Chem. Lett. 2004,
33, 210.
‡ The University of Hong Kong.
§ The University of Texas.
(1) (a) Maye, M. M.; Luo, J.; Han, L.; Kariuki, N. N.; Zhong, C.-J. Gold
Bull. 2003, 36, 75. (b) Corti, C. W.; Holliday, R. J.; Thompson, D. T.
Appl. Catal., A 2005, 291, 253. (c) Maye, M. M.; Lim, I.-I. S.; Luo,
J.; Rab, Z.; Rabinovich, D.; Liu, T.; Zhong, C.-J. J. Am. Chem. Soc.
2005, 127, 1519.
(6) (a) Nicholson, P. G.; Ruiz, V.; Macpherson, J. V.; Unwin, P. R. Chem.
Commun. 2005, 1052. (b) Bouhelier, A.; Bachelot, R.; Lerondel, G.;
Kostcheev, S.; Royer, P.; Wiederrecht, G. P. Phys. ReV. Lett. 2005,
95, 267405/1. (c) Yoshida, Y.; Fujii, J.; Saito, G.; Hiramatsu, T.; Sato,
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10.1021/ic0608243 CCC: $33.50
Published on Web 09/08/2006
© 2006 American Chemical Society
Inorganic Chemistry, Vol. 45, No. 20, 2006 8165

Ho et al.
clusters,8 organometallics,8 oxo species,10 and mixed-metal
systems (e.g., with thallium11 and silver),12 phosphine gold(I)
thiolates also demonstrate important luminescence charac-
teristics.13 Indeed, the formation of aurophilic interactions
in solution has been used as a probe for detecting alkali metal
ions.14 Here, a dinuclear phosphine gold thiolate has been
functionalized so that each thiolate ligand carries a macro-
cycle designed for specific coordination to K+. When they
encounter K+, the macrocycles encapsulate the ion in a
sandwich fashion, bringing the two gold atoms in close
proximity which triggers luminescence because of the
formation of an aurophilic (i.e., Au‚‚‚Au) interaction. In
addition to their role in luminescence, aurophilic interactions
play an important role in the supramolecular aggregation
patterns of gold compounds.
bonding interactions and aurophilic interactions, and this
notion inspired the pioneering work of Schmidbaur.16
Therefore, the structural chemistry of gold compounds
attracts great attention that goes well beyond the determi-
nation of molecular structure and constantly reveals many
highlights, such as the formation of luminescent hydrogen-
bonded arrays,17 and investigation of the influence of
temperature dependence,18 polymorphism, and phase transi-
tions19 upon luminescence.
In the present paper, the crystal structures of an unprec-
edented complete series of phosphine gold(I) thiolates (i.e.,
[R3PAu{SC(OMe)dNC6H4NO2-4}], R ) Et, Cy, Ph (1-
3), and [(Ph2P-R-PPh2){AuSC(OMe)dNC6H4NO2-4}2], R )
CH2, (CH2)2, (CH2)3, (CH2)4, Fc (4-8)) are presented, where
the thiolate ligand is derived from O-methyl-N-(4-nitrophe-
nyl)thiocarbamide, SdC(OMe)N(H)C6H4NO2-4.20 Such a
complete series allows for a systematic analysis of the
principles dictating supramolecular aggregation in their
crystal structures, as well as the correlation of their photo-
luminescent properties with the fine-tuning of the weak
Au‚‚‚Au interactions.
Metal complexes derived from related O-alkyl-N-
arylthiocarbamides are known. Neutral forms of these ligands
are known to coordinate gold21 and palladium22 via the thione
sulfur atom. Usually, the ligand is found in the deprotonated
form (i.e., as a carbonimidothioate) and has been shown to
function as a thiolate ligand coordinating gold via the sulfur
atom in [Ph3PAu{SC(OMe)NdPh}],23 related to the present
report. More frequently, the anion coordinates as a S, N
chelate as, for example, in complexes of rhenium24 and
technetium.25 Bridging modes (i.e., µ2 via sulfur and nitro-
gen26 and µ3 via bidentate sulfur and nitrogen)27 have also
been observed in some copper complexes.
Gold complexes are known to exhibit a broad range of
fascinating supramolecular architectures arising from, in
addition to conventional intermolecular forces such as
hydrogen bonding, the formation of the aforementioned
aurophilic interactions.15 Such aurophilic interactions are
known to provide energy of stabilization to structures of the
same order of magnitude as hydrogen-bonding interactions.16
Hence, many supramolecular arrays can be thought of in
terms of complementarity or competition between hydrogen-
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Experimental Section
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Materials. The chemicals and their sources used in the synthesis
were sodium tetrachloroaurate(III) dihydrate (Aldrich), triethylphos-
phine gold(I) chloride (Strem), tricyclohexylphosphine (Fluka),
triphenylphosphine (Fluka), bis(diphenylphosphino)methane (Al-
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8166 Inorganic Chemistry, Vol. 45, No. 20, 2006

Phosphine Gold(I) Carbonimidothioates
drich), 1,2-bis(diphenylphosphino)ethane (Aldrich), 1,3-bis(diphe-
nylphosphino)propane (Aldrich), 1,4-bis(diphenylphosphino)butane
(Aldrich), 1,1′-bis(diphenylphosphino)ferrocene (Aldrich), thiodi-
glycol (Aldrich), and 4-nitrophenyl isothiocyanate (Lancaster).
Dichloromethane, used in the photophysical measurements (Lab-
Scan), was purified and distilled in a nitrogen atmosphere using
standard procedures prior to use. Methanol (Merck) and ethanol
(Merck), used in photophysical measurements, were of GR grade,
and all other solvents were of analytical grade and used without
further purification.
4.50. Found: C, 45.35; H, 5.85; N, 4.07; S, 4.66%. IR: ν(C-S)
1109m, 890m, ν(C-N) 1578s, ν(C-O) 1161m cm-1 31P{1H}: δ
.
57.1.
