Luminescent gold(I) and copper(I) phosphane complexes containing the 4-nitrophenylthiolate ligand: Observation of π→π* charge-transfer emission

Article abstract of DOI:10.1002/ejic.200700675

Gold(I) and copper(I) phosphane complexes containing the 4-nitrophenylthiolate ligand, namely [(PCy₃)Au(SC₆H ₄NO₂-4)] (1) (PCy₃ = tricyclohexylphosphane), [Au₂(μ-dcpm)-(SC₆H

Full text of DOI:10.1002/ejic.200700675

FULL PAPER
DOI: 10.1002/ejic.200700675
Luminescent Gold(I) and Copper(I) Phosphane Complexes Containing the 4-
Nitrophenylthiolate Ligand: Observation of πǞπ* Charge-Transfer Emission
Cheng-Hui Li,[a] Steven Chi Fai Kui,[b] Iona Hiu Tung Sham,[b] Stephen Sin-Yin Chui,[b] and
Chi-Ming Che*[a,b]
Keywords: Gold / Copper / Phosphane / S ligands / Phosphorescence
Gold(I) and copper(I) phosphane complexes containing the
4-nitrophenylthiolate ligand, namely [(PCy3)Au(SC6H4NO2-
transfer transition. The assignment is supported by the re-
sults of DFT and TDDFT calculations on the model com-
plexes [PH3Au(SC6H4NO2-4)] and [(µ2-SC6H4NO2-4)2(µ3-
SC6H4NO2-4)2(CuPH3)4]. The emissions of solid samples and
glassy solutions (methanol/ethanol, 1:4, v/v) of 1–4 at 77 K
are assigned to the [π(S)Ǟπ*(C6H4NO2-4)] charge-transfer
excited state. Metallophilic interactions are not observed in
both solid state and solutions of complexes 1–3.
4)] (1) (PCy3
= tricyclohexylphosphane), [Au2(µ-dcpm)-
(SC6H4NO2-4)2] (2) [dcpm = bis(dicyclohexylphosphanyl)-
methane], [Au2(µ-dppm)(SC6H4NO2-4)2] (3) [dppm = bis(di-
phenylphosphanyl)methane], and [(µ2-SC6H4NO2-4)2(µ3-
SC6H4NO2-4)2(CuPPh3)4] (4), were prepared and charac-
terized by X-ray crystal analysis. All of these complexes show
an intense absorption band with λmax at 396–409 nm attrib-
uted to the intraligand (IL) π(S)Ǟπ*(C6H4NO2-4) charge-
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2008)
SC6H4NO2-4)2(CuPPh3)4] (4). Complexes 1–4 represent ex-
amples of d10-metal thiolate complexes of which both the
fluorescence and phosphorescence from intraligand πǞπ*
charge-transfer excited states could be observed.[11–13]
Introduction
Metal complexes with a d10 configuration, in particular
those containing phosphane and/or thiolate ligands, exhibit
interesting photophysical and photochemical properties.[1,2]
It is well documented that metallophilic interaction has a
significant effect on the emission properties of this class of
complexes.[3,4] The emission from the metal-centred
3[5dσ*6pσ] excited state of binuclear gold(I) complexes with
bridging phosphane ligands usually occurs in the UV re-
gion.[5] If the counterion or solvent molecule is in the vicin-
ity of the AuI ion, an exciplex is readily formed and this
leads to a red-shift in emission energy.[5,6] A similar phe-
nomenon has also been found for silver(I) and copper(I)
phosphane complexes.[3,4,7] For d10 metal phosphane com-
plexes containing thiolate ligands, the thiolate to gold(I)
charge-transfer excited state has often been proposed to ac-
count for their photoluminescence.[8–10] In this work, we
have prepared several d10 metal complexes which exhibit
emissive πǞπ* IL (intraligand) charge-transfer excited
states. By utilizing the “donor–acceptor” type p-NO2–
C6H4SH ligand, we have obtained [(PCy3)Au(SC6H4NO2-
4)] (1), [Au2(µ-dcpm)(SC6H4NO2-4)2] (2), [Au2(µ-
dppm)(SC6H4NO2-4)2] (3), and [(µ2-SC6H4NO2-4)2(µ3-
Results and Discussion
Synthesis and Characterizations
Complexes 1–3 were prepared via the reaction of
[(PCy)3AuCl], [Au2(µ-dcpm)Cl2], or [Au2(µ-dppm)Cl2] with
the 4-nitrophenylthiolate ligand in the presence of KOH.
Complex 4 was prepared by reacting [Cu(SC6H4NO2-4)]ϱ
with triphenylphosphane. All four complexes are stable in
both solid state and CH2Cl2 solutions, and have been char-
1
acterized by elemental analyses, H NMR and 31P NMR
spectroscopy, and X-ray diffraction studies. The 31P NMR
spectrum of 4 shows two signals, whereas that of 1–3 shows
a single signal in each case. This is consistent with the fact
that the phosphorus atoms in 4 are in different coordination
environments as revealed by its crystal structure.
