Anagostic, mono- and hexahapta interactions in Tl(I) dithiocarbamates: A new precursor for the preparation of Tl2S nanoparticles

Article abstract of DOI:10.1016/j.poly.2015.09.071

Two new homoleptic complexes, [Tl(bzfdtc)]₂ (1) and [Tl(bu_2-OHbzdtc)]₂ (2) (where bzfdtc = N-benzyl-N-furfuryldithiocarbamate and bu_2-OHbzdtc = (N-butyl-N-(2-hydroxybenzyl)dithiocarbamate), have been prepared an

Full text of DOI:10.1016/j.poly.2015.09.071

Polyhedron 102 (2015) 424–433
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Polyhedron
journal homepage: www.elsevier.com/locate/poly
Anagostic, mono- and hexahapta interactions in Tl(I) dithiocarbamates:
A new precursor for the preparation of Tl S nanoparticles
2
Govindaraju Gomathi , Subbiah Thirumaran , Samuele Ciattini b
a
a,
⇑
a
Department of Chemistry, Annamalai University, Annamalainagar 608 002, India
Centro di Cristallografia Strutturale, Polo Scientifio di Sesto Fiorentino, Via della Lastruccia No. 3, 50019 Sesto Fiorentino, Firenze, Italy
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 5 July 2015
Accepted 30 September 2015
Available online 22 October 2015
Two new homoleptic complexes, [Tl(bzfdtc)]2 (1) and [Tl(bu2-OHbzdtc)]2 (2) (where bzfdtc = N-benzyl-N-
furfuryldithiocarbamate and bu2-OHbzdtc = (N-butyl-N-(2-hydroxybenzyl)dithiocarbamate), have been
prepared and characterized by IR, NMR ( H and C), UV–Vis spectroscopy, cyclic voltammetry and single
crystal X-ray structural analysis. X-ray crystallography revealed that both complexes are dimers. Both
1
13
complexes show two monohapta Tlꢀ ꢀ ꢀC(S
2
) interactions. The Tlꢀ ꢀ ꢀTl distances are 3.635 and 3.719 Å for
Keywords:
Thallium(I) dithiocarbamates
X-ray structure
6
1
and 2, respectively. The phenyl ring of the bzfdtc ligand is coordinated (by a
g interaction) to the
+
Tl ion in complex 1. A rare intramolecular anagostic C–Hꢀ ꢀ ꢀTl interaction is observed in complex 2.
Thallium sulfide nanoparticle samples 3 and 4 have been prepared from complex 1 using conventional
heating and microwave irradiation, respectively. Samples 3 and 4 have been characterized by PXRD,
EDAX, HR-TEM, UV–Vis absorption and fluorescence spectroscopy. PXRD measurements revealed rhom-
Anagostic interaction
Tl
2
S nanoparticles
Powder X-ray diffraction
bohedral and hexagonal phases for samples 3 and 4, respectively. EDAX confirmed the formation of Tl
HR-TEM images showed that the size and morphology of the Tl S nanoparticles are affected by the
method of preparation (conventional heating compared to microwave irradiation).
2
S.
2
Ó 2015 Elsevier Ltd. All rights reserved.