[Ph3PAu{SC(OMe)dNC6H4NO2-4}] (3). mp: 146-147 °C.
Anal. Calcd for C26H22AuN2O3PS: C, 46.76; H, 3.29; N, 4.25; S,
4.54. Found: C, 46.58; H, 3.31; N, 4.18; S, 4.78%. IR: ν(C-S)
1100m, 846m, ν(C-N) 1588s, ν(C-O) 1155m cm-1 31P{1H}:
.
38.0.
[(Ph2PCH2PPh2){AuSC(OMe)dNC6H4NO2-4}2] (4). mp: 184
°C (dec). Anal. Calcd for C41H36Au2N4O6P2S2: C, 40.91; H, 2.64;
N, 4.70; S, 5.02. Found: C, 41.01; H, 3.02; N, 4.67; S, 5.34%. IR:
Synthesis. The phosphine gold(I) chlorides, except for [Et3PAuCl],
were synthesized by the standard literature procedure (i.e., from
the reduction of HAuCl4 by thiodiglycol followed by the addition
of the phosphine).28 Similarly, the ligand employed in this study,
SdC(OMe)N(H)C6H4NO2-4, was prepared from the reaction of
MeOH and 4-nitrophenyl isothiocyanate in accordance with the
literature method.20 The synthesis of the phosphine gold(I) thiolates
was accomplished in quantitative yields using a metathetical reaction
between the phosphine gold(I) chloride and the thiol in the presence
of NaOH or KOH as described previously.23 Crystals of 1-8 for
the X-ray study were obtained in the same manner by layering
ethanol on CH2Cl2 solutions of the complexes 1-7, and in the case
of 8, the solvent combination was ether with CHCl3.
ν(C-S) 1102m, 893m, ν(C-N) 1582s, ν(C-O) 1151m cm-1
31P{1H}: δ 29.4.
.
[{Ph2P(CH2)2PPh2}{AuSC(OMe)dNC6H4NO2-4)}2] (5). mp:
167 °C (dec). Anal. Calcd for C42H38Au2N4O6P2S2: C, 42.56; H,
2.97; N, 4.65; S, 5.08. Found: C, 42.53; H, 3.15; N, 4.61; S, 5.28%.
IR: ν(C-S) 1100m, 892m, ν(C-N) 1577s, ν(C-O) 1150m cm-1
31P{1H}: δ 35.7.
.
[{Ph2P(CH2)3PPh2}{AuSC(OMe)dNC6H4NO2-4}2] (6). mp:
155 °C (dec). Anal. Calcd for C43H40Au2N4O6P2S2: C, 41.77; H,
3.17; N, 4.58; S, 4.92. Found: C, 42.03; H, 3.28; N, 4.56; S, 5.22%.
IR: ν(C-S) 1100m, 892m, ν(C-N) 1580s, ν(C-O) 1150m cm-1
31P{1H}: δ 30.9.
.
[{Ph2P(CH2)4PPh2}{AuSC(OMe)dNC6H4NO2-4}2] (7). mp:
170 °C (dec). Anal. Calcd for C44H42Au2N4O6P2S2: C, 42.39; H,
3.35; N, 4.50; S, 4.87. Found: C, 42.52; H, 3.41; N, 4.51; S, 5.16%.
Characterization and Spectroscopic Measurements. Infrared
spectra for all compounds were recorded as KBr disks on a Bio-
Rad FTS165 FTIR spectrophotometer. 1H and 13C{1H} NMR
spectra were recorded on a Bruker ACF300 FT NMR spectrometer
operating at 300.145 and 75.479 MHz, respectively, with chemical
shifts relative to tetramethylsilane. 31P{1H} NMR data were
recorded on the same instrument operating at 121.442 MHz, but
with the chemical shifts recorded relative to 85% aqueous H3PO4.
Microanalyses were performed on a Perkin-Elmer PE 2400 CHN
Elemental Analyzer. Melting points were determined on a Buchi
Melting Point B-540 apparatus and were uncorrected. All electronic
absorption spectra were recorded on a Hewlett-Packard 8452A
diode-array spectrophotometer. Steady-state emission and excitation
spectra recorded at room temperature and at 77 K were obtained
on a Spex Fluorolog-3-211 fluorescence spectrophotometer with
or without corning filters. All solutions for photophysical studies
were prepared in a two-compartment cell consisting of a 10 cm3
Pyrex bulb equipped with a sidearm to a 1 cm path length quartz
cuvette and sealed from the atmosphere by a Rotaflo HP6/6 quick-
release Teflon stopper. Solutions were degassed under high vacuum
(limiting pressure < 10-3 Torr) with no less than four successive
freeze-pump-thaw cycles. Solid-state photophysical measurements
were carried out with solid samples loaded in a quartz tube inside
a quartz-walled Dewar flask. Liquid nitrogen was placed into the
Dewar flask for low-temperature (77 K) solid-state and glass
photophysical measurements. Emission lifetime measurements were
performed using a conventional laser system. The excitation source
was the 355 nm output (third harmonic) of a Spectra-Physics
Quanta-Ray Q-switched GCR-150-10 pulsed Nd:YAG laser. Lu-
minescence decay signals were recorded on a Tektronix model
TDS620A digital oscilloscope and analyzed using a program for
exponential fits.
IR: ν(C-S) 1105m, 891m, ν(C-N) 1576s, ν(C-O) 1160m cm-1
31P{1H}: δ 33.9.
.
[(Ph2PFcPPh2){AuSC(OMe)dNC6H4NO2-4}2] (8). mp: 163
°C (dec). Anal. Calcd for C50H42Au2FeN4O6P2S2: C, 43.99; H, 3.20;
N, 3.97; S, 4.27. Found: C, 43.81; H, 3.09; N, 4.09; S, 4.68%. IR:
ν(C-S) 1100m, 847m, ν(C-N) 1571s, ν(C-O) 1168m cm-1
31P{1H}: δ 32.2.
.
