Synthesis, structural characterization, photophysical properties and theoretical analysis of gold(I) thiolate-phosphine complexes

Article abstract of DOI:10.1039/c1dt10437c

A series of luminescent dinuclear neutral complexes of stoichiometry [(AuSPh)₂(PPh₂-(C₆H₄) _n-PPh₂)] (n = 1, 2, 3) as well as their tetranuclear cationic derivatives [(Au₂SPh)₂(PPh₂-(C ₆H₄)_n-PPh₂)₂](PF ₆)₂ are reported. Their crystal structures have been elucidated by X-ray studies. These studies indicate that, for the dinuclear species, only when n = 1 the molecules exhibit intermolecular aurophilic interactions. None of the tetranuclear species crystallizes in their molecular form, due to the formation of aggregates through Au...Au interactions. The origin of the luminescence has been analyzed by computational studies indicating that the presence or absence of aurophilic interactions does not affect the luminescent behavior and that intraligand charge transfer processes which involve the thiolate and the diphosphine are responsible for the emissions. The result is in contrast with the thiolate-gold charge transfer processes which dominate the photophysics of gold-thiolate compounds and reveals the influence of the phenylene spacers in the emissive behavior of these compounds.

Full text of DOI:10.1039/c1dt10437c

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PAPER
Synthesis, structural characterization, photophysical properties and
theoretical analysis of gold(I) thiolate-phosphine complexes†
Igor O. Koshevoy,*a Ekaterina S. Smirnova,a,b Matti Haukka,a Antonio Laguna,*b Jessica Camara Chueca,b
Tapani A. Pakkanen,a Sergey P. Tunik,*c Isaura Ospinob and Olga Crespob
Received 15th March 2011, Accepted 5th May 2011
DOI: 10.1039/c1dt10437c
A series of luminescent dinuclear neutral complexes of stoichiometry [(AuSPh)2(PPh2-(C6H4)n-PPh2)] (n
= 1, 2, 3) as well as their tetranuclear cationic derivatives [(Au2SPh)2(PPh2-(C6H4)n-PPh2)2](PF6)2 are
reported. Their crystal structures have been elucidated by X-ray studies. These studies indicate that, for
the dinuclear species, only when n = 1 the molecules exhibit intermolecular aurophilic interactions.
None of the tetranuclear species crystallizes in their molecular form, due to the formation of aggregates
through Au ◊ ◊ ◊ Au interactions. The origin of the luminescence has been analyzed by computational
studies indicating that the presence or absence of aurophilic interactions does not affect the luminescent
behavior and that intraligand charge transfer processes which involve the thiolate and the diphosphine
are responsible for the emissions. The result is in contrast with the thiolate–gold charge transfer
processes which dominate the photophysics of gold-thiolate compounds and reveals the influence of the
phenylene spacers in the emissive behavior of these compounds.
clusters.1,4,7,9,26–28 Additionally, Au ◊ ◊ ◊ Au interactions, which often
Introduction
govern formation of the fascinating supramolecular structures,
The chemistry of gold(I) thiolate complexes has been extensively
were found for many gold(I)-sulfur compounds both in the solid
state and solution.8,18,29,30
studied for decades. These continuing investigations have been
stimulated by the general academic interest to this structurally
versatile class of compounds,1–10 demonstrating rich photophysical
properties over a wide range of the visible spectrum.9,11–20 Acces-
sible modification of the organic functionalities of S-containing
ligands and effectiveness of formation of gold(I)thiolate complexes
allowed for the preparation of certain materials and structures on
their basis,7,19,21 as well as successful applications in the areas of
medicine22 and chemosensing.10,23,24
The structural variations of the polynuclear gold(I) thiolates
arise, on the one hand, from the stereochemical diversity and
bridging coordination of S-atom of the thiols, including the di-
and tri-dentate ones.1,5–7,14,15,25,26 On the other hand, employment of
the multidentate ancillary ligands like phosphines gives additional
possibilities for the construction of polymetallic complexes and
According to the literature data, the photophysical character-
istics of the gold(I) thiolates containing phosphine ligands are
usually determined mainly by the ligand-to-metal (S"Au) charge
transfer, the variation of the emission band is associated with
the electron-withdrawing groups on the thiolate ligand and no
correlation exists between the magnitude of the Au ◊ ◊ ◊ Au distance
and the observed emission energy.9,11,20,31 Besides, it was noted that
despite most aromatic phosphine ligands being emissive species,
their intra-ligand luminescence does not appear, or appears only as
a trace in the high-energy side, compared with the main emission
originated from the S"Au charge transfer.9
Recently, we have been using tertiary diphosphines with
oligophenylene spacers, PPh2-(C6H4)n-PPh2 (n = 1, 2, 3),32,33 in
coordination chemistry of gold(I) alkynyl complexes. In order
to extend our work we intended to investigate the related
thiolate-diphosphine compounds—their structural arrangement
and photophysical behavior in the solid state and solution. Herein
we report synthesis, spectral and structural characterization, and
the photoluminescent studies of the novel digold complexes
[(AuSPh)2(PPh2-(C6H4)n-PPh2)] and their tetranuclear cationic
derivatives [(Au2SPh)2(PPh2-(C6H4)n-PPh2)2](PF6)2 (n = 1, 2, 3).
The latter compounds were found to form supramolecular aggre-
gate (n = 1) and polymeric structures (n = 2, 3) in the solid state. The
emissive characteristics of these compounds unexpectedly were
found to be mainly determined by metal perturbed intra-ligand
(IL) electronic transitions in the bridging phosphine ligands that
aUniversity of Eastern Finland, Joensuu, 80101, Finland. E-mail:
igor.koshevoy@uef.fi; Fax: +358 13 2513390; Tel: +358 13 2513325
bSt.-Petersburg State University, Department of Chemistry, Universitetskii
pr. 26, 198504, St.-Petersburg, Russia. E-mail: stunik@inbox.ru; Fax: +7
812 4283969; Tel: +7 812 4284028
cUniversidad de Zaragoza-CSIC, Instituto de Ciencia de Materiales de
Aragon, Departamento de Quimica Inorganica, E-50009, Zaragoza, Spain.
E-mail: alaguna@unizar.es; Fax: + 34 976 761187; Tel: + 34 976 761185
† Electronic supplementary information (ESI) available: X-ray crystal-
lographic data in CIF for 1–6, 1H-1H COSY spectra of 1–6, ESI-mass
spectra of 4–6, the geometry of the modeled complex 4. CCDC reference
numbers 817752-817757. For ESI and crystallographic data in CIF or
other electronic format see DOI: 10.1039/c1dt10437c
7412 | Dalton Trans., 2011, 40, 7412–7422
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is in contrast with interpretation of the data obtained earlier for
other gold(I) thiolate-phosphine complexes.
