Different emissive properties in dithiolate gold(i) complexes as a function of the presence of phenylene spacers

Article abstract of DOI:10.1039/c3dt53530d

A family of dinuclear neutral thiolate gold complexes of the type RPh ₂PAuS(C₆H₄)_nSAuPPh₂R (n = 2, 3), RPh₂PAuS(C₆H₄)S(C₆H ₄)SAuPPh₂R, RPh₂PAuSCH₂(C ₆H₄)₂CH₂SAuPPh₂R where R represents a pyridine or a phenylene ring, has been prepared and fully characterized. X-ray crystallographic studies showed the presence of aurophilic interactions for those species bearing two phenylene spacers between the gold metal centers, leading to infinite chains. The complexes are emissive in the solid state. Theoretical calculations together with the photophysical analysis seem to indicate that the main excitations involved in the emissive processes are due to a mixture of ILCT transition involving the thiolate and the conjugated phenylene rings, and LL′CT transitions comprising the thiolate and the pyridine or phenyl from the phosphine fragment which contrast with the typical gold thiolate emission, LMCT from the thiolate fragment to the metal center. This journal is the Partner Organisations 2014.

Full text of DOI:10.1039/c3dt53530d

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Different emissive properties in dithiolate gold(I)
complexes as a function of the presence of
phenylene spacers†
Cite this: Dalton Trans., 2014, 43,
6212
Francesco M. Monzittu,a Vanesa Fernández-Moreira,a Vito Lippolis,b
Massimiliano Arca,b Antonio Lagunaa and M. Concepción Gimeno*a
A family of dinuclear neutral thiolate gold complexes of the type RPh2PAuS(C6H4)nSAuPPh2R (n = 2, 3),
RPh2PAuS(C6H4)S(C6H4)SAuPPh2R, RPh2PAuSCH2(C6H4)2CH2SAuPPh2R where R represents a pyridine or
a phenylene ring, has been prepared and fully characterized. X-ray crystallographic studies showed the
presence of aurophilic interactions for those species bearing two phenylene spacers between the gold
metal centers, leading to infinite chains. The complexes are emissive in the solid state. Theoretical calcu-
lations together with the photophysical analysis seem to indicate that the main excitations involved in the
emissive processes are due to a mixture of ILCT transition involving the thiolate and the conjugated phe-
nylene rings, and LL’CT transitions comprising the thiolate and the pyridine or phenyl from the phosphine
fragment which contrast with the typical gold thiolate emission, LMCT from the thiolate fragment to the
metal center.
Received 16th December 2013,
Accepted 2nd February 2014
DOI: 10.1039/c3dt53530d
www.rsc.org/dalton
thiolate-Au phosphine derivatives takes place between 400 nm
and 700 nm and it mainly originates from ligand to metal
Introduction
Phosphine-gold(I)-thiolate derivatives have been intensely charge transfer (LMCT) transitions, from the thiolate fragment
studied due to their potential applications in the development to the gold metal center. However, thiolate to phosphine
of new materials,1 chemosensors2 as well as in the medical charge transfer (LL′CT), gold to thiolate charge transfer
field as novel therapeutic agents.3 These wide range of possibi- (MLCT) and thiolate centered (LC) transitions have been also
lities have awakened an increasing interest in studying their described in the literature for these types of species.5 In
structure and photophysical properties. In particular, thiolate addition, the incorporation of phenyl spacers between the
derivatives are versatile ligands that allow the synthesis of metal centers seems to confer a different approach to the con-
coordination compounds with different features. They can ventional photophysical properties of gold-thiolate derivatives.
accommodate one, two and even three gold centers,4 which Previous work performed by Kosehovoy and coworkers
might promote a completely different spatial distribution. described that, in those cases, thiolates and phosphine intra-
Such great diversity of possible structures could induce diverse ligand charge transfer processes are the primary responsible
photophysical properties, either because gold(I)–gold(I) inter- transitions for the emission.6 Furthermore, aurophilic inter-
actions can occur, or simply because the different packaging actions are relegated to a secondary role as their presence or
modes would alter the luminescence. Typically, emission of absence is irrelevant. More examples supporting this theory
were also reported for dinuclear gold complexes with diphos-
phines containing alkyne and/or phenylene spacers. Once
again, the presence of phenylene spacers in the backbone
aDepartamento de Química Inorgánica, Instituto de Síntesis Química y Catálisis
Homogénea (ISQCH), CSIC – Universidad de Zaragoza, 50009 Zaragoza, Spain.
seems to control the photophysical properties of the com-
plexes. Therefore, in this work, a family of dithiolate phenyl
derivatives was chosen as spacers to synthesize a new series of
E-mail: gimeno@unizar.es; Fax: +34 976761187; Tel: +34 976762291
bDipartimento di Scienze Chimiche e Geologiche, Università degli Studi di Cagliari,
S.S. 554 Bivio per Sestu, 09042-Monserrato(CA), Italy
bimetallic thiolate-gold(I) phosphine derivatives. Then,
a
†Electronic supplementary information (ESI) available: Structural features in the
packing of complexes 2, 4, 6 (Fig. S1–S4); DRUV spectra of L1–L4 (Fig. S5); DRUV
spectra of complexes 2–4, 6–8 (Fig. S6); emission spectra of complexes 2, 4, 5, 7
(Fig. S7); simulated absorption spectrum of 4 in the gas phase (Fig. S8); isosur-
face drawings of selected Kohn–Sham MOs calculated for 4 (Fig. S9). CCDC
976386–976389. For ESI and crystallographic data in CIF or other electronic
format see DOI: 10.1039/c3dt53530d
thorough analysis of their crystalline structure, together
with photophysical studies and theoretical calculations, will
attempt to shed some light on the influence of phenylene
spacers in the emission properties of thiolate-gold(I)
phosphine derivatives.