X-ray Crystallography. Intensity data were measured at 223(2)
K on a Bruker SMART CCD diffractometer employing Mo KR
radiation so that θmax was 30°. Data processing and empirical
absorption correction were accomplished with the programs SAINT29
and SADABS,30 respectively. The structures were solved by heavy-
atom methods,31 and refinement (anisotropic displacement param-
eters, hydrogen atoms in the riding model approximation, and a
2
weighting scheme of the form w ) 1/[σ2(Fo ) + aP2 + bP] for P
2
) (Fo + 2Fc2)/3) was on F2.32 In 1, two positions were resolved
for the C11-C12 residue, and from the refinement, the components
were 0.60(1) and 0.40(1), respectively; only the major component
is shown in Figure 1. Each of the C15-C21 cyclohexyl rings in 2
were found to be disordered over two positions. Each ring had a
chair conformation but of a slightly different orientation. For the
C15-C20 ring, the C16 and C20 atoms were common to both rings,
and for the C15a-C20a ring, the C16 and C19 atoms were
common; from the refinement, each disordered atom was assigned
a site occupancy factor of 0.5. The rings were refined with the
SAME command in SHELX32 with soft constraints of C1-C2 )
1.54(1) Å and C1-C2 ) 2.51(1) Å. Compound 8 was isolated as a
(28) Al-Saa´dy, A. K.; McAuliffe, C. A.; Parish, R. V.; Sandbank, J. A.
Inorg. Synth. 1985, 23, 191.
[Et3PAu{SC(OMe)dNC6H4NO2-4}] (1). mp: 87-89 °C. Anal.
Calcd for C14H22AuN2O3PS: C, 32.20; H, 3.79; N, 5.33; S, 5.98.
Found: C, 31.95; H, 4.21; N, 5.32; S, 6.09%. IR: ν(C-S) 1102m,
(29) SAINT, version 5.6; Bruker AXS Inc.: Madison, WI. 2000.
(30) (a) Sheldrick, G. M. SADABS; University of Go¨ttingen: Go¨ttingen,
Germany, 2000. (b) Blessing, R. Acta Crystallogr. 1995, A51, 33.
(31) Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.; Garc´ıa-
Granda, S.; Smits, J. M. M.; Smykalla, C. The DIRDIF Program
System; Technical Report of the Crystallography Laboratory; Univer-
sity of Nijmegen: Nijmegen, The Netherlands, 1992.
890m, ν(C-N) 1577s, ν(C-O) 1160m cm-1 31P{1H} NMR: δ
.
36.4.
[Cy3PAu{SC(OMe)dNC6H4NO2-4}] (2). mp: 152-154 °C.
Anal. Calcd for C26H40AuN2O3PS: C, 45.35; H, 5.50; N, 4.10; S,
(32) Sheldrick, G. M. SHELXL97, Program for Crystal Structure Refine-
ment; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
Inorganic Chemistry, Vol. 45, No. 20, 2006 8167

Ho et al.
exhibited the expected resonances and integration with the
most notable feature being the absence of a broad resonance
at 8.32 ppm, attributed to the N-H proton, that is evident
in the spectrum of the ligand. Similarly, the 13C{1H} NMR
(see Supporting Information) spectra show the expected
resonances with the most prominent feature being the
approximately 30 and 3 ppm upfield shifts in the resonances
from the quarternary and methyl carbon atoms, respectively,
upon coordination of the ligand. This observation is attributed
to the substantial reorganization of π-electron density in the
ligands because of the deprotonation and subsequent forma-
tion of a formal CdN double bond in the coordinated ligand.
Both the mono- and binuclear complexes show a single
resonance in their 31P{1H} NMR spectra with small (i.e.,
1-5 ppm) downfield shifts compared with their precursor
phosphine gold(I) chloride. The formation of a CdN double
bond in the coordinated ligand is also indicated in the IR
data because the absorptions attributed to ν(C-N) are shifted
toward higher frequencies by over 100 wavenumbers; the
broad absorption at 3236 cm-1 from ν(N-H) in the spectrum
of free ligand is absent in those of the complexes. In addition
to characteristic absorptions of ν(C-S) and ν(C-O), see the
Experimental Section, antisymmetric and symmetric stretches
of the NO2 group are observed at ∼1377 and ∼1558 cm-1,
respectively.
Crystal and Molecular Structures. Full structural char-
acterization of complexes 1-8 was afforded by single-crystal
X-ray crystallography giving an unprecedented complete
series of phosphine gold(I) thiolate structures. Selected
geometric parameters for all structures are collected in Table
2. Two molecules of [Et3PAu{SC(OMe)dNC6H4NO2-4}]
compose the asymmetric unit of 1, as illustrated in Figure
1. Each gold atom exists in the expected linear geometry
defined by a sulfur and phosphorus donor atom. The C1-
S1 bond distances of 1.757(5) and 1.751(4) Å for the
independent molecules have elongated significantly with
respect to the comparable distance in the uncoordinated
ligand (i.e., 1.664(2) Å), which has been reported to exist
as a thione in the solid state and in its theoretical gas-phase
structure.20 This elongation is accompanied by a significant
reduction in the C1-N1 bond distances to 1.262(5) and
1.264(5) Å (cf. 1.345(2) Å for the free ligand).20 Clearly,
these geometric parameters indicate that the ligand is
functioning as a thiolate in coordination to gold. There is a
marked variation in the angles about the C1 atom (Table 2).
