Luminescent thione/phosphane mixed-ligand copper(I) complexes: The effect of thione on structural properties

Article abstract of DOI:10.1016/j.ica.2017.01.007

The reactions of tetrameric clusters [CuX(PPh₃)]₄(X?=?Br or Cl) with a series of small size, five-member ring N-heterocyclic thiones, 5-methyl-1,3,4-thiadiazole-2-thione (mtdztH), 5-amino-1,3,4-thiadiazole-3-thione (atdztH) and 4,5-diphenyl-imidazole-2-thione (dpimdztH), in 1:4?molar ratio, in acetonitrile/methanol mixtures, resulted in the isolation of symmetrical, mixed-ligand phosphane/thione-S-bridged dicopper species of the general type [CuX(PPh₃)(μ-S-thione)]₂, with the copper centers being in distorted tetrahedral coordination environments consisting of a PS₂X donor set. In contrast, analogous reactions with the less basic and more sterically demanding 1-phenyl-tetrazole-5-thione (dpimdztH) afforded mononuclear mixed-ligand complexes with the general formula [CuX(PPh₃)₂(thione)], in which the thione acts in a terminal bonding mode. All copper(I) complexes are found to be photoluminescent in the solid state at ambient temperature, with their emission maxima influenced by the type of heterocyclic thione, as well as (to a smaller extent) the halide present in each case.

Full text of DOI:10.1016/j.ica.2017.01.007

Inorganica Chimica Acta 458 (2017) 138–145
Contents lists available at ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Research paper
Luminescent thione/phosphane mixed-ligand copper(I) complexes: The
effect of thione on structural properties
Alexandra Koutsari, Fani Karasmani, Eleni Kapetanaki, Dini Iflakhah Zainuddin, Antonios G. Hatzidimitriou,
⇑
Panagiotis Angaridis , Paraskevas Aslanidis
Laboratory of Inorganic Chemistry, Department of Chemistry, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece
a r t i c l e i n f o
a b s t r a c t
Article history:
The reactions of tetrameric clusters [CuX(PPh3)]4 (X = Br or Cl) with a series of small size, five-member
ring N-heterocyclic thiones, 5-methyl-1,3,4-thiadiazole-2-thione (mtdztH), 5-amino-1,3,4-thiadiazole-
3-thione (atdztH) and 4,5-diphenyl-imidazole-2-thione (dpimdztH), in 1:4 molar ratio, in acetonitrile/
methanol mixtures, resulted in the isolation of symmetrical, mixed-ligand phosphane/thione-S-bridged
Received 19 October 2016
Received in revised form 15 December 2016
Accepted 8 January 2017
Available online 10 January 2017
dicopper species of the general type [CuX(PPh3)(l-S-thione)]2, with the copper centers being in distorted
tetrahedral coordination environments consisting of a PS2X donor set. In contrast, analogous reactions
with the less basic and more sterically demanding 1-phenyl-tetrazole-5-thione (dpimdztH) afforded
mononuclear mixed-ligand complexes with the general formula [CuX(PPh3)2(thione)], in which the
thione acts in a terminal bonding mode. All copper(I) complexes are found to be photoluminescent in
the solid state at ambient temperature, with their emission maxima influenced by the type of hetero-
cyclic thione, as well as (to a smaller extent) the halide present in each case.
Keywords:
Copper(I) complexes
Phosphanes
Heterocyclic thiones
Crystal structures
Luminescence
Ó 2017 Elsevier B.V. All rights reserved.
1. Introduction
In general, N-heterocyclic thioamides tend to coordinate to cop-
per(I) centers preferably through their soft exocyclic sulfur atom
The photophysical properties of copper(I) coordination com-
pounds have triggered much research efforts in the perspective
of their potential applications as materials for organic light-emit-
ting diodes (OLEDs) and light-emitting electrochemical cells (LECs)
[1]. A number of copper(I) complexes, the majority of them being
mononuclear or binuclear complexes containing N-donor polypyr-
idine [2,3] and/or P-donor phosphane ligands [4–8], have been
reported to be luminescent at room temperature either in the solid
state or in solution. Recently, mixed-ligand copper(I) complexes
incorporating S-donor, N-heterocyclic thiones/thiolates in combi-
nation with arylphosphanes or polypyridines have also revealed
interesting photophysical properties [9–14]. On the basis of both
experimental and theoretical data, the emitting state of this type
of complexes is assigned to be of MLCT character, while their emis-
sion energies were shown to be tunable through suitable thione
modification, related to the strength of the CuAS bond. Further-
more, studies on related luminescent copper-thiolate complexes
of different nuclearities and core geometries revealed that the
metal core structure has a profound effect on their emissive prop-
erties [15].
[16], leading to the formation of simple cationic or neutral com-
plexes with a trigonal [17–20] or tetrahedral [21] ligand arrange-
ment. However, when they are combined with tertiary
phosphanes in a mixed set of ligands around the copper(I) centers,
diverse molecular architectures can be obtained. In our previous
studies on reactions of copper(I) halides with various thiones and
tertiary arylphosphanes as a second bulky
r-donor/p-acceptor
ligand it was reported that, in addition to the usually formed mixed
ligand mononuclear species (Scheme 1A), symmetrical binuclear
complexes were also frequently formed, containing either the
thione ligand coordinated through the exocyclic sulfur atom in a
l-S-bridging mode (Scheme 1C) [22,23], or the halides as bridging
ligands in a Cu2( -X)2 core structure (Scheme 1B) [24]. On the
l
basis of our observation that halide bridges were preferably
formed by the ‘‘soft” iodide rather than the ‘‘hard” chloride ion, it
was initially assumed that the type of structure that is adopted
(terminal or bridging thione/halide) is determined by the choice
of the halide used in each case [25]. However, there are quite a
few examples of related complexes in the literature in which the
reverse trend has been observed [26–28]. Consequently, not only
the copper(I) halide starting material, but also the nature of the
thione should be taken into account.