[(AuSPh)2(4,4¢¢-PPh2(C6H4)3PPh2)] (3)
Prepared analogously to 1 using PPh2(C6H4)3PPh2 instead of
1
PPh2C6H4PPh2. Yield: 94%. 31P{ H} NMR (CDCl3; d): 37.8 (s).
1H NMR (CDCl3; d): Ph-thiolate ligand: 7.65 (d, ortho-H, J =
7.8 Hz, 4H), 7.01 (t, para-H, J = 7.3 Hz, 2H), 7.13 (m, meta-H,
J = 7.3, 7.8 Hz, 4H); diphosphine: 7.76–7.68; 7.62–7.49 (m, 32H).
Anal. Calc. for C54H42Au2P2S2: C, 53.56; H, 3.50; S 5.30. Found:
C, 53.69; H, 3.41; S 5.58.
Experimental
General comments
[AuCl(tht)],34 (AuSPh)n,35 PPh2(C6H4)nPPh2 (n = 1, 2, 3),33,36
[Au2(PPh2(C6H4)nPPh2)2](PF6)2 (n = 1, 2, 3)32,37 were synthesized
according to published procedures. Other reagents and solvents
were used as received. Solution 1H and 31P NMR spectra
were recorded using Bruker Avance 400 and Bruker DPX 300
spectrometers. The chemical shifts (d, ppm) were referenced to
residual solvent resonances and external 85% H3PO4 in the 1H and
31P spectra, respectively. The 2D COSY spectra were run using
standard Bruker pulse sequence. Mass spectra were determined
on a Bruker APEX-Qe ESI FT-ICR instrument, in the ESI+
mode, solvent CH2Cl2. Microanalyses were carried out in the
analytical laboratory of St.-Petersburg State University. UV-Vis
spectra were recorded on a Shimadzu UV 3600 spectropho-
tometer. DRUV spectra were recorded using an EVOLUTION
600 spectrophotometer equipped with a Praying Mantis diffuse
reflectance accessory. Solid state samples were mixed with silica.
The intensities were recorded in Kubelka-Munk units. Steady-
state photoluminescence spectra were recorded with a Jobin-Yvon
Horiba Fluorolog FL-3-11 spectrometer using band pathways of
3 nm for both excitation and emission. The lifetimes were measured
using a Fluoromax phosphorimeter accessory containing a UV
xenon flash tube. The lifetime data were fit using the Jobin-Yvon
software package38 and the Origin 5.0 program.39
[(Au2SPh)2(1,4-PPh2C6H4PPh2)2](PF6)2 (4)
The following reactions were carried out under nitrogen atmo-
sphere.
Method A. (AuSPh)n (28 mg, 0.092 mmol) was suspended in
CH2Cl2 (10 cm3) and [Au2(PPh2C6H4PPh2)2](PF6)2 (71 mg, 0.045
mmol) was added. The reaction mixture was stirred overnight in
the absence of light to give nearly transparent pale-yellowish solu-
tion. It was filtered and evaporated. Repetitious recrystallization
from CH2Cl2/acetone/heptane mixture at room temperature gave
colorless crystals of 4, which were collected, washed with diethyl
ether and vacuum dried. Yield: 65 mg, 66%.
Method B. Au(tht)Cl (32 mg, 0.1 mmol) was dissolved in CH2Cl2
(10 cm3) and PPh2C6H4PPh2 (22.5 mg, 0.05 mmol) was added.
The colorless transparent reaction mixture was stirred for 10 min
and a solution of AgPF6 (25.5 mg, 0.1 mmol) was added causing
immediate precipitation of AgCl. The suspension was stirred
for an additional 30 min, filtered and added to a solution of
1 (53 mg, 0.05 mmol) in CH2Cl2 (10 cm3). The pale-yellowish
reaction mixture was stirred for 3 h in the absence of light and then
further treated as in method A. Yield: 76 mg, 70%. ES MS (m/z):
[(Au2SPh)2(PPh2C6H4PPh2)2]2+ 949.1 (calcd 949). 31P{ H} NMR
1
(CD2Cl2; d): 36.0 (s), -143.0 (sept, 2P, PF6). 1H NMR (CD2Cl2; d):
Ph-thiolate ligand: 7.58 (4H, m, ortho protons), 7.23–7.31 (6H, AB
system of meta and para protons); diphosphine: 7.26 (8H, protons
of phenylene spacer, A2¥2 system, J(H-H) ca. 7 Hz, J(P-H) ca.
15 Hz), 7.60 (8H, t, para-H, J(H-H) ca. 7 Hz), 7.42 (16 H, m,
meta-H, J(H-H) ca. 7 Hz), 7.48 (16H, m, ortho-H, J(H-H) ca. 7
Hz, J(P-H) ca. 13 Hz). Anal. Calc. for C72H58Au4F12P6S2: C, 39.50;
H, 2.67; S 2.93. Found: C, 39.44; H, 2.59; S 2.77.
[(AuSPh)2(1,4-PPh2C6H4PPh2)] (1)
(AuSPh)n (137 mg, 0.448 mmol) was suspended in CH2Cl2 (15 cm3)
and slight excess of 1,4-PPh2C6H4PPh2 (108 mg, 0.242 mmol) was
added. The reaction mixture was stirred for 1.5 h in the absence of
light to give nearly transparent colorless solution. It was passed
through a layer of silica (2 cm) and evaporated. Recrystallization
from CH2Cl2/benzene/heptane mixture at +5 ◦C gave crystalline
pale-yellowish solid, which was collected, washed with pentane
[(Au2SPh)2(4,4¢-PPh2(C6H4)2PPh2)2](PF6)2 (5)
1
and vacuum dried. Yield: 210 mg, 89%. 31P{ H} NMR (CDCl3;
Prepared analogously to 4 (method A) using [Au2(PPh2(C6H4)2-
PPh2)2](PF6)2 instead of [Au2(PPh2C6H4PPh2)2](PF6)2. Yield: 71%
(method B 75%). ES MS (m/z): [(Au2SPh)2(PPh2(C6H4)2PPh2)2]2+
1
d): 38.1 (s). H NMR (CDCl3; d): Ph-thiolate ligand: 7.62 (d,
ortho-H, J = 7.7 Hz, 4H), 7.01 (t, para-H, J = 7.3 Hz, 2H), 7.12
(m, meta-H, J = 7.3, 7.7 Hz, 4H); diphosphine: 7.60–7.50 (m, 24H).
Anal. Calc. for C42H34Au2P2S2: C, 47.65; H, 3.24; S 6.06. Found:
C, 47.75; H, 3.25; S 6.42.
