Luminescent metal complexes containing naphthalene and anthracene units 1

1





Chapter 1

Structural and Spectroscopic Properties of
d
10
Metal Thiolates

2

1.1 Introduction
Metal-thiolate complexes have been known since the beginning of coordination
chemistry. However, there is an increasing interest in the study of this species in the last two
decades which is due to a diversity of factors. First, metal-thiolate complexes are of great
importance, mainly because of the wide occurrence of cysteine thiolate in the coordination
sphere of many metal ions in various metalloproteins.
1
On the practical side, there is a growth in
the utilization of metal thiolates in medicine. For example, gold thiolates compounds are used in
the treatment of arthritis or cancers.
2
In addition, volatile metal-thiolates are common starting
materials for chemical vapor deposition of layers of metals or sulfides form vapor phase.
3
But
most important, the chemical and physical properties of metal-thiolate complexes are very rich:

there are numerous studies of the structures, reactivity, electronic spectroscopy and
electrochemistry of metal-thiolates continues to attract the attention of chemists.
There are many aspects of metal thiolate chemistry but we are particularly interested in
the photophysical, spectroscopic and structural properties of polynuclear d
10
metal thiolates. As
an emerging class of inorganic materials,
4
the polynuclear d
10
metal complexes display intriguing
structural diversity and interesting physical properties and chemical reactivity. Metals of a d
10

electronic configuration commonly form complexes with coordination numbers varying from
two to four and accordingly with a variety of geometries. For example, linear, trigonal planar and
tetrahedral copper(I) complexes are known. Accordingly, polynuclear d
10
metal complexes are
expected to display even greater structural complexity. While metal-ligand interactions play a
key role in defining the structures of the d
10
polynuclear complexes, the importance of d
10
-d
10

metal-metal interactions cannot be underestimated. In principle, the interaction between the
closed-shell d
10

metal centers would not lead to any chemical bonding. However, due to
configuration mixing of the filled nd orbitals with the empty orbitals derived from higher energy
(n+1)s and (n+1)p atomic orbitals, there is a weak attraction between the metal centers (Figure
1.1). This interactions, known as metallophilicity, have been widely observed in polynuclear
Cu(I), Ag(I) and Au(I) complexes and have a determining effect on the structures of the
complexes.
3

n+1p
z
n+1p
z
nd
z
2
nd
z
2
pσ
p
σ
∗
dσ∗
dσ
HOMO
LUMO
dσ∗−pσ∗
mixing
dσ−pσ
mixin

g
Figure 1.1
dσ∗−>pσ
transition


In addition to the structural effect, the d
10
-d
10
metal-metal interactions also have
pronounced effect on the electronic spectroscopy of the compounds. Because of the metal-metal
interactions, the highest occupied molecular orbital (HOMO) of a d
10
-d
10
bimetallic complex is
the filled dσ* orbital and the lowest unoccupied molecular orbital (LUMO) is the empty pσ
orbital. The lowest energy fully allowed electronic transition is
1
dσ*→pσ transition. Due to the
strong spin-orbital coupling, especially for heavy metals like Ag and Au, the transition would
lead to the formation of the spin-forbidden
3
dσ*
1
pσ
1
excited state. Previous studies on many
binuclear d

10
-d
10
Au
I
-Au
I
, Pt
0
-Pt
0
, Pd
0
-Pd
0
, Ag
I
-Ag
I
and Cu
I
-Cu
I
showed that the
3
dσ*
1
pσ
1
is

emissive and the complexes can display long-lived (µs) phosphorescence in solution or solid
state. As an electron is promoted from an antibonding dσ* to a bonding pσ orbital, the bond order
4

between the d
10
metal centers increases the
3
dσ*
1
pσ
1
excited state, leading to a contraction of the
metal core in the clusters.
5

In combination with different ligands, the ground state and excited state electronic
structures of the polynuclear d
10
complexes could be altered significantly as the involvement of
ligand orbitals in the frontier orbitals cannot be neglected. In accord, a number of luminescent
polynuclear d
10
metal complexes have been suggested to emit from an excited state other than
that of a pure metal-centered origin. Because of the completely filled d-shell, there is no ligand
field d-d transition in the polynuclear d
10
metal complexes.
6
However, depending on the nature

