Supramolecular aggregation of mononuclear triorganophosphinegold(I) 2-mercaptobenzamides: Solution structures, thermal decomposition, and photoluminescence

Article abstract of DOI:10.1021/ic701022e

The crystal structures of R₃PAu[SC₆H ₄C(=O)NH₂-2], R = Et (1), Ph (2), and Cy (3) show linear coordination geometries for gold defined by sulfur and phosphorus atoms. Supramolecular aggregation via {...H-N-C=O}₂ synthons lead to dimeric aggregates in each case. In (1) and (2), the aggregates are spherical, but steric effects exerted by cyclohexyl rings in (3) dictate a rodlike form; no Au...Au interactions were noted in the crystal structures. Solvent dependence in their NMR spectra is correlated with intra- and intermolecular hydrogen bonding. The compounds uniformly decompose under controlled conditions to give gold. The complexes excited by UV light produce strong blue-green luminescence. The configuration interaction singles (CIS) post-Hartree-Fock (HF) calculations for the compounds indicate that it is the charge transfer from the sulfur and π-orbitals of SC₆H₄C(= O)NH₂-2 to gold that produce the emission from gold. The assignment of the observed luminescence is presented in terms of the relaxed excited states of gold, in which the vibronic interactions for three p-orbitals of gold are taken into account.

Full text of DOI:10.1021/ic701022e

Inorg. Chem. 2007, 46, 8228−8237
Supramolecular Aggregation of Mononuclear Triorganophosphinegold(I)
2-Mercaptobenzamides: Solution Structures, Thermal Decomposition,
and Photoluminescence
Jun-Gill Kang,*,† Hyung-Kook Cho,† Changmoon Park,† Sock-Sung Yun,*,† Jae-Kyung Kim,‡
Grant A. Broker,§ Douglas R. Smyth, and Edward R. T. Tiekink*,§
Department of Chemistry, Chungnam National UniVersity, Yuseong, Daejon 305-764, Republic of
Korea, High ExplosiVes Team, Agency for Defense DeVelopment (ADD), P.O. Box 35-5, Yuseong,
Daejon 305-600, Republic of Korea, Department of Chemistry, The UniVersity of Texas, One
UTSA Circle, San Antonio, Texas 78249-0698, Department of Chemistry, The UniVersity of
Adelaide, Australia 5005
Received May 25, 2007
The crystal structures of R3PAu[SC6H4C(dO)NH2-2], R ) Et (1), Ph (2), and Cy (3) show linear coordination
geometries for gold defined by sulfur and phosphorus atoms. Supramolecular aggregation via {‚‚‚
H−N−CdO}
2
synthons lead to dimeric aggregates in each case. In (1) and (2), the aggregates are spherical, but steric effects
exerted by cyclohexyl rings in (3) dictate a rodlike form; no Au‚‚‚Au interactions were noted in the crystal structures.
Solvent dependence in their NMR spectra is correlated with intra- and intermolecular hydrogen bonding. The
compounds uniformly decompose under controlled conditions to give gold. The complexes excited by UV light
produce strong blue-green luminescence. The configuration interaction singles (CIS) post-Hartree
−Fock (HF)
calculations for the compounds indicate that it is the charge transfer from the sulfur and -orbitals of SC6H4C(
π
d
O)NH2-2 to gold that produce the emission from gold. The assignment of the observed luminescence is presented
in terms of the relaxed excited states of gold, in which the vibronic interactions for three p-orbitals of gold are taken
into account.
Introduction
Au‚‚‚Au interactions can be significant and most important
in the determination of supramolecular aggregation patterns
because they are comparable in energy to hydrogen-bonding
interactions.5,6 Indeed, such considerations lead to studies
investigating the competition between/complementarity of
hydrogen-bonding and aurophilic interactions.7-9 Beyond
aesthetics, gold compounds are now well-known to demon-
strate solid-state and solution luminescence characteristics.
Accordingly, a full range of gold compounds have been
The structural chemistry of gold(I) compounds continues
to attract significant attention because of the wide variety
of supramolecular structural motifs observed in their solid-
state chemistry, as well as their predilection to furnish
luminescent materials: mono- and multinuclear complexes
of Au(I) produce characteristic luminescence over a wide
range of 350-700 nm. The rich structural diversity of gold
compounds is contributed to by the possibility of the
formation of attractive aurophilic interactions that are at-
tributed to correlation and relativistic effects.1-4 These
(2) Pyykko¨, P. Chem. ReV. 1997, 97, 597.
(3) Pyykko¨, P. Angew. Chem., Int. Ed. 2004, 43, 4412.
(4) Schmidbaur, H.; Cronje, S.; Djordjevic, B.; Schuster, O. Chem. Phys.
2005, 311, 151.
* To whom correspondence should be addressed. E-mail: jgkang@
cnu.ac.kr (J.-G.K.); ssyun@cnu.ac.kr (S.-S.Y.); Edward.Tiekink@utsa.edu
( E.R.T.T.).
(5) Schmidbaur, H. Nature (London) 2001, 413, 31.
(6) Pyykko¨, P.; Runeberg, N.; Mendizabal, F. Chem.sEur. J. 1997, 3,
1451.
(7) Schneider, W.; Bauer, A.; Schmidbaur, H. Organometallics 1996, 15,
5445.
(8) Hollatz, C.; Schier, A.; Riede, J.; Schmidbaur, H. Chem. Commun.
1999, 111.
(9) (a) Smyth, D. R.; Vincent, B. R.; Tiekink, E. R. T. CrystEngComm
2000, 2, 115. (b) Smyth, D. R.; Vincent, B. R.; Tiekink, E. R. T. Z.
Kristallogr. 2001, 216, 298.
† Chungnam National University.
‡ Agency for Defense Development (ADD).
§ The University of Texas.
The University of Adelaide. Present address: Department of Nuclear
Medicine, PET & Bone Densitometry, Royal Adelaide Hospital, South
Australia 5000, Australia
(1) Schmidbaur, H. Chem. Soc. ReV. 1995, 24, 391.