Crystal Structures
[a] Coordination Chemistry Institute and the State Key Labora-
tory of Coordination Chemistry, Nanjing University,
Nanjing 210093, PR China
The crystal data of 1–4 are listed in Table 5,[14] while se-
lected bond lengths and angles of 1–3 and 4 are listed in
Tables 1 and 2, respectively. Complex 1 has a slightly bent
geometry [P(1)–Au(1)–S(1) 171.64(5)°, Figure 1] in which
the nitro group is almost coplanar with the thiophenyl moi-
ety. The Au–P distance [2.268(2) Å] of 1 is slightly longer
[b] Department of Chemistry and the HKU-CAS Joint Laboratory
on New Materials, The University of Hong Kong,
Pokfulam Road, Hong Kong SAR, PR China
E-mail: cmche@hku.hk
Supporting information for this article is available on the
WWW under http://www.eurjic.org/ or from the author.
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C.-H. Li, S. C. F. Kui, I. H. T. Sham, S. S.-Y. Chui, C.-M. Che
FULL PAPER
than that for other literature-reported gold(I) phosphane
complexes containing thiolate ligands (2.239–2.257 Å).[15]
This is presumably due to the inductive effect of the nitro
group. On the other hand, the Au–S distance of 2.297(2) Å
in 1 is comparable to that in [(PPh3)Au{SC6H4(m-Cl)}]
[2.292(2) Å][15] and falls within the range of typical values
(2.291–2.314 Å) reported for gold(I) phosphane thiolate
complexes.[15] Neighbouring molecules of 1 are arranged in
a tilted head-to-tail fashion at a dihedral angle of 22.7°.
The tilting could be related to the intermolecular hydrogen
bonding [O(2)···H(11B) 2.498 Å] and short C···H contacts
[C(21)···H(9A) 2.868 Å and C(24)···H(10B) 2.745 Å].
Figure 2. Molecular structure of 2 with thermal ellipsoids at 30%
probability. Hydrogen atoms are omitted for clarity.
thiolate; where n = 1), the anti conformation is less com-
monly encountered as AuI···AuI interaction would favour a
syn conformation.[16,17,18] Since the bridging diphosphane
ligand in 3 has only one –CH2– unit, the dipolar interaction
between the two 4-nitrophenylthiolate ligands accounts for
the anti conformation.
Figure 1. Molecular structure of 1 with thermal ellipsoids at 30%
probability. Hydrogen atoms are omitted for clarity.
The coordination geometry of the Au atom in 2 slightly
deviates from linearity [P(1)–Au(1)–S(1) 173.34(7)°, Fig-
ure 2]. Each molecule of 2 has a C2 symmetry with a crys-
tallographic twofold rotation axis that passes through the
carbon atom [C(1)] of the methylene group and lies on the
P–CH2–P plane of the dcpm ligand. The Au–P distance
[2.264(2) Å] of 2 is comparable to that of 1 [2.268(2) Å]
while its Au–S distance [2.303(2) Å] is slightly longer
[2.297(2) Å for 1]. The two P–Au–S moieties bridged by the
diphosphane ligand are directed away from each other, pre-
sumably due to the chelating effect of the dcpm ligand and
the dipolar repulsion between the two 4-nitrophenylthiolate
ligands (Figure 2). The planes of the two 4-nitrophenyl moi-
eties in 2 are almost parallel as in the case of 1. Interest-
ingly, there is weak hydrogen bonding between O(1) of the
4-NO2C6H4S ligand and C–H moieties of the dcpm ligand
[O(1)···H(1A) 2.456 Å, O(1)···H(9B) 2.676 Å, and O(1)···
H(7B) 2.692 Å] in addition to that involving O(2) [O(2)···
H(9A) 2.719 Å].
Figure 3. Molecular structure of 3 with thermal ellipsoids at 30%
probability. Hydrogen atoms are omitted for clarity.
AuI···AuI interaction has not been observed in the solid
state of 1–3. The shortest AuI···AuI distance in 2 is 4.522 Å
(Table 1). This distance is significantly longer than the sum
of van der Waals radii (3.7 Å) for two gold atoms. The ab-
sence of aurophilic interactions is probably a consequence
of steric hindrance of the phosphane ligands and dipolar
repulsive interaction of the 4-nitrophenylthiolate ligands.
Table 1. Selected bond lengths [Å] and angles [°] for 1–3.
1
2
3
X-ray crystal structure analysis revealed that 3 adopts an
anti conformation in the solid state. Figure 3 depicts the
molecular structure of 3, in which there are two chemi-
cally equivalent but crystallographically inequivalent
Au(1)–P(1)
Au(1)–S(1)
Au(2)–P(2)
Au(2)–S(2)
2.268(2)
2.297(2)
–
–
–
2.264(2)
2.303(2)
–
2.257(2)
2.289(3)
2.267(2)
2.284(3)
5.387
7.414
175.2(1)
175.4(7)
–
AuSC6H4NO2-4 moieties bridged by a dppm ligand. The AuI···AuI (intramolecular)
4.522
8.425
AuI···AuI (intermolecular) 7.690
P(1)–Au(1)–S(1)
P(2)–Au(2)–S(2)
anti conformation is imposed by the sterically bulky phenyl
groups of the dppm ligand, and is stabilized by intermo-
lecular hydrogen bonding [O(1)···H(37B) 2.334 Å, O(4)
···H(37A) 2.426 Å, and O(2)···H(5) 2.654 Å], short O···C
contact [between a NO2 group and the C–H group on the
171.64(5) 173.34(7)
–
–
The structure of 4 is depicted in Figure 4. Unlike [(µ3-
methylene, O(1)···C(37) 3.219 Å], and weak C–H interac- SPh)2(µ-SPh)2(CuPPh3)4] with a “step” structure,[19] it has
tions [C(12)···H(29) 2.830 Å and C(1)···H(11) 2.900 Å]. It is a Cu4S4 core in a distorted “open” cubane-like framework.