⇑
Corresponding author.
E-mail address: panosangaridis@chem.auth.gr (P. Angaridis).
http://dx.doi.org/10.1016/j.ica.2017.01.007
0020-1693/Ó 2017 Elsevier B.V. All rights reserved.

A. Koutsari et al. / Inorganica Chimica Acta 458 (2017) 138–145
139
atoms, while hydrogen atoms were generated geometrically and
refined using a riding model. Details of crystal data and structure
refinement parameters are shown in Table 1. Molecular plots were
obtained by using the program ORTEP-3 [32].
NH
X
X
S
PPh3
S
Cu
Cu
Ph3P
HN
X
(B)
2.4. Syntheses of compounds
Ph3P
Ph3P
HN
Cu
S
Compounds 1a, 1b, 2, 3, 4a and 4b were synthesized according
to the following general synthetic procedure. A suspension of
0.125 mmol of [CuX(PPh3)]4 (0.203 g of [CuBr(PPh3)]4 for 1a, 2, 3
and 4a or 0.180 g of [CuCl(PPh3)]4 for 1b and 4b) in 30 mL of ace-
tonitrile was heated at 50 °C for 1 h. To the resulting mixture, a
solution of 0.5 mmol of the appropriate thione in 30 mL of metha-
nol was added dropwise. The reaction mixture was further stirred
at 70 °C for 2 h and then it was filtered off in order to remove a
small amount of insoluble material. The filtrate was set aside in
dark to evaporate slowly at room temperature and over a period
of a few days crystals of the product were obtained, which were fil-
tered off and dried in air.
HN
Cu
S
S
(A)
X
PPh3
X
Cu
Ph3P
NH
(C)
Scheme 1. Common binding modes of N-heterocyclic thiones.
Against this background, we decided to further investigate the
factors that govern the synthesis of thione/phosphane mixed-
ligand copper(I) complexes with specific structures, and to gain
more insight into the relationship between their structures and
luminescence properties. Herein we report on the coordination
behavior of four five-membered ring heterocycles thiones, derived
from 1,3,4-thiadiazole, imidazole and tetrazole, in combination
with triphenylphosphane, and the study of the photoluminescent
properties of the resulting copper(I) compounds.
2.4.1. [CuBr(PPh3)(l-S-mtdztH)]2, 1a
Yellow crystals. Yield: 0.178 g (66%). Anal. Calcd for 1aꢂCH3CN
(%): C, 47.31; H, 3.70; N, 6.27. Found (%): C, 47.20; H, 3.61; N,
6.38. IR (cmꢀ1): 3446 br, 2960 w, 2805 w, 2731 w, 1584 w, 1541
w, 1477 s, 1461 s, 1434 s, 1386 w, 1292 m, 1200 w, 1181 w,
1158 w, 1126 w, 1095 w, 1060 w, 1047 m, 1026 w, 997 w, 858
w, 803 w, 756 s, 748 s, 705 m, 694 s, 626 w, 591 w, 519 w, 505
w, 495 w, 430 w. UV–vis (CHCl3), k/nm (loge): 252 (4.41), 310
(4.59).
2. Experimental
2.1. General procedures and chemicals
2.4.2. [CuCl(PPh3)(l-S-mtdztH)]2, 1b
Yellow crystals. Yield: 0.177 g (71%). Anal. Calcd for 1bꢂCH3CN
(%): C, 51.41; H, 4.02; N, 6.81. Found (%): C, 51.29; H, 3.89; N,
6.89. IR (cmꢀ1): 3483 vw, 3049 w, 2958 w, 2778 w, 2715 w,
1667 w, 1585 w, 1541 m, 1471 s, 1434 s, 1387 w, 1297 s, 1200
m, 1181 vw, 1159 s, 1129 s, 1096 m, 1048 s, 1027 m, 997 w, 981
vw, 933 vw, 863 s, 844 vw, 747 s, 694 s, 627 w, 618 w, 593 vw,
All manipulations were carried out under atmospheric
conditions, unless otherwise mentioned. Solvents were purified
according to established methods and allowed to stand over
molecular sieves for at least 24 h prior to use. Copper(I) halides,
triphenylphosphane,
(mtdztH),
5-methyl-1,3,4-thiadiazole-2(3H)-thione
(atdztH),
5-amino-1,3,4-thiadiazole-2(3H)-thione
520 s, 505 s, 494 s, 431 m. UV–vis (CHCl3), k/nm (loge): 251
(4.45), 309 (4.31).
4,5-diphenyl-1H-imidazole-2(3H)-thione (dpimdztH) and 1-phe-
nyl-1H-tetrazole-5(4H)-thione (ptztH) were obtained from
commercial sources and used without any purification. The
compounds [CuCl(PPh3)]4 and [CuBr(PPh3)]4 were prepared
according to literature procedures from the respective copper(I)
halide and triphenylphosphane in refluxing CHCl3 [29].
2.4.3. [CuBr(PPh3)(l-S-atdztH)]2, 2
Yellow-green crystals. Yield: 0.172 g (64%). Anal. Calcd for
2ꢂCH3CN (%): C, 45.08; H, 3.51; N, 8.76. Found (%): C, 45.22; H,
3.60; N, 8.65. IR (cmꢀ1): 3276 w, 311 87 w, 3049 w, 2901 w,
2759 w, 1612 s, 1548 s, 1484 s, 1433 s, 1368 m, 1333 m, 1178 w,
1157 s, 1095 m, 1069 m, 1045 s, 997 w, 930 w, 853 w, 745 s,
692 s, 640 w, 618 w, 543 w, 520 s, 503 s, 491 m, 429 w, 401 w.