of the ligands coordinating to the metal centers, the complexes can display low-energy charge-
transfer transitions. In general, there are three types of intramolecular charge-transfer transitions,
which are classified according to the nature of the orbitals involved: (i) metal-to-ligand-charge-
transfer (MLCT), (ii) ligand-to-metal-charge-transfer transition (LMCT) and (iii) ligand-to-
ligand-charge-transfer transition (LLCT).
MLCT transitions occur with a transfer of electron from a metal-centered orbital to an
empty orbital which is predominantly ligand-based orbital. Such transitions tend to be prominent
in systems composed of an easily oxidized metal and a ligand containing a low energy acceptor
orbital. As d
10
metal ions are considered electron-rich, it can display low-energy MLCT
transition if the ligands contain low-lying empty orbitals.
[Cu(diimine)
2
]
+
(where diimine denotes the derivative of 1,10-phenanthroline or 2,2’-
bipyridine) complexes exhibited strong absorption in the visible region,
7
which was assigned as
metal-to-ligand charge-transfer (MLCT) transition where the electron was promoted from a 3d
orbital of copper to a low-lying π* orbital of the ligand (Figure 1.2). Because the emission
intensity varied with the temperature, therefore emission originated from at least two different
excited states. Kirchloff et al. proposed that the two states, separated by about 1800 cm
-1
,
represented the singlet and triplet spin states derived form the lowest energy MLCT state.
7e
and
this result was analysized by detailed group theoretical assignments.

7k

1
MLCT has higher energy
and greater radiative rate constant compared with
3
MLCT. Later short-lived emissions from
copper(I) bis-(diimine) compounds were examined using a time-correlated single photon
5

counting (TCSPC) technique with picosecond time resolution by Zainul.
8
On 400nm laser
excitation of [Cu(dmphen)
2
]
+
in CH
2
Cl
2
solution, prompt
1
MLCT fluorescence with a quantum
yield of (2.8 ± 0.8)×10
-5
was observed. [Ag(phen)(CN)]·(phen) (phen = 1,10-phenanthroline)
also showed both metal-to-ligand charge transfer (MLCT) mixed with the cyanide-to-ligand
charge transfer and [π
L

-π
L
*] of the uncoordinated phen species in the solid state.
9
(Figure 1.3)

N
N
N
N
R
R
R
R
Cu
N
N
N
N
Cu
R=CH
3
,

C
4
H
9
F
i

g
u
r
e

1
.
2
+
+


N
N
Ag C N
F
i
g
u
r
e

1
.
3


LMCT transitions originate from an electron transition which involves a filled ligand
orbital and an empty metal orbital. Usually metal complexes which contain electron-rich ligands
and/or high-valent metal center would display low-energy LMCT transition. Especially, ligands

which contain more than one lone-pair of electrons would have a lower LMCT energy because
the lone-pair electrons are higher in energy. Accordingly, many complexes containing
chalcogenides (S
2-
, Se
2-
) and thiolates (SR
-
) show low energy LMCT absorption bands in their
6

electronic spectroscopy. Notably LMCT transition is the lowest energy allowed transitions for
many mononuclear and polynuclear d
10
metal complexes which contain sulfides S
2-
or thiolates
ligands. Some of the complexes are photoluminescent and the emission is derived from the
3
LMCT excited states. For example [Cu
6
(µ-P^P)
4
(µ
3
-SePh)
4
](BF
4
)

2
(P^P=dppm, 1; (Ph
2
P)
2
NH),
2) (Figure 1.4).
10
The absorption shoulders at ca. 290 nm with tails extending to ca. 400 nm were
likely to arise form chalcogenolate ligand-centered and chalcogenolate–to-copper charge-transfer
(LMCT) transitions. Excitation of degassed acetone solution of 1 and 2 at λ > 350 nm produced a
low energy emission band at 626 and 700 nm, respectively. Such emission was assigned to
3
[PhSe
—
Cu
6
] LMCT transition mixed with copper-centered d-s state.

C
u
Cu Cu
Cu
Cu
Cu
P
Ph
2
Ph
2

P
P
Ph
2
PPh
2
Se
Se
Ph
2
P
Ph
2
P
Ph
2
P
PPh
2
Se Se
F
i
g
u
r
e

1
.
4

2+
2+
C
u
Cu Cu
Cu
Cu
Cu
P
Ph
2
Ph
2
P
HN
P
Ph
2
NH
PPh
2
Se
Se
Ph
2
P
HN
Ph
2
P

Ph
2
P
NH
PPh
2
Se Se
1
2


Phosphinidene group, like unsubstituted chalcogenide, is also a good σ-donor. [Cu
4
(µ-
dppm)
4
(µ
4
-PPh)](BF
4
)
2
11
(Figure 1.5) showed low energy absorption band at 466 nm which was
likely to be originated for the [P(phosphinidene)→Cu] ligand–to-metal charge-transfer (LMCT)
transition. Excitation in the solid state and in fluid solution at λ= 500 nm resulted in intense long-
lived red luminescence. The observed lifetime in the microsecond range indicated the spin-
forbidden nature of emission, which was tentatively assigned to be originated predominantly
from the triplet ligand–to-metal charge-transfer (LMCT) transition [P(phosphinidene)→Cu].
7