1
. Introduction
ductors have been extensively studied due to their potential appli-
cations and novel properties [23]. The thallium sulfide system is
highly interesting because of the number of phases that it contains,
Dithisiderable interest in coordination chemistry [1]. Dithiocar-
bamates are highly versatile ligands that interact with main group
metals and stabilize a variety of oxidation states in different
coordination geometries [2,3]. The coordination numbers and
geometries can be influenced by the relativistic effect of
including Tl
are the double sulfides: Tl [Tl S
2
S, Tl
4
S
3
, TlS, TlS
2
I
, Tl
2
S
3
and Tl
] and Tl
2
S
9
. Here, TlS and Tl
4
S
3
III
I
III
2
3 3
[Tl S ], respectively,
whereas TlS
2
2
, Tl S
5
and Tl S
2 9
may be considered as poly sulfides,
TlxSSn [24]. Thallium is an important ingredient in high temperature
oxide superconductors [25,26]. Thallium compounds are useful in
the production of optical glass, lenses for IR equipment and scintilla-
tion sensors [27]. Thallium monosulfide is an incongruent compound
and it is used as a semiconductor [28,29]. Thallium chalcogenide
coated polymers find use in photonic applications [30,31]. Metal
dithiocarbamate complexes have been used as single source precur-
sors for the preparation metal sulfide nanoparticles [32]. The phase
and morphology of the metal sulfides are often influenced by the
precursor as well as by the solvent and thermolysis temperature
[33]. In this paper we report the synthesis, spectroscopic and single
2
stereochemically active 6s lone pair of electrons on metal centres
[
1,4–7]. Thallium as a heavy element of group 13 has stable oxida-
tion states of +1 and +3 [8]. Limited studies on thallium(I)
dithiocarbamate complexes have been reported so far [4,5,9–21]
because of the complexity of thallium(I) dithiocarbamate com-
plexes which contain dimeric molecules of the same type but with
different arrangements of the dimers. The linkages of the dimers
lead to polymeric structures. These linkages are strongly influ-
enced by the size and nature of the N-bound organic moiety of
dithiocarbamate ligands [22].
The physical and chemical properties of materials deviate from
those of the bulk on the reduction of size to the nanometer scale.
Among the different classes of materials, nanostructural semicon-
crystal X-ray structures of [Tl(bzfdtc)]
(where bzfdtc = N-benzyl-N-furfuryldithiocarbamate and bu2-OH
bzdtc = (N-butyl-N-(2-hydroxybenzyl)dithiocarbamate). The prepa-
2 2
(1) and [Tl(bu2-OHbzdtc)] (2)
-
ration of Tl S nanoparticles from complex 1 using conventional
2
heating and microwave irradiation methods and their characteriza-
tion by PXRD, HR-TEM, EDS analysis, UV–Vis absorption and fluores-
cence spectroscopy are also presented.
⇑
Corresponding author at: Department of Chemistry, Annamalai University,
Annamalainagar 608 002, Tamil Nadu, India. Tel.: +91 9842897597.
E-mail address: sthirumaran@yahoo.com (S. Thirumaran).
http://dx.doi.org/10.1016/j.poly.2015.09.071
0
277-5387/Ó 2015 Elsevier Ltd. All rights reserved.

G. Gomathi et al. / Polyhedron 102 (2015) 424–433
425
Table 2
2
. Experimental
Selected bond lengths (Å) and bond angles (°) for complexes 1 and 2.
All reagents and solvents were commercially available high
1
2
grade materials [Merck/Sd fine/Himedia] and used as received. Ele-
mental analysis was performed using a Perkin Elmer 2400 series II
CHN analyzer. IR spectra were recorded on a thermo NICOLET AVA-
TAR 330 FT-IR spectrophotometer for complex 1 and a THERMO
i
Tl1–S2
Tl1–S1
Tl1–S2
Tl1–S1
3.055(3)
3.082(3)
3.062(3)
3.114(3)
3.6451(8)
1.728(10)
1.711(11)
1.347(15)
57.90(7)
107.12(7)
80.97(8)
57.64(7)
107.67(7)
79.72(8)
53.22(6)
54.49(6)
53.91(6)
53.17(5)
84.8(4)
Tl1–S2
Tl1–S2
Tl1–S1
Tl1–S1
Tl1–Tl1
S1–C1
S2–C1
S2–Tl1–S2
S2–Tl1–S1
S2–Tl1 –S1
3.0205(13)
i
i
3.0647(13)
3.0909(14)
3.1492(15)
3.7195(4)
1.713(5)
1.738(5)
104.64(3)
57.82(3)
79.28(3)
79.03(3)
56.77(3)
106.83(3)
52.86(2)
51.78(2)
54.14(3)
52.69(3)
84.66(16)
83.91(16)
73.17(3)
86.48(16)
86.20(15)
75.35(3)
i
i
i
Tl1–Tl1
S1–C1
S2–C1
N1–C1
S2–Tl1–S1
S2–Tl1–S2
SCIENTIFIC NICOLET iS
5
IR spectrometer for complex 2. The
H/ C NMR spectra were recorded on a BRUKER 400/100 MHz
NMR spectrometer at room temperature in CDCl solvent. The
powder X-ray diffraction (XRD) patterns of the Tl S nanoparticles
were recorded at room temperature using a Bruker D8 Advance
X-ray diffraction system with Mo K radiation. High resolution–
1
13
i
3
2
i
i
i
i
i
i
i
S1 –Tl–S2
S2–Tl1–S1
a
i
i
i
i
S2 –Tl1 –S1
S2 –Tl1–S1
i
i
transmission electron microscopy (HR-TEM) was performed with
a JEOL 3010, 300kv instrument equipped with a UHR polepiece.