worth noting that for [Au{P-(CH2)n-P}X2] (X = halide or Most of the Cu···S distances (2.254–2.552 Å) fall within the
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Luminescent Gold(I) and Copper(I) Phosphane Complexes
range of values reported for steric bulky polynuclear cop- (O···H distance of 2.459–2.683 Å) or those of neighbouring
per(I) thiolate complexes with phosphane ligands.[19–21] p-NO2C6H4S ligands (2.441–2.698 Å), (ii) O···C contacts
However, the Cu(1)–S(2) [3.957(5) Å] and Cu(3)–S(4) (3.109–3.214 Å), (iii) C···H interactions between aryl C
[2.964(4) Å] distances are too long to be considered as a atoms of the p-NO2C6H4S ligand and H atoms of the tri-
bond and some of the angles significantly deviate from 90° phenylphosphane ligand (2.741–2.825 Å). Of particular
(77–121°) revealing that 4 would be more appropriately de- interest is that one of the NO2 groups is involved in a bifur-
scribed to have a distorted “open” cubane structure cated H-bond network [N(2)–O(6)···H(4)–C(4) 2.459 Å and
(Table 2). Such distortion might be caused by steric repul- N(2)–O(6)···H(55)–C(68) 2.521 Å]. Both the copper and
sion between triphenylphosphane and p-NO2C6H4S li- sulfur atoms in 4 individually have two coordination modes.
gands. In the crystal structure of 4, there are two S···H con- Two of the copper atoms are triply coordinated [µ3; Cu(1)
tacts [S(2)···H(60) 2.955 Å] formed between two neighbour- and Cu(3); denoted by Cutrig] and the other two copper
ing molecules in each unit cell.[22] The crystal structure also atoms are in a tetrahedral environment [µ4; Cu(2) and
reveals the presence of other intermolecular interactions in- Cu(4); denoted by Cutet]. For the sulfur atoms, S(2) and
cluding (i) hydrogen bonding which involve the O atoms of S(4) are doubly bridging (µ2) while S(1) and S(3) are triply
NO2 groups and the phenyl C–H of phosphane ligands bridging (µ3). The Cu–S distances range with the coordina-
tion modes of the copper and sulfur atoms: Cutet–(µ3-S)
(average: 2.468 Å) Ͼ Cutet–(µ2-S) (2.348 Å) Ͼ Cutrig–(µ3-S)
(2.268 Å) and Cutrig–(µ2-S) (2.287 Å). The six Cu–Cu dis-
tances, in the range of 3.02–4.12 Å, are greater than the sum
of van der Waals radii of 2.80 Å, thus there is no CuI···CuI
interaction in 4.
Table 2. Selected bond lengths [Å] and angles [°] for 4.
Cu(1)–S(1)
Cu(1)···S(2)
Cu(1)–S(3)
Cu(1)–P(1)
Cu(3)–S(2)
Cu(3)–S(3)
Cu(3)···S(4)
Cu(3)–P(3)
S(2)···H(60)
P(1)–Cu(1)–S(1)
S(1)–Cu(1)–S(3)
P(2)–Cu(2)–S(4)
2.271(2)
3.957(4)
2.279(2)
2.184(2)
2.287(3)
2.254(2)
2.964(4)
2.195(3)
2.955(4)
140.36(9)
95.65(9)
129.33(9)
Cu(2)–S(1)
Cu(2)–S(2)
Cu(2)–S(4)
Cu(2)–P(2)
Cu(4)–S(1)
Cu(4)–S(3)
Cu(4)–S(4)
Cu(4)–P(4)
2.467(2)
2.395(3)
2.332(3)
2.243(3)
2.385(3)
2.552(3)
2.318(2)
2.223(3)
3.0248(2)
124.0(1)
86.07(8)
116.89(9)
118.87(9)
99.17(7)
124.9(1)
94.06(7)
123.67(9)
143.93(8)
98.98(9)
91.44(9)
121.0(1)
117.5(1)
80.81(8)
81.15(8)
Cu(2)···Cu(4)
P(1)–Cu(1)–S(3)
S(1)–Cu(4)–S(3)
P(2)–Cu(2)–S(2)
P(2)–Cu(2)–S(1)
S(2)–Cu(2)–Cu(4)
P(3)–Cu(3)–S(2)
S(3)–Cu(4)–Cu(2)
P(4)–Cu(4)–S(1)
P(4)–Cu(4)–Cu(2)
S(4)–Cu(2)–S(1)
S(4)–Cu(4)–S(3)
Cu(1)–S(1)–Cu(2)
Cu(3)–S(3)–Cu(1)
Cu(1)–S(3)–Cu(4)
Cu(4)–S(4)–Cu(2)
P(2)–Cu(2)–Cu(4) 143.78(8)
S(2)–Cu(2)–S(1)
P(3)–Cu(3)–S(3)
S(3)–Cu(3)–S(2)
P(4)–Cu(4)–S(4)
P(4)–Cu(4)–S(3)
S(4)–Cu(2)–S(2)
S(4)–Cu(4)–S(1)
Cu(1)–S(1)–Cu(4)
Cu(4)–S(1)–Cu(2)
Cu(3)–S(3)–Cu(4)
95.0(1)
129.8(1)
105.05(9)
122.51(9)
122.0(1)
89.62(9)
101.78(9)
84.73(9)
77.10(7)
98.25(9)
Cu(3)–S(2)–Cu(2) 101.7(1)
Absorption Spectroscopy
The spectroscopic data of 1–4 are summarized in Table 3.