Cu
Cu
Cu
Cu
P
P
P
P
P
P
P
P
P
Ph
F
i
g
u
r
e

1
.
5
2
+


Au

12
(µ
2
-dppm)
6
(µ
3
-S)
4
](PF
6
)
4
,
12
showed absorption at 332 nm. Excitation with
wavelength λ > 350nm produced a long-lived orange-red emission in solid state and a green
emission in solution at room temperature respectively, which was assigned to
3
[LMCT] S-Au
mixed with metal-centered (ds/dp) states modified by Au
I
-Au
I
interaction. (Figure 1.6)

S
S
S S
Au

Au
Au
Au
Au
Au
Au
Au
Au
Au
Au
Au
Ph
2
P
PPh
2
Ph
2
P
PPh
2
PPh
2
P
Ph
2
PPh
2
Ph
2

P
Ph
2
P
Ph
2
P
Ph
2
P
Ph
2
P
F
i
g
u
r
e

1
.
6
4+
Au
1
2
(µ
2
-dppm)

6
(µ
3
-S)
4
](PF
6
)
4


LLCT transition is commonly observed in complexes which contain an electron-rich
ligand and a ligand which possesses low-lying empty orbitals. If the filled orbitals (lone-pair) of
the electron-rich ligand is higher in energy than the metal orbitals and the low-lying empty
orbitals of the other ligand are more stabilized than the empty metal orbitals, then the lowest
8

energy electron transition would involve a transfer of electron from the filled orbital of the
electron-rich ligand to the empty orbital of the other ligands. Compared with vast examples of
MLCT and LMCT, there are only few example of d
10
metal complexes with LLCT emission.
Most examples are Zn(II), Pt(II) and Pd(II) complexes.
13
The LLCT absorption band energy is
almost insensitive to the metal. In the (hydrotris- (pyrazolyl)borato)(triphenylarsine)copper(I)
[CuTpAsPh
3
] (Figure 1.7).
14

The spectrum of the arsine complex contained low-energy bands
(with a band maximum at 606 nm in emission and a weak shoulder centered at about 400 nm in
absorption). The lowest energy electronic transition was assigned to ligand to ligand charge
transfer (LLCT) with some contribution from the metal. This assignment was consistent with
molecular orbital calculations that showed the HOMO to consist primarily of σ orbitals on the Tp
ligand (with some metal orbital character) and the LUMO to be primarily antibonding orbitals on
the AsPh
3
ligand (also with some metal orbital character). The absorption shoulder showed a
strong negative solvatochromism, indicative of a reversal or rotation of electric dipole upon
excitation, and consistent with a LLCT. The complex (dmp)CuBH
4
(dmp=2,9-dimethyl-1,10-
phenanthroline) displayed a long-wavelength absorption at λ
max
= 465 nm which was assigned to
a BH
4
-
-dmp-ligand-to-ligand charge transfer (LLCT) transition. In solid state, the LLCT state
was emissive at λ
max
=626 nm.
15

N N
NN
N
N
Cu

B
As
H
Cu
H
H
B
H H
F
i
g
u
r
e

1
.
7
N N


1.2 The Structural and Spectroscopic Properties of d
10
Au(I), Ag(I) and Cu(I) thiolate
9

Chacogenides are well known to possess a variety of bonding characteristics and there
have been a number of polynuclear d
10
metal complexes with thiolates as the bridging ligand.

They commonly act as a µ
2
-, µ
3
- and µ
4
- bridging ligand but a µ
8
- bridging mode has been
observed. A large number of Au complexes with thiolate ligands have been reported compared
with other d
10
metal complexes The mutual attraction between gold(I) center is easier to form
compared with silver(I) or copper(I). Gold(I) thiolates are often photoluminescent at room
temperature and the emission properties can be strongly affected by the presence of aurophilic
Au…Au interactions and nature of thiolates.
16
Luminescence has thus become an important
diagnostic tool for aurophilicity. A remarkable example of the luminescence of a gold(I)
compound which showed strong solvent dependence was published by Che et al.
17
The
quenching of the luminescence of the simple dinuclear gold(I) quinoline-8-thiolate in polar
solvents such CH
3
CN and CH
3
OH was attributed to an equilibrium between two forms A and B
complexes. A transfered to B in the polar solvent (Figure 1.8).

N
S
Au Au
Ph
3
P
PPh
3
N
S
Au
Au
PPh
3
PPh
3
A
B
F
i
g
u
r
e

1
.
8
+
+

K


A trinuclear complex [(8-QNS)
2
Au(AuPPh
3
)
2
]·BF
4
(8-QNS= quinoline-8-thiolate), with
intramolecular gold(I)-gold(I) distances of 3.0952(4) and 3.0526(3) Å, was aggregated to form a
novel hexanuclear supermolecule, {[(8-QNS)
2
Au(AuPPh
3
)
2
]}
2
·(BF
4
)
2
, via a close intermolecular
gold(I)-gold(I) contact of 3.1135(3) Å.
18
The compound also showed interesting spectroscopic
and luminescence properties dependent on the solvent polarity. It emitted at ca. 440 and 636 nm

in CH
2
Cl
2
and only at ca. 450 nm in CH
3
CN. The long-lived emission at ca. 636 nm in CH
2
Cl
2

10

was quenched by polar solvents such as CH
3
CN and CH
3
OH, which was suggested to be related
to the presence or absence of gold(I)-gold(I) interactions due to scrambling of the [AuPPh
3
]
+

units ( Figure 1.9).