Energy dispersive X-ray analysis (EDS) was carried out with an
Oxford EDAX housed in the TEM. UV–Vis absorption spectra were
measured on a Shimadzu UV-1650 PC double beam UV–Visible
spectrophotometer with the samples dispersed in ethanol at room
temperature. Fluorescence spectra were recorded using a Perkin
Elmer 1555 fluorescence spectrophotometer at room temperature.
S1–Tl1–S1
S2–Tl1–S1
S2–Tl1–Tl1
S1–Tl1–Tl1
S2 –Tl1–Tl1
–Tl1–Tl1
C1–S1–Tl1
C1–S1–Tl1
Tl1–S1–Tl1
S1–Tl1–S1
S2–Tl1–Tl1
S2–Tl1 –Tl1
S1–Tl1–Tl1
S1–Tl1–Tl1
C1–S1–Tl1
C1–S1–Tl1
i
i
i
i
i
i
i
i
i
i
S1
i
i
i
83.5(4)
72.88(6)
85.6(4)
72.33(7)
119.9(8)
120.4(7)
119.8(7)
Tl1–S1–Tl1
i
i
i
i
C1 –S2 –Tl1
i
i
C1–S2–Tl1
C1–S2–Tl1
Tl1–S2 –Tl1
i
i
Tl1–S2–Tl1
N1–C1–S1
N1–C1–S2
S1–C1–S2
2.1. X-ray crystallography
Diffraction data for 1 and 2 were recorded on Bruker axis Kappa
For complex 1, symmetry: i = 1 ꢁ x, 2 ꢁ y, 2 ꢁ z; for complex 2, symmetry:
i = 1.5 ꢁ x, ½ + y, z.
apex II and Xcalibur, Sapphire 3 diffractometers, using graphite-
monochromated Mo K radiation (k = 0.71073 Å) at an ambient
a
temperature. The structures were solved by SIR 92 [34] and refined
by full-matrix least square methods in SHELXL-97 [35]. All non-
hydrogen atoms were refined anistrophically and the hydrogen
atoms were refined isotropically. Details of the crystal data and
structure refinement parameters for 1 and 2 are summarized in
Table 1. Selected bond lengths and angles for 1 and 2 are given
in Table 2.
2
.3. Preparation of complex 1
N-benzyl-N-furfurylamine (0.75 g, 4 mmol) and carbon
disulfide (0.3 mL, 4 mmol) were dissolved in ethanol (20 mL) and
stirred for 30 min at 5 °C. Thallium(I) chloride (0.8 g, 4 mmol)
was dissolved in 30 mL of hot water and added to the solution. A
pale yellow powder precipitated, which was filtered and dried
(
Scheme 1).
2
.2. Preparation of the amines
ꢁ1
Yield: 73%. Mp: 120 °C. IR (KBr, cm ): 1447 (vC–N), 979 (vC–S).
1
3 2
H NMR (400 MHz, CDCl ) d, ppm: 5.37 (s,–CH -(furyl)); 5.20
N-benzyl-N-furfurylamine and N-butyl-N-(2-hydroxybenzyl)
(
s, –CH
2
–(benzyl)); 6.36–7.38 (aromatic protons). 13C NMR
amine were prepared by general methods, as reported earlier [36].
Table 1
Crystal data, data collection and refinement parameters for 1 and 2.