While the S1-C1-N1 angle is, as expected, ∼120°, the S1-
C1-O1 angle is significantly contracted to 113° with a
concomitant expansion of the S1-C1-N1 angle to ap-
proximately 126°. The reason for these distortions can be
traced to the formation of an attractive Au‚‚‚O interaction
(i.e., Au‚‚‚O1 are 2.957(3) and 2.968(3) Å for the indepen-
dent molecules). These distances are within the sum of the
van der Waals radii for gold and oxygen of 3.20 Å,36 and
while not representing significant bonding interactions, they
are likely to be at least partly responsible for the deviation
of the P-Au-S angles from the ideal l80°. Similar intramo-
Figure 1. (a) Molecular structures for the two independent molecules of
the asymmetric unit of [Et3PAu{SC(OMe)dNC6H4NO2-4}] (1); the atomic
labels for the lower view have an “a” to distinguish this molecule from the
upper view, see also Figures 2, 4, 5, and 7. (b) Supramolecular association
in 1 via Au‚‚‚S and Au‚‚‚Au interactions.
dichloroform solvate. When significant, the largest residual electron
density peaks in the refinements were in close vicinity to the gold
atom. Crystallographic data and final refinement details are given
in Table 1. Figures 1-8 were drawn with Ortep-3 for Windows33
at the 50% probability level in each case. Data manipulation and
interpretation were accomplished with teXsan35 and PLATON,34
respectively.
Results and Discussion
Synthesis and Characterization. The series of mono-
nuclear complexes, [R3PAu{SC(OMe)dNC6H4NO2-4}], was
prepared for R ) Et (1), Cy (2), Ph (3), and the dinuclear
complexes, [(Ph2PRPPh2){AuSC(OMe)dNC6H4NO2-4}2],
for R ) CH2 (4), (CH2)2 (5), (CH2)3 (6), (CH2)4 (7), and Fc
(8) were synthesized in almost quantitative yields from the
metathetical reaction between the phosphine gold(I) chloride
and the sodium salt of the [SdC(OMe)NC6H4NO2-4],
generated in situ. The complexes are air and light stable and
are soluble in common organic solvents. They have been
characterized by elemental analysis and a range of spectro-
scopic methods. The 1H NMR (see Supporting Information)
(33) Farrugia, L. J. J. Appl. Crystallogr. 1997, 30, 565.
(34) teXsan: Structure Analysis Software; Molecular Structure Corp.: The
Woodlands, TX, 1997.
(35) Spek, A. L. PLATON, A Multipurpose Crystallographic Tool; Utrecht,
The Netherlands, 2006.
(36) Bondi, A. J. Phys. Chem. 1964, 68, 441.
8168 Inorganic Chemistry, Vol. 45, No. 20, 2006

Phosphine Gold(I) Carbonimidothioates
Table 1. Crystallographic Parameters and Refinement Details for 1-8
1
2
3
4
formula
fw
cryst syst
space group
a (Å)
C14H22AuN2O3PS
526.33
triclinic
P1h
11.3183(7)
13.7355(8)
14.4994(9)
98.896(1)
109.317(1)
114.323(1)
1824.13(19)
4
C26H40AuN2O3PS
688.60
triclinic
P1h
9.8613(11)
11.7552(14)
25.971(3)
97.21(1)
100.37(1)
104.63(1)
2818.9(6)
4
C26H22AuN2O3PS
670.45
monoclinic
P21/c
9.1839(3)
16.0097(6)
17.0530(6)
90
100.948(1)
90
2461.69(15)
4
C41H36Au2N4O6P2S2
1200.73
monoclinic
C2/c
27.9440(14)
10.8454(6)
30.0702(15)
90
115.497(1)
90
8225.6(7)
8
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
µ (cm-1
)
8.279
1.917
5.378
1.623
6.157
1.809
7.358
1.939
Dx (g cm-3
)
no. reflns
10 486
16 038
7121
11 974
no. obsd reflns with I > 2σ(I)
R (obsd data)
7705
0.037
9221
0.071
5811
0.028
7797
0.036
a and b in weighting scheme
0.028, 0
0.079
0.037, 8.234
0.200
0.021, 0
0.061
0.051, 0
0.112
Rw (all data)
CCDC no.
600356
600357
600358
600359
5
6
7
8
formula
fw
cryst syst
space group
a (Å)
C42H38Au2N4O6P2S2
1214.76
monoclinic
P21/c
11.9428(5)
31.5866(13)
11.6265(5)
90
106.658(1)
90
4201.8(3)
4
C43H40Au2N4O6P2S2
1228.78
orthorhombic
Pbcn
19.077(3)
8.5623(13)
26.017(4)
90
C44H42Au2N4O6P2S2
C50H42Au2FeN4O6P2S2‚2CHCl3
1242.81
monoclinic
P2/n
22.3284(7)
8.5861(3)
23.9840(7)
90
98.111(1)
90
4552.1(3)
4
1609.45
monoclinic
C2/c
23.1341(11)
12.1157(6)
21.9265(10)
90
109.478(1)
90
5794.0(5)
4
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
90
90
4249.8(11)
4
7.123
µ (cm-1
)
7.203
1.920
6.651
1.813
5.754
1.845
Dx (g cm-3
)
1.921
no. reflns
12169
6147
13160
8396
no. obsd reflns with I > 2σ(I)
R (obsd data)
9054
0.046
4228
0.044
7526
0.055
6594
0.031
a and b in weighting scheme
0.023, 0
0.083
0.051, 0
0.111
0.042, 8.192
0.126
0.045, 0
0.087
Rw (all data)
CCDC no.
600360
600361
600362
600363
lecular Au‚‚‚O interactions have been noted previously in
structural phosphine gold thiolate chemistry.37 The major
differences between the two independent molecules of 1 in
the asymmetric unit are conformational and are reflected in
the torsion angle data collected in Table 2. These data
indicate that the Au/S1/C1/O1/N1 portion of the thiolate
ligand is essentially planar but that this planarity does not
extend to the aromatic ring. In addition, as evident in Figure
1, there is a significant twist about the P1-C11 bond
resulting in a different relative orientation of this ethyl
substituent; the respective Au/P1/C11/C12 torsion angles are
-60.2(9) and 23.9(8)°. In the crystal structure of 1, the
independent molecules associate about a pseudocenter of
inversion to form a dimeric pair mediated by Au‚‚‚Au and
Au‚‚‚S interactions. The Au‚‚‚Au separation is 3.6086(4) Å,
and in reference to the labels in Figure 2, the Au‚‚‚S
separations are shorter at 3.4648(14) (a) and 3.5384(14) Å
(b); the sum of the van der Waals radii for gold and sulfur
is 4.0 Å.36 Increasing the size of the phosphorus-bound R
groups, to Cy (2) and Ph (3), precludes such intermolecular
associations.