2.2. Instrumentation
Infra-red spectra were recorded on a Nicolet FT-IR 6700 spec-
trophotometer as KBr discs in the region of 4000–400 cmꢀ1. UV–
vis electronic absorption spectra were obtained on a Shimadzu
UV–vis (CHCl3), k/nm (log
e): 250 (4.46), 316 (4.19).
160A spectrophotometer as solutions 1.0 ꢁ 10ꢀ4
M
in CHCl3.
2.4.4. [CuBr(PPh3)( -S-dpimdztH)]2, 3
l
Pale-yellow crystals. Yield: 0.246 g (75%). Anal. Calcd for
3ꢂ2CH3CN (%): C, 59.17; H, 4.53; N, 4.06. Found (%): C, 59.31; H,
4.40; N, 4.19. IR (cmꢀ1): 3573 w, 3431 w, 3051 w, 1629 w, 1596
w, 1571 w, 1503 s, 1480 s, 1434 s, 1209 w, 1184 w, 1157 w,
1094 m, 1071 m, 1026 w, 998 w, 913 w, 846 w, 762 mw, 744 m,
693 s, 582 w, 545 m, 518 m, 505 m., 434 w. UV–vis (CHCl3), k/
Solid-state and solution emission/excitation spectra were obtained
on a Hitachi F-7000 fluorescence spectrometer. Elemental analyses
were performed on a PerkinElmer 240B elemental microanalyzer.
2.3. X-ray crystal structure determinations
nm (loge): 252 (4.69), 289 (4.77).
Suitable single crystals of all compounds were mounted on thin
glass fibers with the aid of an epoxy resin. X-ray diffraction data
were collected on a Bruker Apex II CCD area-detector diffractome-
ter, equipped with a Mo Ka (k = 0.71073 Å) sealed tube source, at
2.4.5. CuBr(PPh3)2(ptztH), 4a
Off-white crystals. Yield: 0.342 g (81%). Anal. Calcd for 4a (%): C,
61.03; H, 4.29; N, 6.62. Found (%): C, 60.87; H, 4.16; N, 6.48. IR
(cmꢀ1): 3447 br, 3045 w, 2924 w, 1594 vw, 1498 m, 1481 m,
1435 m, 1389 m, 1373 m, 1302 m, 1232 w, 1094 w, 1047 w,
1020 w, 997 w, 765 m, 740 m, 692 s, 559 w, 519 m, 509 m, 487
295 K, using the u and
x scans technique. The program Apex2
(Bruker AXS, 2006) was used in data collection, cell refinement,
and data reduction [30]. Structures were solved and refined with
full-matrix least-squares using the program Crystals [31]. Aniso-
tropic displacement parameters were applied to all non-hydrogen
w, 419 w. UV–vis (CHCl3), k/nm (loge): 271 (4.31).

140
A. Koutsari et al. / Inorganica Chimica Acta 458 (2017) 138–145
Table 1
Crystal data, data collection and refinement parameters for compounds 1a, 1b, 2, 3, 4a and 4b.
1aꢂCH3CN
1bꢂCH3CN
2ꢂCH3CN
3ꢂ2CH3OH
4a
4b
Chemical formula
Formula weight
Crystal system
Space group
Temperature (K)
Unit cell parameters
a (Å)
C
44H41Br2Cu2N5P2S4 C44H41Cl2Cu2N5P2S4 C42H39Br2Cu2N7P2S4 C68H62Br2Cu2N4O2P2S2 C43H36BrCuN4P2S
C43H36ClCuN4P2S
801.80
Monoclinic
P21/n
1116.95
Triclinic
P-1
1028.04
Triclinic
P-1
1118.93
Triclinic
P-1
1380.24
Triclinic
P-1
846.25
Monoclinic
P21/n
295
295
295
295
295
295
9.2028(4)
11.8572(6)
12.5384(6)
111.068(2)
98.927(2)
104.711(2)
1187.94(10)
1
9.2116(4)
11.6591(5)
12.5237(5)
110.458(2)
99.197(2)
104.249(2)
1175.81(9)
4
9.038(3)
11.417(4)
12.439(5)
111.06(2)
100.09(3)
102.33(2)
1124.7(8)
1
10.4050(3)
12.7045(5)
13.9816(6)
112.551(2)
111.236(2)
90.765(2)
1565.92(11)
1
16.4535(5)
14.2300(5)
18.3630(6)
90
113.150(2)
90
16.3509(12)
14.2672(10)
18.2914(14)
90
113.013(4)
90
b (Å)
c (Å)
a
(°)
b (°)
c
(°)
Volume (Å3)
3953.2(2)
4
3927.5(5)
4
Z
Radiation type, k (Å)
Absorption coefficient (mmꢀ1
Crystal size (mm)
Diffractometer
Mo K
2.86
0.40 ꢁ 0.32 ꢁ 0.24
Bruker Kappa
Apex2
a
, 0.71073
Mo K
1.30
0.46 ꢁ 0.36 ꢁ 0.14
Bruker Kappa
Apex2
a
, 0.71073
Mo K
3.02
0.28 ꢁ 0.19 ꢁ 0.13
Bruker Kappa
Apex2
a
, 0.71073
Mo K
2.12
a
, 0.71073
Mo K
1.73
a
, 0.71073
Mo K
0.80
a, 0.71073
)
0.32 ꢁ 0.17 ꢁ 0.11
0.36 ꢁ 0.32 ꢁ 0.16 0.33 ꢁ 0.27 ꢁ 0.21
Bruker Kappa Apex2
Bruker Kappa
Apex2
Bruker Kappa
Apex2
Absorption correction
Tmin, Tmax
Number of measured,
independent and observed
Numerical
0.40, 0.50
15,514, 4815, 3163
Numerical
0.63, 0.83
24,393, 7179, 4357
Numerical
0.56, 0.68
19,003, 4502, 3601
Numerical
0.70, 0.79
24,821, 6996, 4573
Numerical
0.57, 0.76
28,202, 8108,
4779
Numerical
0.81, 0.85
80,888, 9641,
5085
[I > 2.0
Rint
(sinh/k)max (Åꢀ1
R[F2 > 2 (F2)], wR(F2), S
r(I)] reflections
0.029
0.628
0.043, 0.073, 1.00
0.024
0.718
0.028, 0.049, 1.00
0.034
0.624
0.039, 0.088, 1.00
0.033
0.646
0.044, 0.071, 1.00
0.045
0.628
0.042, 0.062, 1.00
0.045
0.667
0.042, 0.062, 1.00
)
r
No. of reflections
No. of parameters
No. of restraints
3143
265
2
1.02, ꢀ0.74
4357
265
2
0.37, ꢀ0.36
3601
265
8
1.73, ꢀ0.96
4573
370
6
1.67, ꢀ1.05
4779
469
0
0.49, ꢀ0.54
5085
469
0
0.58, ꢀ0.51
D
qmax
,
D
qmin (e Åꢀ3
)
2.4.6. CuCl(PPh3)2(ptztH), 4b
(X = Br, Cl) clusters with a series of small size, five-member ring
heterocyclic thiones, namely mtdztH, atdztH, dpimdztH and ptztH
(Scheme 2), in acetonitrile/methanol mixtures, in 1:4 molar ratio.