8228 Inorganic Chemistry, Vol. 46, No. 20, 2007
10.1021/ic701022e CCC: $37.00
© 2007 American Chemical Society
Published on Web 09/07/2007

Triorganophosphinegold(I) 2-Mercaptobenzamides
explored in this context, such as organometallic species,10-13
thiolates,14,15 oxo-species,16 and mixed-metal systems, for
example, with thallium17 and silver,18-20 where interactions
between closed-shell systems are again important. Phosphi-
negold(I) thiolates also demonstrate luminescence,21-24 and
research into the question as to the source of these photo-
physical and photochemical properties is of considerable
interest.25,26 While the formation of aurophilic interactions
in specialized phosphinegold(I) thiolates has been directly
correlated with luminescence and has led to the development
of novel analytical detection systems,27-29 phosphinegold(I)
thiolates and related systems that crystallize without Au‚‚‚
Au interactions can also be luminescent with their lumines-
cence assigned to charge transfer from ligand to gold.30-33
In connection with the above, previously, we investigated
the spectroscopic properties of (o-tolyl)3PAuCl34 and of a
series of pseudo-polymorphs of (o-tolyl)3PAu[SC6H4CO2H-
2]31 and performed configuration interaction singles (CIS)
post-Hartree-Fock (HF) calculations to model their elec-
tronic structures. The pseudo-polymorphs of (o-tolyl)3PAu-
[SC6H4CO2H-2] produced strong luminescence, peaking at
500 nm, while (o-tolyl)3PAuCl produced weak luminescence,
peaking at 450 nm. The observed luminescence of these
compounds was strongly associated with S-to-Au and Cl-
to-Au charge transfers, respectively. As a contribution to the
delineation of the mechanisms responsible for the lumines-
cence properties observed in mononuclear phosphinegold-
(I) thiolates, the series of compounds R3PAu[SC6H4C()O)-
NH2-2], R ) Et (1), Ph (2), and Cy (3), was synthesized,
and their structural and optical properties were comprehen-
sively investigated. This included the measurements of the
absorption, photoluminescence, and excitation spectra. In
addition, the CIS post-HF calculations on the molecular
orbitals and excited states of the complexes were performed
to reveal the nature of the absorbing and emitting states
presented.
Experimental Section
Synthesis and Spectroscopic Characterization. The R3PAu-
[SC6H4C()O)NH2-2], R ) Et (1), Ph (2), and Cy (3), compounds
were prepared in high yields from the reaction of the R3PAuCl
precursor and 2-mercaptobenzamide in the presence of KOH using
established procedures.35 Slow evaporation of an ethanol solution
of 1 and of an acetone solution of 3 afforded suitable crystals for
the X-ray study. Vapor diffusion of diethyl ether into a chloroform
solution of 2 yielded suitable crystals. Melting points were routinely
determined using a Gallenkamp digital melting point apparatus.
Infrared spectra for all compounds were recorded as KBr discs on
a Perkin-Elmer Spectrum BX FT-IR spectrophotometer in the range
of 400-4000 cm-1. 1H (and 1H-1H COSY), 13C, and 31P{1H} NMR
were recorded on a Varian Gemini 2000 spectrometer operating at
300.145, 75.479, and 121.501 MHz, respectively. 1H-13C HSQC,
HMQC, and HMBC 2-D NMR measurements were performed on
a Varian INOVA NMR spectrometer operating at 599.952 and
(10) Chen, J.; Mohamed, A. A.; Abdou, H. E.; Bauer, J. A. Krause; Fackler,
J. P., Jr.; Bruce, A. E.; Bruce, M. R. M. Chem. Commun. 2005, 1575.
(11) Tang, H.-S.; Zhu, N.; Yam, V. W.-W. Organometallics 2007, 26, 22.
(12) Elbjeirami, O.; Yockel, S.; Campana, C. F.; Wilson, A. K.; Omary,
M. A. Organometallics 2007, 26, 2550.
(13) Barnard, P. J.; Wedlock, L. E.; Baker, M. V.; Berners-Price, S. J.;
Joyce, D. A.; Skelton, B. W.; Steer, J. H. Angew. Chem. 2006, 45,
5966.
(14) Schmidbaur, H.; Graf, W.; Mu¨ller, G. Angew. Chem., Int. Ed. Engl.
1988, 27, 417.
(15) Codina, A.; Ferna´ndez, E. J.; Jones, P. G.; Laguna, A.; Lo´pez-de-
Luzuriaga, J. M.; Monge, M.; Olmos, M. E.; Pe´rez, J.; Rodr´ıguez, M.
A. J. Am. Chem. Soc. 2002, 124, 6781.
(16) Bojan, V. R.; Fernandez, E. J.; Laguna, A.; Lopez-de-Luzuriaga, J.
M.; Monge, M.; Olmos, M. E.; Silvestru, C. J. Am. Chem. Soc. 2005,
127, 11564.
(17) Fernandez, E. J.; Laguna, A.; Lopez-De-Luzuriaga, J. M.; Elena O.
M.; Perez, J. Chem. Commun. 2003, 1760.
(18) Catalano, V. J.; Moore, A. L. Inorg. Chem. 2005, 44, 6558.
(19) Wang, Q.-M.; Lee, Y.-A.; Crespo, O.; Deaton, J.; Tang, C.; Gysling,
H. J.; Gimeno, M. C.; Larraz, C.; Villacampa, M. D.; Laguna, A.;
Eisenberg, R. J. Am. Chem. Soc. 2004, 126, 9488.
(20) Colis, J. C. F.; Staples, R. J.; Tripp, C.; Labrecque, D.; Patterson, H.
J. Phys. Chem. B 2005, 109, 102.
(21) Assefa, Z.; McBurnett, B. G.; Staples, R. J.; Fackler, J. P., Jr; Assmann,
B.; Angermaier, K.; Schmidbaur, H. Inorg. Chem. 1995, 34, 75.
(22) Yam, V. W.-W.; Chan, C.-L.; Cheung, K.-K. J. Chem. Soc., Dalton
Trans. 1996, 4019.
1
150.873 MHz for H and 13C NMR, respectively. Spectra were
measured in CDCl3 or DMSO-d6, where indicated, and referenced
to TMS (85% H3PO4 for 31P{1H} NMR) or the appropriate solvent
resonance. Microanalyses were performed by Chemical & Micro-
analytical Services Pty Ltd (CMAS), Belmont, Victoria, Australia.
Et3PAu[SC6H4C(dO)NH2-2] (1). Colorless crystals in 75%
yield. Obsd (Calcd): C, 33.45 (33.41); H, 4.55 (4.53%); N, 2.91
(3.00%). IR (KBr, cm-1): 1666 (s) ν(C-O); 3123 (m), 3339 (m)
ν(N-H). mp: 146-148 °C. 13C{1H} NMR (DMSO-d6): δ 8.9
(Câ), 17.0 d (CR, 1JC-P ) 33.5 Hz), 123.0 (C5), 128.0 (C6), 128.4
(C4), 134.8 (C3), 138.5 (C1), 140.0 (C2), 170.2 (CdO). 31P NMR
(DMSO-d6): δ 39.5.
(23) Tzeng, B.-C.; Chan, C.-K.; Cheung, K.-K.; Che, C.-M.; Peng, S.-M.
Chem. Commun. 1997, 135.
Ph3PAu[SC6H4C(dO)NH2-2] (2). Colorless crystals in 89%
yield. Obsd (Calcd): C, 47.64 (47.69); H, 6.30 (6.24%); N, 2.07
(2.22%). IR (KBr, cm-1): 1661 (s) ν(C-O); 3114 (m), 3338 (m)
ν(N-H). mp: 166-167 °C. 13C{1H} NMR (DMSO-d6): δ 123.4
(C5), 128.0 (C6), 128.1 (C4), 128.9 d (CR, 1JC-P ) 56.7 Hz), 129.5
(24) Bardaj´ı, M.; Calhorda, M. J.; Costa, P. J.; Jones, P. G.; Laguna, A.;
Reyes, Pe´rez, M.; Villacampa, M. D. Inorg. Chem. 2006, 45, 1059.