N
S
Au Au
Ph
3

P
PPh
3
N
S
Au
N
S
Au
Au
Ph
3
P
Ph
3
P
N
S
Au
+
+
F
i
g
u
r
e

1
.

9
A
B


This unique behavior can be exploited in the development of sensing materials for
different analytes. For example, a dinuclear gold(I) crown-ether complex which showed a high
selectivity towards potassium ions.
1, 9
Dinuclear gold(I) crown-ether complexes
[Au
2
(P^P)(SB15C5)
2
] {P^P = dppm or dcpm (bis(dicyclohexylphosphino)methane), SB15C5=4'-
sulfanylmonobenzo[15]-crown-5} were found to form 1+1 adducts with potassium ions with log
K values of 3.4 and 4.0, respectively. This indicated that one potassium ion was sandwiched
between the two benzo-15-crown-5 rings of the dinuclear Au(I) molecule (Figure 1.10), which
has also been confirmed by electrospray-ionization mass spectrometric (ESI-MS) studies. The
emission spectrum of the former showed a drop in intensity at ca. 502 nm, with the concomitant
formation of a long-lived emission band at ca. 720 nm (to = 0.2 ms) upon addition of potassium
ion . Such a change in emission spectral traces was absent in the crown-free analogues. Thus, it
was likely that the binding of K
+
brings the two gold(I) centers in close proximity to each other,
resulting in some weak Au…Au interactions. These intramolecular Au···Au interactions were
then reported by the emission properties of the complexes. The low-energy emission band has
been proposed to arise from a LMMCT [RS
2
- Au

2
] excited State.
11


Au
A
u
S
S
O
O
O
O
O
R
2
P
PR
2
O
O
O
O
O
O
O
R=C
5
H

11
R=Ph
Au Au
S
S
O
O
O
O
O
R
2
P
PR
2
O
O
O
O
O
O
O
K
+
K
+
F
i
g
u

r
e

1
.
1
0


Aurophilic bonding is very efficient in groups with more than two gold atoms in close
contact. Aggregation between two pairs of gold atoms thus leads to four-atom clusters in the
form of a square, a rhombus, or even a tetrahedron. Oxidation of Ph
3
PAu(SC
6
H
4
CH
3
) and
dppe[Au(SC
6
H
4
CH
3
)]
2
with (Cp
2

Fe)PF
6
resulted in formation of [(Ph
3
P)
4
Au
4
(í-
SC
6
H
4
CH
3
)
2
](PF
6
)
2
and [(dppe)
2
Au
4
(í-SC
6
H
4
CH

3
)
2
](PF
6
)
2
separately (Figure 1.11). The first
tetranuclear cluster consisted two monocationic Au
2
(PPh
3
)
2
(í-SC
6
H
4
CH
3
)
+
units via Au-Au
interaction. The latter Au
4
S
2
core adopted a chair configuration with a gold single bond between
Au(1)-Au(2) 2.961(1) Å and a sulfur-bridged nonbonded Au-Au interaction of 3.844 Å.

12

S
AuAu
Au
Au
P
P
Ph
Ph
Ph Ph
Ph
Ph
S
P
Ph
Ph
Ph
P
Ph
PhPh
S
Au
Au
Au
Au
Ph
2
P
PH

2
S
PPh
2
P
P
h
2
Ph
2
P
F
i
g
u
r
e

1
.
1
1
2+
2+



At the same time a series of neutral, dinuclear gold(I) complexes,
21
(Figure 1.12)

containing phosphorous and sulfur ligands have been studied by luminescence spectroscopy. All
complexes showed luminescence at room temperature in the solid state. The Stokes shifts
averages 6×10
-5
using time delays of 10-50 µs confirmed the phosphorescent nature of the
emission. The origin of the luminescence of complexes was consistent with a S-Au CT excited
state that was perturbed by substitute electronic effect leading to the red shifts in emission. The
emission range 495-515 nm increased with more electron donating sulfur ligands. Au complexes
also exhibited low energy emission at ca. 600 nm, attributed to a ligand-to-metal charge transfer
(thiolate→Au(I)) origin. Similar red shifts in emission energies were formed the basis for
assignment of LMCT emission.