Two independent molecules compose the asymmetric unit
of 2. As shown in Figure 2 and from the torsion angle data
collected in Table 2, there are conformational differences
between them with respect to the relative orientations of the
cyclohexyl rings. In terms of geometric parameters, they
match closely those found in 1. The same is true for the R
) Ph analogue (3), Figure 3, and indeed for subsequent
structures, and so these are not discussed further in any detail.
Consistent with the increased size of the Cy and Ph groups,
the intramolecular Au‚‚‚O distances are elongated with
respect to the situation in 1. The remaining structures to be
described are dinuclear gold species.
The dppm ligand in (Ph2P(CH2)PPh2){Au[SC(OMe)d
NC6H4NO2-4]}2 (4) (Figure 4a) adopts a syn conformation
allowing for the formation of an intramolecular Au‚‚‚Au
interaction of 3.1589(4) Å. This interaction in effect clips
the two halves of the molecule into an “A-frame” conforma-
tion, as seen in the torsion angle defined by P1/Au1/Au1a/
P1a of 23.60(6)°. The dimers of 4 further associate with a
centrosymmetrically related dimer (-x, -y, -z) to form the
(37) Siasios, G.; Tiekink, E. R. T. Z. Kristallogr. 1993, 204, 95. (b) Siasios,
G.; Tiekink, E. R. T. Z. Kristallogr. 1993, 205, 261. (c) Ro¨mbke, P.;
Schier, A.; Schmidbaur, H. J. Chem. Soc., Dalton Trans. 2001, 2482.
Inorganic Chemistry, Vol. 45, No. 20, 2006 8169

Ho et al.
Table 2. Crystallographic Parameters (Å, deg) for 1-8
1
1a
2
2a
3
4
4a
Au-S1
Au-P1
S1-C1
O1-C1
N1-C1
N1-C2
Au‚‚‚O
2.3059(11)
2.2510(13)
1.757(5)
1.346(5)
1.262(5)
1.389(6)
2.957(3)
2.3165(11)
2.2601(12)
1.751(4)
1.344(5)
1.264(5)
1.406(6)
2.968(3)
2.306(2)
2.269(2)
1.744(9)
1.353(11)
1.276(12)
1.406(12)
3.066(6)
2.301(2)
2.266(2)
1.748(11)
1.351(11)
1.253(13)
1.411(12)
3.172(8)
2.3119(7)
2.2573(7)
1.754(3)
1.354(3)
1.267(4)
1.401(4)
2.989(2)
2.3103(15)
2.2651(14)
1.751(6)
1.346(7)
1.266(7)
1.402(8)
3.082(5)
2.3023(14)
2.2522(14)
1.763(6)
1.349(7)
1.259(7)
1.422(8)
2.963(5)
S1-Au-P1
Au-S1-C1
S1-C1-O1
S1-C1-N1
O1-C1-N1
C1-O1-C8
C1-N1-C2
172.61(5)
101.27(16)
113.3(3)
126.5(4)
120.2(4)
116.3(4)
121.7(4)
174.77(4)
102.44(15)
113.4(3)
126.1(4)
120.5(4)
116.0(4)
120.6(4)
174.71(8)
104.9(3)
114.5(6)
124.6(8)
120.9(8)
116.4(8)
118.4(8)
171.89(11)
107.5(3)
114.4(8)
125.2(8)
120.5(10)
114.3(8)
120.5(9)
177.47(3)
103.29(10)
112.98(19)
127.0(2)
119.9(3)
116.6(2)
174.56(6)
103.8(2)
114.8(4)
126.0(5)
119.2(5)
115.5(5)
122.5(6)
173.67(5)
101.9(2)
113.6(4)
126.0(5)
120.4(6)
114.9(5)
120.3(6)
121.9(3)
Au-S1-C1-O1
Au-S1-C1-N1
S1-C1-N1-C2
P1-Au-S1-C1
C1-N1-C2-C3
14.6(5)
-2.0(4)
178.2(5)
-0.5(8)
2.8(7)
3.5(8)
-179.0(8)
3.9(14)
157.7(10)
82.5(13)
13.1(9)
-167.0(10)
1.0(17)
152.8(7)
-85.1(15)
-3.0(2)
-179.6(3)
-2.0(4)
17.4(7)
-16.7(5)
165.1(5)
-2.5(9)
-34.8(8)
-103.1(8)
-6.4(5)
174.6(6)
-2.5(10)
55.7(6)
-165.8(5)
-1.2(9)
-10.6(6)
116.2(6)
99.2(7)
-69.2(4)
-96.1(9)
5
5a
6
7
7a
8
Au-S1
Au-P1
S1-C1
O1-C1
N1-C1
N1-C2
Au‚‚‚O
2.3102(13)
2.3105(14)
2.2662(14)
1.747(6)
1.355(6)
1.261(7)
1.406(7)
3.086(4)
2.3255(15)
2.2679(15)
1.758(6)
1.375(7)
1.248(7)
1.402(8)
2.938(4)
2.3032(19)
2.2418(16)
1.749(7)
1.352(8)
1.257(8)
1.406(8)
2.982(5)
2.2975(19)
2.3274(9)
2.2651(9)
1.747(4)
1.356(4)
1.260(5)
1.397(5)
3.102(3)
2.2568(13)
1.744(6)
1.358(6)
1.276(6)
1.397(7)
3.049(4)
2.2449(15)
1.759(8)
1.358(8)
1.261(8)
1.390(8)
2.975(5)
S1-Au-P1
Au-S1-C1
S1-C1-O1
S1-C1-N1
O1-C1-N1
C1-O1-C8
C1-N1-C2
177.78(5)
103.31(18)
115.1(4)
125.6(4)
119.3(5)
115.9(4)
120.7(5)
172.36(5)
105.4(2)
114.3(4)
127.3(5)
118.4(5)
114.9(4)
125.2(5)
172.29(5)
101.8(2)
112.4(4)
128.1(5)
119.5(6)
115.1(5)
125.0(5)
176.62(6)
102.6(3)