(25) Fung, E. Y.; Olmstead, M. M.; Vickery, J. C.; Balch, A. L. Coord.
Chem. ReV. 1998, 171, 151.
(26) van Zyl, W. E.; Lopez-de-Luzuriaga, J. M.; Fackler, J. P., Jr. J. Mol.
Struct. 2000, 516, 99.
(27) Yam, V. W.-W.; Chan, C.-L.; Li, C.-K. Angew. Chem., Int. Ed. 1998,
37, 2857.
(28) Yam, V. W.-W.; Cheng, E. C.-C. Gold Bull. 2001, 34, 20.
(29) Li, C.-K.; Lu, X.-X.; Wong, K. M.-C.; Chan, C.-L.; Zhu, N.; Yam,
V. W.-W. Inorg. Chem. 2004, 43, 7421.
(30) Hao, L.; Mansour, M. A.; Lachicotte, R. J.; Gysling, H. J.; Eisenberg,
R. Inorg. Chem. 2000, 39, 5520.
(31) Yun, S.-S.; Kim, J.-K.; Jung, J.-S.; Park, C.; Kang, J.-G.; Smyth, D.
R.; Tiekink, E. R. T. Cryst. Growth Des. 2006, 6, 899.
(32) Ho, S. Y.; Cheng, E. C.-C.; Tiekink, E. R. T.; Yam, V. W.-W. Inorg.
Chem. 2006, 45, 8165.
3
4
d (Cγ, JC-P ) 11.5 Hz), 132.0 d (Cδ, JC-P ) 2.3 Hz), 133.7 d
(Câ, 2JC-P ) 13.7 Hz), 135.0 (C3), 138.3 (C1), 139.3 (C2), 170.6
(CdO). 31P NMR (DMSO-d6): δ 38.2.
Cy3PAu[SC6H4C(dO)NH2-2] (3). Yellow crystals in 94% yield.
Obsd (Calcd): C, 49.13 (49.11); H, 3.43 (3.46%); N, 2.17 (2.29%).
IR (KBr, cm-1): 1665 (vs) ν(C-O); 3123 (m), 3305 (s) ν(N-H).
mp: 200-210 °C. 13C{1H} NMR (CDCl3): δ 25.8 (Cδ), 27.0 d
2
1
(Câ, JC-P ) 11.7 Hz), 30.8 (Cγ), 33.3 d (CR, JC-P ) 28.1 Hz),
124.1 (C5), 129.4 (C4), 131.4 (C6),135.0 (C1), 136.6 (C3), 140.1
(C2), 170.1 (CdO). 31P NMR (CDCl3): δ 57.4.
(33) Ovejero, P.; Mayoral, M. J.; Cano, M.; Lagunas, M. C. J. Organomet.
Chem. 2007, 692, 1690.
(34) Kang, J.-G.; Park, C.; Tiekink, E. R. T. Bull. Korean Chem. Soc. 2006,
27, 299.
(35) Smyth, D. R.; Tiekink, E. R. T. Z. Kristallogr. NCS 2002, 217, 357.
Inorganic Chemistry, Vol. 46, No. 20, 2007 8229

Kang et al.
Table 1. Crystallographic Data and Refinement Details for
R3PAu[SC6H4C(dO)NH2-2], R ) Et (1), Ph (2), and Cy (3)
Thermal Analysis. The thermal decomposition mechanisms of
1-3 were investigated on a TGA 50 apparatus (Mettler-Toledo
GmbH, Switzerland) fitted with a standard platinum pan. The
conditions of thermogravimetry (TG) were as follows: sample
masses of about 1 mg were heated at a rate of 10 °C min-1 under
a nitrogen atmosphere. The differential scanning calorimetry (DSC)
experiments were carried out with a model 821e apparatus (Mettler-
Toledo GmbH, Switzerland) fitted with a standard aluminum pan.
The conditions of DSC were as follows: sample masses of about
1 mg were heated at a rate of 10 °C min-1 under a nitrogen
atmosphere. A sample of indium was used as the reference. In other
experiments, the decomposition residues obtained by heating 7-8
mg of the samples in an aluminum crucible (70 µL) up to 320-
330 °C under a nitrogen atmosphere were subjected to scanning
electron microscopy (SEM) analysis on a model XL-30-FEG Philips
microscope operating at 20 kV and WD 10 mm. For 1-3, the
respective phase transitions were in the ranges of 147.4-149.3-
151.3, 155.3-165.3-169.2 and 202.7-206.8-209.0, and 188.1-
200.7-203.8 °C. Thermal decomposition for 1 occurred in the
temperature ranges of 261.3-317.7 (DSC) and 144.7-228.0-
320.0 °C (DTG) resulting in 58.02% weight loss. The theoretical
weight loss is 57.85% assuming that gold is the final product. The
formation of gold was confirmed by SEM analysis. For 2, the ranges
were 271.1-324.8 (DSC) and 152.2-300.0-339.7 °C (DTG) with
66.78% weight loss (cf., theoretical 67.79%). For 3, the temperature
ranges were 286.1-331.9 (DSC) and 187.3-324.0-344.7 °C
(DTG) with a weight loss of 68.83% (cf., 68.72% theoretical).
Optical Measurements. For luminescence and excitation spectra
measurements, samples in microcrystalline or powder states were
placed on the cold finger of an Oxford CF-1104 cryostat using
silicon grease. Excited light from either a He-Cd laser or an Oriel
1000-W Xe arc lamp, passed through an Oriel MS257 monochro-
mator, was focused on the sample. The luminescence spectrum was
measured at a 90° angle with respect to the excitation direction
with an ARC 0.5 m Czerny-Turner monochromator equipped with
a cooled Hamamatsu R-933-14 photomultiplier tube. The lumi-
nescence spectra of the complexes were measured at 10 K, 78 K,
and room temperature.
1
2
3
formula
fw
cryst syst
space group
a (Å)
C13H21AuNOPS C25H21AuNOPS C25H39AuNOPS
467.32
monoclinic
P21
611.45
triclinic
P1h
629.59
triclinic
P1h
7.995(1)
17.491(6)
11.664(1)
90
104.55(1)
90
10.576(4)
11.232(4)
10.205(6)
114.62(3)
90.25(4)
91.66(3)
1101.4(9)
2
11.028(2)
13.240(7)
9.756(2)
106.01(3)
97.11(2)
108.65(3)
1261.8(7)
2
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
1578.8(5)
4
Dc (g cm-3
F(000)
)
1.966
1.844
1.657
896
592
628
µ(Mo KR) (mm-1
measured data
unique data
obsd data with
I g 2.0σ(I)
)
9.573
4007
3997
3743
6.886
5329
5054
4358
6.013
6100
5801
4941
variables
309
271
271
R, obsd data;
all data
0.027; 0.063
0.023; 0.057
0.027; 0.067
a; b in weighting
scheme
Rw, obsd data;
all data
0.026; 0.503
0.047; 0.068
1.14
0.028; 0.730
0.034; 0.060
0.82
0.035; 1.825
0.039; 0.071
1.22
largest residual
( e Å-3
)
CCDC no.