Au
Au
Ph
2
P
PPh
2
N
S
S
R'
R=F, R'=C
6
H
11
R=Cl, R'=C
6
H

11
R=Me, R'=C
6
H
11
R=Me, R'=Ph
R=Me, R'=Pr
n
Ph
P
h
F
i
g
u
r
e

1
.
1
2


There are scarce reports on the photophysics of silver(I) chalcogenolate complexes
compared with those of other d
10
metal centers. Silver(I)-thiolate complexes often show similar
structures to copper(I)-thiolate complexes, which are found in many copper-containing proteins.
13

Silver-thiolate complexes became more attractive after Stiilman and co-workers confirmed the
formation of a sequence of clusters from the titration of rabbit liver apo-MTN (MTN =
metallothionein) with Ag(I) ions and proposed that various silver-thiolate clusters may form in
the silver binding site of proteins
22
.
Ford and Vogler
23
reported the photophysical properties of hexanuclear copper(I) and
silver(I) thiolate clusters, [Cu
6
(mtc)
6
], [Ag
6
(mtc)
6
] and [Ag
6
(dtc)
6
] (mtc-= di-n-
propylmonothiocarbamate, dtc-=di-n-propyldithiocarbamate) at 77 K. The solid samples emitted
at 767 nm, 644 nm and 545 nm, respectively. Excited states of these luminescent hexanuclear
copper(I) and silver(I) thiolate complexes have been assigned to a LMCT state (mtc
-
/dtc
-
→Cu

6
or
Ag
6
) mixed with a cluster-centered Cu
6
or Ag
6
(d-s) triplet state.
A series of hexanuclear silver-thiolate complexes [Ag
6
(dppm)
4
(µ
3
-SC
6
H
5
)
4
](PF
6
)
2
and
[Ag
6
(dppm)
4

(µ
3
-SC
6
H
4
CH
3
-p)
4
](PF
6
)
2
(Figure 1.13) with bridging dppm ligands
24c
have been
synthesized and characterized. Short Ag…Ag contract of 3.3289-3.4768 Å in Ag
6
(dppm)
4
(µ
3
-
SC
6
H
4
Me-p)
4

](PF
6
)
2
were observed, which indicated weak metal…metal interactions compared
to the sum of van der Waals radii for silver (3.4 Å). These complexes were found to exhibit
luminescence at 77 K and the orange-red emission at 566 nm and 578 nm were tentatively
attributed to originate from excited states of a mixture of metal-centred (MC) and metal…metal–
bond-to-ligand charge-transfer (MMLT) character.

14

Ag
Ag
Ag
Ag
Ag
Ag
P
Ph
2
Ph
2
P
P
Ph
2
PPh
2
S

S
Ph
2
P
Ph
2
P
Ph
2
P
PPh
2
S
S
R= Ph

R
=

P
h
M
e
-
p
R
R
R
R
F

i
g
u
r
e

1
.
1
3
2+


Polynuclearic Cu
I
-chalcogenide are drawing considerable attention because of their rich
photophysical, photochemistry and structural diversity.
10, 24-27
The search for new emissive
copper(I) clusters and the discovering new structural motifs are synergistic: many interesting
structures have been discovered in the search for emissive Cu
I
-clusters. Sulfur atom, acted as a
nucleating center, is a good σ-donors for copper ions and is capable of displaying a great
diversity of structure and bonding modes. Trinuclear copper(I)-thiolate complexes
10
(Figure 1.14)
were synthesized and exhibited emission due to a high–energy-ligand-centered emission at 430-
580 nm Their emission spectra showed a longer–lived energy emission at ca. 580-640 nm, with
emission lifetimes in the microsecond range, which suggested that the emission were

phosphorescence in nature. The electronic absorption spectra in dichloromethane were
characterized by absorption shoulder at ca. 250nm and 260-295 nm. The high energy absorption
at 250-270 nm was assigned as an intraligand (IL) transition of dppm since free dppm absorbed
strongly in this region. The absorption shoulder ca. 290 nm with tails extending to ca. 400nm
were likely to arise from thiolate-ligand-centered and sulfido-to–copper ligand-to-metal charge-
transfer (LMCT) transitions.

15

Cu
Cu
S
S
R
R
Cu
Ph
2
P
PPh
2
PPh
2
Ph
2
P
Ph
2
P
Ph

2
P
R=C
6
H
4
-Cl-4
R=C
6
H
4
-CH
3
-4
R=C
6
H
4
-OCH
3
-4
R=C
6
H
3
-(OCH
3
)
2
-3,4

R=benzo-15-crown-5
R
=
t
B
u
+
(BF
4
-
)
F
i
g
u
r
e

1
.
1
4

1.3 Structures of Polynuclear Au(I), Ag(I) and Cu(I) ditholate Complexes
The chemistry of metal complexes contain 1,1-dithiolate ligands continue to attract broad
attention followed the initial work by Delepine.
28
They have been used as fungicides, pesticides,
vulcanization accelerators, flotation agents, and lubricant additives and more recently in the
deposition of ZnS or CdS thin films by metal organic chemical vapor deposition.