The electronic absorption spectra of 1–4 in CH2Cl2 solu-
tions at 298 K show an intense band with λmax at 396–
409 nm and a shoulder at 254–259 nm (Figure 5). Com-
plexes 3 and 4 show additional shoulders at 277–280 nm
(Table 3). Assignment of the absorption bands are based
on comparison with the spectroscopic data of [Au(PR3)Cl]
complexes, and on the coordination number of copper
atoms as well as coordination mode of the thiolate li-
Figure 4. (a) Molecular structure of 4 with thermal ellipsoids at
30% probability. Hydrogen atoms and the phenyl groups on the
triphenylphosphane ligands are omitted for clarity. (b) Interaction
between two molecules of 4 in the unit cell viewed along the b-axis. gands.[9,16,18,23] The shoulders at 254–259 nm are attributed
Eur. J. Inorg. Chem. 2008, 2421–2428
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C.-H. Li, S. C. F. Kui, I. H. T. Sham, S. S.-Y. Chui, C.-M. Che
FULL PAPER
to π(phenyl)Ǟπ(phenyl)* transitions since the 4-nitrophen-
ylthiolate ligand exhibits a similar absorption shoulder.
Complexes 3 and 4 absorb more strongly than 1 and 2 in
the spectral region 277–280 nm, presumably this is caused
by the intraligand transition of the phenyl groups of the
phosphane ligands. The intense band with λmax at 396–
409 nm is red-shifted from the gold complexes (1–3, 396–
399 nm) to the copper complex (4, 409 nm, Table 3), indi-
cating that the energy of this transition is affected by the
metal ion. An ethanolic solution of KSC6H4NO2-4 exhibits
an intense absorption at λmax = 420 nm, while that of the
free ligand is at 356 nm. On the basis of these findings, we
assign the absorption at λmax = 396–409 nm to the
[π(S)Ǟπ*(C6H4NO2-4)] intraligand charge-transfer transi-
tion and the shift in λmax values could be accounted for by
the perturbation in electronic charge on the thiolate S atom
by H+, CuI, or AuI.
The solvent effect on the absorption spectra of 1–4 has
been studied (Table 4 and the absorption spectra of 1–4 in
various solvents are given in the Supporting Information).
Figure 5. Absorption spectra of (a) 1, (b) 2, (c) 3, and (d) 4 in
CH2Cl2 solutions at 298 K.
Table 4. Solvent effect on the absorption spectra of 1–4.
Complex Solvent[a]
λabs [nm]
ε [dm3 mol–1 cm–1]
Table 3. Absorption and photophysical data for 1–4.
1
2
3
4
CH2Cl2
MeOH (96%) + CH2Cl2 (4%)
MeCN (96%) + CH2Cl2 (4%)
(CH3)2CO (96%) + CH2Cl2 (4%) 392 (18820)
THF
DMF
DMSO
C6H6 (96%) + CH2Cl2 (4%)
EA (96%) + CH2Cl2 (4%)
396 (16810)
385 (12890)
391 (13330)
T [K] Medium
λabs [nm][a]
λem [nm][c]
τ [µs][d]
ε [dm3 mol–1 cm–1][b]
1
298
CH2Cl2
254 (sh, 7120),
396 (18800), 465 (25)
nonemissive
397 (20470)
399 (18780)
402 (19700)
393 (19080)
394 (21700)
298
77
solid
solid
nonemissive
450, 470 (Ͻ0.08)
531 (3.6), 564
452,
471 (Ͻ0.08),
533 (3.8), 564
77
MeOH/
EtOH, 1:4
CH2Cl2
MeOH (96%) + CH2Cl2 (4%)
MeCN (96%) + CH2Cl2 (4%)
(CH3)2CO (96%) + CH2Cl2 (4%) 400 (34990)
THF
DMF
DMSO
C6H6 (96%) + CH2Cl2 (4%)
EA (96%) + CH2Cl2 (4%)
398 (33050)
390 (28300)
396 (40060)
2
3
298
CH2Cl2
254 (sh, 25030),
399 (40800), 470 (30)
nonemissive
399 (33340)
405 (33050)
409 (38130)
393 (22320)
393 (21530)
298
77
solid
solid
nonemissive
475 (sh, Ͻ0.08)
546, 577 (4.3)
468 (Ͻ0.08),
546 (4.4), 576
77
MeOH/
EtOH, 1:4
CH2Cl2
MeOH (96%) + CH2Cl2 (4%)
MeCN (96%) + CH2Cl2 (4%)
(CH3)2CO (96%) + CH2Cl2 (4%) 398 (37350)
THF
DMF
DMSO
C6H6 (96%) + CH2Cl2 (4%)
EA (96%) + CH2Cl2 (4%)
397 (41500)
392 (30100)
394 (34610)
298
CH2Cl2
257 (sh, 23730),
277 (20980),
397 (34860), 490 (45)
nonemissive
298