1
1025.1 (calcd 1025). 31P{ H} NMR (CD2Cl2; d): 35.8 (s), -143.0
(sept, 2P, PF6). 1H NMR (CD2Cl2; d): ABC system of Ph-thiolate
ligand with the signal centered at: meta-H 7.30 (4H), para-H
7.41 (2H), ortho-H 7.43 (4H); diphosphine: 7.73 and 7.42 (m, -
P(C6H4)2P- 16H), 7.64 and 7.47–7.56 (m, PPh2, 40H). Anal. Calc.
for C84H66Au4F12P6S2: C, 43.09; H, 2.84; S 2.74. Found: C, 43.03;
H, 3.02; S 2.55.
[(AuSPh)2(4,4¢-PPh2(C6H4)2PPh2)] (2)
Prepared analogously to 1 using PPh2(C6H4)2PPh2 instead of
1
PPh2C6H4PPh2. Yield: 95%. 31P{ H} NMR (CDCl3; d): 37.9 (s).
[(Au2SPh)2(4,4¢¢-PPh2(C6H4)3PPh2)2](PF6)2 (6)
1H NMR (CDCl3; d): Ph-thiolate ligand: 7.64 (d, ortho-H, J =
7.8 Hz, 4H), 7.01 (t, para-H, J = 7.3 Hz, 2H), 7.12 (m, meta-H,
J = 7.3, 7.8 Hz, 4H); diphosphine: 7.71–7.66; 7.60–7.49 (m, 28H).
Anal. Calc. for C48H38Au2P2S2: C, 50.80; H, 3.38; S 5.65. Found:
C, 50.74; H, 3.39; S 5.84.
Prepared analogously to 4 (method A) using [Au2(PPh2(C6H4)3-
PPh2)2](PF6)2 instead of [Au2(PPh2C6H4PPh2)2](PF6)2. Yield: 84%
(method B 91%). ES MS (m/z): [(Au2SPh)2(PPh2(C6H4)3PPh2)2]2+
1
1101.1 (calcd 1101). 31P{ H} NMR (CD2Cl2; d): 35.5 (s), -143.0
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(sept, 2P, PF6). 1H NMR (CD2Cl2; d): Ph-thiolate ligand: 7.73 (4H,
dd, ortho protons, J(H-H) ca. 8 and 1.4 Hz), 7.34–7.42 (6H, AB
system of meta and para protons); diphosphine: 7.39 (8H, s, protons
of central phenylene spacer), 7.62 (8H, A2¥2 m, ortho-protons of
P-C6H4 spacers, J(H-H) ca. 7 Hz, J(P-H) ca. 14 Hz), 7.48 (8H,
d, meta-H of P-C6H4 spacers, J(H-H) ca. 7 Hz), 7.44–7.56 (40 H,
unresolved m, PC6H5). Anal. Calc. for C96H74Au4F12P6S2: C, 46.24;
H, 2.99; S2.57. Found: C, 46.32; H, 3.05; S 2.75.
between C109 and O5 was fixed to 1.15 A. Also, C109–C110
and C109–C111 bond lengths as well as anisotropic displacement
parameters of C109, C110, C111, and O5 were set to be equal.
Acetone carbon C105 was restrained so that its Uij components
approximate to isotropic behavior. The OH hydrogen atom in 6
was located from the difference Fourier map but constrained to
ride on its parent atom, with Uiso = 1.5. Other hydrogens in all other
structures were positioned geometrically and constrained to ride
˚
˚
on their parent atoms, with C–H = 0.95–0.99 A and Uiso = 1.2–1.5
U
eq (parent atom). The crystallographic details are summarized in
X-Ray diffraction studies
the corresponding footnote‡ and Table S1†.
The crystals of 1–6 were immersed in cryo-oil, mounted in a
Nylon loop, and measured at a temperature of 100 K. The X-
ray diffraction data were collected on a Nonius KappaCCD
Computational details for DFT and TD-DFT calculations
The molecular coordinates used in the theoretical studies of
(1–6) were obtained from the X-ray diffraction data and for
the complex 4 [(Au2SPh)2(1,4-PMe2C6H4PMe2)2](PF6)2 used as
a model. This model was chosen to represent the experimental
geometry by substituting from the X-ray diffraction structure
the C6H5 rings by CH3 group, to keep the computational cost
feasible. In both the ground-state calculations and the subsequent
calculations of the electronic excitation spectra, the B3LYP
functional48 as implemented in Gaussian49 was used. The two first
triplet transitions were calculated within the TDDFT formalism as
implemented in Gaussian. The excitation energies were obtained at
the density functional level using the time dependent perturbation
theory approach (TDDFT), which is a DFT generalization of the
˚
diffractometer using Mo-Ka radiation (l = 0.710 73 A). The
Denzo-Scalepack40 or EvalCCD41 program packages were used
for cell refinements and data reductions. The structures were
solved by direct methods using the SHELXS-97,42 SIR97,43
or SUPERFLIP44 programs with the WinGX45 graphical user
interface. A semi-empirical absorption correction (SADABS)46
was applied to all data. Structural refinements were carried out
using SHELXL-97.42 The anisotropic displacement parameters of
the adjacent carbon atoms in the phenyl rings were restrained
to be similar. In 1 the geometry of CH2Cl2 solvent molecule
was restrained by fixing C–Cl and Cl–Cl distances. The CH2Cl2
carbon (C45) was further restrained so that its Uij components
approximate to isotropic behavior. The crystal of 2 was found to
be twinned via a 180◦ rotation about the direct axis (1,0,0). The
two components were determined using the ROTAX47 program
and the BASF value was refined to 0.29. The asymmetric unit of
2 contains two benzenes, of which one is disordered over two sites
with occupancies 0.61 and 0.39. A rigid bond restraint was applied
to all carbon atoms of the disordered benzene molecules. The
anisotropic displacement parameters in the direction of the bond
were restrained to be equal within an s.u. of 0.01. Furthermore,
carbon atoms C55A, C55B, and C42 were restrained so that their
Uij components approximate to isotropic behavior. Due to the
poor data quality the structure of 2 is used solely as supporting
material. In 4 the fluorine atoms of the PF6- anions were disordered
over two sites with occupancy ratio 0.65/0.35. The fluorine atoms
were refined with equal anisotropic displacement parameters. One
of the acetone solvent molecules was also disordered over two
sites with occupancies 0.53/0.47. Furthermore, one of the phenyl
rings was disordered over two sites. The carbon atoms of the
‡ Crystal data for 1: C90H81Au4Cl6P4S4, M = 2415.23, colourless plate, 0.42
3
¯