6212 | Dalton Trans., 2014, 43, 6212–6220
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X-ray analysis
Synthesis and characterisation
Single crystals suitable for X-ray diffraction analysis of com-
plexes 2, 4, 5 and 6 were obtained by slow diffusion of hexane
into a dichloromethane solution. The unit cells of complexes
2, 4, and 5 are formed by 4 complex molecules each, whereas
only 2 complex molecules are displayed in the unit cell of
complex 6. Moreover, all of them presented half molecule as an
asymmetric unit and species 2, 4 and 6 displayed an inversion
center. As expected, in all cases the gold atom presented a
distorted linear geometry with a S–Au–P angles between
175.06(4)° and 179.16(7)°, and the Au–S and Au–P distances
ranging from 2.286(2) Å to 2.3048(11) Å and from 2.244(2) Å to
2.2597(11) Å, respectively, which are within the expected values
for S–Au–P derivatives.7c,8 A summary of distances and angles
is presented in Fig. 1.
Dithiolate AuI complexes
Gold(I) complexes (1–8) were synthesized by reaction of the
corresponding dithiolate ligand with either ClAuPPh3 or
ClAuPPh2Py in the presence of cesium carbonate to assist
the thiol deprotonation and subsequent metal coordination
(see Scheme 1). Spectroscopic characterization of each gold
complex was performed using IR, 1H, 31P and 13C NMR spectro-
scopy, and UV-vis spectroscopic measurements. Infrared
spectroscopy showed in all cases the disappearance of a ν(S–H)
stretching band at ca. 2550 cm−1 indicating the deprotonation
of the thiol groups. 31P-NMR spectra presented a significant
low-field shift of the phosphine peak, from ca. 33 ppm to
ca. 38 ppm after coordination of the dithiolate species to the
gold phosphine derivatives, which is in agreement with
analogous NMR spectroscopy data reported for different
thiolate-gold(I) phosphine complexes.7 Moreover, the chemical
shifts observed in 13C-NMR and 1H-NMR spectroscopy corro-
borate the success of the coordination reaction. Thus, the syn-
thesized complexes 1–8 showed, in all cases, that the SCipso
carbons were shifted to low field as well as the disappearance
of the signal belonging to S–H protons in 1H-NMR spec-
troscopy. Further analytical data provided by mass spec-
trometry are in concordance with the expected gold(I) species
1–8 (Table 1). Additionally, suitable crystals of 2, 4, 5 and 6
were obtained that allowed structural characterization by X-ray
diffraction.
Only complex 5 showed intermolecular AuI⋯AuI interaction
of 3.0336(11) Å, which lead to the formation of infinite chains
in the crystal lattice together with point to face, C–H⋯π, inter-
actions9 between the phenylene spacer and one adjacent
PPh2Py unit and between two adjacent PPh2Py molecules, see
Fig. 2. Point to face interactions between the phenylene
spacers and the phosphine derivative units were also observed
for complexes 2 and 6. Furthermore, these species presented
S–S and S–(H-PyPh2P) short contacts at ca. 3.235 Å and
2.743 Å, respectively. These short contacts and the C–H⋯π
interactions are responsible for their molecular packing (see
ESI, Fig. S1–S3†). The closest AuI⋯AuI distances for complexes
2 and 6 are 4.565 Å and 5.484 Å respectively, values relatively
long to be considered as aurophilic interactions (3.0–3.3 Å).10
In contrast, complex 4 did not show any phenylene–PPh3
interaction and presented a torsion angle between the phenyl-
ene spacers of 1.1(4)°. Such torsion angle is much smaller
than those found for complexes 2, 5 and 6, values between
30.63(8)° and 35.31(1)° (see Fig. 1). The short contacts present
in complex 4 are those that were formed between the gold
atom and a proton from a neighboring triphenylphosphine
unit; the distance AuI⋯H is 2.850 Å (ESI, Fig. S4†).
Optical properties
As commented previously L1 and L2 are similar ligands where
the donating groups, the thiolates, are connected by 2 and 3
phenyl rings, respectively, acting as spacers, thus allowing the
electronic communication between the two ends of the ligand.
However, L3 and L4 do not have such properties due to the
presence of a thioether between the two phenyl rings in the
case of L3, and a methylene group between the phenyls and
the donating thiolates in L4. As a result of this, a remarkable
difference in the optical properties can be observed for the
4 families of complexes. UV-visible spectra of ligands L1–L4
and complexes 1–8 were measured in the solid state. Ligands
L1, L2, and L3 showed the same absorption profile, a single
structureless band around 300 nm that could be assigned to
π→π* transitions within the phenylene rings. By contrast L4
displayed two absorption bands centered at 215 nm and at
277 nm. In this case, the high energetic band transition could
Scheme 1 Synthesis and numbering of gold(I) species synthesized. (i)
Cs2CO3, CH2Cl2/MeOH, 2 h, Ar.