602447
602448
602446
X-ray Crystallography. Intensity data for 1-3 were measured
at 173 K on a Rigaku AFC7R diffractometer fitted with Mo KR
radiation, so that θmax was 27.5°. The structures were solved by
heavy-atom methods.36 Typically, refinement was on F2,37 using
data that had been corrected for absorption effects with an empirical
procedure,38 with non-hydrogen atoms modeled with anisotropic
displacement parameters, with hydrogen atoms in their calculated
positions, and using a weighting scheme of the form w ) 1/[σ2-
2
2
(Fo ) + (aP)2 + bP], where P ) (Fo + 2Fc2)/3). For 1, in which
two independent molecules comprise the asymmetric unit, the
structure was refined as a racemic twin precluding the determination
of absolute structure. One of the triethylphosphine ligands in 1 was
found to be disordered, and this was resolved by modeling (isotropic
refinement) the methylene-carbon atoms over two sites; from the
refinement, the site occupancies were found to be equal. The
maximum residual electron density peak of 1.14 e Å-3 in 1 was
located in the vicinity of the disordered residue, and in the case of
3, it was in the vicinity of the gold atom. Figure 2 was drawn at
the 50% probability level using ORTEP,39 Figures 3 and S2 were
drawn with DIAMOND,40 and data manipulation and analyses were
performed with teXsan41 and PLATON.42 Crystallographic data and
refinement details are given in Table 1.
Results and Discussion
Syntheses and Characterization. The Et3PAu[SC6H4C-
(dO)NH2-2] (1), Ph3PAu[SC6H4C(dO)NH2-2] (2), and Cy3-
PAu[SC6H4C(dO)NH2-2] (3) compounds were readily syn-
thesized from the metathetical reaction between the R3PAuCl
precursor and HSC6H4C(dO)NH2-2 in the presence of base.
A single amide ν(CdO) band was observed in their IR spec-
tra, with a stretching frequency in the range of 1652-1668
cm-1. Two N-H absorptions were also observed with fre-
quencies typically near 3120 and 3320 cm-1. In their NMR,
unambiguous assignment of the proton resonances was deter-
mined by the 2D methods of 1H-1H COSY, 1H-13C HSQC
(or HMQC), and 1H-13C HMBC and, interestingly, showed
significant solvent dependence in terms of their chemical
shifts.
The doublet of doublets corresponding to H6 in R3PAu-
[SC6H4C(dO)NH2-2] comes into resonance at approximately
8.05 ppm in CDCl3 solution but occurs at approximately 7.35
ppm in DMSO-d6. The shift of up to 0.70 ppm suggests that
the amide group undergoes a conformational flip. The
chemical shift of approximately 8.05 ppm in CDCl3 indicates
that the H6 proton is deshielded because of anisotropy of
(36) 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.
(37) Sheldrick, G. M. SHELXL97, Program for Crystal Structure Refine-
ment; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
(38) Walker, N.; Stuart, D. Acta Crystallogr., Sect. A 1983, 39, 158.
(39) Johnson, C. K. ORTEP. Report ORNL-5138; Oak Ridge National
Laboratory: Oak Ridge, TN 1976.
(40) DIAMOND, Visual Crystal Structure Information System, version 2.1e;
Crystal Impact: Bonn, Germany, 2002.
(41) teXsan: Structure Analysis Software; Molecular Structure Corp.: The
Woodlands, TX, 1997.
(42) Spek, A. L. PLATON, A Multipurpose Crystallographic Tool; Utrecht
University: Utrecht, The Netherlands, 2006.
8230 Inorganic Chemistry, Vol. 46, No. 20, 2007

Triorganophosphinegold(I) 2-Mercaptobenzamides
intramolecular O-H‚‚‚S interaction or an intermolecular
O-H‚‚‚O interaction, thereby allowing for the possibility
of structural isomer formation.
Crystallography. The molecular structure of Et3PAu-
[SC6H4C(dO)NH2-2] (1) is shown in Figure 2a, and selected
geometric parameters are collected in Table 2 for this and
the remaining structures described herein. Two independent
molecules comprise the crystallographic asymmetric unit of
1, but these are virtually identical. Indeed, there are only
minor conformational differences between the molecules,
mainly associated with the phosphine ligands, in that for the
first independent molecule, two of the terminal methyl groups
are orientated toward the gold atom whereas the other is
directed away. By contrast, for the second molecule, all three
methyl groups are directed toward the gold atom. The
familiar linear P-Au-S coordination geometry is observed
with the Au-S bond distance being significantly longer than
the Au-P bond. The magnitude of the C2-S2 bond indicates
that the anion is coordinating as a thiolate ligand. There is
a significant twist about the S2-C2 bond, and further, the
amide residue is not coplanar with the aromatic ring as seen
in the torsion angle data included in Table 2. Such a
conformation most likely alleviates some of the steric
pressure in this region of the molecule. This is also reflected
in the significant deviations from the ideal 120° angles about
the C2 atom. Relief of at least some of this steric pressure
can be envisioned in a scenario where there is a twist about
the C1-C7 bond that places the oxygen atom in close
proximity to gold. Indeed, such interactions are well-known
in phosphinegold(I) thiolate chemistry.44-48 However, in this
case, the imperative for the observed conformation is the
formation of an intramolecular N-H‚‚‚S interaction.49 This
leaves the remaining N-H atoms available for intermolecular
interactions so that the two molecules comprising the
asymmetric unit associate about a pseudo-center-of-inversion,
resulting in the formation of the {‚‚‚H-N-CdO}2 synthon
as shown in Figure 2a.
Figure 1. Proposed solution structures of R3PAu[SC6H4C(dO)NH2-2] in
(a) CDCl3 and (b) DMSO-d6 solution.
the carbonyl π-bond. The proximity of the H6 proton to the
carbonyl bond is the result of an intramolecular N-H‚‚‚S
hydrogen bond locking the amide group into that particular
geometry, as shown in Figure 1a. Further evidence for the
formation of an intramolecular hydrogen bond comes from
the chemical shifts of the two amide protons. The proton
participating in the intramolecular hydrogen bond, Ha, is
deshielded and appears downfield in the range of 8.72-8.86
ppm. The second amide proton, Hb, comes into resonance
near 6.0 ppm, approximately 2.7 ppm upfield from Ha. Upon
titration of small aliquots of DMSO-d6 into a CDCl3 solution
of Cy3PAu[SC6H4C(dO)NH2-2] (3), the H6 resonance
progressively moves upfield as shown in Figure S1; Table
1
S1 lists the H resonances. In 100% DMSO-d6, the amide
group is orientated such that the H6 proton is removed from
the deshielding zone of the carbonyl π-bond. Furthermore,
the signals from the amide protons, Ha and Hb, progressively
move toward each other, indicating that their chemical
environments become similar in DMSO-d6 solution. Because
the spectral features of each 1 and 2 resemble those just
described for 3, it is concluded that similar structures exist
for all three compounds. The proposed solution structure of
R3PAu[SC6H4C(dO)NH2-2] in DMSO-d6 solution is shown
in Figure 1b, indicating intermolecular hydrogen bonds
between the amide protons and the polar DMSO-d6 solvent.