113.1(5)
125.1(5)
121.8(6)
117.2(6)
119.4(6)
176.98(9)
103.1(2)
112.5(5)
126.5(6)
121.1(7)
115.7(6)
122.2(6)
174.73(4)
105.63(13)
114.0(3)
126.3(3)
119.7(3)
115.0(3)
121.7(4)
Au-S1-C1-O1
Au-S1-C1-N1
S1-C1-N1-C2
P1-Au-S1-C1
C1-N1-C2-C3
12.4(4)
-168.1(5)
1.6(8)
9.9(14)
-110.6(6)
-5.5(5)
172.3(5)
-4.1(9)
-115.2(4)
67.0(8)
-2.0(5)
178.0(5)
-1.2(10)
6.6(5)
-13.1(5)
169.6(6)
-4.9(10)
-4.2(13)
110.0(8)
-8.2(5)
8.1(3)
-172.4(4)
1.9(6)
93.3(4)
91.4(6)
171.4(6)
4.4(10)
-95.7(15)
-126.9(8)
-91.7(8)
tetrameric unit shown in the lower view of Figure 4b. The
primary contacts between the dimers are provided by
Au‚‚‚S interactions so that Au‚‚‚S1i is 3.6978(18) Å. The
dinuclear structure of [(Ph2PCH2PPh2){AuSC(OMe)dNC6H4-
NO2-4}2] (5) (Figure 5) adopts a somewhat twisted A-frame
conformation, with P1/Au1/Au1a/P1a being 52.87(5)°, and
it also features an intramolecular Au‚‚‚Au interaction that is
shorter (i.e., 3.1171(3) Å) than that observed in 4. An even
shorter intramolecular Au‚‚‚Au interaction of 3.0820(6) Å
is found in the dppp analogue (6) (Figure 6). The molecule
has crystallographically imposed 2-fold symmetry (-x, y,
1/2 - z), and the twist in the molecule, as reflected in the
P1/Au1/Aui/Pi torsion angle of 72.28(6)° suggests the dppm-,
dppe-, and dppp-containing molecules contort to maximize
the Au‚‚‚Au interactions. An entirely different conformation
is found in the dppb analogue (7) (Figure 7), for which an
anti conformation is found. It is likely that, for the shorter
(CH2)n bridges between the phosphorus atoms, the Au‚‚‚Au
interactions are able to stabilize the syn conformation, but
beyond the n ) 3 threshold, intramolecular Au‚‚‚Au interac-
tions are not found. Indeed, all of the known [{Ph2P(CH2)2-
PPh2}{Au(SR)}2] structures38-41 feature a similar anti con-
formation, and only in two structures are intermolecular
Au‚‚‚Au interactions found.38,41 It is clear that, generally,
syn conformations are rare in dppb complexes involving gold,
with the notable exception being found in the structure of
[{Ph2P(CH2)4PPh2}(AuCl)2], in which an approximate syn
arrangement is stabilized by intermolecular Au‚‚‚Cl interac-
tions provided by a solvent dichloromethane molecule.42 In
the case of 7, it is likely that intermolecular aurophilic
interactions are precluded because of the size of the thiolate
ligand combined with the presence of the intramolecular
Au‚‚‚O interactions that serve to reduce the residual Lewis
(38) Narayanaswamy, R.; Young, M. A.; Parkhurst, E.; Ouellette, M.; Kerr,
M. E.; Ho, D. M.; Elder, R. C.; Bruce, A. E.; Bruce, M. R. M. Inorg.
Chem. 1993, 32, 2506.
(39) Tzeng, B.-C.; Zank, J.; Schier, A.; Schmidbaur, H. Z. Naturforsch. B
1999, 54, 825.
(40) Maspero, A.; Kani, I.; Mohamed, A. A.; Omary, M. A.; Staples, R.
J.; Fackler, J. P., Jr. Inorg. Chem. 2003, 42, 5311.
(41) Onaka, S.; Yaguchi, M.; Yamauchi, R.; Ozeki, T.; Ito, M.; Sunahara,
T.; Sugiura, Y.; Shiotsuka, M.; Nunokawa, K.; Horibe, M.; Okazaki,
K.; Iida, A.; Chiba, H.; Inoue, K.; Imai, H.; Sako, K. J. Organomet.
Chem. 2005, 690, 57.
(42) Schmidbaur, H.; Bissinger, P.; Lachmann, J.; Steigelmann, O. Z.
Naturforsch. B 1992, 47, 1711.
8170 Inorganic Chemistry, Vol. 45, No. 20, 2006

Phosphine Gold(I) Carbonimidothioates
Figure 2. Molecular structures for the two independent molecules of the
asymmetric unit of [Cy3PAu{SC(OMe)dNC6H4NO2-4}] (2). For each
molecule, only one component of the disordered C15-C20 ring is shown
for clarity.
Figure 4. (a) Molecular structure of [(Ph2PCH2PPh2){AuSC(OMe)d
NC6H4NO2-4}2] (4). (b) Supramolecular association in 4 via Au‚‚‚S
interactions to form a tetramer.