29
In addition,
the variable coordination modes of dithiolate ligands to metal makes structural studies more
interesting. They can act as chelating, bridging, tridentae [η
2
(µ
2
-S-µ
1
-S)], and tetradentate [η
2
(µ
2
-
S-µ
1
-S)] ligands of which the tetrametallic tetraconnective coordination mode, [η
2
(µ
2
-S,- µ
2
-S)],
is the least observed and only a handful of reports have appeared. 1,1-dicyanoethylene-2,2’-
dithiolate(i-mnt) and 1-(diethoxyphosphinyl)-1-cyanoethylene-2,2-dithiolates
(S
2
CC(CN)P(O)(OEt)
2
)

2
) are frequently used as dithiolate ligand to form d
10
-metal clusters.
The specific feature of gold(I) complexes is direct closed-shell interactions between the
metal cencers (“aurophilicity”). Even though this interaction is weak and comparable in its
energy to hydrogen bonding, the effect is strong enough to have a marked influence on the
configuration, comformation and oligomerization of almost all gold(I) compounds. They can
form chain, 2-dimentional framework or 3-dimetional network by intermolecular aurophilic and
hydrogen bonding interaction and lead to a large viariety of dimers, oligomers, and polymers.
37

Moreover, polyfunctional ligand such as dithiol will bring more diversity structure.
Au
2
S
2
unit is very commonly observed in the Au-dithiolate complexes. If two sulfur
atoms in the dithiolate ligand are separated quite far away, every sulfur atom can be regarded as
16

an independent donor to form mono or dinulear complexes; if the two sulfur atoms are close,
they will connect one Au together. Some dinuclear gold complexes
31
are shown in Figure 1.15

S
S
Au
Au

Ph
3
P
PPh
3
S
Au
Cy
3
P
S
Au
PCy
3
S S
Au
Au
PPh
2
PPh
3
F
i
g
u
r
e

1
.

1
5


Treatment of AuClSMe
2
with equimolar sodium (aza-15-crown-5)dithiocarbamate
(O
4
NCS
2
) featured a dinuclear structure containing two azacrown ether rings ( Figure 1.16), and
there was a short intramolecular Au-Au distance of 2.7820(5) Å.
32


.
O
O
O
O
N
O
O
O
O
N
S
S
S

S
Au
Au
F
i
g
u
r
e

1
.
1
6
2-


Other dinuclear gold(I)
33
complexes with 1,1-dithiolate type ligands were investigated.
The presence or absence of intermolecular Au interaction in the solid state had a profound
17

influence on the nature of the luminescence of the compounds exhibit. Increasing temperature,
the blue shift observed in the emission bands which was consistent with increase in Au-Au
separation as a result of thermal expansion. This fact indicated that the Au-Au distance had a
significant influence on the HOMO-LUMO gap.

Au
Au

S
S
Ph
2
P
PPh
2
2
N
N
Au
Au
S
S
Ph
2
P
PPh
2
N
N
Au
Au
S
S
PPh
2
Ph
2
P

N
N
F
i
g
u
r
e

1
.
1
7


A series of annular dinuclear Au(I) complexes containing diphosphine and dithiolate
ligand were synthesized. Each molecule had two gold atoms bridged by a dithiolate ligand on
one side and a diphosphine ligand on the other side and form a dinuclear ring. The tendency of
the digold(I) compounds to aggregate through an intermolecular Au-Au interaction depended on
the ligands. Molecular aggregation also occured in the solution. Concentration–dependent
absorption spectra of Au-dtc compounds suggested that equilibrium between the monomer and
dimmer existed. Emission at 400-440 nm assignable to spin-allows metal-centered transitions
from monomeric Au
2
at lower concentrations and dimeric Au
4
at higher concentrations were
observed (Figure 1.17). To the open ring dinulear compound only S-Au
3
LMCT excited state

was observed at 77 K. On the contrary, the annular gold compounds gave emission band at 550
nm which was assigned as spin forbidden dithiolate ligand to gold charge transfer
3
(LMCT).
36

Gold complexes showing luminescence without Au-Au interaction was rarely reported.
(n-Bu
4
N)
2
[Au
2
(S
2
-1,3-C6H
4
)
2
] ( Figure 1.18) were designed without Au-Au interaction and
18

showed weak luminescent in solvent.
34
This emission originated from a metal-perturbed ligand-
centered transition. The relatively long life time of the excited state) and the large stokes shift
suggested that the emission was phosphorescence.