Table 1 Relevant spectroscopic data for complexes 1–8
Complex
31P{1H} (ppm)
13C{1H}a (ppm)
m/z
1
2
3
4
5
6
7
8
38.75
38.77
38.88
37.85
37.98
37.13
38.01
35.97
141.7
142.8
142.3
147.6
141.2
142.2
142.6
146.7
1135.0b
1210.1c
1166.0c
1162.1c
1137.1c
1213.2b
1168.9c
1164.9c
NMR spectra measured in CD2Cl2. a –SCipso b MS(ES). c MS(MALDI+).
.
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Fig. 2 (a) Diamond diagrams of aurophilic interactions and (b) ORTEP
diagram of C–H⋯π interactions in complex 5. Au(1)⋯Au(1): 3.0336(11) Å,
C(15)–H(2)⋯π: 2.894 Å, C(3)–H(22)⋯π: 2.734 Å, C(21)–H(13)⋯π: 2.792 Å,
C(22)–H(13)⋯π: 2.734 Å, C(23)–H(13)⋯π: 2.866 Å.
Fig. 3 DRUV spectra of L1 and complexes 1 and 5.
Fig. 1 Diamond diagrams of species 2, 4, 5, 6 (hydrogen atoms omitted
for clarity). Selected bond length, angles and torsion angles for: (2) Au(1)–
S(1) 2.3048(11) Å, Au(1)–P(1) 2.2597(11) Å; S(1)–Au(1)–P(1) 175.06(4)°,
Au(1)–S(1)–C(1) 109.34(16)°; C(9)–C(8)–C(4)–C(3) 30.63(8)°; (4) Au(1)–
P(1) 2.2582(6) Å, Au(1)–S(1) 2.3035(6) Å; P(1)–Au(1)–S(1) 176.13(2)°,
C(30)–S(1)–Au(1) 101.99(8)°; C(33)–C(34)–C(34)–C(35) 1.1(4)° (5) Au(1)–
S(1) 2.286(2) Å, Au(1)–P(1) 2.244(2) Å, Au(1)–Au(1) 3.0336(11) Å,
S(1–)Au(1)–P(1) 179.16(7)°, S(1)–Au(1)–Au(1) 76.83(5)°, P(1)–Au(1)–Au(1)
10.99(7)°, C(1)–S(1)–Au(1) 104.4(2)°; C(3)–C(4)–C(4)–C(5) 30.97(1)°; (6)
Au(1)–P(1) 2.257(2) Å, Au(1)–S(1) 2.296(2) Å, P(1)–Au(1)–S(1) 178.16(9)°,
Au(1)–S(1)–C(27) 104.1(3)°, C(29) C(30)–C(33) C(34) 33.77(1)°.
fragments, i.e. LL′CT and ILCT respectively, see Fig. 3 for com-
plexes 1 and 5 (see ESI, Fig. S5† for other ligands and Fig. S6
for the complexes). These results contrast with the typical be-
haviour observed for gold(I) thiolate complexes, i.e. electronic
transitions from the thiolate to the gold metal center,
LMCT,5b,12 highlighting the important role of the phenylene
spacers in the spectroscopic properties of this family of
complexes.
Emission and excitation spectra of ligands L1–L4 and com-
plexes 1–8 were collected in the solid state at 298 K and 77 K.
These experiments were performed only in the solid state due
to the low solubility of the complexes. Table 2 includes the
excitation and emission data and Fig. 4 shows some examples
of the emission spectra of these complexes (see ESI, Fig. S7,†
for the emission spectra of complexes 2, 4, 5, 7 and ligand L2).
In all cases, L1, L3 and L4 showed weak luminescence;
only L2 displayed a structured emission band centered at
be assigned to n→σ* transitions within the S–C bonds
(–CH2S– fragment), whereas the peak at 277 nm might be due
to π→π* transitions in the phenylene rings.11 Analysis of the
complexes absorption profile showed also a similar pattern to
that of the single ligands. The maximum absorption is gene-
rally red-shifted by about 30 nm upon complexation, which
could be tentatively assigned to transitions involving the
thiolate and the conjugated phenylene rings as well as the
thiolate and the pyridyl or phenyl groups from the phosphine
6214 | Dalton Trans., 2014, 43, 6212–6220
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thiolate and the conjugated phenylene rings. Moreover, ligand
to ligand charge transfer (LL′CT) transitions can also happen
from the thiolate to the pyridyl or phenyl groups from the
phosphine fragments. In fact, complex 5 is thought to have
both types of transitions as the emission profile is not as
well structurally defined as the one seen for 1, 2 and 6, which
might indicate an energy transfer process from the thiolate
to the pyridyl of the phosphine fragment, in concordance
with previous reports on similar complexes.6,14 Moreover,
lifetimes in the microsecond domain together with the con-
siderably large Stoke shift suggest a phosphorescent nature of
this emission. It is also worth noting that the lifetime value of
Table 2 Luminescence data for complexes 1–8
λem/nm (τ/μs) 298 K
λem/nm 77 K
a
c
1
2
3
4
5
6
7
8
442 (12), 516, 547sh, 593sh (54)a
448 (10), 544, 585 sh, 632sh (662)b
467 (12), 546 (12)a
516, 554sh, 598sh
540, 580sh, 630sh
532d
467 (12)e
473, 502, 541sh
f
c
g
c
418, 467, 513, 552sh
510, 550sh, 590sh
539, 582sh, 632sh
532g
d
464, 548, 582sh, 639sh
467, 546h
466
f
473, 503, 542sh
b
c
d
a λexc = 380 nm. λexc = 385 nm. λexc = 370 nm. λexc = 400 nm. e λexc
=
325 nm. f λexc = 350 nm. g λexc = 390 nm. h λexc = 360 nm.