¥ 0.20 ¥ 0.14 mm , triclinic, space group P1, a = 16.7048(6), b = 16.7988(4), c
◦
˚
= 16.8964(6) A, a = 78.948(2), b = 68.399(2), g = 79.416(2) , V = 4293.4(2)
3
-3
˚
˚
A , Z = 2, Dc = 1.868 g cm , F000 = 2326, Mo-Ka radiation, l = 0.71073 A,
T = 100(2)K, 2qmax = 55.0◦, 76565 reflections collected, 19581 unique (Rint
= 0.0448). Final GooF = 1.029, R1 = 0.0478, wR2 = 0.1223, R indices based
on 15643 reflections with I > 2s(I) (refinement on F2), 975 parameters,
9 restraints; wR2 = 0.1380 (all data).Crystal data for 3: C72H60Au2P2S2, M
= 1445.19, colourless plate, 0.46 ¥ 0.17 ¥ 0.14 mm3, triclinic, space group
¯
˚
P1, a = 12.0886(3), b = 15.6319(4), c = 16.4470(4) A, a = 96.8910(10), b =
◦
3
-3
˚
99.389(2), g = 100.712(2) , V = 2976.45(13) A , Z = 2, Dc = 1.613 g cm , F000
= 1424, Mo-Ka radiation, l = 0.71073 A, T = 100(2)K, 2qmax = 55.0◦, 51042
˚
reflections collected, 13495 unique (Rint = 0.0490). Final GooF = 1.061, R1
= 0.0332, wR2 = 0.0616, R indices based on 10215 reflections with I >
2s(I) (refinement on F2), 703 parameters, 0 restraints; wR2 = 0.0709 (all
data)Crystal data for 4: C162H152Au8F24O6P12S4, M = 4726.45, colourless
3
¯
block, 0.28 ¥ 0.15 ¥ 0.09 mm , triclinic, space group P1, a = 14.7817(2),
˚
b = 15.1252◦(2), c = 20.7653(2) A, a = 85.5220(10), b = 87.6520(10), g =
3
-3
˚
60.9750(10) , V = 4047.13(9) A , Z = 1, Dc = 1.939 g cm , F000 = 2264,
Mo-Ka radiation, l = 0.71073 A, T = 100(2)K, 2qmax = 60.1◦, 85127
˚
reflections collected, 23604 unique (Rint = 0.0359). Final GooF = 1.077,
R1 = 0.0304, wR2 = 0.0628, R indices based on 19166 reflections with I
> 2s(I) (refinement on F2), 1014 parameters, 56 restraints; wR2 = 0.0676
(all data).Crystal data for 5: C43H35Au2Cl2F6P3S, M = 1255.51, colourless
disordered rings were constrained with fixed C–C bond lengths
◦
˚
and C–C–C angles (1.39 A and 120 respectively). The occupancies
were refined to 0.52/0.48. In 5 the CH2Cl2 solvent molecule was
disordered over two sites with equal occupancies. Furthermore,
the chlorine atoms in the second part of the CH2Cl2 molecule were
disordered over three sites with occupancies 0.24/0.13/0.13. Also,
all non-hydrogen atoms of the disordered CH2Cl2 molecules were
restrained so that their Uij components approximate to isotropic
behavior. One of the phenyl rings (C7–C17) was also disordered
over two sites with occupancies 0.51/0.49. All phenyl rings were
slightly disordered and therefore the carbon atoms were fitted
3
¯
block, 0.18 ¥ 0.13 ¥ 0.08 mm , triclinic, space group P1, a = 12.4289(9), b◦=
˚
14.5787(11), c = 14.9984(11) A, a = 64.147(2), b = 81.263(2), g = 71.597(3) ,
3
-3
˚
V = 2320.3(3) A , Z = 2, Dc = 1.797 g cm , F000 = 1200, Mo-Ka radiation, l
= 0.71073 A, T = 100(2)K, 2qmax = 55.3◦, 30867 reflections collected, 10607
˚
unique (Rint = 0.0413). Final GooF = 1.040, R1 = 0.0527, wR2 = 0.1304,
R indices based on 7573 reflections with I > 2s(I) (refinement on F2),
440 parameters, 148 restraints; wR2 = 0.1440 (all data).Crystal data for
6: C217H202Au8Cl4F24O9P12S4, M = 5627.20, colourless block, 0.26 ¥ 0.12
3
¯
¥ 0.10 mm , triclinic, space group P1, a = 13.3559(14), b◦= 19.399(2), c =
˚
21.065(3) A, a = 85.626(11), b = 89.917(8), g = 78.127(10) , V = 5324.8(11)
3
-3
˚
˚
˚
A , Z = 1, Dc = 1.755 g cm , F000 = 2736, Mo-Ka radiation, l = 0.71073 A,
T = 100(2)K, 2qmax = 50.5◦, 68671 reflections collected, 18105 unique (Rint
= 0.0363). Final GooF = 1.072, R1 = 0.0459, wR2 = 0.1135, R indices based
on 15295 reflections with I > 2s(I) (refinement on F2), 1235 parameters,
9 restraints; wR2 = 0.1226 (all data).
to a regular hexagon with C–C distance of 1.39 A. In a crystal
of 6 the solvent molecules were partially lost. One of the acetone
molecules (C104–106, O4) was disordered over two sites with equal
occupancies 0.5. In the second acetone molecule the C–O distance
7414 | Dalton Trans., 2011, 40, 7412–7422
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Hartree–Fock linear response (HF-LR) or random-phase approx-
imation (RPA) method.50 The TDDFT do not take into account
the spin–orbit splitting. In all calculations, the Karlsruhe split-
valence-quality basis sets augmented with polarization functions
were used (SVP) for C, H atoms and TZVP for S and P atoms.51
The Stuttgart effective core potential was used for Au.52
Elemental analysis of 1–3 and NMR spectroscopic data of
these complexes are compatible with the structure suggested in
1
Scheme 1. The 1D H and COSY spectra of 1–3 (see Figures
S1–S3, Supporting Information†) display well separated high field
signals of meta-(ca. 7.1 ppm) and para-(ca. 7.0 ppm) protons of the
phenylthiolate ligand together with the doublet of ortho-protons
(ca. 7.6 ppm) in the low field part of the spectra. The latter signals
are masked by the resonances of the phosphine ligand protons in
the 1D spectrum but are clearly resolved in the corresponding 2D
COSY spectra. Quite expectedly the positions of these signals are
nearly identical in 1–3 because of the minor effect of the number
of phosphine ligand spacers onto shielding of the thiolate ligand
protons. Aromatic protons of the phosphine ligands generate a
poorly resolved set of signals in the 7.8–7.45 ppm range that
correlates well with the 1H spectroscopic data obtained for closely
analogous binuclear gold(I) alkynyl-phosphine complexes.32,33 The
relative intensities of the thiolate and phosphine proton signals in
the 1H NMR spectra are in complete agreement with the suggested
molecular structure.
