The syntheses and structures of Zn(II) heterocyclic piperidine and tetrahydroquinoline dithiocarbamates and their use as single source precursors for ZnS nanoparticles

Article abstract of DOI:10.1016/j.poly.2013.08.061

We report the synthesis and single X-ray structures of bis(dipiperidinyldithio-carbamato)zinc(II) and bis(ditetrahydroquinolinyldithiocarbamato)zinc(II) complexes. The complexes were thermolysed in hexadecylamine (HDA) and tri-n-octylphosphine oxide (TOPO) at different reaction temperatures to produce HDA and TOPO capped ZnS nanoparticles. The microstructure and morphology of the as-prepared ZnS nanoparticles were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM) and high transmission electron microscopy (HRTEM). Predominantly close to spherical shaped particles were observed in the TEM images of all samples. The optical properties of the particles studied by UV-Vis and photoluminescence (PL) spectroscopy showed evidence of quantum confinement.

Full text of DOI:10.1016/j.poly.2013.08.061

Polyhedron 67 (2014) 129–135
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
The syntheses and structures of Zn(II) heterocyclic piperidine and
tetrahydroquinoline dithiocarbamates and their use as single source
precursors for ZnS nanoparticles
Linda D. Nyamen a,b, Adeola A. Nejo , Viswanadha S.R. Pullabhotla , Peter T. Ndifon ,
a,d
a
b
c
e
c
a,
⇑
Mohammad Azad Malik , Javeed Akhtar , Paul O’Brien , Neerish Revaprasadu
a
Department of Chemistry, University of Zululand, Private Bag X1001, KwaDlangezwa 3880, South Africa
Department of Inorganic Chemistry, University of Yaoundé I, PO Box 812, Yaoundé, Cameroon
School of Chemistry and Materials Science Centre, The University of Manchester Oxford Road, Manchester M13 9PL, UK
Department of Basic Sciences, Babcock University, Ilishan-Remo, Ogun State, Nigeria
b
c
d
e
Nanoscience and Materials Synthesis Lab, Department of Physics, COMSATS, Institute of Information Technology (CIIT), Chak Shahzad, Islamabad, Pakistan
a r t i c l e i n f o
a b s t r a c t
Article history:
We report the synthesis and single X-ray structures of bis(dipiperidinyldithio-carbamato)zinc(II) and
bis(ditetrahydroquinolinyldithiocarbamato)zinc(II) complexes. The complexes were thermolysed in
hexadecylamine (HDA) and tri-n-octylphosphine oxide (TOPO) at different reaction temperatures to pro-
duce HDA and TOPO capped ZnS nanoparticles. The microstructure and morphology of the as-prepared
ZnS nanoparticles were characterized using X-ray diffraction (XRD), transmission electron microscopy
Received 21 June 2013
Accepted 21 August 2013
Available online 3 September 2013
Keywords:
ZnS
Nanoparticles
Dithiocarbamates
(TEM) and high transmission electron microscopy (HRTEM). Predominantly close to spherical shaped par-
ticles were observed in the TEM images of all samples. The optical properties of the particles studied by
UV–Vis and photoluminescence (PL) spectroscopy showed evidence of quantum confinement.
Ó 2013 Elsevier Ltd. All rights reserved.
1
. Introduction
complexes, thiocarboxylate compounds of the type [Zn(SOCR)
Lut) ] [R = CH , C(CH ; Lut = 3,5-dimethylpyridine (lutidine)]
have produced good quality ZnS nanoparticles [7]. The thermolysis
of zinc ethylxanthate [Zn(C OCS ] in octylamine (OA) or TOP
gave ZnS nanorods whose dimensions and shape where controlled
by using a combination of different ligands [8].
2
(
2
3
3 3
)
Zinc sulfide (ZnS), a direct band gap semiconductor with band
gap energy of 3.68 eV, is one of the most important materials in
photonics research [1,2]. It has been used as a base material for
cathode-ray tube luminescent materials, as efficient phosphors in
flat-panel displays, in thin film electroluminescent devices and
infrared windows. In the last two decades, new developments in
processing and characterization techniques have led to a better
understanding of the chemical, physical and optical properties of
these types of nanostructured materials.
The use of precursor compounds, either dual source or single
source is a well established route to nanostructured materials.