1
2
Empirical formula
C
13
H
12NOS
2
Tl
C
12
H
16NOS
2
Tl
FW
466.73
458.75
Crystal dimensions/mm
Crystal system
Space group
a (Å)
b (Å)
c (Å)
0.43 ꢂ 0.21 ꢂ 0.13
0.3 ꢂ 0.2 ꢂ 0.1
orthorhombic
Pbca
11.0950(4)
9.3810(2)
27.5690(8)
90.00
90.00
90.00
2869.44(15)
8
2.124
monoclinic
1
P2 /c
10.2363(2)
8.81170(10)
16.0169(3)
90
101.405(2)
90
1416.1(4)
4
2.189
a
(°)
b (°)
(°)
c
3
V (Å )
Z
D
l
calc (g cmꢁ3)
ꢁ
1
(cm
)
24.571
11.532
F(000)
k (Å)
872
CuK
1728
MoK 0.71073
a
0
a
1.54184
h range (°)
4.41-72.34
4.10-32.41
Index ranges
ꢁ12 6 h 6 12, 10 6 k 6 10, ꢁ19 6 l 6 17
ꢁ16 6 h 6 15, ꢁ13 6 k 6 13, ꢁ39 6 l 6 36
Reflections collected
Observed reflections [I > 2
Weighting scheme
13061
14525
r
(I)] 2283
3568
Calc. W = 1/(
r
2(F
2
o
) + (0.1220p)2 + 1.2067p) where p = (F2
o
+ 2F2
c
)/3 Calc. W = 1/(
r
2(F
2
) + (0.0247p)2 + 9.0917p) where p = (F2
o
+ 2F2
c
)/3
Number of parameters refined
163
0.0679, 0.1652
1.147
158
0.0760, 0.0850
1.034
2
2
2
R[F > 2
r
(F )], wR(F )
Goodness-of-fit (GOF)

4
26
G. Gomathi et al. / Polyhedron 102 (2015) 424–433
(
m, N–CH
2
–CH
2
–CH
–CH
); 4.52 (s, 2OH–C
2
–CH
–CH
–CH
3
); 1.33 (dd, N–CH
–CH ); 3.89 (m, N–CH
–N); 5.29 (s, 2OH–C
2
–CH
2
–CH
–CH
–CH
2
–CH
3
);
1
.67 (dd, N–CH
2
2
2
3
2
2
–CH
2
–
CH
3
6
H
4
2
1
6
H
4
2
–N);
3
6
.88–7.23 (aromatic protons). C NMR (100 MHz, CDCl
3.9 (N–CH –CH –CH –CH ); 20.0 (N–CH –CH –CH –CH
–CH –CH –CH ); 51.6 (N–CH –CH –CH –CH ); 53.4
2OH–C –CH –N); 117.1–131.8 (aromatic carbons); 155.7 (ipso
). Anal. Calc. for C24 Tl : C, 31.41;
H, 3.51; N, 3.05. Found: C, 30.8; H, 3.40; N, 2.97%.
3
) d, ppm:
1
2
2
2
3
2
2
2
3
); 28.6
(
N–CH
2
2
2
3
2
2
2
3
(
6
H
4
2
carbons); 202.6 (NCS
2
H
32
4
S N
2
O
2
2
2.5. Preparation of thallium sulfide (Tl
2
S) (sample 3)
0
.5 g of [Tl(bzfdtc)] was dissolved in 15 ml ethylenediamine in
2
a round bottom flask and then the contents of the flask were
refluxed for 1 h. The black precipitate obtained was filtered off
and washed with methanol.
2.6. Preparation of thallium sulfide (Tl
2
S) (sample 4)
0
.5 g of [Tl(bzfdtc)] was dissolved in 15 ml ethylenediamine in
2
a 100 ml beaker and then the reaction was carried out by
microwave irradiation for 2 min. The black precipitate obtained
was filtered off and washed with methanol.