Figure 3. Molecular structure of [Ph3PAu{SC(OMe)dNC6H4NO2-4}] (3).
acidity of the gold centers. The final structure to be described
is that of the Fc analogue, [{Ph2P(Fc)PPh2}{AuSC(OMe)d
NC6H4NO2-4}2] (8). The molecule (Figure 8) has crystal-
lographic 2-fold symmetry (-x, y, 1/2 - z) and features an
intermolecular Au‚‚‚Au interaction of 2.9765(3) Å (i.e., the
shortest among the structures described herein). The P1/Au/
Aui/P1i torsion angle is 85.12(3)°, reinforcing the trend
between shorter Au‚‚‚Au interactions and the orthogonal
P/Au/Au/P relationship. The P1/Cg1/Cg1i/P1i angle is
55.39(5)°, where Cg1 is the ring centroid of the Cp ring,
and this indicates a conformation of the Fc group between
synclinal staggered (36°) and synclinal eclipsed (72°); the
Fe‚‚‚Cg1 distance is 1.642(2) Å.43 Complex 8 was character-
ized as its chloroform solvate so that, for each dinuclear
species, there are two chloroform molecules. The solvent
molecules associate with the complex via a C26-H‚‚‚S1ii
interaction so that H‚‚‚Sii is 2.75 Å, C26‚‚‚S1ii is 3.533(7)
Å, and the angle at H is 137° (for ii -x, -1 + y, 1/2 - z).
Figure 5. Molecular structure of [(Ph2P(CH2)2PPh2){AuSC(OMe)d
NC6H4NO2-4}2] (5).
The availability of the complete “set” of structures, 1-8,
allows a few general conclusions to be made.
First and foremost, there is no significant influence exerted
by the nature of the phosphine ligand in 1-8 on the mode
of coordination of the thiolate ligand. Thus, the geometric
parameters within the thiolate ligand are experimentally
equivalent throughout the entire series. In the same way, in
(43) Bandoli, G.; Dolmella, A. Coord. Chem. ReV. 2000, 209, 161.
Inorganic Chemistry, Vol. 45, No. 20, 2006 8171

Ho et al.
Figure 6. Molecular structure of [{Ph2P(CH2)3PPh2}{AuSC(OMe)d
NC6H4NO2-4}2] (6).
Figure 8. Molecular structure of [{Ph2P(Fc)PPh2}{AuSC(OMe)dNC6H4-
NO2-4}2] (8).
disposition of the thiolate ligand to the P1-Au-S1 vector
(i.e., the P1/Au/S1/C1 torsion angles vary from coplanarity
(e.g., 3° in 1a) to orthogonal (e.g., 87° in 8)). In terms of
supramolecular aggregation, in the mononuclear complexes,
Au‚‚‚Au and Au‚‚‚S interactions are found in 1 but are absent
in 2 and 3, an observation that can be readily correlated with
the presence of the large phosphorus-bound R groups in the
latter that preclude the close approach of the molecules.44
Significant twisting in the dinuclear structures, [{Ph2P(CH2)n-
PPh2}{AuSC(OMe)dNC6H4NO2-4}2], n ) 1-3, and [{Ph2P-
(Fc)PPh2}{AuSC(OMe)dNC6H4NO2-4}2], as shown in the
P1/Au/Au′/P1′ torsion angle data, allows for the formation
of intramolecular Au‚‚‚Au interactions so that the Au‚‚‚Au
contacts vary from a long 3.1589(4) Å in 4 to 2.9765(3) Å
in 8. Steric constraints preclude the formation of both intra-
and intermolecular Au‚‚‚Au interactions in the case of the n
) 4 complex, 7. Having established the crystal and molecular
structures of 1-8, we thought it would be of significant
interest to determine the luminescence characteristics of these
complexes in the solid state to establish relationships between
the adopted structure, in particular, the presence of Au‚‚‚Au
interactions or otherwise and photoluminescence.
Photophysical Behavior. The electronic absorption data
of complexes 1-8 in dichloromethane are tabulated in Table
3. In general, they are dominated by a number of ill-defined
high-energy absorption shoulders at ∼260-262, 266-270,
and 274-298 nm and a low-energy absorption band at
∼330-334 nm. An additional absorption tail beyond 420
nm is also observed for 8. The electronic absorption spectra
of 4 and 8 in dichloromethane at 298 K are shown in Figure
9 as selected examples. By comparison with the absorption
data of the ligand and those of related gold(I) phosphine
systems,13c,14 the shoulders at ∼260-262 nm can readily be
attributed to the a carbonimidothioate ligand-centered π-π*
transition since the ligand itself also exhibits a similar
shoulder at ∼256 nm. The absorption shoulder at ∼266-
270 nm observed for complexes 2 and 4-8 is assigned as
Figure 7. Molecular structure of [{Ph2P(CH2)4PPh2}{AuSC(OMe)d
NC6H4NO2-4}2] (7).
terms of the gold atom, the Au-S distances lie in the narrow
range from 2.2975(19) (for 7a) to 2.3274(9) Å (8) (i.e.,
encompassing structures with and without, respectively,
Au‚‚‚Au interactions); the R ) Et structure, with a close
Au‚‚‚Au interaction, has an experimentally equivalent Au-S
distance of 2.3059(11) Å to that observed in 7a, without a
significant Au‚‚‚Au contact. The Au-P distances lie within
an even narrower range from 2.2418(16) (7) to 2.269(2) Å
(2). A common feature of all eight structures is the planarity
of the S1/O1/N1/C1 chromophore and its conformation with
respect to the gold atom, as well as the orientation of the
nitrogen-bound aromatic ring to the central chromophore,
as reflected in the C1/N1/C2/C3 torsion angle data. Confor-
mational differences in the structures occur in the relative
(44) Smyth, D. R.; Vincent, B. R.; Tiekink, E. R. T. Z. Kristallogr. 2001,
216, 298.
8172 Inorganic Chemistry, Vol. 45, No. 20, 2006

Phosphine Gold(I) Carbonimidothioates
Table 3. Photophysical Data for the Ligand,
[SdC(OMe)N(H)C6H4NO2-4], and Complexes 1-8
abs in CH2Cl2
emission
em (nm)
(τ0 (ms))
λ
abs (nm)
medium
(T (K))
λ
compound
ligand
(ꢀ (M-1cm-1))
solid (298)
solid (77)
nonemissive
256 sh (7000),
330 (17 450)
535 (0.0057)
510 (5.72, 59.22)b
nonemissive
glass (77)a
CH2Cl2 (298)
1
2
3
4
5
6
7
8
solid (298)
solid (77)
481c
538 (5.14)
523 (4.46)
486c
482c
526 (3.26)
521 (6.02)
488c
334 (13 550)
glass (77)a
CH2Cl2 (298)
solid (298)
solid (77)
260 sh (8300),
298 sh (9750),
332 (16 000)
glass (77)a
CH2Cl2 (298)
Figure 10. Emission (s) and excitation (- - -) spectra of 4 in dichlo-
romethane at 298 K.