With the first three thiones, binuclear, thione-S bridged com-
Off-white crystals. Yield: 0.268 g (67%). Anal. Calcd for 4b (%): C,
64.41; H, 4.53; N, 6.99. Found (%): C, 64.58; H, 4.30; N, 6.78. IR
(cmꢀ1): 3448 br, 3047 w, 2925 w, 1595 w, 1498 w, 1481 w, 1435
m, 1390 w, 1373 m, 1301 w, 1233 w, 1186 w, 1095 w, 1046 m,
1020 w, 998 w, 910 w, 847 w, 765 w, 741 m, 692 s, 618 w, 558
pounds with the general formula [CuX(PPh3)(l-S-thione)]2 (1a,
1b, 2, and 3) were isolated in crystalline form (Scheme 3). Views
of the molecular structures of these binuclear compounds are
shown in Figs. 1–4, while selected bond length and angle parame-
ters are summarized in Table 2. Complexes 1a, 1b, 2, and 3 are cen-
trosymmetric and contain a basic structural unit consisting of two
copper atoms and two doubly bridging sulfur atoms of thione
s, 520 s, 511 s, 487 m, 435 w, 425 w. UV–vis (CHCl3), k/nm (loge):
257 (4.94).
3. Results and discussion
ligands that form a four-membered Cu2(l-S2) ring. The copper cen-
ters are in distorted tetrahedral coordination environments which
3.1. Syntheses and structures
are completed by a halide, and a phosphane ligand. All compounds
exhibit the usual planar, asymmetric Cu2(l-S2) core with a short
Among the different synthetic methods that have been reported
for the synthesis of thione/phosphane mixed-ligand copper(I) com-
plexes, the most effective one uses a binary acetonitrile/methanol
solvent mixture, as acetonitrile is known to stabilize the low oxida-
tion state of the metal, while methanol to facilitate the crystalliza-
tion of the product. In a typical procedure, a suitable copper(I)
halide, dissolved in acetonitrile, reacts with two equivalents of
the triarylphosphane to form an intermediate complex, which is
then treated with a methanol solution of one equivalent of a thione
to give the final product. The complexes isolated by this method
are either mononuclear, four-coordinate complexes with the gen-
eral formula [CuX(PR3)2(thione)], or binuclear compounds contain-
CuAS distance (ranging from 2.323 to 2.354 Å) and a long CuAS
distance (2.465–2.551 Å) (Table 2). The CuAP and CuAhalide bond
lengths do not differ significantly among the four complexes and
they fall in ranges that are normally found for analogous binuclear,
halide- or thione-S-bridged copper(I) compounds [18,33,34]. The
Cuꢂ ꢂ ꢂCu interatomic distances in the four binuclear compounds
are found to be in the range of 2.754–3.016 Å. The shorter inter-
metallic distance observed for compound 3, with the imidazole-
based bridging thione, is smaller than the sum of the van der Waals
ing a Cu2(l-X)2 or a Cu2(l-S-thione)2 core structure (Scheme 1)
S
[21]. More recent studies have shown that by utilizing [CuX
(PPh3)]4 tetrameric clusters as starting material in reactions with
four equivalents of a thione under similar experimental conditions,
binuclear complexes with a mixed set of thione/phosphane ligands
and either l-X or l-S bridges are preferably formed.
In order to explore the factors that might favor the formation of
mononuclear or binuclear structures, or one type of bridge over the
S
HN
NH
S
S
S
HN
HN
S
N
HN
N
N
N
NH2
atdztH
Scheme 2. N-Heterocyclic thiones used in this work.
N
mtdztH
dpimdztH
ptztH
other, i.e.
l-X or l-S, we explored the reactivity of [CuX(PPh3)]4

A. Koutsari et al. / Inorganica Chimica Acta 458 (2017) 138–145
141
N
HN
S
S
S
S
X
PPh3
X
Cu
Cu
HN
S
Ph3P
N
S
NH
N
1a for X = Br
1b for X = Cl
X = Cl, Br
S
NH2
N
HN
S
HN
N
S
X = Br
NH2
[CuX(PPh3)]4
1/4
S
S
Br
PPh3
Br
Cu
Cu
Ph3P
S
NH
N
X = Br
S
2
H2N
Ph
NH
Ph
HN
Ph
Ph
HN
NH
Fig. 2. X-ray structure ORTEP diagram of compound 1b with displacement
ellipsoids drawn at the 35% probability level. All hydrogen atoms have been
omitted for clarity.