3
. Results and discussion
3.1. Infrared spectral studies
Infrared spectra of complexes 1 and 2 are shown in Figs. S1 and
S2. In the IR spectra of the complexes, a strong band observed at
447 and 1457 cm- for 1 and 2, respectively, is assigned to the
1
1
N–CS stretching mode [37]. This indicates that the C–N bond
2
order is intermediate between a single and a double bond [38],
suggesting strong electron delocalization in the dithiocarbamate
moiety. A band with medium intensity due to the stretching mode
ꢁ1
of the C–S bond appeared at 979 and 1036 cm
for 1 and 2,
respectively [39]. In the IR spectrum of 2, a broad band observed
ꢁ
1
at 3444 cm is characteristic of the vOH vibration.
3.2. NMR spectral studies
NMR spectra were recorded at room temperature using TMS
3
as an internal reference. CDCl C
was used as the solvent. The 13
NMR spectra were recorded in the proton decoupled mode.
The structures of the ligands are shown in Schemes 1 and 2.
1
13
The H and C NMR spectra of complexes 1 and 2 are given in
Figs. S3–S6.
Scheme 1. Preparation of complex 1.
1
3
.2.1. H NMR spectral studies
The 1H NMR spectrum of 1 shows two singlets at d 5.20 and
.37 ppm due to the methylene protons of the benzyl and furyl
5
(
3 2 2
100 MHz, CDCl ) d, ppm: 47.7 (–CH –(benzyl)); 55.2 (–CH –
groups. A triplet at d 2.68 ppm and a singlet at d 5.29 ppm observed
in 2 are assigned to the methylene protons adjacent to the nitrogen
atom. These methylene protons are affected by the complexation
to a maximum extent as a result of deshielding. In complex 2 the
other methylene and methyl protons appear in the upfield region
at d 0.91–1.33 ppm. The hydroxy proton resonates at d 5.29 ppm.
The signals in the downfield region d 6.88–7.23 ppm are due to
the aromatic protons.
(
1
4
furyl)); 109.7, 110.5, 142.4, 150.1 (furyl ring carbons); 127.7–
36.3 (aromatic ring carbons). Anal. Calc. for C26H S N O Tl : C,
24 4 2 2 2
3.03; H, 3.33; N, 3.86. Found: C, 42.81; H, 3.27; N. 3.78%.
2
.4. Preparation of complex 2
A method similar to that described for the synthesis of 1 was
adopted, however N-butyl-N-(2-hydroxybenzyl)amine was used
instead of N-benzyl-N-furfurylamine (Scheme 2).
1
3
3.2.2. C NMR spectral studies
ꢁ1
Yield: 71%. Mp: 90 °C. IR (KBr, cm ): 1457 (vC–N), 1036 (vC–S),
In complex 1, two signals observed in the aliphatic region
(d 47.7 and 55.2 ppm) are due to the furfuryl and benzyl methylene
1
3
444 (vOH).
H
NMR (400 MHz, CDCl
3
)
d, ppm: 0.94

G. Gomathi et al. / Polyhedron 102 (2015) 424–433
427
HO
HO
+
CH OH
3
NH2 OHC
2
h stirring
N
NaBH /D
4
CM
4 h stirring
2
HO
N
H
CS
2
/TlCl
OH
S
Tl S
N
C
S
C
N
Tl
S
HO
Scheme 2. Preparation of complex 2.
Fig. 1. ORTEP of complex 1.
carbons. The proton and carbon chemical shift values of the
furfuryl methylene group are lower than those of the benzyl
methylene group. This is due to the delocalization of lone pair
electrons of the oxygen atom within the furyl ring which increases
the electron density on methylene unit of the furfuryl group [39].
In complex 2, two signals at d 51.6 and 53.40 ppm are due to the
methylene carbon atoms of the butyl and hydroxybenzyl groups.
A weak signal observed at d 155.7 ppm is assigned to the ipso
2
carbon atom. The NCS carbon signals of 1 and 2 appeared at d
206.7 and 202.6 ppm, respectively, indicating partial double bond
character of the N–C bond in the dithiocarbamate ligand.
3.3. Electronic spectral studies
Electronic spectra of complexes 1 and 2 are given in Fig. S7.