The 13C and 31P{1H} chemical shifts and 31P{1H}-13C
coupling constants are consistent with compounds of this
type.43 The assignment of the aromatic thiolate 13C reso-
The molecular structure and formation of a {‚‚‚H-N-
CdO}2 synthon is also repeated in the structure of Ph3PAu-
1
nances was aided by the 2D methods of H-13C HSQC
(45) (a) Siasios, G.; Tiekink, E. R. T. Z. Kristallogr. 1993, 204, 95. (b)
Siasios, G.; Tiekink, E. R. T. Z. Kristallogr. 1993, 205, 261.
(46) Ro¨mbke, P.; Schier, A.; Schmidbaur, H. J. Chem. Soc., Dalton Trans.
2001, 2482.
(47) Barreiro, E.; Casas, J. S.; Couce, M. D.; Sa´nchez, A.; Sordo, J.; Varela,
J. M.; Va´quez-Lo´pez, E. M. Dalton Trans. 2003, 4754.
1
(or HMQC) and H-13C HMBC and also shows some
solvent dependence, but it is not as dramatic as that for the
1H NMR.
Analogous solution behavior as just described was ob-
served for the related R3PAu[SC6H4C()O)OH-2]43 systems
and in this case, both forms similar to those shown in Figure
1 were crystallized.44 Despite our best attempts, only one
crystal form was ever isolated in the present study because
of the dual hydrogen-bonding capacity of the amide func-
tionality that always allows for the formation of intra- and
intermolecular hydrogen bonding, that is, N-H‚‚‚S and
N-H‚‚‚O interactions, respectively. In contrast, in R3PAu-
[SC6H4C(dO)OH-2], the acidic hydrogen can form an
(48) Ho, S. Y.; Tiekink, E. R. T. CrystEngComm 2007, 9, 368.
(49) Geometric parameters describing selected intermolecular interactions
in R3PAu[SC6H4C(dO)NH2-2], R ) Et (1), Ph (2), and Cy (3). (1):
N1-H1a‚‚‚O1a ) 1.97 Å, N1‚‚‚O1a ) 2.825(13) Å, angle at H )
163° for symmetry operation x, y, z; N1-H1b‚‚‚S2 ) 2.58 Å, N1‚‚
‚S2 ) 3.145(9) Å, 123° (x, y, z); N1a-H1a1‚‚‚O1 ) 2.02 Å, N1a‚‚
‚O1 ) 2.871(14) Å, 164° (x, y, z); N1a-H1b1‚‚‚S2a ) 2.56 Å, N1a‚
‚‚S2a ) 3.127(10) Å, 123° (x, y, z); C21a-H21c‚‚‚O1a ) 2.51 Å,
C21a‚‚‚O1a ) 3.48(3) Å, 164° (1 + x, y, z); C12-H12a‚‚‚Cg(C1a-
C6a) ) 2.94 Å, C12‚‚‚Cg(C1a-C6a) ) 3.514(13) Å, 118° (-1 + x,
y, -1 + z). (2) : N1-H1a‚‚‚O1 ) 1.99 Å, N1‚‚‚O1 ) 2.869(5) Å,
176° (-x, 1 - y, 1 - z); N1-H1a‚‚‚S2 ) 2.53 Å, N1‚‚‚S2 ) 3.118-
(4) Å, 125° (x, y, z); C13-H13‚‚‚Cg(C21-C26) ) 3.00 Å, C13‚‚‚
Cg(C21-C26) ) 3.716(5) Å, 134° (1 - x, -y, 1 - z); C34-H34‚‚
‚Cg(C1-C6) ) 2.91 Å, C34‚‚‚Cg(C1-C6) ) 3.666(5) Å, 137° (1 -
x, -y, -z); C5-H5‚‚‚Cg(C31-C36) ) 2.84 Å, C5‚‚‚Cg(C31-C36)
) 3.731(6) Å, 156° (x, 1 + y, z). (3): N1-H1a‚‚‚O1 ) 2.02 Å, N1‚
‚‚O1 ) 2.893(6) Å, 174° (-x, -1 - y, -1 - z); N1-H1b‚‚‚S2 )
2.25 Å, N1-H1b‚‚‚S2 ) 3.008(4) Å, 144° (x, y, z).
(43) de Vos, D.; Clements, P.; Pyke, S. M.; Smyth, D. R.; Tiekink, E. R.
T. Metal-Based Drugs 1999, 6, 31.
(44) Smyth, D. R.; Vincent, B. R.; Tiekink, E. R. T. Cryst. Growth Des.
2001, 1, 113.
Inorganic Chemistry, Vol. 46, No. 20, 2007 8231

Kang et al.
Figure 2. Molecular structures, atom-labeling scheme, and hydrogen-bonding interactions for (a) the two independent molecules of Et3PAu
[SC6H4C(dO)NH2-2] (1), (b) centrosymmetrically related molecules of Ph3PAu[SC6H4C(dO)NH2-2] (2), and (c) centrosymmetrically related molecules
of Cy3PAu[SC6H4C(dO)NH2-2] (3).
[SC6H4C(dO)NH2-2] (2), Figure 2b. The comparable inter-
atomic bond distances are equal within experimental error,
but there is a marginally greater distortion away from the
linear geometry about the gold atom in 2 compared with
that in 1. The result of the intermolecular hydrogen bonding
in each of 1 and 2 is the formation of spherical aggregates.
In Cy3PAu[SC6H4C(dO)NH2-2] (3), Figure 2c, where the
coordination geometry and geometric parameters are basi-
cally equivalent to those observed in the preceding structures,
the shape of the supramolecular aggregate is distinct despite
the formation of the prevalent {‚‚‚H-N-CdO}2 synthon.