O’Brien and co-workers extensively investigated the synthesis of
ME (M = Cd, Zn; E = S, Se) nanoparticles and related core/shell
composites from bis(alkyldithio-/diselenocarbamates) of Zn and
Cd [3–5]. The synthesis involves the dissolution of the precursor
in tri-n-octylphosphine (TOP) followed by decomposition in a
H
2 5
2 2
)
The microwave thermolysis of the single molecular precursor
zinc diethyldithiocarbamate [Zn(DDTC)
reported by Sun et al. [9].
2
] in ethylene glycol was
Zhang et al. [10] used the same precursor to synthesize uniform,
hexagonal-phase ZnS nanorods by the solvothermal decomposition
method. By varying reaction conditions such as the reaction tem-
perature, reaction time and concentration of hydrazine hydrate
aqueous solutions, crystalline ZnS nanorods with uniform diame-
ters were produced. There have been several reports on the sys-
tematic growth of ZnS nanoparticles by variation of capping
groups to control the particle size [11–13].
In this paper, we report the synthesis and single X-ray struc-
tures of bis(dipiperidinyldithiocarbamato)zinc(II) and bis(dite-
trahydroquinolinyldithiocarbamato)zinc(II) complexes and their
use as single source precursors for the preparation of ZnS nanopar-
ticles. We have previously reported the synthesis of the cadmium
and lead analogues and their use as precursors for CdS and PbS
nanoparticles, respectively [14,15].
suitable high-boiling coordinating solvent. Precursors based on
0
zinc
DA)Zn(ESiMe
also been used to synthesize ZnS [6]. Another class of Zinc
trimethylsilylchalcogenolate
complexes
(N,N -TME-
3
)
2
(E = S, Se) and (3,5-Me
2
-C N) Zn(ESiMe
5
H
3
2
3 2
) have
⇑
Corresponding author. Tel.: +27 359026152; fax: +27 359026568
E-mail address: nrevapra@pan.uzulu.ac.za (N. Revaprasadu).
0
277-5387/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2013.08.061

1
30
L.D. Nyamen et al. / Polyhedron 67 (2014) 129–135
2
. Experimental
formed was filtered, washed with excess distilled water and dried
overnight in an oven at 70 °C.
[Zn(pip-dtc) ], (pip = piperidinyl, dtc = dithiocarbamato,) yield:
2.1. Chemicals
2
ꢀ1
8
7%. IR (cm , ATR): 979,
Microanalysis: Calc. for C12
7.09. Found: C, 36.50; H, 5.01; N, 6.68%.
[Zn(thq-dtc) ], (thq = tetrahydroquinoline, dtc = dithiocarbama-
to), yield: 74%. IR (cm , ATR): 968,
(Zn–S). Microanalysis: Calc. for C20
H, 4.31; N, 5.70. Found: C, 48.82; H, 4.02; N, 5.45%.
v
(C@S); 1438,
v
(C@N); 360,
v(Zn–S).
Hexadecylamine (HDA), tri-n-octylphosphine oxide (TOPO), tol-
20
H N
S
2 4
Znꢁ½H
2
O: C, 36.49; H, 5.36; N,
uene, tri-n-octylphosphine (TOP) 90%, 1,2,3,4,tetrahydroquinoline
8% (Aldrich). Piperidine 99% (Sigma–Aldrich). Petroleum ether,
9
2
ꢀ1
methanol 99.5%, dichloromethane, carbon disulfide 99.5%, chloro-
form, sodium hydroxide 98%, zinc acetate dihydrate 99%, and ace-
tone (Merck) were used as purchased without any further
purification.
v
20
(C@S); 1413,
v
2
(C@N); 358,
O: C, 48.91;
v
H
N
2
4
S Znꢁ½ H
3
3
.3. Preparation of nanoparticles
3
. Instrumentation
.3.1. Synthesis of hexadecylamine (HDA) capped ZnS nanoparticles
.5 g of the [Zn(pip-dtc) ] complex was dissolved in 6.0 mL of
0
2
The crystalline phase the material was identified by X-ray dif-
ꢀ
1
tri-n-octylphosphine (TOP). The solution was injected into 3.0 g
of hot hexadecylamine (HDA) in a three-necked flask at 180 °C.