S
S

Au
A
u
S
S
F
i
g
u
r
e

1
.
1
8
2
-


When the sulfur atoms are close enough, more complex compounds such as trinuclear
(Figure 1.19) and tetranuclear will be formed. A toluenedithiolate ligand unit bridged three
AuPPh
3
+
fragment. The neighboring gold thiolate and bis(gold)sulfonium groups were intimately
aggregated to give V-shaped triatomic gold units of high stablility.
31a
The reaction of
biphenylene-4,4-dithiol with equimolor [tri(p-tolyl)phosphine)gold chloride afforded another

kind of trinuclear complex.
31c
One of the sulfur atoms at the ends of the biphenylene units beard
only one gold atom, with the other represents a sulfonium center bearing two gold atoms. This
trinuclearunits were lined up head-to-tail to form strings by aurophilic bonding.

19

S
Au
Tol
3
P
S
Au
PTol
3
Au PTol
3
S
S
Au
Au
Au
PPh
3
PPh
3
Ph
3

P
+
S
A
u
Tol
3
P
S
Au
PTol
3
Au
PTol
3
n
2n+
F
i
g
u
r
e

1
.
1
9

In tetranuclear [Au
2
(C
6
H
4
S
2
-1,3)(PEt
3
)
2
],
35
the four gold atoms were arranged in the form
of a parallelogram with transannular Au…Au edge of 3.052(9) Å and 3.129(1) Å, and a short
transannular Au…Au distance of 3.114(1) Å. Such complex had exceedingly high gold content
by weight (Figure 1.20).

Au
Au
Au
Au
H
S
S
S
S
PEt
3

Et
3
P
F
i
g
u
r
e

1
.
2
0


Treatment of phenylene-1,4-dithiol with tris-{[tri(p-tolyl)phosphine]gold(I)} oxonium
tetrafluoroborate gave tetranuclear complex biphenylene-4,4’-bis{[tri9c-hexyl]phosphine}gold
thiolate (Figure 1.21). The dications were aggregated into chains through intimated aurophilic
20

bonding between the gold atoms of the sulfonium group. At either end of the phenylene
centerpiece, the gold atoms of two neighboring dication formed tetranuclear units with short Au-
Au distance.

S
S
Au
Au
Tol

3
P
PTol
3
Au
PTol
3
Au
T
o
l
3
P
F
i
g
u
r
e

1
.
2
1
2+


Ag dithiolate complexes and copper dithiolate complexes show similar structure but Ag
has ability to form huge cluster and polymer. A neutral, tetranuclear silver(I) compounds,
[Ag

4
(dppm)
4
(S
2
CC(CN)P(O)(OEt)
2
)
2
]](PF
6
) ( Figure 1.22)
37
was obtained from the reaction of
Ag
2
dppm
2
(CH
3
CN)
2
(PF
6
)
2
and K
2
S
2

CC(CN)P(O)(OEt)
2
. 1,1-dithiolate ligand displayed a
tetrametallic tetraconnective (µ
2
-S, µ
2
-S) bridging. The Ag-Ag distance was 2.9827 Å.

Ag Ag
Ag
Ag
P
P
P
P
P
P
P
P
S
S
S
S
C
N
P
O
O
O

N
P
O O
O
F
i
g
u
r
e

1
.
2
2


21

Ag
4
(µ-dppm)
4
(µ
4
-i-mnt)
2
(Figure 1.23) is also a tetranuclear complex with a silver-
silver separation of 3.376(2)Å and the four silver atoms form a distorted square plane bridged by
four dppm and two i-mnt (S,S-C=C(CN)

2
)

ligands. Each silver atom is coordinated by two
phosphorus and two sulfur atoms in a distorted tetrahedral environment.
38

Ag
Ag
Ag
Ag
Ph
2
P
PPh
2
PPh
2
Ph
2
P
PPh
2
PPh
2
Ph
2
P
Ph
2

P
S
S
S
S
N
N
N
N
F
i
g
u
r
e

1
.
2
3


Another kind of tetranuclear silver in [Bu
4
N]
2
[Ag
4
(i-mnt)
4

],
39
four silver atoms located at
the vertices of a slightly distorted tetrahedron. Four i-mnt groups acted as tridentate ligand. A
sulfur atom of each ligand coordinated to only one silver atom with the other S atoms bridges
across the Ag
3
triangle to two adjacent silver atoms. The Ag-Ag distances were in the range of
2.943(2) Å to 3.045(2) Å (Figure 1.24).

22

Ag
Ag
Ag
Ag
S
S
C
C
C
N
C
N
S
S
C
C
C
N

C
N
S
S
CC
C
N
C
N
S
S
C
C
C
N
C
N
F
i
g
u
r
e

1
.
2
4
4-

A novel pentanuclear silver complex, [Ag
5
(dppm)
4
(S
2
CC(CN)P(O)(OEt)
2
)
2
]](PF
6
)
37
was
got with a short Ag-Ag distance of 2.9827 Å ( Figure 1.25).