The adoption of the rod or cylinder type of arrangement in
8232 Inorganic Chemistry, Vol. 46, No. 20, 2007

Triorganophosphinegold(I) 2-Mercaptobenzamides
Table 2. Selected Interatomic Parameters for
R3PAu[SC6H4C(dO)NH2-2], R ) Et (1), Ph (2), and Cy (3)
Table 3. Electronic Absorption Data (Recorded in CH2Cl2 Solution)
for HSC6H4C(dO)NH2-2, Ph3P, Et3PAu[SC6H4C(dO)NH2-2] (1),
Ph3PAu[SC6H4C(dO)NH2-2] (2), and Cy3PAu[SC6H4C(dO)NH2-2] (3)
1, 1a
2
3
λ/nm (ꢀ × 10-3/M-1 cm-1
305(0.2), 246(0.4), 203(0.1)
286(0.3), 247(0.4), 190(0.1)
)
Au-S2
Au-P1
S2-C2
C7-O1
C7-N1
2.315(4), 2.319(4)
2.262(4), 2.253(4)
1.780(12), 1.778(11)
1.238(13), 1.257(14)
1.316(14), 1.330(15)
2.3095(14)
2.2610(13)
1.786(4)
1.233(5)
1.332(5)
2.3120(16)
2.2680(15)
1.782(4)
1.235(5)
1.326(6)
HSC6H4C(d)NH2-2
Ph3P
1
2
3
323 sh (2.2), 282 sh (5.4), 230 (12.6)
319 sh (3.6), 291 sh (6.1), 237 (33.1)
323 sh (2.5), 282 sh (5.9), 230 (13.3)
P1-Au-S2
Au-S2-C2
C2-C1-C6
C2-C1-C7
C6-C1-C7
O1-C7-N1
O1-C7-C1
N1-C7-C1
Au/S2/C2/C1
C2/C1/C7/O1
C2/C1/C7/N1
178.89(12), 178.23(12)
102.6(4), 102.6(4)
176.66(4)
102.91(12)
118.9(3)
126.4(3)
114.6(3)
122.4(4)
119.9(4)
117.6(3)
-60.2(3)
151.8(4)
-32.6(6)
178.46(4)
103.07(14)
118.4(4)
127.9(4)
113.7(4)
121.1(4)
119.2(4)
119.7(4)
-140.8(4)
174.7(5)
-6.1(8)
proximate rotor conformation: the Au-P1-Cispo-C torsion
angles are 17.0(4), 48.4(4), and 54.6(4)° for the C32, C16,
and C26 rings, respectively, and the P‚‚‚P distance is 6.85
Å. Additional C-H‚‚‚π interactions involving the mercap-
tobenzoate ring also stabilize the structure.49 The well-defined
supramolecular aggregation patterns operating in the crystal
structures of both 1 and 2 is somewhat lacking in the crystal
structure of 3. As indicated by the crystal packing diagram
shown in Figure S2, molecules stack into columns along the
c-direction to form rows of gold atoms. However, there are
no Au‚‚‚Au interactions of note, and in the absence of
hydrogen bonding, C-H‚‚‚π, and π‚‚‚π interactions, the
crystal packing is best described as being stabilized by
hydrophobic interactions between interdigitated dimeric
aggregates.
Spectroscopic Properties. Absorption and Reflectance.
The absorption spectra of the uncoordinated HSC6H4C(d
O)NH2-2 and Ph3P molecules and of Et3PAu[SC6H4C(dO)-
NH2-2] (1), Ph3PAu[SC6H4C(dO)NH2-2] (2), and Cy3PAu-
[SC6H4C(dO)NH2-2] (3), all dissolved in CH2Cl2, were
measured in the 225-600 nm range (Table 3). As shown in
Figure 4a, the absorption spectra of 1 and 3 are almost
identical with three absorption bands appearing at 323, 282,
and 230 nm. Hereafter, these bands are referred to as A, B,
and C absorption bands in order of increasing energy. The
intensities of the A and B absorption bands were very weak,
compared with that of the C absorption band. The absorption
spectrum of 2 is slightly different with the three absorption
bands appearing at 319, 291, and 237 nm but with the
C-absorption band being significantly more intense than those
of the others. The reflectance spectra of the uncoordinated
[HSC6H4C(dO)NH2-2] and Ph3P molecules and of 1-3 were
also measured in the powdered state (see Table 4). As shown
in Figure 4b, the reflectance spectrum of 2 is very different
from those of 1 and 3. For the latter, the reflectance spectrum
showed less well-defined band shapes, compared with the
absorption spectrum measured in solution. Assuming that
the peak position of the solution state was blue-shifted by
approximately 110 nm, the positions of the A, B, and C
absorption bands of the powdered state were indicated by
arrows in the reflectance spectrum (see Figure 4b).
120.0(11), 120.5(11)
126.6(10), 125.1(11)
113.3(10), 114.4(11)
123.0(10), 121.9(11)
119.5(10), 119.1(11)
117.5(10), 119.0(11)
-128.1(9), 123.7(8)
-147.7(12), 147.9(12)
35.7(16), -34.6(18)
3 is dictated by steric considerations, as have been discussed
in closely related R3PAu(S2COR′), R ) alkyl or aryl,46,47
and Cy3PAu(SC6H4CO2H-2)44 systems. Put simply, if the
hydrogen-bonded dimer in 3 adopts the same conformation
as seen in each of 1 and 2, there would be impossible steric
interactions between the cyclohexyl rings. Thus, while the
{‚‚‚H-N-CdO}2 synthon persists, the shape of the ag-
gregate is rodlike. In terms of molecular geometry, the more-
open arrangement allows the amide moiety to be effectively
coplanar with the remaining portion of the thiolate ligand.
The dimeric aggregates in 1 associate to form a chain
as shown in Figure 3a. The primary mode of association
between the molecules of 1 is interactions of the type
C-H‚‚‚O that extend in the a-direction.49 Chains are linked
via C-H‚‚‚π interactions involving the C12-H atom and the
ring centroid of (C1a-C6a)i. The net result of the aforemen-
tioned contacts is a layer arrangement running parallel to
(101). The dimeric aggregates in 2 also associate into a chain
along (011), but this time via Au‚‚‚S2i interactions of 3.345-
(2) Å between centrosymmetrically related molecules (sym-
metry: i -x, -y, -z).49 Chains are linked into layers via
6-fold phenyl embraces;50,51 the Ph3P group has an ap-
PL and Excitation Spectra. The PL spectrum of Et3PAu-
[SC6H4C(dO)NH2-2] (1) in the solid-state was measured at
10 K, 78 K, and room temperature (RT). As shown in Figure
5a, whereas 1 had significant luminescence intensity at 78.8
K, at RT, the intensity was markedly decreased. There were
no remarkable differences in the spectral shapes measured
Figure 3. (a) Chain mediated by C-H‚‚‚O interactions in the structure
of Et3PAu[SC6H4C(dO)NH2-2] (1). (b) Chain mediated by Au‚‚‚S interac-
tions in the structure of Ph3PAu[SC6H4C()O)NH2-2] (2). For clarity, only
hydrogen atoms involved in hydrogen-bonding interactions are shown.
(50) Scudder, M.; Dance, I. J. Chem. Soc., Dalton Trans 1998, 329.
(51) Scudder, M.; Dance, I. J. Chem. Soc., Dalton Trans 1998, 3167.
Inorganic Chemistry, Vol. 46, No. 20, 2007 8233

Kang et al.
pendent on temperature, as shown in Figure 5e. At 78 K,
the PL spectrum is well resolved into three main Gaussian
components, peaking at 457, 503, and 556 nm. The high-
energy component, which did not appear or appeared as only
a trace for 1 and 2, gained in intensity to form the observed
band. The excitation spectra of the three emissions were also
measured at 78 K. As shown in Figure 5f, the excitation
spectrum of ME is significantly different from those of 1
and 2. Not only did the 350 nm band appear as a main
excitation band but also the 450 nm band. The ME and low-
energy emission bands were produced strongly by the 450
nm excitation, while the high-energy band was produced by
the 350 nm excitation. The 450 nm excitation corresponds
to the A absorption band. The series of the bands are ascribed
to the vibronic distortion.