complex
2 (662 μs) is larger in comparison with that
of complex 1 (54 μs). Such a difference was also previously
seen in similar species and it could be related to the increase
in the number of phenylene spacers, i.e. from 2 in complex 1
to 3 in complex 2.6 In contrast, the band at ca. 460 nm which
is only observed at 298 K can be assigned LC (–PPh3/–PPh2Py)
emission.15,16 At the same time, the short lifetime observed
for this transition might indicate a fluorescent transition
character. As commented previously, photophysical behavior
of complexes 3, 7, 4 and 8, metallic species derived from L3
and L4 respectively, is likely to differ from those observed for
complexes 1, 5, 2 and 6 due to the different electronic com-
munication within the ligand system. Therefore, complexes 3
and 7 showed a broad band at 467 nm and a shoulder at
ca. 525 nm of similar intensity, whereas complexes 4 and 8
presented a peak at 467 nm and a much smaller band around
550 nm at room temperature. These emissions are relatively
weak in comparison with those seen for complexes 1, 2, 5 and
6 under the same conditions, and they are not observable
with the naked eye under irradiation with a hand-held UV-
lamp. In both cases, the band at ca. 460 nm could be thought
to be an LC (–PPh3/PPh2Py) transition.15,16 In contrast, at 77 K
these complexes showed an increase in the luminescence
intensity as well as changes in the band profile. A featureless
broad emission band at ca. 540 nm and two differentiated
bands at ca. 503 nm and 543 nm remained for complexes 3
and 7 and complexes 4 and 8, respectively. Assignment
of these bands seems to have a much more complicated
explanation, where not only the phenyl rings and the thiolate
are implicated, but also the ancilliary ligands, i.e. PPh3 and
PPh2Py, and the thioether in the case of complexes 3 and 7.
Typically the emission displayed by luminescent phosphine-
gold(I)-thiolate fragments is attributed to ligand-to-metal
charge transfer transitions (LMCT), which could be modified by
changes in both the phosphine and the thiolate ligand and also
by the presence of AuI⋯AuI interactions.5b However, in this
case, ancillary ligands, the thiolates and the phenylene spacers
appear to be the primary contributors to the luminescence of
these complexes, and aurophilic interactions do not seem to
influence the photophysical behavior. Such results suggest
that the phenylene spacers play a key role in the photophysical
properties. Recently, a similar behavior was observed for gold
(I)-thiolate complexes with phosphines bearing phenylene
spacers.6
Fig. 4 Emission spectra at 298 K (red line) and 77 K (blue line) of
species (a) 1, (b) 6, (c) 3, (d) 8 (metallic species derived from L1, L2, L3
and L4 respectively).
ca. 400 nm that could be assigned to intra-ligand charge trans-
fer (ILCT) transitions within the phenylene rings. Lumine-
scence of ClAuPPh3 and ClAuPPh2Py, gold complexes used as
the starting material in the reactions comes from transitions
within the phosphine unit.13 Analysis of the photophysical
properties of complexes 1–8 suggests that the different emis-
sion and excitation spectra patterns seem to be more influ-
enced by the different ligands structure than by the metallic
fragment, i.e. –(AuPPh3) and –(AuPPh2Py). Specifically, com-
plexes 1, 2, 5 and 6, metallic species formed with L1 and L2,
have a similar behavior. At room temperature they present two
emission bands at ca. 450 nm and 550 nm, the latter being a
well resolved structured band as well as the main component
of emission. However, at 77 K the emission centered at
ca. 450 nm disappears and only the well-structured band at
ca. 550 nm remains, which did not show any apparent change.
The energy gap between vibronic peaks, between 1200 and
1300 cm−1, is typical for the excited states of aromatic systems,
emphasizing the importance of the conjugated phenylene
rings of the ligands L1 and L2 in the excited state. Therefore, it
seems reasonable to associate the highly structured band to
intra-ligand charge transfer (ILCT) transitions, involving the
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DFT calculations
In order to investigate the origin of the electronic transitions
responsible for the absorption and emission properties of
complexes 1–8, DFT calculations were carried out on represen-
tative members of the complex families. In particular, the
investigation concerned complex 4 and a discrete model of
complex 5, 5′, featuring two L′ AuPPh2Py units joined by
1
Au⋯Au interactions (L′ = monothiolate form of L1) (see the
1
Experimental section for the computational set-up chosen).
Ground state geometry optimization was performed in both
cases and a good agreement was found between calculated
and experimental geometrical parameters. In particular, for
complex 4 the calculated Au–P (2.313 Å) and Au–S (2.327 Å)
bond distances are slightly longer than the structural values,
with a calculated S–Au–P angle of 178.64°, and the aromatic
rings of the phenylene spacer are coplanar as observed in
the crystal structure. Also the optimized geometry of complex
5′ very well reproduces the structural features of the repetitive
unit in the 1D chains held by Au⋯Au interactions in complex
5. The calculated Au–P, Au–S and Au⋯Au distances (2.347,
2.316, and 3.303 Å, respectively) are slightly overestimated.