Br
S
S
PPh3
Br
Cu
Cu
Ph3P
HN
Ph
NH
Ph
3
Scheme 3. Synthesis of compounds 1a, 1b, 2 and 3.
Fig. 3. X-ray structure ORTEP diagram of compound 2 with displacement ellipsoids
drawn at the 35% probability level. All hydrogen atoms have been omitted for
clarity.
Fig. 1. X-ray structure ORTEP diagram of compound 1a with displacement
ellipsoids drawn at the 35% probability level. All hydrogen atoms have been
omitted for clarity.
possible to identify any other product from the corresponding
reaction mixtures. Views of the molecular structures of the two
mononuclear compounds are shown in Figs. 5 and 6, while selected
bond length and angle parameters are summarized in Table 2.
Crystals structures of these two mononuclear compounds have
been reported in the past, however, the compounds were obtained
from different synthetic routes and exhibit different crystal and
structural parameters [35]. The tetrahedral coordination environ-
ment around the metal centers, formed by two phosphorus atoms
of two triphenylphosphane molecules, a halide ligand, and the exo-
cyclic sulfur atom of the heterocyclic thione, is slightly distorted,
with the largest deviations being reflected by the PACuAX angles
of 101.80° and 103.72° for 4a and 4b, respectively. In addition,
the CuAS and CuAhalide distances in these mononuclear
compounds are longer than the corresponding distances of the
binuclear compounds discussed above.
radii of two copper(I) atoms, suggesting a weak bonding interac-
tion between the two closed-shell metal ions. All complexes are
further stabilized through the formation of intramolecular hydro-
gen-bonds between the halide ligand of the copper atoms and
the closest NH group of the thione heterocycle Table 2.
In contrast to the abovementioned results, analogous reactions
of [CuX(PPh3)]4 (X = Br, Cl) with the phenyl-substituted tetrazole
ptztH, under identical experimental conditions as above, resulted
in the isolation of mononuclear complexes with the formula [CuX
(PPh3)2(ptztH)] (X = Br (4a), X = Cl (4b)), as shown in Scheme 4. The
formulas of the two compounds are not in agreement with the
corresponding reaction stoichiometry; however, it has not been

142
A. Koutsari et al. / Inorganica Chimica Acta 458 (2017) 138–145
Scheme 4. Synthesis of compounds 4a and 4b.
Overall, there is a number of factors that might favor the forma-
tion of either binuclear or mononuclear mixed-ligand thione/phos-
phane/halide copper(I) compounds. Among them, electronic
factors determining the thione Lewis basicity as well as stereo-
chemical demands imposed by each of the ligands should primarily
be taken into account. As far as the Lewis basicity of the thione-S
atom concerns, it seems reasonable to assume that strong
thione-S bases tend to bind to more copper centers, favoring the
formation of S-bridged dimers. In this context, considering that
the basicity of azoles decreases when the number of imino nitro-
gens increases and when there are substituents with electron with-
drawing resonance effects, the low basicity of the thione-S atom in
the tetrazole-based thione ligand ptztH (used in 4a and 4b) could
be responsible for the formation of mononuclear complexes,
whereas the increased basicity in the diazole- and imidazole-based
thione ligands mtdztH, atdztH, dpimdztH (used in 1a, 1b, 2, and 3)
accounts for the formation of S-bridged dimers. Steric hindrance
Fig. 4. X-ray structure ORTEP diagram of compound 3 with displacement ellipsoids
drawn at the 35% probability level. All hydrogen atoms have been omitted for
clarity.
Table 2
Selected bond lengths (Å) and angles (°) for the centrosymmetric binuclear compounds 1a, 1b, 2, 3, and the mononuclear compounds 4a and 4b.
X
P
P
HN
Cu
Y
Y
Cu
HN
Y
S
P#
X#
S
X
P
Cu#
S#
NH
1a
1b
2
3
4a
4b
X = Br
Y = S
X = Cl
Y = S
X = Br
Y = S
X = Br
Y = NH
X = Br
Y = NPh
X = Cl
Y = NPh
Bond distances (Å)
CuAP
2.2355(13)
2.2301(5)
2.2211(16)
2.2453(11)
2.2617(10)
2.2861(11)
2.5291(6)
2.3910(10)
N/A
2.2567(9)
2.2835(9)
2.3931(9)
2.3964(8)
N/A
CuAX
2.4512(8)
2.3394(13)
2.4654(14)
2.943
2.3175(6)
2.3543(5)
2.4713(5)
3.016
2.4387(10)
2.3231(14)
2.4816(15)
2.983
2.4962(7)
2.3318(11)
2.5505(14)
2.754
CuAS
CuAS#
Cuꢂ ꢂ ꢂCu#
N/A
N/A
Bond angles (o)
PACuAX
112.59(4)
112.58(5)
116.16(2)
112.14(1)
115.94(5)
113.70(5)
108.97(4)
116.92(4)
101.80(3)
107.24(3)
110.53(4)
104.03(4)
108.75(3)
N/A
103.72(3)
107.37(4)
109.97(3)
103.36(3)
107.76(3)
N/A
PACuAS
XACuAS
114.97(4)
104.50(4)
113.64(5)
97.39(4)
112.75(2)
102.68(2)
113.56(2)
97.94(2)
113.59(4)
103.32(5)
111.72(5)
96.45(4)
112.21(3)
111.50(4)
107.67(4)
97.80(3)
SACuAS#
PACuAS#
XACuAS#
N/A
N/A
N/A
N/A
Hydrogen bonding
1a
1b
2
3
4a
4b
NAX
NAH
XAH
NAHAX
3.234
0.854
2.383
174.07
3.064
0.853
2.223
168.61
3.264
0.855
2.429
165.15
3.274
0.842
2.518
149.86
3.170
0.870
2.320
165.29
3.000
0.856
2.163
165.96

A. Koutsari et al. / Inorganica Chimica Acta 458 (2017) 138–145
143
3.2. Infra-red spectroscopy
Corroborating evidence for the identity of the six copper(I) com-
pounds in bulk form, as well as verification of the coordination
mode of the heterocyclic sulfur containing ligands, has been
obtained by Infra-red spectroscopy. The IR spectra of all com-
pounds display bands attributed to vibrations of both triph-
enylphosphane and the corresponding sulfur donor ligands. For
example, compounds 1a and 1b contain the mtdztH ligand. The
IR spectra of free mtdztH, as well as those of the binuclear com-
pounds 1a and 1b, do not show any bands in the 2600–
2500 cmꢀ1 region, where the
m(SH) mode is expected to appear,
suggesting that the ligand, either free or in its coordinating mode,
exists mainly in its thioketo, instead of the tautomeric thiole, form
[39]. The free ligand band at 1550 cmꢀ1, assigned to
m(C@N) mode,
is shifted to lower frequency at 1541 cmꢀ1 in complexes 1a and 1b
[40]. On the contrary, the free ligand band at 1268 cmꢀ1, having
contributions mainly from the m(CAN) mode, is shifted to higher
frequency at 1296 cmꢀ1, in agreement with the electron shift
!