77
solid
solid
nonemissive
443 (Ͻ0.08),
608 (2.5)
459 (Ͻ0.08),
547 (2.6)
399 (44200)
407 (35420)
407 (32800)
394 (33700)
393 (38600)
77
MeOH/
EtOH, 1:4
4
298
CH2Cl2
259 (sh, 62110),
280 (sh, 48715),
409 (34610), 530 (70)
nonemissive
CH2Cl2
MeOH (96%) + CH2Cl2 (4%)
MeCN (96%) + CH2Cl2 (4%)
406 (34000)
408 (22900)
434 (18190)
298
77
solid
solid
631 (0.2)
485 (Ͻ0.08),
634 (3.4)
469 (Ͻ0.08),
523 (4.0), 554
(CH3)2CO (96%) + CH2Cl2 (4%) 404 (11160)
THF
401 (20400)
440 (26980)
445 (18800)
401 (39180)
403 (31260)
DMF
77
MeOH/
EtOH, 1:4
DMSO
C6H6 (96%) + CH2Cl2 (4%)
EA (96%) + CH2Cl2 (4%)
[a] Absorption maximum at 5ϫ10–5 . [b] Molar extinction coeffi-
cient. [c] Emission maximum. [d] Emission lifetime.
[a] EA = ethyl acetate.
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Luminescent Gold(I) and Copper(I) Phosphane Complexes
The solvent effect on the absorption λmax of 1–3 is minimal; λmax are blue-shifted from 608 and 634 nm in the solid state
for example, the [π(S)Ǟπ*(C6H4NO2-4)] transition of 1 to 547 and 523 nm in glassy solutions, respectively. This
spans only a narrow range of 385–402 nm when the solvent blue-shift in emission λmax is not surprising since excited-
changes from methanol to dimethyl sulfoxide. In contrast, state structural distortion is diminished in frozen glassy
the absorption λmax of 4 undergoes a larger shift upon solutions. The excitation spectra (Figure 6) recorded for the
changing the solvent from CH2Cl2 (406 nm) to CH3CN emission of 1–4 in glassy solutions individually show a
(434 nm), DMF (440 nm), and DMSO (445 nm).
band with λmax at 392–413 nm. On the basis of the similar-
ity between the excitation spectra and the corresponding
absorption spectra, in addition to the results of emission
lifetime measurements, the lower energy emissions (λmax at
523–634 nm, Table 3) of 1–4 in the solid state and glassy
Emission Spectroscopy
3
solutions at 77 K are assigned to the [π(S)Ǟπ*(C6H4NO2-
The photophysical data of 1–4 are summarized in
Table 3. Complexes 1–4 are nonemissive in CH2Cl2 solu-
tions. At 298 K, a solid sample of 4 exhibits an intense
emission with λmax at 631 nm while 1–3 are nonemissive
under the same conditions. Upon excitation at 360 nm at
77 K, solid samples of 1–4 individually show dual emissions
with λmax at 443–485 and 564–634 nm (Table 3). For each
complex, the lower energy emission is more intense than
the higher energy one. The higher energy emission, in each
case, has a lifetime in the nanosecond time regime while
the lifetimes of all the lower energy emissions are in the
microsecond time regime; hence the emission with λmax at
443–485 nm correspond to fluorescence while that at 564–
634 nm is phosphorescence. The solid state emission of 1 is
vibronically structured with peak maxima at 450, 470, 531,
and 564 nm. The average vibronic spacing is 1023 cm–1 and
could be assigned to υ(C=C) stretching in the
π*(C6H4NO2-4) excited states.
4)] (intraligand charge-transfer) excited state.
The polarization ratios of the lower energy emissions of
1–4 were estimated using the following equation.
IVV·IHH
Polarization ratio:
IVH·IHV
where IVV is intensity with both polarizers at 0°; IHH is in-
tensity with both polarizers at 90°; IVH is intensity with
polarizers crossed (excitation: vertical; emission: horizon-
tal); IHV is intensity with polarizers crossed (excitation:
horizontal; emission: vertical). The polarization ratios are:
0.74 for 1 at 533 nm; 1.07 for 2 at 546 nm; 0.99 for 3 at
547 nm; 1.09 for 4 at 523 nm.