The gold–gold distance, although overestimated, accounts
for a direct metal–metal interaction, also testified by a non-
negligible Wiberg bond index (0.150). The calculated bond
angles are very close to those observed experimentally (P–Au–S
177.52, P–Au–Au 104.15, S–Au–Au 77.97°), including the
torsion angle between the aromatic rings of the dithiolate
spacer (34.74°).
The pattern of singlet excited states (ESs) was computed at
the TD-DFT level for 4 and 5′ at their optimized geometries. In
both cases a good agreement was found between the experi-
mental DRUV spectra recorded for 4 and 5 and the spectra
simulated on the basis of computed vertical absorption tran-
sitions (see Fig. 3 for 5′ and Fig. S8 in the ESI† for 4). In par-
ticular, the experimental broad absorption band observed at
320 nm for 5 is computed for 5′ to be the sum of different elec-
tronic transitions, the most intense falling at 396, 321 and
249 nm and arising from the vertical transitions S0→S1,
S0→S16 and S0→S55, respectively (1, 2, and 3 in Fig. 5 and 6).
Fig. 6 Isosurface drawings of the Kohn–Sham MOs calculated for 5’
involved in the principal singlet vertical electronic transitions (1 and 2 in
Fig. 5). Contour value = 0.05 e.
The transition S0→S1 (calculated at E = 3.130 eV, oscillator
strength f = 0.131) presents a contribution from the 254/
HOMO → 255/LUMO and 253/HOMO−1 → 256/LUMO+1
monoelectronic excitations from molecular orbitals (MOs)
mainly localized on the S atom to orbitals mainly localized on
the pyridine ring and therefore of the type LL′CT (Fig. 6). The
transition S0→S16 (the most intense, f = 0.356; E = 3.867 eV)
arises mainly from four excitations from 254/HOMO or 253/
HOMO−1 MOs to MOs mainly localized on the pyridine ring
(264/LUMO+9 and 262/LUMO+7) or on the aromatic rings of
the phenylene spacer (263/LUMO+8); hence, these transitions
can be considered LL′CT and ILCT in nature.
Fig. 5 Simulated absorption spectrum for 5’ in the gas phase with cal-
culated TD-DFT singlet vertical transitions.
6216 | Dalton Trans., 2014, 43, 6212–6220
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Transitions involving the AuI centers fall in the UV region accessory containing a UV xenon flash tube. The lifetime data
such as the S0→S55 calculated at 250 nm (E = 4.960 eV; f = were fit using Origin 5.0.
0.079). These MLCT transitions involve the excitations from
Starting materials
MOs localized on the Au and S atoms to those on the ligand
and the pyridine rings in particular. No transitions are found ClAuPPh3, ClAuPPh2Py were prepared according to literature
which involve a charge transfer between the two interacting procedures.17 Other starting materials and solvents were pur-
AuI centers.
chased from commercial suppliers and used as received unless
Analogous conclusions can be drawn by analysing the simu- otherwise stated.
lated spectrum of 4. The most intense computed vertical tran-
sitions correspond to mono-electronic excitations of the type
LL′CT and ILCT. Excitations involving the metal centers
General procedure for the synthesis of the complexes 1–8
Synthesis of 1. Cs2CO3 (53.8 mg, 0.246 mmol) was added to
are calculated at higher energies and are of the type MLCT (see a solution of L1 (22.5 mg, 0.103 mmol) in 15 ml of methanol.
ESI, Fig. S9†).
After stirring for few minutes a solution of ClAuPPh3
(102.3 mg, 0.206 mmol) in 2 ml of CH2Cl2 was added dropwise
into the mixture and it was further stirred for one hour at
room temperature until a solid appeared. The precipitate was
separated by filtration and washed several times with metha-
Conclusions
In summary, we have synthesised and characterized new nol and diethyl ether to give 1 as a pale green solid (85.3 mg,
dithiolate gold phosphine complexes with different spacers 73%). NMR (CD2Cl2 20 °C): 31P NMR (162 MHz) 38.75, s;
between both thiolate units. Structural characterization by 1H NMR (400 MHz) 7.27–7.33, m, 4H (3-thiol), 7.46–7.64, m,
X-ray diffraction studies showed that only in one case, complex 34H (Ph and 2-thiol); 13C NMR (101 MHz) 126.7, s, (2-thiol),
5, aurophilic interactions are present and led to the formation 130.0, d (J = 11.4 Hz), (m-Ph), 130.6, s, (ipso-Ph), 132.5, d, (J =
of a chain polymer. Theoretical calculations combined with 2.5 Hz), (p-Ph), 132.3, s, (1-thiol), 135.0, d, (J = 13.8 Hz),
photophysical analysis indicate that the main emission orig- (o-Ph), 136.6, s, (4-thiol), 141.7, s, (3-thiol).). Anal. Calcd for
inates from excited states due to a mixture of ILCT transition C48H38Au2P2S2: C, 50.80; H, 3.38; found: C, 50.47; H, 3.15;
involving the thiolate and the conjugated phenylene rings and MS (ES): m/z calcd for C48H38P2S2Au2 (M+) 1134.1, found
LL′CT transitions comprising the thiolate and the pyridine or 1135.0.
phenyl from the phosphine fragment. Radiative relaxation
Synthesis of 2. This compound was prepared similarly to 1
could also occur through intersystem crossing (ISC) from these using L2 instead of L1. The product obtained was a yellow
singlet excited states to triplet states. These results emphasize solid (90.0 mg, 81% yield).
the importance of the phenylene spacers between the metal
1
NMR (CD2Cl2 20 °C): 31P NMR (162 MHz) 38.77, s; H NMR
centers in the luminescent properties, as the typical gold (400 MHz) 7.37–7.41, m, 4H (6-thiol), 7.47–7.64, m, 38H (Ph,
thiolate emission was normally assigned to LMCT from the 3-thiol and 2-thiol); 13C NMR (101 MHz) 127.1, s, (3-thiol),
thiolate fragment to the metal center.