!
€
H N AC@ S :! Cu, upon coordination of the thioketo form of
mtdztH through its sulfur atom to the copper center. Accordingly,
the frequency shift of the strong band of free thione from 764 to
747 cmꢀ1 of the binuclear compounds is associated with the
(C@S) vibration mode [41]. Analogous conclusions are drawn from
the IR spectra of the other compounds.
m
Fig. 5. X-ray structure ORTEP diagram of compound 4a with displacement
ellipsoids drawn at the 35% probability level. All hydrogen atoms have been
omitted for clarity.
3.3. Photophysical measurements
The UV–Vis electronic absorption spectra of compounds 1a, 1b,
2 and 3, recorded in chloroform at room temperature, are domi-
nated by two intense bands with maxima in the ꢃ250 and
ꢃ290–315 nm regions, while only the broad high energy band at
271 and 257 nm is shown in the spectra of 4a and 4b respectively.
With reference to the absorption spectrum of free PPh3, which
exhibits absorption bands at 245 nm, the high energy bands can
be considered as intraligand p⁄
p transitions on the phenyl
groups of the phosphane moiety [4]. The lower energy band, which
lies in the region where the free thiones absorb, can be attributed
to a thione originating intraligand transition.
The photoluminescence properties of compounds 1a, 1b, 2, 3,
4a, and 4b were examined on solid-state samples at room temper-
ature. Complexes 1a, 1b, 2 and 3 were found to be emissive with
maxima of emission bands in the 430–498 nm range (Table 3
and Fig. 7). At first sight, their emission maxima seem to be
slightly dependent on the thione ligand present in each case.
In particular, photoexcitation of solid samples of complexes
[CuBr(PPh3)(l-S-mtdztH)]2 (1a) and [CuCl(PPh3)(l-S-mtdztH)]2
(1b) in the 310 nm region results in strong and broad emission
bands with maxima located at 498 nm and 493 nm, respectively.
These low lying emissions cannot be of pure phosphane originating
intra-ligand nature, because of their significant red shift relative to
the solid-state emission spectrum of the free PPh3, which consists
of a broad band with maximum at 433 nm [42] after photoexcita-
tion at 335 nm. On the other hand, excitation of a solid state
Fig. 6. X-ray structure ORTEP diagram of compound 4b with displacement
ellipsoids drawn at the 35% probability level. All hydrogen atoms have been
omitted for clarity.
reasons should not be ruled out as well, since the two mononuclear
complexes 4a and 4b are obtained only for the more sterically
demanding, N1-phenyl substituted ptztH. Last, the solubility of
the complexes in the particular solvent mixture might also influ-
ence the formation of one type over the other. In particular the iso-
lation of specific solid-state structures of copper(I)/phosphane/
halide complexes is heavily influenced by choice of crystallization
solvent [36], while in many cases dynamic equilibrium schemes
have been proposed to exist in solutions of phosphane-containing
heteroleptic copper(I) complexes, which contain species with dif-
ferent solubility properties [37,38].
Table 3
Photoluminescence data for compounds 1a, 1b, 2, 3, 4a and 4b.
Compound
kmax (emission), nm
[CuBr(PPh3)(
l
-S-mtdztH)]2 (1a)
498
493
488
428
408
404
[CuCl(PPh3)(l-S-mtdztH)]2 (1b)
[CuBr(PPh3)(
l
-S-atdztH)]2 (2)
-S-dpimdztH)]2 (3)
[CuBr(PPh3)(
l
CuBr(PPh3)2(ptztH) (4a)
CuCl(PPh3)2(ptztH) (4b)

144
A. Koutsari et al. / Inorganica Chimica Acta 458 (2017) 138–145
therefore more appropriate to suppose that these emissions are
of thione originating intra-ligand nature, since the solid sample
of the free ligand ptztH also shows a very weak fluorescence with
maximum at 390 nm. Finally, and not unexpectedly, the emission
band of the Br-derivative 4a is slightly red-shifted compared to
that of its Cl-counterpart 4b, indicating involvement of the halide
ligand in the emissive excited state, as in the case of 1a and 1b.
All the compounds under investigation are also luminescent in
dilute dichloromethane solutions, exhibiting emission characteris-
tics similar to the ones in solid state, which might give an indica-
tion about their stability in dichloromethane solution.
4. Concluding remarks
Herein, we present the syntheses and solid-state structures of a
series of copper(I) complexes containing a mixed set of halide (Cl
or Br), PPh3 and five-membered ring heterocyclic thione ligands.