The solution turned to a whitish color and a drop in temperature
of 15 °C was observed. The reaction was allowed to stabilize at
fraction (XRD), employing a scanning rate of 0.05° min in a 2h
range from 20° to 80°, using a Bruker AXS D8 diffractometer
equipped with nickel filtered Co K
a radiation (k = 1.5418 Å) at
4
0 kV, 40 mA and at room temperature. The morphology and par-
1
80 °C. Aliquots of samples were taken and methanol added result-
ticle sizes of the samples were characterized by a JEOL 1010 TEM
with an accelerating voltage of 100 kV, Megaview III camera, and
Soft Imaging Systems iTEM software. The detail morphological
and structural features were investigated using HRTEM images
with a JEOL 2010 transmission electron microscope operated at
an accelerating voltage of 200 kV. A Varian, Cary 50 UV–Vis spec-
trophotometer was used for the optical measurements and the
samples were placed in silica cuvette (1 cm path length), using tol-
uene as reference solvent. A Perkin Elmer, LS 55 Luminescence
spectrometer was used to measure the photoluminescence of the
particles. The samples were placed in a quartz cuvette (1 cm path
length). Microanalysis was performed on a Perkin-Elmer auto-
mated model 2400 series II CHNS/O analyzer. Infrared spectra were
recorded on a Bruker FT-IR tensor 27 spectrophotometer directly
on small samples (10 mg) of the compounds in the range 200–
ing in the formation of a flocculent precipitate. The precipitate was
separated by centrifugation, and dispersed in toluene to give off-
white HDA–capped ZnS nanoparticles.
The above reaction procedure was repeated using the [Zn(thq-
2
dtc) ] complex.
3.3.2. Synthesis of tri-n-octylphosphine oxide (TOPO) capped ZnS
nanoparticles
0.5 g of the [Zn(pip-dtc) ] complex was dissolved in 6.0 mL of
2
TOP. The solution was injected into 3.0 g of the hot TOPO in a
three-necked flask at 240 °C. The solution turned to a whitish color
and a drop in temperature of 48 °C was observed. The reaction was
allowed to stabilize at 240 °C. Aliquots of samples were taken and
methanol added resulting in the formation of a flocculent precipi-
tate. The precipitate was separated by centrifugation, and dis-
persed in toluene to give whitish TOPO-capped ZnS nanoparticles.
The above reaction procedure was repeated using the [Zn(thq-
ꢀ1
1
4
000 cm . The H NMR spectra of both the ligands and metal
complexes were obtained using a Bruker advance III 400 MHz
spectrophotometer.
2
dtc) ] complex.
3
3
.1. Synthesis of the precursors
4
. Results and discussion
.1.1. Preparation of the ligands
Carbon disulfide (6.0 mL, 0.1 mol,) was added in small portions
to an equimolar mixture of sodium hydroxide (4.0 g, 0.1 mol) and
the corresponding amine (piperidine/ tetrahydroquinoline,
4
.1. Characterization of the precursors
The zinc complexes of the dithioligands were isolated in pure
0
.1 mol) and cooled in an ice bath at 0 °C. After 15 min, the solidi-
form from water in good yields. The zinc complexes synthesized
where diamagnetic and white in colour. The H NMR, IR and ther-
mal analyses of the dithioligands have been previously reported
fied mass was then dried in air and recrystallised in a mixture of
acetone/petroleum ether. The product was collected and washed
with chloroform and suction dried.
1
[
14,15].
Na(pip-dtc) yield: 90%. 1H NMR (400 MHz, DMSO-d6): d 1.41
The 1H NMR data of [Zn(pip-dtc)
2
] showed three signals at
ꢀ
1
(
m, 2H, 3-CH
2
), 1.53 (t, 2H, 4-CH
(O–H); 967, (C@S); 1468,
Na: C, 32.87; H, 6.44; N, 6.39. Found: C,
2.57; H, 6.29; N, 5.96%.
Na(thq-dtc), yield: 62%. H NMR (400 MHz, CD
H, 3-CH2), 2.73 (t, 2H, 4-CH ), 4.58 (t, 2H, 2-CH
2
), 4.28 (t, 2H, 2-CH
2
). IR (cm ,
chemical shifts 1.41, 1.53 and 4.28 ppm for the aliphatic methylene
protons. The aromatic proton signals of [Zn(thq-dtc) ] appear in
ATR): 3367,
Calc. for C
v
H
v
v
(C@N). Microanalysis:
2
6
14NS
2
O
2
the downfield region of 7.14–7.88 ppm. Apart from these signals,
the signals observed at 2.07, 2.79 and 4.28 ppm are assigned to
the aliphatic methylene protons present in the complex. The minor
changes in some of chemical shift of the protons for the zinc com-
plexes of the dithioligands may be due to the coordination of the
ligands to the metal atom.