Complex 1 is pale yellow and 2 is colourless. Three bands observed

4
28
G. Gomathi et al. / Polyhedron 102 (2015) 424–433
Fig. 2. ORTEP of complex 2.
Fig. 3. View of the sulfur parallelogram (a) 1 and (b) 2.
around 315, 270 and 236 nm for both the complexes are due to
3.4. Cyclic voltammetric studies
⁄
intraligand
and S–C@S groups and an n ?
p
?
p
transitions, mainly associated with N–C@S
⁄
p
transition located on the sulfur
The cyclic voltammograms of 1 and 2 are shown in Fig. S8.
The reduction potentials for complexes 1 and 2 are observed
at ꢁ0.9152 and ꢁ0.6019 V, respectively. The reductions are
atoms (Figs. S7(a) and (b)). There are no d–d transitions as Tl(I)
2
1
has a 6s 6p configuration [40].

G. Gomathi et al. / Polyhedron 102 (2015) 424–433
429
bonded to the two sulfur atoms of the dithiocarbamate ligand at
distances of Tl1-S1 = 3.062(3) and Tl1-S2 = 3.082(3) Å in complex
1
2
and Tl1-S1 = 3.0909(14) and Tl1-S2 = 3.0205(13) Å in complex
. Each thallium center in the asymmetric unit is bonded with
two sulfur atoms of another centrosymmetrically related
dithiocarbamate ligand at distances of 3.114 (3) and 3.055 (3) Å
in complex 1, and 3.0647(13) and 3.1492(14) Å in complex 2, lead-
ing to a dimer. In addition, two monohapto interactions involving
thallium and the C atom of the CS
at distances of Tlꢀ ꢀ ꢀC1S = 3.376 and Tlꢀ ꢀ ꢀC1 S
and Tlꢀ ꢀ ꢀC1S = 3.422 and Tlꢀ ꢀ ꢀC1 S
2
moiety are observed to occur
i
2
2
= 3.386 Å for 1,
2
= 3.391 Å for 2, with the car-
i
2
bon atom of dithiocarbamate ligands of an asymmetric unit and
centro symmetrically related unit, respectively. In the dimeric unit,
the thallium atoms are situated on either side of a sulfur parallel-
ogram (Fig. 3) with edges of ꢃ2.9 and ꢃ3.9 Å, forming a bicapped
parallelogram. In the dimer, the Tlꢀ ꢀ ꢀTl distances for 1 and 2 are
3
.6451(8) and 3.7195(4) Å, respectively, which are shorter than
the sum of the van der Waals radii (3.92 Å), exhibiting the presence
of a Tlꢀ ꢀ ꢀTl interaction.
In the case of complex 1, each thallium atom in the binuclear
molecule is bonded to four sulfur atoms and there is a cation–
interaction (the arene -system counts as a single donor), thus
forming a distorted square pyramid. The centroid of the aryl ring
p
p
+
Fig. 4. Tl -arene interaction in complex 1.
+
(
C3–C8) is situated 3.237 Å from the Tl ion. Since Carene–Tl dis-
tances vary only slightly within a narrow range from 3.462 to
+
6
3
.571 Å, the Tl –arene interaction can be regarded as true
g –coor-
dination, Fig. 4. Two intramolecular C–Hꢀ ꢀ ꢀS (C9–H9ꢀ ꢀ ꢀS2 = 2.517
(
11) Å) and C2–H2ꢀ ꢀ ꢀS1 = 2.572(11) Å) interactions take place
between methylene hydrogen atoms (of benzyl and furfuryl
groups) and the thioureide sulfur atom. This complex also displays
a weak intermolecular C–Hꢀ ꢀ ꢀS interaction (Fig. 5, Table 3).
In complex 2, a C–Hꢀ ꢀ ꢀTl interaction is observed (Fig. 6).
Generally, three types of C–Hꢀ ꢀ ꢀM interactions are found, i.e. (i)
hydrogen ion (ii) agostic and (iii) anagostic interactions [41–61].