Computational Results
DFT calculations on the model complexes [(PH3)-
Au(SC6H4NO2-4)] and [(µ2-SC6H4NO2-4)2(µ3-SC6H4NO2-
4)2(CuPH3)4] were performed. The mononuclear [(PH3)-
Au(SC6H4NO2-4)] was used to model 1–3 as there is no
AuI···AuI interaction found in their crystal structures. The
complex [(µ2-SC6H4NO2-4)2(µ3-SC6H4NO2-4)2(CuPH3)4]
was used to model 4. The geometries of the model com-
plexes were fully optimized in their ground states without
symmetry constraint. The quality of the optimized struc-
tures (Figure 7) was checked by comparing the results with
the X-ray crystal structures of 1–4. For [(PH3)-
Au(SC6H4NO2-4)], the calculated Au–S and Au–P distances
are 2.354 and 2.333 Å, respectively, which are in good
agreement with the experimental values (Au–S 2.29–2.32 Å,
Au–P 2.26–2.28 Å for 1–3). On the other hand, the calcu-
lated S–C (1.783 Å), N–C (1.466 Å), and N–O (1.236 Å)
distances are slightly longer than the experimental values of
1.74–1.75, 1.39–1.50, and 1.20–1.27 Å found for 1–3,
respectively. The complex [(µ2-SC6H4NO2-4)2 (µ3-
SC6H4NO2-4)2(CuPH3)4] has a distorted cubane structure
as in 4. The calculated Cu–P (2.195–2.228 Å) and Cu–S
(2.267–2.466 Å) distances are also comparable to those of
4 (2.19–2.25 and 2.26–2.47 Å, respectively).
Dual emissions have also been observed for 1–4 in glassy
solutions (methanol/ethanol, 1:4, v/v) at 77 K (Figure 6).
The emissions with λmax at 452–469 nm are comparable in
energy to the high energy solid-state emission of 1–4 re-
corded at 77 K. For 3 and 4, their lower energy emission
On the basis of the optimized structures of the model
complexes depicted in Figure 7, TD-DFT calculations were
performed to check the assignment of the absorption spec-
tra. The calculated lowest energy dipole allowed transitions
could be compared to the intense absorptions of 1–4 at λmax
= 396–409 nm. The lowest energy absorption for [(PH3)-
Au(SC6H4NO2-4)] was calculated at 405 nm. This corre-
Figure 6. Excitation (dashed) and emission (solid) spectra of (a) 1,
(b) 2, (c) 3, and (d) 4 in glassy solutions (methanol/ethanol, 1:4, v/
v) at 77 K.
Eur. J. Inorg. Chem. 2008, 2421–2428
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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2425

C.-H. Li, S. C. F. Kui, I. H. T. Sham, S. S.-Y. Chui, C.-M. Che
FULL PAPER
Figure 7. DFT-optimized geometries of (a) [(PH3)Au(SC6H4NO2-
4)] and (b) [(µ2-SC6H4NO2-4)2(µ3-SC6H4NO2-4)2(CuPH3)4].
sponds to the transition from HOMO to LUMO. Popula-
tion analysis revealed that the HOMO of [(PH3)-
Au(SC6H4NO2-4)] is mainly of S(pπ) orbital character
(62.04% pπ orbital of the sulfur atom and 34.75% pπ orbital
of the p-nitrophenyl moiety), while the LUMO is domi-
nated by pπ orbitals of the p-nitrophenyl moiety (97.87%)
as depicted in Figure 8.
Figure 8. Representation of the (a) HOMO and (b) LUMO for
[(PH3)Au(SC6H4NO2-4)] involved in the lowest energy transition.
Figure 9. Representation of the (a) HOMO-1, (b) HOMO, (c)
LUMO, (d) LUMO+1, (e) LUMO+2, and (f) LUMO+3 for [(µ2-
SC6H4NO2-4)2(µ3-SC6H4NO2-4)2(CuPPh3)] involved in the lowest
energy transitions.
For
[(µ2-SC6H4NO2-4)2(µ3-SC6H4NO2-4)2(CuPH3)4],
several electronic transitions at 397–415 nm have been cal-
culated. These transitions involve electronic excitation from
HOMO-1 and HOMO to several unoccupied molecular or-
bitals from LUMO to LUMO+3. The HOMO-1 and
HOMO of [(µ2-SC6H4NO2-4)2(µ3-SC6H4NO2-4)2(CuPH3)4]
are mainly of S(pπ) character (HOMO-1, 50.5% pπ orbital
of the sulfur atom and 45.3% pπ orbital of the p-nitrophenyl
moiety; HOMO, 50.69% pπ orbital of the sulfur atom and
45.12% pπ orbital of the p-nitrophenyl moiety), while the
LUMO to LUMO+3 are localized on the pπ orbitals of the
p-nitrophenyl groups (89.94%, 88.59%, 89.42%, and
87.13% for LUMO, LUMO+1, LUMO+2, and LUMO+3,
respectively) as depicted in Figure 9. The metal ions of both
Concluding Remarks
A series of gold(I) and copper(I) phosphane complexes
containing the 4-nitrophenylthiolate ligand have been syn-
thesized and structurally characterized. No metal–metal in-
teraction was found in the crystal structures of 1–4. Com-
plexes 1–4 exhibit phosphorescence at 560–632 nm in ad-
dition to fluorescence at 440–485 nm. The intense absorp-
tion at 395–410 nm is assigned to the π(S)Ǟπ*(C6H4NO2-
4) transition and the assignment is supported by the results
of DFT and TD-DFT calculations. Accordingly, the phos-
phorescence of 1–4 is assigned to the 3[π(S)Ǟπ*(C6H4NO2-
4)] excited state.