Ag
Ag
Ag
Ag
P
P
P
P
Ag
S
S
O

S
S
C
P
P
P
P
O
P
N
O
O
N
P
O
O
Figure 1.25
-


In the recent decade, many polysilver(l)-thiolate complexes, such as
[Ag
4
(SCH
2
C
6
H
4
CH

2
S)
3
]
2-
,
40a
[Ag
9
(SCH
2
C
6
H
4
CH
2
S)
6
]
3-
,
40b
[Ag
6
(i-mnt)
6
]
6-
(Figure 1.26),

40d

[Ag
8
(i-mnt)
6
]
4-
{i-mnt: S
2
C=C(CN)
2
)} (Figure 1.27)
40c
and [Ag
11
(µ
5
-S)(S
2
CNEt
2
)
9
]
40e
have been
reported.
23

Ag
Ag
Ag Ag
Ag
Ag
S
S
C
C
C
N
C
N
S
S C
C
C
N
C
N
S
S
C
C
C
N
C
N
S
S

C
C
C
N
C
N
S
SC
C
C
N
C
N
S
S
C
C
C
N
C
N
F
i
g
u
r
e

1
.

2
6
6-


Ag
Ag
S
S
C C
C
N
C
N
Ag
Ag
Ag
Ag
Ag
Ag
S
S
C
C
C
N
C
N
S
S

C
C
C
N
C
N
S
S
CC
C
N
C
N
S
S
C
C
C
N
C
S
S
C
C
C
N
C
N
N
F

i
g
u
r
e

1
.
2
7
4-

In nonanuclear complex,
41
(PPh
4
)
3
Ag
9
(SCH
2
CH
2
S)
6
, eight silver atoms formed a cubane-
like metal skeleton with a further silver atom in the center( Figure 1.28).
24

Ag
Ag
Ag
Ag
Ag
Ag
Ag
S
S
S
S
S
S
H
S
S
S
S
S
Ag
S
Ag
3-
F
i
g
u
r
e

1
.
2
8


Four kinds of tetracopper clusters were reported. They had a common feature that a
tetranuclear core inside and copper-copper interaction existed. In [Me
4
N]
2
[Cu
4
(C
8
H
6
S
8
)
3
] (Figure
1.29),
42
three dithiolate ligands, 2-[4,5-bis(methylsulfanyl)-1,3-dithiol-2-ylidene]-4,5-bis(2-
cyanoethylsulfanyl)-1,3-dithiole, connected tetrahedral Cu
4
cluster. The Cu-Cu bonds ranged
2.684(2)-2.739(2) Å. Such similar tetranuclear core was also observed in
[Ph

4
P]
2
[Cu
4
(SCH
2
CH
2
S)
3
].
41


C
Cu
C
u
C
u
S
S
S
SH
S
S
S
S
S

S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
F
i
g
u
r
e

1
.
2
9
2-

25

Two neutral, tetranuclear copper(I) compounds,
[Cu
4
(dppm)
4
(S
2
CC(CN)P(O)(OEt)
2
)
2
]](PF
6
)
2
and
Cu
4
(dppm)
3
(OPPh
2
CH
2
PPh
2
)[S
2
CC(CN)P(O)(OEt)
2

]
2
, ( Figure 1.30)
37b
was isolated from the
same reaction of Cu
2
dppm
2
(CH
3
CN)
2
(PF
6
)
2
and K
2
S
2
CC(CN)P(O)(OEt)
2
. 1,1-dithiolate ligand
displayed a tetrametallic tetraconnective (µ
2
-S, µ
2
-S) bridging.

Cu Cu
Cu
Cu
P
P
P
P
P
P
P
P
S
S
S
S
C
N
P
O
O
O
N
P
O O
O
Cu Cu
Cu
Cu
P
P

P
P
P
P
P
P
S
S
S
S
C
N P
O
O
O
N
P
O
O
O
F
i
g
u
r
e

1
.
3

0
O


In [(Bu
4
N)]
4
[Cu
4
(i-mnt)
4
] (Figure 1.31),
43
the anion revealed discrete units of four
copper atoms, at the vertices of a distorted tetrahedron. With four i-mnt groups acting as
‘tridentate’ligand, a sulfur atom of each ligand coordinated to only one copper atoms with the
other S atoms bridges across the Cu
3
triangle to two adjacent copper atoms. So that each copper
atom was in an approximately trigonal geometry with an almost planar arrangement of the three
sulfur atoms coordinated to it. The Cu-Cu distances associated with the copper atoms bridged by
the sulfur atoms bond to C range from 2.718 to 2.725 Å. The remaining Cu-Cu distances ranged
from 2.814-2.825 Å.