Molecular Orbitals and Electronic Transitions. The
main objective of the theoretical investigation was to model
the electronic structures and to determine the properties of
luminescence. On the basis of the X-ray data, the molecular
orbitals (MOs) and the electronic structures of 1-3 were
calculated at the HF level52 (see Tables S2-S4). The
electronic transitions were calculated with the ZINDO
semiempirical method from Gaussian 03.52 The results
for some low-lying excited states and the oscillator strengths
of the three complexes are listed in Table S5-S7, respec-
tively.
Figure 4. (a) Absorption (measured in CH2Cl2 solution) and (b) reflection
spectra of spectrum 1, HSC6H4C(dO)NH2-2; 2, Ph3P; 3, Et3PAu[SC6H4C
(dO)NH2-2]; 4, Ph3PAu[SC6H4C(dO)NH2-2]; and 5, Cy3PAu[SC6H4C
(dO)NH2-2].
For 1-3, the combinations of the π-orbital of the benzene
ring and the nonbonding p-orbitals of the sulfur, oxygen,
and nitrogen atoms resulted in the HOMOs. The first HOMO,
h1, comprises one-nodal π-bonding orbital from the benzene
ring and the p-orbitals of the sulfur atom, each with different
parity, forming the antibonding character between the
benzene ring and the sulfur atom. The contributions of the
benzene ring and the sulfur atom were almost equal. The h2
HOMO was composed largely of another one-nodal π-bond-
ing orbital of the benzene ring as a main part, as well as a
contribution from the nonbonding p-orbitals of the oxygen,
nitrogen, and sulfur atoms. With h1, three additional HOMOs
were formed by the combination of the π-orbital of the
benzene ring and the nonbonding p-orbitals of the sulfur.
For 2, several low-energy HOMOs correspond to the
π-orbitals of the benzene rings in Ph3P. Minor contributions
from the π-orbitals of Ph3P were also made to some low-
Table 4. Emission and Excitation Data Et3PAu[SC6H4C(dO)NH2-2]
(1), Ph3PAu[SC6H4C(dO)NH2-2] (2), and Cy3PAu[SC6H4C(dO)NH2-2]
(3) in the Powdered State at T ) 10 Ka
excitation
emission
1
2
3
324 (vb), 356 (p)
321 (vb), 356 (p)
310 (vb), 365 (m), 440 (p)
503 (p), 563 (sh)
492 (p), 545 (sh)
457 (m), 503 (p), 556 (sh)
a vb ) very broad, p ) peak, sh ) shoulder, m ) medium.
at the three temperatures. The PL spectrum resolved into
two Gaussian components, peaking at 500 and 566 nm,
respectively. The 500 nm band is a main emission component
(hereafter, referred to as ME). The excitation spectra of these
two components were also measured at 10 K. As shown in
Figure 5b, a sharpened 350 nm peak appeared with a weak
400 nm peak and a broad band as a high-energy shoulder.
The 350 nm peak corresponds to the C absorption band, and
the weak 400 nm band could be the B absorption. Data are
summarized in Table 4.
The spectral features of Ph3PAu[SC6H4C(dO)NH2-2] (2)
are very similar to those of 1, but the bands are blue-shifted,
see Figure 5c and d. The PL spectrum was also resolved
into two components: the 483 nm band as ME and a weak
and broad 545 nm band as a shoulder. As shown in Figure
5d, the excitation spectra of these two components measured
at 10 K are also very similar to those of 1. The excitation
spectrum of the main emission comprises a sharpened
component at 356 nm and a high-energy shoulder.
(52) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb,
M. A.; Cheeseman, J. R.; Montgomery, J. A., Jr.; Vreven, 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.; Bakken, V.; 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, revision C.02; Gaussian, Inc.: Wallingford,
CT, 2004.
In contrast to the above, the PL spectral shape of Cy3-
PAu[SC6H4C(dO)NH2-2] (3) is very different and is de-
8234 Inorganic Chemistry, Vol. 46, No. 20, 2007

Triorganophosphinegold(I) 2-Mercaptobenzamides
Figure 5. (a) PL at T ) 10 K (spectrum 1), 78 K (2), and RT (3) and (b) excitation at T ) 10 K: λems ) 497 (spectrum 1) and 585 nm (2) spectra of
Et3PAu[SC6H4C()O)NH2-2] (1). (c) PL at T ) 10 K (spectrum 1), 78 K (2), and RT (3) and (d) excitation at T ) 10 K: λems ) 490 (spectrum 1) and 573
nm (2) spectra of Ph3PAu[SC6H4C(dO)NH2-2] (2);. (e) PL at T ) 10 K (spectrum 1), 50 (2), 78 (3), 100 (4), 120 (5), 140 (6), and 160 K (7) and (f)
excitation at T ) 10 K: λems ) 470 (spectrum 1), 503 (2), and 574 nm (3) spectra of Cy3PAu[SC6H4C(dO)NH2-2] (3).
energy HOMOs of mercaptobenzamide. The first two lowest
unoccupied molecular orbitals (LUMOs) correspond to the
empty pz- and py-orbitals of the gold atom, nearly perpen-
dicular to the S-Au-P molecular axis. For 1 and 2, the l1
LUMO is composed of the pz of gold as the main component
with the px-orbital as a minor component, while the l2 LUMO
is composed of the py of the gold atom as the main
component. For 3, the l1 LUMO is composed of not only
the pz- and px-orbitals but also the py-orbital of gold with
the contribution of the pz-orbital the greatest and the px-orbital
the least. The l2 is characterized by the linear combination
of the py- and pz-orbitals of gold. For 1 and 3, the next several
LUMOs were filled by the π*-bonds of benzene ring of
amide and the p-orbitals of sulfur with minor contributions
from gold. For 3, the next several LUMOs correspond
primarily to the π*-orbitals of the benzene ring in the
triphenylphosphine moiety. The π*-orbitals of the benzene
ring in the mercaptobenzamide moiety appear at slightly
higher energy levels. The electron density isocontours of the
HOMOs and LUMOs of the Au(I) complexes are shown in
Figure 6.
The simulated absorption spectra of a single, gas-phase
molecules produced three distinguishable bands (see Figure
S3). If one assumes that there is a 120 nm red-shift for the
liquid phase, those bands are in agreement with the observed
A, B, and C absorption of the liquid phase. The calculated
excited states (listed in Tables S5-S7) can be also classified
to three groups, and these groups are responsible for the A,
B, and C absorption bands, respectively. For 1 and 2, the
first four excited states (1A-4A) are involved in the A
absorption band. The first 1A excited state corresponded to
Figure 6. Contour plots of the highest- and lowest-energy molecular
orbitals for (a) Et3PAu[SC6H4C(dO)NH2-2] (1), (b) Ph3PAu[SC6H4C(d
the intraligand transitions of the amide group. However, the
oscillator strength of the transition from the ground state to
1A is almost negligible. The 2A, 3A, and 4A states arose
from the h1,h3 f l1 or h1 f l2 transitions. For the A band,
O)NH2-2] (2), and (c) Cy3PAu[SC6H4C(dO)NH2-2] (3).
the transition from the X ground state to the 4A excited state
is predominant, compared with the transitions to the 2A and
Inorganic Chemistry, Vol. 46, No. 20, 2007 8235

Kang et al.