[(PH3)Au(SC6H4NO2-4)]
and
[(µ2-SC6H4NO2-4)2(µ3-
SC6H4NO2-4)2(CuPH3)4] have no more than 5% contri-
bution to the molecular orbitals involved in the calculated
electronic transitions at 397–415 nm. Therefore, the calcu-
lated electronic transitions at 405 nm in the cases of 1–3 Experimental Section
and 397–415 nm in the case of 4 are assigned to the intrali-
Reagents and Instrumentation: 1H NMR and 31P NMR spectra
gand charge-transfer transition mainly from the π electrons
(pπ) of the S atom to the π* orbitals of the p-nitrophenyl
moiety. The calculated transition energies are in good agree-
ment with the experimental values, 396 nm for 1 and
409 nm for 4 (Table 3).
were recorded with Bruker AMX-300/400 spectrophotometers at
298 K in CDCl3. Elemental (C, H, and N) analyses were performed
with a Perkin–Elmer 240C analyzer. UV/Vis absorption spectra
were obtained with a Perkin–Elmer Lambda 19 UV/Vis spectro-
photometer. Emission spectra were recorded with a SPEX Fluo-
2426
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© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2008, 2421–2428

Luminescent Gold(I) and Copper(I) Phosphane Complexes
rolog-3 spectrophotometer. Low-temperature (77 K) emission spec- adding diethyl ether (20 mL). The solid was washed with diethyl
tra were recorded with the sample in glassy [methanol/ethanol (4:1,
v/v)] solution or in solid form placed in a quartz tube (with a 5 mm
diameter) in a Dewar immersed with liquid nitrogen. The emission
spectra were corrected for the efficiency of the monochromator and
photomultiplier and stability of the xenon lamp. Emission lifetime
ether and dried in vacuo. The crude product was recrystallized by
vapour diffusion of diethyl ether into dichloromethane solution.
Yield 0.38 g, 86%. C37H54Au2N2O4P2S2 (1110.82): calcd. C 40.01,
H 4.90, N 2.52; found C 39.78, H 4.85, N 2.76. 1H NMR
3
(300 MHz, CDCl3): δ = 7.91 (d, J = 8.2 Hz, 4 H, aryl H ortho to
3
measurements were carried out with a Quanta Ray DCR-3 pulsed S), 7.60 (d, J = 8.1 Hz, 2 H, aryl H meta to S), 2.23–1.29 (m, 44
Nd:YAG laser system (pulse output 355 nm, 8 ns).
H, dcpm; 2 H, –PCH2P–) ppm. 31P{1H} NMR (400 MHz, CDCl3):
δ = 50.25 (s) ppm.
All reactions were conducted under a nitrogen atmosphere at room
temperature using standard Schlenk techniques. 4-Nitrothiophenol,
PCy3 (tricyclohexylphosphane), dppm [bis(diphenylphosphanyl)-
methane], and dcpm [bis(dicyclohexylphosphanyl)methane] were
obtained from commercial sources. [(PCy3)AuCl], [Au2(µ-dppm)-
Cl2], and [Au2(µ-dcpm)Cl2] were prepared using the procedure de-
scribed for the synthesis of [Au(PR3)X].[24] [Cu(SC6H4NO2-4)]ϱ was
prepared using the method described for [Cu(SC6H5)]ϱ.[25]
[Au2(µ-dppm)(SC6H4NO2-4)2] (3): Complex 3 was prepared in a
similar manner to 2, except that dppm was used instead of dcpm.
Yield 75%. C37H30Au2N2O4P2S2 (1086.62): calcd. C 40.90, H 2.78,
N 2.58; found C 40.92, H 2.90, N 3.09. 1H NMR (300 MHz,
CDCl3): δ = 3.73 (m, 2 H, –PCH2P-), 7.27–7.99 (m, 8 H, C6H4;
20 H, dppm) ppm. 31P{1H} NMR (400 MHz, CDCl3): δ = 31.53
(s) ppm.
[(PCy3)Au(SC6H4NO2-4)] (1): A solution of KSC6H4NO2-4, pre-
pared in situ by reacting HSC6H4NO2-4 (0.155 g, 1.00 mmol) and
KOH (1 molar equiv.) in MeOH (10 mL), was added dropwise to a
CH2Cl2 solution (20 mL) of [(PCy3)AuCl] (0.247 g, 0.500 mmol).
The mixture was stirred overnight before the solvent was removed.