Despite the fact that all complexes were synthesized under identi-
cal experimental conditions, their solid state structures reveal two
distinct structural motifs: either binuclear, centrosymmetric com-
Fig. 7. Normalized emission spectra of compounds 1a, 1b, 2 and 3 in solid state at
room temperature.
plexes of the type [CuX(PPh3)(l
2-S-thione)]2 with two doubly
bridging sulfur atoms of a thione ligand, or mononuclear com-
plexes of the type CuX(PPh3)2(S-thione) with the thione present
in a terminal bonding mode. Although there are no clear-cut con-
clusions to draw from, it seems that a number of factors, including
differences in Lewis basicity and steric factors of the heterocyclic
thiones used in each case, play an important role in the formation
of a specific structure in crystalline form. Furthermore, all com-
plexes are photoluminescent in the solid state at ambient temper-
ature, exhibiting emission maxima in the 400–490 nm range, while
their emission properties are strongly affected by the Lewis basic-
ity of the thione-S donor atom of the respective heterocyclic
thione, as well as (to a smaller extent) by the halide present in each
case.
sample of free mtdztH in the UV region produces a rather weak and
structured fluorescence emission with a maximum at 470 nm.
Thus, based on previous results obtained by TD-DFT calculations
on similar systems [6], we tentatively attribute the blue-green
emission of these complexes to a mixed MLCT/LLCT excited state
composed of a metal-to-ligand charge transfer (MLCT) of the type
CuI?p⁄(PPh3) and to an intraligand charge transfer (LLCT)
mediated by the copper central metal atom. Regarding the
participation of the thione ligand to the emissive excited state,
there are controversial views in the literature. Thus, while the case
of a CuI?S@CAN(S,N)thione MLCT is suggested [43], this possibility
is excluded by others, because sulfur is considered to preferentially
acts as a reducing ligand [44]. Furthermore, in accordance with
previous results from related compounds [8,9,45] a small shift
(ꢃ10 nm) of the emission energy is observed upon changing the
halide ligand, indicating the participation of a halide-to-ligand
charge-transfer in the emissive excited sites [46,47]. The character-
istics of the emission band of compound 2 are similar to those of
complexes 1a and 1b, whereby the maximum of the emission band
is at slightly higher energy (488 nm) and red-shifted by 30 nm
compared to the free ligand’s emission.
Acknowledgements
The authors would like to acknowledge the Aristotle University
Research Committee Program ‘‘Enhancing Young Researchers at
the rank of Assistant Professor” (Contract No 93300) for support
for this work.
Appendix A. Supplementary data
Excitation of a solid sample of [CuBr(PPh3)(l-S-dpimdztH)]2 (3)
in the 270 nm region results in a very intense blue luminescence
with the broad emission band showing a maximum at 428 nm.
This emission appears to be red-shifted by 20 nm in comparison
to the similarly intense emission band of the free ligand dpimdztH.
While the ligand’s emission could obviously be due to either n?p⁄
CCDC 1483508–1483513 contain the supplementary crystallo-
graphic data for compounds 1a, 1b, 2, 3, 4a, and 4b, respectively.
These data can be obtained free of charge via http://www.
ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge Crys-
tallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK;
fax: (+44) 1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk. Sup-
plementary data associated with this article can be found, in the
online version, at http://dx.doi.org/10.1016/j.ica.2017.01.007.
or p?
p⁄ transitions, it is difficult to assess its contribution to the
overall constitution of the emissive excited state of the complex
3. However, the quest for the origin of the lowest lying emissive
state in this specific case should additionally take into account
the possibility of a metal centered state as, unlike in the above-
mentioned dicopper complexes, the Cuꢂ ꢂ ꢂCu separation of
References
2.754 Å in
interaction.
3 is indicative of a weak intermetallic bonding
[1] H. Yersin (Ed.), Highly Efficient OLEDs with Phosphorescent Materials, Wiley-
VCH, Weinheim, 2008.
[2] D.R. McMillin, K.M. McNett, Chem. Rev. 98 (1998) 1201.
[3] D. Felder, J.-F. Nierengarten, F. Barigelletti, B. Ventura, N. Armaroli, J. Am.
Chem. Soc. 123 (2001) 6291.
Solid samples of the mononuclear compounds CuX(PPh3)2
(thione), X = Br (4a) and X = Cl (4b), upon photoexcitation at
360 nm, display very weak violet luminescence with emission
maxima at 408 and 404 nm, respectively. These emissions are sig-
nificantly blue shifted compared to the ones of the other four com-
pounds; however, this fact is unlikely to be associated with the
nuclearity of the complexes, since a contribution of a cluster-cen-
tered emission in the dicopper species 1a, 1b, and 2 is expected
to be negligible due to the large Cuꢂ ꢂ ꢂCu separation. It would be
[4] C. Kutal, Coord. Chem. Rev. 99 (1990) 213.
[5] P.C. Ford, A. Vogler, Acc. Chem. Res. 26 (1993) 220.
[6] V. Pawlowski, G. Knör, C. Lennartz, A. Vogler, Eur. J. Inorg. Chem. (2005) 3167.
[7] E. Gariati, E. Lucenti, C. Botta, U. Giovanella, D. Marinotto, S. Righetto, Coord.
Chem. Rev. 306 (2016) 566.
[8] K. Tsuge, Y. Chishina, H. Hashiguchi, Y. Sasaki, M. Kato, S. Ishizaka, N. Kitamura,
Coord. Chem. Rev. 306 (2016) 636.
[9] P. Aslanidis, P.J. Cox, K. Kapetangiannis, A.C. Tsipis, Eur. J. Inorg. Chem. (2008)
5029.

A. Koutsari et al. / Inorganica Chimica Acta 458 (2017) 138–145
145
[10] M.G. Babashkina, D.A. Safin, A. Klein, M. Bolte, Eur. J. Inorg. Chem. (2010) 4018.
[11] P. Aslanidis, P.J. Cox, A.C. Tsipis, Dalton Trans. 39 (2010) 10238.