Hydrogen bonds are 3-center-4-electron interactions within an
almost linear geometry. Agostic interactions are usually referred
to as 3-centered-2-electron interactions and characterized by
Mꢀ ꢀ ꢀH distances of ꢃ1.8–2.2 Å and C–Hꢀ ꢀ ꢀM bond angles of ꢃ90–
1
30°. Anagostic interactions are characterized by Mꢀ ꢀ ꢀH distances
of 2.3–2.9 Å and large Mꢀ ꢀ ꢀH–C bond angles ꢃ110–170°. Anagostic
8
interactions are stabilized by d complexes. C–Hꢀ ꢀ ꢀTl interactions
are rare [62–65]. In the present study, an intermolecular C–Hꢀ ꢀ ꢀTl
(
2
Hꢀ ꢀ ꢀTl = 3.198 Å and \C–Hꢀ ꢀ ꢀTl = 131.91°) is observed in complex
. The Hꢀ ꢀ ꢀTl distance is larger than the values found in complexes
8
of d metal ions (Mꢀ ꢀ ꢀH ꢃ2.3–2.9 Å) [66]. This is due to the
+
larger size of the Tl ion. Further stabilization of the complex is
provided by intramolecular C–Hꢀ ꢀ ꢀS (H2Aꢀ ꢀ ꢀS1 = 2.633(11) and
H6Aꢀ ꢀ ꢀS2 = 2.531(10) Å) interactions with the hydrogen atoms of
the dithiocarbamate methylene group and O–Hꢀ ꢀ ꢀS (Hꢀ ꢀ ꢀS 2.467
(
10) Å) interactions (Fig. 7, Table 3).
3.6. Characterization of thallium sulfide nanoparticles
Tl S synthesized from complex 1 using conventional heating
2
and microwave irradiation methods are represented as samples 3
and 4, respectively. The PXRD patterns for samples 3 and 4 are
given in Fig. 8. In the case of sample 3, the sharp diffraction peaks
reveal that the obtained Tl S nanoparticles are well crystalline. The
2
diffraction peaks located at 2h = 29.3°, 32.9°, 39.1°, 44.6° and 54.4°
Fig. 5. Intramolecular and intermolecular C–Hꢀ ꢀ ꢀS interactions in 1.
irreversible and one electron processes. A one electron reduction
process with the formation of Tl has been already proposed [66]:
+
ꢁ
Tl + e ? Tl. This indicates that the oxidation state of thallium
can be indexed respectively as (033), (116), (306), (330) and
in both the complexes is +1.
(
229) planes of the rhombohedral phase with lattice constants
a = 12.2(7) and c = 18.17(6), which are in good agreement with
the Joint Committee on Powder Diffraction Standards JCPDS file
No 89-2013 [67]. The presence of (012), (113) and (122) planes
in the diffraction patterns of sample 4 is characteristic of the
3
.5. Single crystal X-ray structural analysis of complexes 1 and 2
ORTEP diagrams of complexes 1 and 2 are shown in Figs. 1 and
2, respectively. In the asymmetric unit, the thallium center is
2
hexagonal phase of Tl S. This is in good agreement with the JCPDS

4
30
G. Gomathi et al. / Polyhedron 102 (2015) 424–433
Fig. 6. Intermolecular anagostic interaction in complex 2.
2
Fig. 8. Powder XRD patterns of Tl S (a) sample 3 and (b) sample 4.
and 11) are ca. 3.2 and 3.5 Å, corresponding to the (113) and
(
229) crystal planes of TlS samples 3 and 4, respectively.
The UV–Vis absorption spectra of samples 3 and 4 in ethanol are
shown in Fig. 12. The absorption maxima is observed at 273 nm for
Fig. 7. Intramolecular SꢀꢀꢀH–C and SꢀꢀꢀH–O interactions in complex 2.
sample 3 and 293 nm for sample 4. Both samples reveal a blue shift
2
with respect to bulk Tl S, indicating a quantum confinement effect
file No 44-0889 [68].The remaining diffraction peaks can also be
assigned to the rhombohedral phase (JCPDS File no 89-2076) [67].
The energy dispersive X-ray spectra of 3 and 4 are shown in
Figs. 9(a) and (b). The energy dispersive X-ray spectroscopic stud-
ies of samples 3 and 4 confirm that the elemental composition of
[69].