Results and discussion
Synthesis
Reactions of gold(I) phenyl-thiolate polymer with slight excess of
the corresponding diphosphine afford binuclear neutral thiolate-
diphosphine complexes 1–3 in excellent yield, see Scheme 1. This
mild synthetic procedure53 analogous to that commonly used
in silver(I) chemistry54 is an effective alternative to the widely
employed metathetical reaction of phosphine gold(I) chloride and
thiol in the presence of a deprotonation agent11,15–17,24,55–57 or the
reaction of a thiol with a Au(acac)(phosphine) complex, known
as the “acac method”.2,56,58
X-ray crystallographic study of 1–3 revealed that the structure
shown in Scheme 1 is retained in the crystal cell. The solid state
structures of these compounds together with selected structural
parameters are shown in Fig. 1, 2, S4†. Poor diffraction of the
crystals of 2 didn’t allow for high-quality refinement, therefore
these crystallographic data are used as supporting material only.
The complexes 2 and 3 exist in crystalline state as independent
isolated molecules and do not show any intermolecular aurophilic
contacts typical for gold(I) complexes.60,61 In contrast to these
structural patterns the solid state structure of 1 shows the
Scheme 1 Synthesis of the complexes 1–3.
It has been already shown that neutral gold(I) thiolate-
phosphine complexes can be effectively oxidized, e.g., by Fc+
or add cationic coordinatively unsaturated metal centers to
form various polymetallic assemblies.8,27,56,59 Indeed, treatment
of the dimers 1–3 with stoichiometric amounts of Fc(PF6)
resulted in formation of the tetranuclear dicationic complexes
[(Au2SPh)2(PPh2(C6H4)nPPh2)2](PF6)2 (n = 1 (4), 2 (5), 3 (6)),
Scheme 2, method C. However, this preparative route was found
to be ineffective as the purification workup required tedious
recrystallization and gave the title compounds in relatively low
yields. Therefore we investigated other synthetic options, namely
depolymerization of (AuSPh)• with cationic diphosphine com-
plexes [Au2(PPh2(C6H4)nPPh2)2](PF6)2 (n = 1, 2, 3) or addition of
the labile species [{Au(SC4H8)}2PPh2(C6H4)nPPh2](PF6)2 (n = 1,
2, 3) generated in situ to the dimers 1–3 (Scheme 2, methods A
and B). These protocols afforded the same tetragold complexes
4–6 obtained via the oxidation process but in considerably higher
yields (66–91%).
˚
intermolecular Au-Au contacts (3.190 A) to form infinite “zig-zag”
chains as shown in Fig. 1. Local environment of gold(I) ions in 1–3
features essentially linear P-Au-S geometry with the Au-S and Au-
˚
P distances in the ranges 2.29–2.31 and 2.25–2.27 A, respectively. It
is worth noting that aurophilic bonding in the solid state structure
of 1 does not affect the molecular structural parameters within the
gold(I) environment.
˚
Fig. 1 Solid state structure of 1. Selected interatomic distances (A)
are: Au(1)–P(1) 2.271(2), Au(1)–S(1) 2.310(2), Au(2)–P(2) 2.257(2),
Au(2)–S(2) 2.302(2), Au(1)–Au(2) 3.1960(4), Au(1B)–P(1B) 2.267(2),
Au(1B)–S(1B) 2.309(2), Au(2B)–P(2B) 2.260(2), Au(2B)–S(2B) 2.308(2),
Au(1B)–Au(2B) 3.1901(5). Selected bond angles (◦) are: P(1)–Au(1)–S(1)
175.03(7), P(2)–Au(2)–S(2) 179.17(6), P(1B)–Au(1B)–S(1B) 173.06(7),
P(2B)–Au(2B)–S(2B) 179.35(7).
Elemental analysis and ESI mass-spectroscopic data (Figures
S5–S7†) for the complexes 4–6 indicate that these molecules
contain four gold(I) ions, which coordinate two diphosphine
and two thiolate ligands. The most probable molecular structure
Scheme 2 Synthesis of the complexes 4–6.
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Fig. 2 Solid state structure of 3. One of two independent molecules
˚
is shown. Selected interatomic distances (A) are: Au(1)–P(1) 2.251(1),
Au(1)–S(1) 2.290(1), Au(2)–P(2) 2.261(1), Au(2)–S(2) 2.299(1). Selected
bond angles (◦) are: P(1)–Au(1)–S(1) 176.64(4), P(2)–Au(2)–S(2) 179.20(4).
Fig. 4 Solid state structure of the complex 5. Counterions (PF6-) omitted
for clarity. Selected interatomic distances (A) are Au(1)–P(1) 2.267(3),
˚
Au(1)–S(1) 2.333(2), Au(1)–Au(2) 3.0368(5), Au(1)–Au(2) interchain
3.4373(6), Au(2)–P(2) 2.269(3), Au(2)–S(1) 2.336(2). Selected bond angles
(◦) are: P(1)–Au(1)–S(1) 177.1(1), P(2)–Au(2)–S(1) 176.65(9).
compatible with this stoichiometry is shown in Scheme 2. The 1D
and COSY proton NMR spectra of 4–6 (see Experimental and
Figs. S8–S10†) are in complete agreement with the presence
of one thiolate and one phosphine ligand per two Au(I) ions in
the dicationic molecule. In contrast to 1–3 the thiolate ligand
in 4–6 occupies a bridging position between two cations that
causes low field shift of the phenyl-thiolate resonances and their
overlapping with the signals of the phosphine ligands in 1D
spectra. Nevertheless, correlations observed in the 2D COSY
spectra allow for differentiation of two groups of multiplets and
their assignment to corresponding ligands.
Compounds 4–6 were also studied using X-ray crystallography.
Their solid state structures are shown Fig. 3–5. In contrast to 1–
3 none of the 4–6 complexes crystallize in their molecular form
due to formation of supramolecular aggregates, the structures of
which are dictated by a network of aurophilic interactions. In the
solid state structures of 4–6 it is possible to isolate a common
structural motif (Chart 1), which consists of four gold(I) ions
and two thiolate ligands brought together by Au-S bonding and
aurophilic interactions.
Chart 1 Schematic view of the {Au4P4(m-SPh)2} unit found in 4–6.