260 sh (9350),
268 sh (8200),
276 sh (7100),
332 (14 200)
solid (298)
solid (77)
nonemissive
517 (2.28)
518 (3.90)
481c
510c
541 (2.21)
529 (4.70)
488c
glass (77)a
CH2Cl2 (298)
260 sh (28 950), solid (298)
270 sh (26 800), solid (77)
276 sh (24 050), glass (77)a
332 (30 100)
CH2Cl2 (298)
260 sh (18 600), solid (298)
266 sh (17 350), solid (77)
471 (0.0050)
541 (3.90)
530 (0.73,3.96)b
482c
276 (15 350),
332 (29 650)
glass (77)a
CH2Cl2 (298)
solid (298)
solid (77)
491 (0.0048)
543 (4.73)
518 (3.86)
482c
268 sh (15 500),
276 sh (13 100),
332 (29 650)
glass (77)a
CH2Cl2 (298)
Figure 11. Solid-state emission spectra of 4-7 at 77 K.
260 sh (16 200), solid (298)
268 sh (14 450), solid (77)
500 (0.0053)
537 (2.60)
538 (3.15)
484c
fact that such a band is also present in the absorption
spectrum of the carbonimidothioate ligand and the close
resemblance of the absorption energy between the ligand and
all the complexes. The absorption tail beyond 420 nm for 8
is attributed to a ferrocenyl-centered absorption.
274 (12 600),
332 (28 750)
glass (77)a
CH2Cl2 (298)
solid (298)
solid (77)
nonemissive
nonemissive
506c
262 sh (27 150),
274 sh (21 050),
332 (31 650)
glass (77)a
CH2Cl2 (298)
nonemissive
Photoexcitation of complexes 1-7 with λ > 350 produces
green and blue luminescence in the solid state and in solution,
respectively. Excitation spectra recorded for the bluish-green
emission in dichloromethane solutions at 298 K indicate an
excitation band maximum at ∼380-387 nm. Figure 10
shows the emission and excitation spectra of 4 in dichlo-
romethane at 298 K as a selected example. In view of the
close similarity of their emission energies with respect to
that observed for the ligand itself, together with the relatively
long radiative lifetimes in millisecond range at 77 K, an
a In EtOH-MeOH-CH2Cl2 4:1:1 (v/v) at 77 K. b Double exponential
decay. c Luminescence lifetime shorter than 0.1 µs.
3
emission origin attributed to a [n(S) f π*(C6H4NO2)]
intraligand donor-acceptor charge transfer, probably mixed
3
with some [S(3p) f Au(6s/6p)] ligand-to-metal charge-
transfer (LMCT) character, is suggested. The observed
shortening of the intraligand donor-acceptor charge-transfer
phosphorescence lifetimes when the free ligand is coordi-
nated to the gold(I) center can be rationalized as the “partial”
relaxation of the forbidden triplet-singlet radiative decay
by the heavy gold atom that possesses significant spin-orbit
coupling. It is also noteworthy to mention that the change
of the ancillary phosphines, as well as the presence or
absence of Au‚‚‚Au interactions, either intermolecularly or
intramolecularly, do not impose significant differences on
the emission energy and excitation maxima of the metal
Figure 9. Electronic absorption spectra of 4 and 8 in dichloromethane at
298 K.
the intraligand transition of the phosphine ligands resulting
from the presence of the phenyl groups. This is supported
by the absence of such an absorption shoulder in 1 and 2,
bearing aliphatic phosphines. The band at ∼330-334 nm is
1
suggestive of having a [n(S) f π*(C6H4NO2)] intraligand
donor-acceptor-type charge-transfer character, based on the
Inorganic Chemistry, Vol. 45, No. 20, 2006 8173

Ho et al.
complexes. Nevertheless, from the solid-state emission
spectra of complexes 4-7 at 77 K (Figure 11), a subtle
emission energy trend of 7 (537 nm) > 4 (541 nm) ≈ 5
(541 nm) > 6 (543 nm) is indicated, which is in line with
the decrease in the short intramolecular Au‚‚‚Au distances
that vary from none (7) > 3.1589(4) Å (4) ≈ 3.1171(3) Å
Acknowledgment. E.R.T.T. acknowledges the support
of the National University of Singapore (R-143-000-213-
112). V.W.-W.Y. acknowledges support from the University
Development Fund (UDF) of The University of Hong Kong
and The University of Hong Kong Foundation for Educa-
tional Development and Research Limited.
3
(5) > 3.0820(6) Å (6). This may be suggestive of a [n(S)
Supporting Information Available: Crystallographic data
(CIF) for the eight structures reported herein, as well a full listing
of 1H and 13C NMR data. This material is available free of charge
via the Internet at http://pubs.acs.org.
f π*(C6H4NO2)] intraligand donor-acceptor charge-transfer
excited-state bearing 3[S(3p) f Au(6s/6p)] LMCT character
that has been modified by the weak closed-shell Au‚‚‚Au
interactions, albeit small. Complex 8, on the other hand, does
not show significant photoluminescence under ambient
conditions. Such a phenomenon is not unusual and is
attributed to the intramolecular quenching by the ferrocenyl
moiety.45
IC0608243
(45) Fery-Forgues, S.; Delavaux-Nicot, B.; Lavabre, D.; Rurack, K. J.
Photochem. Photobiol. A 2003, 155, 107. (b) Thornton, N. B.;
Wojtowicz, H.; Netzel, T.; Dixon, D. W. J. Phys. Chem. B 1998, 102,
2101.
8174 Inorganic Chemistry, Vol. 45, No. 20, 2006