127.5, s, (2-thiol), 130.1, d (J = 11.5 Hz), (m-Ph), 130.7, s, (ipso-
Ph), 132.5, d (J = 2.5 Hz), (p-Ph), 133.5, s, (6-thiol), 135.0, d (J =
13.8 Hz), (o-Ph), 136.3, s, (5-thiol), 140.0, s, (4-thiol), 142.8, s,
(1-thiol). Anal. Calcd for C54H42Au2P2S2: C, 52.78; H, 3.61;
found: C, 52.93; H, 3.23; MS(MALDI+/DIT): m/z = 1210.1 [M]+.
Synthesis of 3. This compound was prepared similarly to 1
Experimental section
Instrumentation
Mass spectra were recorded on a BRUKER ESQUIRE 3000 using L3 instead of L1. The product obtained was a yellow
PLUS, with the electrospray (ESI) technique and on a BRUKER solid (97.5 mg, 83% yield).
MICROFLEX (MALDI-TOF), with a Dithranol or a T-2-(3-(4-
1
NMR (CD2Cl2 20 °C): 31P NMR (162 MHz) 38.88, s; H NMR
tbutyl-phenyl)-2-methyl-2-propenylidene)malononitrile matrix.
(400 MHz) 7.01–7.06, m, 4H (3-thiol), 7.42–7.60, m, 34H
1H, 13C{H} and 31P NMR spectroscopy, including 2D exper- (Ph and 2-thiol); 13C NMR (101 MHz) 129.6, d (J = 11.5 Hz),
iments, were recorded at room temperature on a BRUKER (m-Ph), 130.1, s, (ipso-Ph), 130.8, s, (4-thiol), 131.2, s, (3-thiol),
AVANCE 400 spectrometer (1H, 400 MHz, 13C, 100.6 MHz, 31P, 132.1, d (J = 2.5 Hz), (p-Ph), 133.2, s, (2-thiol), 134.6, d (J =
162 MHz) with chemical shifts (δ, ppm) reported relative to the 13.8 Hz), (o-Ph), 142.3, 2, (1-thiol). Anal. Calcd for
solvent peaks of the deuterated solvent. Infrared spectra were C48H48Au2P3S3·0.5CH2Cl2: C, 48.17; H, 3.25; found: C, 47.97;
recorded in the range 4000–250 cm−1 on a Perkin-Elmer Spec- H, 2.95; MS(MALDI+/DCTB): m/z = 1166.0 [M]+.
trum 100 FTIR spectrometer. UV/vis spectra were recorded
Synthesis of 4. This compound was prepared similarly to 1
with a Jasco V-670 spectrophotometer fitted with a Praying using L4 instead of L1. The product obtained was a white solid
Mantis diffuse reflectance accessory. Room temperature (74.4 mg, 74% yield).
steady-state emission and excitation spectra were recorded
1
NMR (CD2Cl2 20 °C): 31P NMR (162 MHz) 37.85, s; H NMR
with a Jobin-Yvon-Horiba fluorolog FL3-11 spectrometer fitted (400 MHz) 4.16, s, 4H (1-thiol), 7.28–7.33, m, 4H (4-thiol),
with a JY TBX picosecond detection module. Phosphorescence 7.37–7.51, m, (Ph and 3-thiol); 13C NMR (101 MHz) 32.9, s,
lifetimes were recorded with a Fluoromax phosphorimeter (1-thiol), 127.4, s, (4-thiol), 129.6, s, (3-thiol), 129.8, d (J =
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11.2 Hz), (m-Ph), 130.9, d (J = 53.7), (ipso-Ph), 132.2, d (J =
Synthesis of 8. This compound was prepared similarly to 1
2.4 Hz), (p-Ph), 134.9, d (J = 14.0 Hz), (o-Ph), 139.1, s, (5-thiol), using ClAuPPh2Py instead of ClAuPPh3 and L4 instead of L1.
147.6, s, (2-thiol). Anal. Calcd for C50H42Au2P2S2: C, 51.62; H, The product obtained was a white solid (75.6 mg, 80% yield).
3.64; found: C, 51.37; H, 3.46; MS(MALDI+/DCTB): m/z =
NMR (CD2Cl2 20 °C): 31P NMR (162 MHz) 35.97, s wide;
NMR (CDCl3 20 °C): H NMR (400 MHz) 4.24, s, 4H (1-thiol),
1
1162.1 [M]+.