Fluorescence spectra of samples 3 and 4 are given in Fig. 13. The
emission spectra were measured with a 270 nm excitation source.
In the case of sample 3, two broad emission peaks are observed at
362 and 419 nm. Only one broad emission peaks appeared at
362 nm for sample 4. In both cases, the emission peak at 362 nm
is due to the core state radioactive decay from the conduction band
to the valence band. The additional emission at 419 nm in the flu-
orescence spectrum of sample 3 is attributed to the recombination
2
samples 3 and 4 is Tl S.
HR-TEM images of samples 3 and 4 are shown in Figs. 10 and
1. The HR-TEM image of sample 3 shows that the particles are
1
nanometric size and shapeless, in sample 4, the particles are spher-
ical in shape and the diameters of the particles are ꢃ10 nm. The
lattice plane spacing calculated from the HRTEM images (Figs. 10
of trapped electrons/holes in some surface defect states of the Tl
particles.
2
S

G. Gomathi et al. / Polyhedron 102 (2015) 424–433
431
2 2
Fig. 9. EDAX spectra of (a) Tl S (sample 3) and (b) Tl S (sample 4).
Table 3
Geometric details of the hydrogen bonding (Å, °) for complexes 1 and 2 (D – donor; A – acceptor; H – hydrogen).
Interactions
D–H
Hꢀ ꢀ ꢀA
Dꢀ ꢀ ꢀA
D–Hꢀ ꢀ ꢀA
Complex 1
C(2)–H(2A)ꢀ ꢀ ꢀS1
C(9)–H(9A)ꢀ ꢀ ꢀS2
C(6)–H(6A)ꢀ ꢀ ꢀS1
0.970
0.969
0.931
2.572(11)
2.517(11)
2.897(12)
3.069(12)
2.997(11)
3.063(11)
119.98
110.48
140.45
Complex 2
C(2)–H(2A)ꢀ ꢀ ꢀS1
C(6)–H(6A)ꢀ ꢀ ꢀS2
O(1)–H(1)ꢀ ꢀ ꢀS2
0.970
0.970
0.634
2.633(11)
2.531(10)
2.467(10)
3.010(10)
3.052(10)
3.101(11)
103.43
113.65
177.06
4
. Conclusions
the size and electronic effects of the dithiocarbamate ligands and
crystal packing effects. Tl S nanoparticles have been prepared from
2
Complexes 1 and 2 have been prepared and characterized by
complex 1 using conventional heating and microwave irradiation
methods. The microwave irradiation method yields spherical shape
particles within 2 min. Shapeless particles are obtained after 1 h
with the conventional heating method. Hence, the more suitable
elemental analyses, spectroscopic techniques and single crystal
X-ray structural analysis. Interestingly, various interactions,
1
6
namely
g
–Tl–C(S2), Tlꢀ ꢀ ꢀTl,
g
–Tlꢀ ꢀ ꢀC phenyl ring, anagostic
Tlꢀ ꢀ ꢀH–C, intramolecular C–Hꢀ ꢀ ꢀS, intermolecular C–Hꢀ ꢀ ꢀS and
method for the preparation of Tl
irradiation method.
2
S nanoparticles is the microwave
O–Hꢀ ꢀ ꢀS interactions, are observed. These interactions depend on

4
32
G. Gomathi et al. / Polyhedron 102 (2015) 424–433
2
Fig. 10. HR-TEM image of Tl S (sample 3).
2
Fig. 11. HR-TEM image of Tl S sample 4.
(
a)
0
0
0
0
0
.4
.3
.2
.1
.0
200
(b)
(
b)
(
a)
0
250
3
00
400
500
600
700
800
300
350
400
450
500
nm
S (a) sample 3 and (b) sample 4.
Wavelength (nm)
Fig. 12. UV–Vis spectra of Tl
2
2
Fig. 13. Photoluminescence spectra of Tl S (a) sample 3 (b) sample 4.

G. Gomathi et al. / Polyhedron 102 (2015) 424–433
433
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