The residue was extracted using dichloromethane and precipitation
was induced by adding diethyl ether (20 mL). The solid was washed
with diethyl ether and dried in vacuo. Recrystallization of the crude
product was carried out via vapour diffusion of diethyl ether into
dichloromethane solution. Yield 0.52 g, 82%. C24H37AuNO2PS
(631.54): calcd. C 45.64, H 5.91, N 2.22; found C 45.44, H 5.74, N
[(µ2-SC6H4NO2-4)2(µ3-SC6H4NO2-4)2(CuPPh3)4]
(0.215 g, 0.820 mmol) was added to
(4):
PPh3
a
suspension of
[Cu(SC6H4NO2-4)]ϱ (0.179 g, 0.820 mmol) in dichloromethane
(20 mL). The mixture was stirred for 5 h and a clear red solution
was obtained. Removal of the solvent gave a red solid which was
washed with diethyl ether. Yield 0.32 g, 79%. C96H76Cu4N4O8P4S4
(1919.89): calcd. C 60.05, H 3.99, N 2.92; found C 60.01, H 3.91,
N 2.98. 1H NMR (300 MHz, CDCl3): δ = 7.19–7.69 (m, 16 H,
C6H4; 60 H, PPh3) ppm. 31P{1H} NMR (400 MHz, CDCl3): δ =
31.39 (s), –1.21 (s) ppm.
X-ray Crystallography: The diffraction data of 1–4 (Table 5) were
obtained with a Siemens (Bruker) SMART CCD diffractometer
using graphite-monochromated Mo-Kα radiation (λ = 0.71073 Å).
Cell parameters were retrieved using the SMART software and re-
fined using SAINT on all observed reflections.[26] Data were col-
1
3
2.50. H NMR (300 MHz, CDCl3): δ = 7.93 (d, J = 8.4 Hz, 2 H,
aryl H ortho to S), 7.62 (d, 3J = 8.4 Hz, 2 H, aryl H meta to S),
2.13–1.23 (m, 33 H, Cy) ppm. 31P{1H} NMR (400 MHz, CDCl3):
δ = 58.73 (s) ppm.
[Au2(µ-dcpm)(SC6H4NO2-4)2] (2):
A solution of HSC6H4NO2 lected using the following strategy: 606 frames of 0.3° in ω with φ
(0.124 g, 0.600 mmol) and KOH (0.045 g, 0.60 mmol) in methanol
(20 mL) was added to a dichloromethane solution (20 mL) of
[Au2(dcpm)Cl2] (0.349 g, 0.400 mmol). The mixture was stirred
overnight before the solvent was removed. The residue was ex-
tracted with dichloromethane and precipitation was induced by
= 0°, 435 frames of 0.3° in ω with φ = 90°, and 235 frames of 0.3°
in ω with φ = 180°. An additional 50 frames of 0.3° in ω with φ =
0° were collected to allow for decay correction. The raw intensity
data sets were reduced using SAINT and corrected for Lorentz
and polarization effects. Absorption corrections were applied using
Table 5. Crystal data for 1–4.
1
2
3
4
Formula
Mr [gmol–1]
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
β [°]
γ [°]
C24H37AuNO2PS
631.54
monoclinic
P21/c
9.429(3)
24.699(7)
10.609(3)
90.00
99.241(5)
90.00
C37H54Au2N2O4P2S2
1110.82
monoclinic
C2/c
18.006(9)
12.942(9)
17.117(8)
90.00
95.00(5)
90.00
4
3974(4)
1.857
7.601
C37H30Au2N2O4P2S2
1086.62
C96H76Cu4N4O8P4S4
1919.89
triclinic
triclinic
¯
¯
P1
P1
10.876(2)
11.102(2)
15.990(3)
72.58(3)
82.19(3)
86.23(3)
2
1824.4(7)
1.978
8.276
14.130(3)
14.858(3)
22.812(5)
88.78(3)
86.90(3)
63.99(3)
2
4297.7(15)
1.484
1.209
Z
4
V [Å3]
2438.8(1)
1.720
6.204
Dcalc [gcm–3]
M [mm–1]
F(000)
1256
2168
1036
1968
2θmax [°]
56.20
52.90
10693 (4034)
222
0.905
0.066
0.075
1.534/–1.107
50.14
6801 (6426)
442
1.07
0.050
0.130
0.892/–2.398
50.80
15979 (15312)
1081
0.923
0.251
0.169
0.679/–0.411
No. of reflections (unique) 13214 (5271)
Parameters
GoF
271
0.973
0.074
0.123
R1[a][I Ͼ 2σ(I)]
wR2[b][I Ͼ 2σ(I)]
Residual peak/hole [eÅ–3] 1.485/–2.715
[a] R1 = Σ||Fo| – |Fc||/Σ|Fo|. [b] wR2 = [Σw(|Fo| – |Fc|)2/Σw|Fo|2]1/2
.
Eur. J. Inorg. Chem. 2008, 2421–2428
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
2427

C.-H. Li, S. C. F. Kui, I. H. T. Sham, S. S.-Y. Chui, C.-M. Che
FULL PAPER
SADABS supplied by Bruker.[27] The structures were solved by di-
rect methods using the program SHELXL-97 and refinement of F2
by full-matrix least-squares procedures was carried out with
SHELXTL software.[28] All non-hydrogen atoms were anisotropi-
cally refined. The hydrogen atoms were located theoretically and
not refined.[14]
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We gratefully acknowledge financial support by the National Natu-
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Research Scheme (N_HKU 742/04).
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Received: June 29, 2007
Published Online: April 15, 2008
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© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2008, 2421–2428