Synthesis of 5. This compound was prepared similarly to 1 7.25–7.29, m, 2H (4-Py), 7.29–7.33, m, 4H (4-thiol), 7.33–7.47,
using ClAuPPh2Py instead of ClAuPPh3. The product obtained m, 12H (Ph), 7.49–7.64, m, 14H (Ph, C-Py and 3-thiol), 7.70,
was a pale green solid (82.5 mg, 79%).
t (J = 7.5 Hz), 2H (4-Py), 8.71, ddd (J = 3.9, 1.7, 0.8 Hz), 2H
NMR (CD2Cl2, 20 °C): 31P NMR (162 MHz) δ 37.98, s; (6-Py); 13C NMR (101 MHz) 32.6, s, (1-thiol), 125.0, d (J =
1H NMR (400 MHz) 7.27–7.34, m, 4H (3-thiol), 7.38–7.45, m, 2.2 Hz), (5-Py), 127.0, s, (4-thiol), 128.9, s, (3-thiol), 129.0, d
2H (5-Py), 7.45–7.60, m, 16H (Ph and 2-thiol), 7.68–7.77, m, 8H (J = 2.4 Hz), (m-Ph), 131.4, d (J = 32.3), (3-Py), 131.5, d (J =
(Ph), 7.82, ddd (J = 7.7, 3.8, 1.8 Hz), 2H (4-Py), 7.89, t (J = 2.3 Hz), (p-Ph), 134.6, d (J = 14.1 Hz), (o-Ph), 136.43, d (J =
7.4 Hz), 2H (3-Py), 8.77–8.83, m, 2H (6-Py); 13C NMR (101 MHz) 10.6 Hz), (4-Py), 138.6, s, (5-thiol), 146.7, s, (2-thiol), 151.2,
125.6, d (J = 2.4 Hz), (5-Py), 126.4, s (3-thiol), 129.5, d (J = d (J = 14.4 Hz), (6-Py). Anal. Calcd for C48H40Au2N2P2S2: C,
11.5 Hz), (m-Ph), 129.8, d (J = 56.9 Hz), (ipso-Ph), 131.4, d (J = 49.49; H, 3.46; N, 2.40; found: C, 49.28; H, 3.39; N, 2.24;
31.2 Hz), (3-Py), 132.2, d (J = 2.5 Hz), (p-Ph), 133.0, s, (2-thiol), MS(MALDI+/DIT): m/z = 1164.9 (18.80%) [M]+.
135.0, d (J = 13.7 Hz), (o-Ph), 136.3, s, (4-thiol), 137.0, d (J =
Crystallography
10.4 Hz), (4-Py), 141.2, s, (1-thiol), 151.7, d (J = 15.6 Hz), (6-Py),
155.2,
d
(J
=
79.1 Hz), (ipso-Py). Anal. Calcd for The crystals were mounted in an inert oil on glass fibers and
C46H36Au2N2P2S2: C, 48.60; H, 3.19; N, 2.46; found: C, 48.24; transferred to the cold gas stream of an Xcalibur Oxford Diffr-
H, 3.06; N, 2.28; MS(MALDI+/DIT): m/z = 1137.1 (15.5 m%) action (2, 4, 6) or a Bruker Smart 1000 CCD (5) diffractometer
[M]+.
equipped with a low-temperature attachment. Data were col-
Synthesis of 6. This compound was prepared similarly to 1 lected using monochromated Mo Kα radiation (λ = 0.71073 Å).
using ClAuPPh2Py instead of ClAuPPh3 and L2 instead of L1. Scan type: ω. Absorption correction based on multiple scans
The product obtained was a pale yellow solid (82.5 mg, 79% was applied using spherical harmonics implemented in
yield).
SCALE3 ABSPACK18 scaling algorithm (2, 4, 6) or with a
NMR (CD2Cl2 20 °C): 31P NMR (162 MHz) 37.13, s; H NMR program SADABS (5). The structures were solved by direct
(400 MHz) 7.34–7.46, m, 6H (5-Py and 6-thiol), 7.46–7.65, methods and refined on F2 using the program SHELXL-97.19
m, 20H (Ph, 3-thiol and 2-thiol), 7.68–7.78, m, 8H (Ph), 7.82, All non-hydrogen atoms were refined anisotropically. In all
tdd (J = 7.7, 3.9, 1.8 Hz), 2H (4-Py), 7.85–7.92, m, 2H (3-Py), cases, hydrogen atoms were included in calculated positions
8.77–8.84, m, 2H (6-Py); 13C NMR (101 MHz) 125.6, d (J = and refined using a riding model. Refinements were carried
2.3 Hz), (5-Py), 126.7, s, (3-thiol), 127.1, s, (2-thiol), 129.5, d out by full-matrix least-squares on F2 for all data. Additional
(J = 11.5 Hz), (m-Ph), 131.4, d (J = 30.9 Hz), (3-Py), 132.2, d (J = details of the data collection and refinement are given
2.5 Hz), (p-Ph), 133.0, s, (6-thiol), 135.0, d (J = 13.8 Hz), (o-Ph), in Table 3. CCDC 976386 (2), 976387 (4), 976388 (5) and
135.9, s, (5-thiol), 137.0, d (J = 10.4 Hz), (4-Py), 139.6, s, 976389 (6).
1
(4-thiol), 142.2, s, (1-thiol), 151.7, d (J = 15.5 Hz), (6-Py). Anal.