3A. According to the atomic charges determined from the
Mulliken population analysis, for the X f 4A transition of
1, the changes of the atomic charges of gold, sulfur, and
carbon atoms of the benzene ring are +0.61, -0.30, and
-0.12, respectively. For the X f 4A transition of 2, the
charge of gold was increased by 0.62, while the charges of
sulfur and the benzene ring were decreased by 0.29 and 0.11,
respectively. This result indicated that the A-absorption band
was associated with electronic transitions of the lone-pair
electrons of sulfur to gold as a main part and π-electrons of
benzene ring to gold as a minor. In contrast with the cases
of 1 and 2, the 4A excited-state of 3 is not close to the 3A
state but rather to the 5A state (see Figure S3c), so that the
4A excited state is involved in the B absorption band. For
3, the X f 3A transitions with f ) 0.124 is predominant
and responsible for the A absorption band. This transition
corresponds to the h1 f l2 charge transfer from sulfur to
gold. For the B band of 1, two transitions were found to be
predominant with f ) 0.136 and 0.216, respectively (see
Table S5). Both of these two excited states arose mainly from
the h6 and h7 to l1 transitions. Here, the h7 HOMO was
contributed from s- and d-orbitals of gold (57%) and the
lone-pair electrons of phosphorus (31%). The changes in the
atomic charges of gold, sulfur, and the π-orbital of the
benzene ring are 0.42, -0.12, and -0.12, respectively, for
the former transition, and 0.55, -0.13, and -0.15, respec-
tively, for the latter transition. Although the contribution of
phosphorus to h7 is large, the changes of the atomic charge
of phosphorus for the two transitions are -0.04 and -0.08,
respectively. Accordingly, the B absorption band can be
attributed primarily to the charge transfers to gold from sulfur
and the benzene ring and to a lesser extent from phosphorus
and oxygen. Similarly, for 2 and 3, the largest transition
probability in the B-absorption band was found in the charge-
transfer transition. For the C-band, several transitions have
relatively large probabilities. For 1, the transition with the
largest probability of f ) 0.895 was associated with the π
f π* transitions of benzene ring as a main part and the
charge transfer from sulfur to gold as a minor part. For this
transition, the charges of gold and sulfur were changed by
0.17 and -0.16, respectively. The transition with the second
largest oscillator strength of f ) 0.244 corresponds to the
charge transfer from the sulfur atom and the benzene ring
to gold. The changes in the atomic charges of gold, sulfur,
and the π-orbital of benzene ring are 0.49, -0.11, and -0.10,
respectively. Accordingly, the C absorption band can be
characterized by the π f π* transitions of benzene ring
mainly with the charge transfers. In contrast with 1 and 3,
complex 2 has other π-electron systems, that is, in Ph3P.
The charge transfers from the Ph3P moieties to gold were
also found to contribute the transition probabilities to the
C-absorption band.
excited states is associated with the l1 and l2 LUMOs,
composed of the three p-orbitals of gold. Therefore, the
observed spectral features can be interpreted in terms of the
relaxed excited states (RESs) of Au(I). The vibronic interac-
tions (VIs) are very important in understanding electronic
spectra if they are of suitable magnitude. The linear vibronic
interaction, known as the dynamic Jahn-Teller effect (JTE),
can be estimated from the observed excitation and lumines-
cence spectra. Because the dynamic JT energy, EJT, is half
the Stoke’s shift, EJT is 4290 cm-1 for 1, 2600 cm-1 for 2,
and 1810 cm-1 for 3. These strong JTE values indicated that
the RESs of Au(I) can be formulated in terms of the vibronic
interactions.
For 1 and 2, the l1-orbital is the linear combination of the
px- and pz-orbitals, and the l2-orbital is predominantly the
py-orbital of gold. The 2A and 4A excited states adapt the
l1-orbital in the main, and the 3A adapts l2. Here, the energy
gap between the 3A and the 4A states is only 0.04 eV,
indicating that these two states are nearly degenerate. The
VI of the 2-fold electronic states coupling to the bending
mode (known as the Renner-Teller effect) is of primary
importance for three-atom linear molecules. Upon bending,
the VI can lead to splitting of the 2-fold states into symmetric
A′ state as a lower level and antisymmetric A′′ electronic
state as a higher level, respectively, with respect to reflection
in the molecular plane (xz). As shown in Figure 6a and b,
the l1 and l2 MOs are symmetric and antisymmetric,
respectively, with respect to the reflection. Accordingly, the
4A state becomes A′ and the 3A state A′′. For 1 and 2, upon
the C-band excitation the A′(4A) level gains the population
mainly via the nonradiative relaxation and produces the
strong ME, while the lowest A′(2A) level produces the weak
luminescence as the low-energy shoulder.
For 3, the l1 and l2 orbitals, containing the py component
are perpendicular to the molecular plane, as shown in Figure
6c. The VI coupling to the bending mode can lead the 2A
and 3A excited states to two A′′ RESs. The energy gap
between the 2A and 3A is 0.29 eV, indicating that these two
levels separated from each other. Accordingly, the A′′(2A)
and A′′(3A) RESs are responsible for the weak low-energy
and the main luminescence, respectively. The 457 nm high-
energy luminescence of 3, which was not observed for the
other two complexes, could be associated with the 4A excited
state. This state arose from the charge transfer from sulfur
(h4) to Au (l1) and the energy gap between this state and
the 3A state is ∼1.0 eV. The A′′(4A) parabola could be
apparently separated from the A′′(3A) parabola and may give
rise to the high-energy band with the characteristic band
shape observed for 3.
Acknowledgment. We gratefully acknowledge The Uni-
versity of Adelaide for a Postgraduate Research Award
(D.R.S.) and the Australian Research Council for support
of the X-ray facility. We thank Mr. Phil Clements for expert
assistance with some of the 2D NMR experiments. This
thermal decomposition work was supported by KOSEF
research project R01-2001-00055. J.G.K. and H.K.C. ac-
knowledge Alti-electronic Co. for financial support.
Assignment of Luminescence. Given that the observed
luminescence of the complexes was produced by the charge
transfer from the sulfur and the π-orbitals of the mercapto-
benzamide moiety to the first two LUMOs of each complex,
the A-band excited states is responsible for the observed
luminescence: 2A-4A for 1 and 2 and 2A-3A for 3. These
8236 Inorganic Chemistry, Vol. 46, No. 20, 2007

Triorganophosphinegold(I) 2-Mercaptobenzamides
Supporting Information Available: Crystallographic informa-
tion files for structures 1-3, tables of H NMR data, calculated
HF molecular orbitals, and CI excited states with high oscillator
and simulated absorption spectra for single gas-phase molecules
of 1-3. This material is available free of charge via the Internet at
http://pubs.acs.org.
1
strength and predominant transitions for 1-3, and figures showing
solvent dependence of H spectra for 3, unit cell diagram for 3,
1
IC701022E
Inorganic Chemistry, Vol. 46, No. 20, 2007 8237