(SPh)2}(Ph2PC6H4PPh2)2Au2SPh]4+ an isolated tetracation shown
in Fig. 3. This structure can be considered as a result of
dimerization of the molecules shown in Scheme 2. Formation of
the {PhSAu2P2} and {Au4(SPh)2} structural patterns does not
change the linear geometry about the gold(I) centers, the P-Au-
S angles equal to 171.4◦ and 176.9◦ in the digold and 177.0◦ in
the tetragold fragments. The Au-Au distances found in the solid
˚
state structure of 4 (3.0130(2) A in {Au2} and 3.0846(2), 3.1505(2)
˚
A in {Au4} fragments) fall in the range of typical aurophilic
-
contacts.60,61
Fig. 3 Solid state structure of the complex 4. Counterions (PF6
)
˚
omitted for clarity. Selected interatomic distances (A) are Au(1)–S(1)
2.340(1), Au(1)–Au(2) 3.0130(2), Au(2)–P(1) 2.268(1), Au(2)–S(1)
2.336(1), Au(3)–P(2) 2.272(1), Au(3)–S(2) 2.340(1), Au(3)–Au(4¢)
3.0847(2), Au(3)–Au(4) 3.1505(2), Au(4)–P(3) 2.265(1), Au(4)–S(2)
2.339(1), Au(4)–Au(3¢) 3.0846(2). Selected bond angles (◦) are:
P(1)–Au(2)–S(1) 171.36(4), P(4¢)–Au(1)–S(1) 176.91(4), P(2)–Au(3¢)–S(2)
176.89(4), P(3)–Au(4)–S(2) 176.97(4).
In the case of 5 the {PhSAuPh2P(C6H4)2PPh2Au} units form
infinite chains, which in turn are bound to each other through
formation of the {Au4(SPh)2} fragments. These fragments cross-
link the chains to give the 2D supramolecular structure shown in
Fig. 4. The Au-Au distances bridged by the thiolate ligands (inside
˚
the chains) are substantially shorter (3.0368(5) A) compared to the
unsupported Au-Au contacts between the chains (3.4373(6) A),
˚
These gold(I) ions additionally coordinate four other ligands
thus accomplishing the corresponding structural pattern. This
structural motif was revealed earlier in a good deal of gold(I) thi-
olate complexes containing monophosphine and some bidentate
ligands of various nature,27,30,53,57,62 but it was mainly presented as
an isolated structural unit because of saturation of the metal ion
vacancies and ligand coordination functions. In a very few crystal
structures containing bidentate thiols this unit was found to be
incorporated into polymeric chains.6,63 In the case of 4 formation of
this structural pattern affords the [PhSAu2(Ph2PC6H4PPh2)2{Au4
which still could be considered as weak aurophilic bonds. Linear
geometry about the gold(I) centers remains unchanged to give the
values of P-Au-S angles very close to 177◦.
The solid state structure of
6 (Fig. 5) displays an-
other way of intermolecular aurophilic bonding to give an
infinite double stranded chain formed by the molecular
[(PhSAu2)(PPh2(C6H4)3PPh2)2(Au2SPh)]2+ units, which are bound
to each other by unsupported aurophilic contacts. These contacts
give rise to formation of the {Au4(SPh)2} units, which links
together the monomeric units of this chain. It is interesting that
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-
˚
Fig. 5 Solid state structure of the complex 6. Counterions (PF6 ) omitted for clarity. Selected interatomic distances (A) are Au(1)–P(4) 2.275(2),
Au(1)–S(1) 2.350(2), Au(1)–Au(2¢) 3.0169(5), Au(1)–Au(2) 3.0806(6), Au(2)–P(1) 2.276(2), Au(2)–S(1) 2.350(2), Au(2)–Au(1¢) 3.0168(5), Au(3)–P(2)
2.275(2), Au(3)–S(2) 2.352(2), Au(3)–Au(4) 3.0391(6), Au(3)–Au(4¢) 3.0767(6), Au(4)–P(3¢) 2.277(2), Au(4)–S(2¢) 2.358(2), Au(4)–Au(3¢) 3.0767(6). Selected
bond angles (◦) are: P(1)–Au(2)–S(1) 171.69(8), P(4)–Au(1)–S(1) 171.40(7), P(2)–Au(3)–S(2) 170.38(8), P(3)–Au(4)–S(2) 173.91(9).
in contrast to the structures of 4 and 5 the unsupported Au–
Au contacts (3.039 and 3.017 A) are shorter compared to those
are probably retained in solution in complexes 4–6, as shown in
Scheme 2.
˚
˚
bridged by thiolate ligands (3.077 and 3.081 A).
All the complexes are weakly luminescent in the fluid medium
both at 298 and 77 K. The 2, 5 and 3, 6 couples of com-
plexes show very similar excitation and emission patterns in
dichloromethane solution both at room and low temperature,
although the diphosphine Ph2P(C6H4)3PPh2 displays dual emis-
sion in dichloromethane solution at 298 K (see Table 1 and
Fig. 6). The room temperature emission spectra for these couples
of complexes display broad bands centered at 390 nm and 375
nm, respectively. Considerable magnitude of Stokes shift together
with the luminescence lifetime in microsecond domain point to a
phosphorescent nature of the emission.
Upon cooling the solutions down to 77 K the emission bands are
substantially red shifted, ca. 100 nm (500 cm-1) for 2, 5 and 170
nm (800 cm-1) for 3, 6, and transformed into the well resolved
vibronically structured bands with vibronic progression of ca.
1200 cm-1, typical for the excited states of aromatic systems. The
same phenomenon is observed for the free diphosphines, although
the vibronic structure is not so clearly resolved. Luminescence
Photophysics
Solution studies
The UV/vis spectra of the complexes 1–6 display absorption bands
between 237 and 305 nm (Figure S11†). The similar patterns
have been observed for other complexes with oligophenylene
spacers.32,33,64 Absorption bands near 300 nm have been attributed
to the promotion of an electron from s(Au-P) orbital to the
empty p* antibonding orbital located at the bridging phenylene
groups. Higher energy absorptions (below 250 nm) have been
assigned to the IL transitions. In addition, compound 6 displays
an absorption shoulder at 328 nm. Absorption bands at similar
energies have been mentioned in previous works9,12,65 for either
charge transfer processes (S"Au) or the presence of gold ◊ ◊ ◊ gold in-
teractions which, according to mass-spectroscopic measurements,
Fig. 6 Emission spectra of the complexes 2, 5 and 3, 6 and the diphosphines Ph2P(C6H4)nPPh2 (n = 2, 3) in dichloromethane at 298 K and 77 K.