[12] I. Papazoglou, P.J. Cox, A.G. Papadopoulos, M.P. Sigalas, P. Aslanidis, Dalton
Trans. 42 (2013) 2755.
[13] V.W.W. Yam, C.H. Lam, W.K.M. Fung, K.K. Cheung, Inorg. Chem. 40 (2001)
3435.
[28] M.A. Tsiaggali, E.G. Andreadou, A.G. Hatzidimitriou, A.A. Pantazaki, P.
Aslanidis, J. Inorg. Biochem. 121 (2013) 121.
[29] G. Costa, E. Reisenhofer, L. Stefani, J. Inorg. Nucl. Chem. 27 (1963) 2582.
[30] Apex2, Version 2 User Manual, M86-E01078, Bruker Analytical X-ray Systems,
Inc., Madison, WI, 2006.
[31] P.W. Betteridge, J.R. Carruthers, R.I. Cooper, K. Prout, D.J. Watkin, J. Appl.
Crystallogr. 36 (2003) 1487.
[32] L.J. Farrugia, J. Appl. Crystallogr. 45 (2012) 849.
[14] A. Gallego, O. Castillo, C.J. Gómez-García, F. Zamora, S. Delgado, Inorg. Chem.
51 (2012) 718.
[15] R. Langer, M. Yadav, B. Weinert, D. Fenske, O. Fuhr, Eur. J. Inorg. Chem. (2013)
3623.
[33] S.K. Hadjikakou, P. Aslanidis, P. Karagiannidis, A. Hountas, A. Terzis, Inorg.
Chim. Acta 184 (1991) 161.
[16] E.S. Raper, Coord. Chem. Rev. 129 (1994) 91.
[17] E.R. Atkinson, D.J. Gardiner, A.R.W. Jackson, E.S. Raper, Inorg. Chim. Acta 98
(1985) 35.
[18] S.C. Kokkou, S. Fortier, P.J. Rentzeperis, P. Karagiannidis, Acta Crystallogr., Sect:
C 39 (1983) 178.
[19] F.A. Devillanova, G. Verani, L.P. Battaglia, A. Bonamartini Corradi, Trans. Met.
Chem. 5 (1980) 362.
[20] J.M. Bret, P. Castan, G. Jugie, A. Dubourg, R. Roques, J. Chem. Soc., Dalton Trans.
(1983) 301.
[34] P. Karagiannidis, S.K. Hadjikakou, P. Aslanidis, A. Hountas, Inorg. Chim. Acta
178 (1990) 27.
[35] S. Shakhatreh, M. Lalia-Kantouri, M. Gdaniec, P.D. Akrivos, J. Coord. Chem. 65
(2012) 251.
[36] K. Chen, J. Shearer, V.J. Catalano, Inorg. Chem. 54 (2015) 6245.
[37] S. De, K. Mahata, M. Schmittel, Chem. Soc. Rev. 39 (2010) 1555.
[38] A. Kaeser, M. Mohankumar, J. Mohanraj, F. Monti, M. Holler, J.-J. Cid, O.
Moudam, I. Nierengarten, L. Karmazin-Brelot, C. Duhayon, B. Delavaux-Nicot,
N. Armaroli, J.-F. Nierengarten, Inorg. Chem. 52 (2013) 12140.
[39] C.N.R. Rao, Chemical Applications of Infrared Spectroscopy, Academic Press,
New York, 1963.
[21] L.P. Nattaglia, A. Bonamartini Corradi, M. Nardelli, M.E. Vidoni, J. Chem. Soc.,
Dalton Trans. (1976) 143.
[22] S.K. Hadjikakou, P. Aslanidis, P.D. Akrivos, P. Karagiannidis, B. Kojic-Prodic, M.
Luic, Inorg. Chim. Acta 197 (1992) 31.
[23] P. Aslanidis, P.J. Cox, S.K. Hadjikakou, C.D. Antoniadis, Eur. J. Inorg. Chem.
(2002) 2216.
[24] S.K. Hadjikakou, C.D. Antoniadis, P. Aslanidis, P.J. Cox, A.C. Tsipis, Eur. J. Inorg.
Chem. (2005) 1442.
[40] A.C. Fabretti, G.C. Franchini, G. Peyronel, Spectrochim. Acta 36A (1980) 517.
[41] A.C. Fabretti, A. Giusti, Polyhedron 5 (1986) 1927.
[42] L. Maini, D. Braga, P.P. Mazzeo, B. Ventura, Dalton Trans. 41 (2012) 531.
[43] L.R.V. Favarin, P.P. Rosa, L. Pizzuti, A. Machulek Jr., A.R.L. Caires, L.S. Bezzena, L.
M.C. Pinto, G. Maia, C.C. Gatto, D.F. Back, Polyhedron (2016), http://dx.doi.org/
10.1016/j.poly.2016.10.003.
[25] P. Aslanidis, S.K. Hadjikakou, P. Karagiannidis, B. Kojic-Prodic, M. Luic,
Polyhedron 13 (1994) 3119.
[44] D.M. Knotter, G. Blasé, J.P.M. van Vliet, G. van Koten, J. Bourassa, Chem. Rev. 99
(1999) 3625.
[26] T.S. Lobana, R. Sharma, R. Sharma, R.J. Butcher, Z. Anorg. Allg. Chem. 634
(2008) 1785.
[27] T.S. Lobana, R. Sultana, G. Hundal, A. Castineiras, Polyhedron 28 (2009) 1573.
[45] P. Aslanidis, P.J. Cox, P. Tsaliki, Polyhedron 27 (2008) 3029.
[46] P.C. Ford, E. Cariati, J. Bourassa, Chem. Rev. 99 (1999) 3625.
[47] M. Henary, J.L. Wootton, S.I. Khan, J.I. Zink, Inorg. Chem. 36 (1997) 796.