Calcd for C52H40Au2N2P2S2·0.5CH2Cl2: C, 50.23; H, 3.29; N, 2.23;
DFT calculations
found: C, 50.10; H, 3.33; N, 2.05; MS (ES): m/z calcd for Quantum-chemical calculations based on the Density Func-
C52H40P2S2N2Au2 (M+) 1212.1, found 1213.2.
tional Theory (DFT) were carried out on compounds 4 and 5′
Synthesis of 7. This compound was prepared similarly to 1 by adopting the mPW1PW20 functional and using the commer-
using ClAuPPh2Py instead of ClAuPPh3 and L3 instead of L1. cial suite of program Gaussian09.21 Schäfer, Horn, and Ahl-
The product obtained was a pale yellow solid (64.9 mg, 71% richs double-ζ plus polarization all-electron basis sets (BSs)22
yield).
were used for all atomic species but gold, for which SBKJC
1
NMR (CD2Cl2 20 °C): 31P NMR (162 MHz) 38.01, s; H NMR BSs23 with relativistic effective core potentials (RECP) were
(400 MHz) 7.02–7.07, m, 2H (3-thiol), 7.37–7.43, m, 2H (5-Py), adopted. The geometry optimizations (with tight cut-off values
7.43–7.5, m, 16H, (Ph and 2-thiol), 7.64–7.75, m, 8H (Ph), on forces and step size) were performed without introducing
7.75–7.87, m, 4H (4-Py and 3-Py), 8.78, ddd (J = 3.9, 1.7, any structural simplification or symmetry restrain. In all cases,
0.8 Hz), 2H (6-Py); 13C NMR (101 MHz) 126.1, d (J = 2.4 Hz), a pruned (99 590) grid was adopted in order to avoid imaginary
(5-Py), 129.9, d (J = 11.5 Hz), (m-Ph), 129.9, d (J = 57.1 Hz), frequencies. NBO populations24 and Wiberg bond indices25
(ipso-Ph), 131.3, s, (4-thiol), 131.7, s, (3-thiol), 131.8, d (J = were calculated at the optimized geometries. Time-dependent
30.8 Hz), (3-Py), 132.6, d (J = 2.5 Hz), (p-Ph), 133.7, s, (2-thiol), (TD) DFT calculations were carried out in order to understand
135.4, d (J = 13.7 Hz), (o-Ph), 137.5, d (J = 10.3 Hz), (4-Py), 142.6, their absorption/emission spectroscopic features. The pro-
s, (1-thiol), 152.1, d (J = 15.7 Hz), (6-Py), 155.5, d (J = 79.5 Hz), grams GaussView26 and Molden 5.027 were used to investigate
(ipso-Py). Anal. Calcd for C46H36Au2N2P2S3: C, 47.27; H, 3.10; the natural charge distributions and MOs’ shapes and to
N, 2.40; found: C, 46.94; H, 3.29; N, 2.15; MS(MALDI+/DIT): m/z generate the simulated absorption spectra based on TD-DFT
= 1168.9 (18.73%) [M]+.
calculations.
6218 | Dalton Trans., 2014, 43, 6212–6220
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Table 3 X-ray crystallographic data of complexes 2, 4, 5 and 6
Compound
2
4
5
6
Formula
Mr
C5H42Au2P2S2·2(CH2Cl2)
1380.72
C50H42Au2P2S2
1162.83
C46H36Au2N2P2S2
1136.76
C52H40Au2N2P2S2
1212.85
Crystal size (mm)
Crystal system
Space group
0.070 × 0.06 × 0.05
Monoclinic
C2/c
0.24 × 0.18 × 0.12
Monoclinic
P2(1)/n
0.24 × 0.20 × 0.18
Monoclinic
C2/c
0.07 × 0.06 × 0.05
Triclinic
P1
ˉ
Cell constants:
a (Å)
b (Å)
c (Å)
α (°)
β (°)
γ (°)
V (Å3)
Z
23.2023(4)
13.8267(2)
18.1353(3)
90
104.409(2)
90
5635.0(16)
4
1.628
5.456
2680
100(2)
55
14.4157(2)
9.02110(10)
16.5956(2)
90
105.8050(10)
90
2076.59(4)
2
1.860
7.270
1124
100(2)
55
14.480(3)
15.850(3)
16.890(3)
90
97.86(3)
90
3840.0(13)
4
1.966
7.862
2184
100(2)
55
8.0066(16)
10.946(2)
13.085(3)
83.58(3)
73.91(3)
80.08(03)
1082.9(4)
1
1.860
6.976
586
100(2)
55
Dx (Mg m−3
)
µ (mm−1
F (000)
T (K)
)
2θmax
No. of refl.: measured
Independent
Transmissions
Rint
27 864
5209
0.7686–0.6971
0.0323
334
20 406
3838
0.4758–0.2743
0.0209
253
24 212
3558
0.3319–0.2541
0.0567
245
6385
4002
0.7218–0.6409
0.0628
271
Parameters
Restraints
56
1.068
0.0746
0.0287
2.255
0
0
0
Goodness of fit on F2
wR (F2, all refl.)
R (I > 2σ(I))
1.059
1.023
1.026
0.0333
0.0133
0.430
0.0998
0.0383
2.600
0.0790
0.0489
1.209
Max. Δρ (e Å−3
)
(b) E. R. T. Tiekink and J.-G. Kang, Coord. Chem. Rev., 2009,
25–3, 1627.
Acknowledgements
The authors gratefully acknowledge the Ministerio de Econo-
mía y Competitividad-FEDER (CTQ2010-20500-C01-C02) and
DGA-FSE (E77) for financial support. VL and MA also thank
Università degli Studi di Cagliari for financial support.
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