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Table 1 Absorption, DRUV, excitation and emission data of diphosphine ligands and compounds 1–6a
298 K
77 K
c
Compound
l
abs /nm (10-5e, l mol-1 cm)
l
exc/nmb
l
em/nmb (t , ms)
l
exc/nmb
l
em/nmb
Solution
Ph2PC6H4PPh2
1
310
241, 330
365
275, 315
450
485
238 (1.12), 254 (0.67), 277sh (0.42),
305sh (0.15)
237 (14.1), 253 (6.8), 279sh (5.3),
303(sh) (2.7)
385d 525d
(307–370)f
4
240, 320
380
350e,d
487
270e, 350
[387, 407,
430]e
Ph2P(C6H4)2PPh2
2
250, 285
241
340
390
270, 340
270, 345
485
463, 495, 523
238(1.85), 253(0.94), 279sh (0.62),
304sh (0.41)
5
237(4.5), 253(2.2), 281sh (1.6),
304sh (0.91)
240, 330
390
270, 340
463, 495, 524
Ph2P(C6H4)3PPh2
3
310, 360
240, 310
370, 420
377
300, 350
276, 362
445
510, 545, 590
238 (6.9), 241 (3.0), 281sh (1.74),
305sh (0.46)
6
238 (3.5), 253 (1.7), 278sh (1.2),
304sh (0.76), 328sh (0.19)
(280–330), 350
375
275, 343
510, 545, 586
Solid phase
DRUV (lmax/nm)
Ph2PC6H4PPh2
295
330
300
308
310
305
315
317
320
270, 370, 400 360, 400
260
445, 470
453 (116)
330, 405
(296–417)
400
335, 370
275, 370
270, 330, 370
275, 390
360
480
462
515
430, 500
510
470, 500, 535
480
490, 520, 560
510, 550, 590
1
4
Ph2P(C6H4)2PPh2
2
5
Ph2P(C6H4)3PPh2
3
6
370
370
330
470
500 (54)
470, 500, 535 (49)
450, 490
505 (1030)
420 (2141)
370, 440 270, 405
357, 396
375
350, 380
a Degassed CH2Cl2 solution. b In the excitation spectra comma separated values indicate more than one maximum of excitation for the same emission. In
the emission spectra comma separated values in the same line belong to a structured band. Emission maxima belonging to different maxima for the same
compound are shown in different lines. c Coefficient of determination (R2) to a first order exponential function is 0.99, except for 1 and 3 in solid phase,
which are 0.98 and 0.95 respectively. d The same excitation maximum appears in both emissions, but the intensity depends on the excitation band. e Most
intense band. f Maximum not well defined.
thermochromism has been described in the literature and the
bathochromic shift of the emission upon lowering temperature
have been attributed to thermal contraction that occurs upon
cooling, which leads to a reduction in the band-gap energy.66 From
this data it seems reasonable to suggest substantial contribution
of the diphosphine orbitals into the molecular ones, which are
responsible for the luminescence originating either from the
intraligand transitions (more or less modified by coordination to
gold) or charge transfer processes.
Behavior of the 1, 4 relatives containing only one phenylene
spacer between the phosphorus coordinating centers is more com-
plicated (Fig. 7). Both complexes display dual emission generated
by two emissive excited states at room temperature for 1 and at
low temperature for 4. In the latter case vibronicallystructured
emission (387, 407, 430 nm) as well as excitation (270, 350 nm)
spectra fit well the emission discussed above for the pairs of
complexes 2, 5 and 3, 6 although the shape of the emission at
lower energy (487 nm) displays more similarity with that of the
free diphoshine and with the emission shown by 1 (485 nm) at
77 K. This red shifted component (487 nm) originates from 350
nm excitation band and could be assigned to IL (diphosphine)
transitions or charge transfer (CT) processes involving either two
ligands (thiolate and diphosphine) or the gold center and one
Fig. 7 Emission spectra of the complexes 1, 4 and the diphosphine
(or both) of the ligands. In contrast, complex 1 gives two emission
Ph2PC6H4PPh2 in dichloromethane at 298 K (top) and 77 K (bottom).
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bands at room temperature at 385 and 525 nm, which are not
resolved in the excitation spectrum. Both emissions are observed
upon excitation at any of the two excitation maxima (see Table 1),
but the emission at higher energies is more intense upon excitation
at higher energy component and excitation at 330 nm leads to more
intense emission at 525 nm. The shorter wavelength component
of the emission looks similar to the emission bands displayed by
4 and free diphosphine under the same conditions and could be
associated IL (diphosphine) transitions modified by coordination
to gold, whereas the band at 525 nm could be related to that at
lower energies for 4 at 77 K, mentioned above.
Dual emission from different triplet states has been previously
described.67 The presence of only one emission in the case of 4 at
room temperature may be explained by quenching processes for
the lower energy emission (the most intense at low temperature),
which are expected to be more effective at higher temperature.
Complex 1 displays dual emission at room temperature. At both
temperatures the emission covers a wide range of about 300 nm. As
quenching processes are expected to be more effective with raising
the temperature we propose coupling of both states upon lowering
the temperature. One of the most important consequences from
the analysis of the data is that the presence (in 4–6) or absence (in
1–3) of intramolecular aurophilic bonding does not substantially
affect the emission parameters of these complexes.
Solid state studies
DRUV spectra have been recorded for 1–6 and for the free
diphosphines (Table 1, see also Figure S12†). The complexes
display one broad band centered between 300 and 330 nm.
These data are consistent with those observed in solution and
aggregation and the solid state seems to have no effect on the
absorption characteristics of the compounds under study.
Except compound 4, which is not emissive in the solid state
at room temperature, the solid samples are luminescent both at
room temperature and at 77 K. The emission lifetimes, which
are in the microsecond domain, are indicative of triplet manifold
luminescence. In general, the position of the emission maxima
in solid state at 298 K emission are red shifted compared to the
values found in solution. A small red shift (in most cases less
than 30 nm) was also observed in the low temperature solid state
spectra, compared with those at 298 K that is in line with solution
thermochromism.66 Complexes 3 and 6 show vibronic progression
at 77 K (Table 1), similar to that observed in solution (Fig. 8).
Once again, it has to be noted that the free diphosphine ligands
display very similar trends in their spectral patterns with those of
the complexes. Therefore it is possible to propose a substantial
contribution of the ligand orbitals among those involved in the
emissive excited states.
We can then conclude that the emissive properties of the
complexes 1–6, either in solution or in the solid state, seem to
be mainly determined by the IL or CT electronic transitions
with substantial contribution of the diphosphine ligand orbitals.
This assignment is in sharp contrast with interpretation of the
data obtained earlier for the gold(I) thiolate complexes containing
mono-11,12,15–17,57,68 and diphosphine8,16,24,31,56 ligands. As shown in
a recent review9 on this topic the main contribution to the
luminescence of the complexes of this type comes from LMCT
(S→Au) excited states. In some cases, particularly for the com-
Fig. 8 The solid state emission spectra of complexes 1–6 and the
corresponding diphosphines PPh2(C6H4)nPPh2 (n = 1–3) at 77 K.
plexes which tend to form aurophilic bonding, the contribution
from (LMMCT, S→(Au ◊ ◊ ◊ Au))11,24,56 as well as the metal centered
(MC) transitions12,15,56,68 may be also observed. In accord with
this assignment none of the gold(I) thiolate-phosphine complexes
studied earlier displays vibronically structured emission (found for
1–6), neither in solution nor in solid state. Another characteristic
feature of the emission observed for the complexes containing
diphosphines with polymethylene spacers, Ph2P-(CH2)n-PPh2 (n =
1–5), is independence of emission characteristics on the structure
of the phosphine ligands,24,31 i.e. their contribution into the excited
states and observed luminescence is absent or negligible. The only
exclusion can be exemplified by the calculations of the electronic
structure of dppm(Au-S-C6H4-(2-NH2))2 complex, where emissive
excited states are related to the LUMO located onto gold(I)
ions and phosphorus atoms, representing Au ◊ ◊ ◊ Au interaction
and Au–P bonding.56 The family of 1–6 differs from the Au(I)-
thiolate phosphine complexes mentioned above by the presence
of conjugated aromatic spacers between (P–Au) coordination
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Table 2 Data for the first singlet→triplet transition for complexes 1–6
Complex
lT (nm)a
Transition
1
2
3
4
5
6
488
496
502
459
862
446
HOMO (193) → LUMO (194)
HOMO (213) → LUMO (214)
HOMO (233) → LUMO (234)
HOMO-1 (399) → LUMO+1 (402)
HOMO-1 (183) → LUMO (185)
HOMO-1 (407) → LUMO (409)
a
lT = Calculated absorption wavelength.
centers. These observations point to unusually important effect
of this conjugation onto luminescence of these species. In order
to verify this point we have carried out the calculations for the
complexes under investigation.
Computational results
DFT calculations were performed in order to elucidate the
electronic structure of complexes 1–6, to check the contribution
of each part of the molecule to the frontier orbitals involved in the
transitions responsible for the photoluminescence. As the lifetime
measurements point to a phosphorescent nature of the observed
emissions, the mechanism of the luminescence is considered to
involve a spin-forbidden transition, and thus the first singlet–
triplet transitions were calculated using the TDDFT methods.
These transitions are assumed to correspond to the emission
observed upon excitation at 340–370 nm. Calculations do not
evaluate the spin–orbit splitting. Thus, only a proposal but not
a complete assignment can be made. The data obtained are
summarized in Table 2 and shown in Fig. 9. For the complexes
1–6 the first singlet–triplet transition is related to the transitions
between the HOMO or HOMO-1 and the LUMO orbitals. The
analysis of the active orbitals shows that for all the complexes
except 5, HOMO and HOMO-1 are mainly located at the phenyl
thiolate ligand with a small contribution from the gold center,
whereas for 5 HOMO is mainly located at the diphosphine and
LUMO – at the phenylthiolate with the contribution of one of the
gold atoms.
The predicted energy values for the excitations show that the
theoretical values appear at lower energy than those obtained
experimentally. It should be pointed out, however, that TDDFT
calculations were mainly performed on the isolated molecules and
ignored the aggregation contribution in the solid state.50,60,69 In
the case of 5 the {PhSAuPh2P(C6H4)2PPh2Au} units form infinite
chains. Another interesting aspect is that the complexes show
broad and vibronically structured bands. However, it has been
shown that DFT calculations could be used to describe large
systems, and the TDDFT approach allows for assignment of the
excitations, which lead to emission.70
Fig. 9 The frontier molecular orbitals responsible for singlet–triplet
transitions in the complexes 1–6.
Two conclusions may be deduced from the DFT and TDDFT
results. The first one is that a gold(I)–gold(I) interaction is not
a necessary condition for luminescence in the gold–phosphine
complexes. Further, this theoretical study also indicates that the
presence of a gold(I)–gold(I) contact does not significantly perturb
the luminescence parameters in this series of complexes. This is
in complete agreement with the general photophysical behavior
of 1–6 (see Table 1), where there is no correlation between
intramolecular aurophilic interactions and the energy or shape
of the bands observed in the excitation and emission spectra.
The luminescence spectra of complexes 4–6, which also have
gold(I)–gold(I) interactions in the solid state, are not affected by
the contributions of the s and s* molecular orbitals (formed by
overlap of filled dz2 orbitals on Au) as long as the highest occupied
molecular orbital remains sulfur in character.
In agreement with the above calculations, we propose the
assignment of the emission as derived from the ligand to ligand
charge transfer processes, namely from phenyl thiolate ligand
orbitals with the contribution from the gold center (LM’) to
the phenylene spacers of the diphosphine [LM’-LCT: PhSAu →
Ph(spacer)] for the 1–4 and 6 complexes, and to the LLM’CT:
diphosphine → SPhAu in 5. It is worth noting that in the both
cases the phenylene spacers of the diphosphine ligands play a key
role in these transitions.
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9 E. R. T. Tiekink and J.-G. Kang, Coord. Chem. Rev., 2009, 253, 1627–
1648.
Conclusions
10 X. He and V. W.-W. Yam, Inorg. Chem., 2010, 49, 2273–2279.
11 J. M. Forward, D. Bohmann, J. P. J. Fackler and R. J. Staples, Inorg.
Chem., 1995, 34, 6330–6336.
12 B.-C. Tzeng, C.-K. Chan, K.-K. Cheung, C.-M. Che and S.-M. Peng,
Chem. Commun., 1997, 135–136.
We present a series of novel gold(I)–thiolate complexes based on
the diphoshosphine ligands with oligophenylene spacers, PPh2-
(C6H4)n-PPh2 (n = 1, 2, 3). The dinuclear species, [(AuSPh)2(PPh2-
(C6H4)n-PPh2)] (1–3) are effectively converted into their tetranu-
clear cationic derivatives of the general formula [(Au2SPh)2(PPh2-
(C6H4)n-PPh2)2](PF6)2 (4–6) using different synthetic pathways.
X-ray crystallographic studies have been performed for all the
compounds, which show that in the solid state the tetranuclear
clusters do not crystallize in their molecular forms found in
solution due to the aurophilic aggregation, the structural topology
of which is unique for each of the complexes studied. The detailed
photophysical measurements reveal luminescence of all the species
both in the solid state and solution. The theoretical calculations
of the electronic structures suggest that thiolate and diphosphine
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for the emissions. Moreover, the presence or absence of aurophilic
interactions does not have any detectable effect on the luminescent
behavior. This origin of luminescence in 1–6 is very different from
the thiolate to gold charge transfer transitions, usually reported
for the gold-thiolate species. The results obtained clearly indicate
an important role that the phenylene spacers of the diphosphines
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Financial support from the Academy of Finland (I.O.K.), Russian
Foundation for Basic Research (grants 09-03-12309-CSIC-a and
09-03-12309) is gratefully acknowledged. We also thank the Di-
reccio´n General de Investigacio´n Cient´ıfica y Te´cnica (CTQ2007-
67273-C02-01), the CSIC/Russian Foundation for Basic Research
(RFBR) (N 2008RU0065) for financial support and to the
Supercomputing Center of Galicia (CESGA-CSIC) for providing
Access to the FINIS TERRAE System.
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