] dis-
played a sharp band in the 970–1006 cm region without any
splitting, which is attributed to the (C=S), indicating that the dith-
ioligands acted as bidentate [16]. The C–N stretching frequencies of
3
1
3
OD): d 2.07 (m,
), 7.08–7.85 (m,
(C@S); 1485,
Na: C, 39.59; H, 5.98;
2
4
(
2
2
ꢀ1
H, Ar–H). IR (cm , ATR): 3324,
C@N). Microanalysis: Calc. for C10
v
H
(O–H); 967,
v
v
18NS
2
O
4
N, 4.62. Found: C, 39.15; H, 5.94; N, 4.27%.
The infrared spectra of the[Zn(pip-dtc)
2
] and [Zn(thq-dtc)
2
ꢀ
1
3
.2. Preparation of the zinc complexes
m
ꢀ1
Zinc acetate (5.0 mmol) was dissolved in distilled water
25.0 mL) and added drop-wise to the corresponding solution of
the zinc complexes were observed at 1487 and 1489 cm for the
[Zn(pip-dtc) ] and [Zn(thq-dtc) ], respectively, which indicate that
(
2
2
the dithiocarbamate ligand (10.0 mmol) and cooled in an ice bath
at 0 °C. The reaction mixture was stirred for 1 h, and the precipitate
a considerable double bond character of the C–N bond in the
dithiocarbamate group’s [17]. The characteristic new bands in

L.D. Nyamen et al. / Polyhedron 67 (2014) 129–135
131
Table 1
of 25 to 900 °C under nitrogen atmosphere. The thermograms of
both complexes showed a similar one-step thermal decomposition
behaviour. The single step decomposition corresponds to a loss of
Crystal data and structure refinement for compounds 1 and 2.
Compounds
Compound 1
Zn
481.99
100(2)
0.71073
Compound 2
Zn
2
771.82
100(2)
0.71073
part of the organic moiety leaving [Zn(SCN)
decompose when heated up to 900 °C. The thermal decomposition
of the [Zn(pip-dtc) ] started at 343 °C with the loss of part of the
organic moiety which corresponded to an endothermic peak in
the DSC thermogram at 341.9 °C ( H = 214.3 J/g). The thermal
decomposition of the [Zn(thq-dtc) ] occurred at a lower tempera-
ture compared to the [Zn(pip-dtc) ] complex because the latter ex-
ists as a dimer in the crystal structure. The [Zn(thq-dtc) ] complex
decomposed at 286 °C which corresponds to an endothermic peak
in the DSC thermogram at 294.5 °C ( H = 188.0 J/g).
2
] which did not
Formula
Formula weight
T (K)
C
20
H
20
N S
2 4
C
24
H
40
N
4
S
8
2
k (Å)
Crystal system
space group
Unit cell dimensions
a (Å)
b (Å)
c (Å)
triclinic
P1ꢀ
triclinic
P1ꢀ
D
2
7.491(2)
7.588(2)
8.6096
9.4597(11)
2
2
17.619(5)
86.911(5)
83.933(5)
87.325(7)
993.6(5)
2
11.1045(13)
102.479(2)
98.001(2)
112.342(2)
791.83(16)
1
a
(°)
b (°)
(°)
D
c
3
V (Å )
Z
D
calc (Mg/m3)
4.1.1. Single crystal X-ray structures of [Zn(pip-dtc)
Zn(thq-dtc) ] (2)
2 2
Single crystals of [Zn(pip-dtc) ] (Compound 1) and [Zn(thq-dtc) ]
2
] (1) and
1.611
1.665
1.619
2.066
[
2
Absorption coefficient
ꢀ
1
(
mm
)
F(000)
Crystal size (mm)
h (°)
496
400
(Compound 2) suitable for X-ray crystal structure determination
were obtained by recrystallization using chloroform. Colourless
crystals measuring about 0.22 ꢂ 0.20 ꢂ 0.18 mm for Compound 1
and 0.5 mm ꢂ 0.4 mm ꢂ 0.3 mm for Compound 2 were mounted
using glass fibres on the goniometer head of a Bruker APEX Diffrac-
tometer and data was collected using graphite monochromated Mo
0.50 ꢂ 0.40 ꢂ 0.30
0.22 ꢂ 0.20 ꢂ 0.18
2.69–26.28
1.94–28.22
Limiting indices
ꢀ9 6 h 6 8,
ꢀ11 6 h 6 11,
ꢀ12 6 k 6 12,
ꢀ14 6 l 6 14
ꢀ
ꢀ
9 6 k 6 9,
21 6 l 6 18
Reflections collected/
unique (Rint
Completeness to h = 26.28
Absorption correction
5611/3892 (0.0193)
6860/3601 (0.0386)
)
a
Ka radiation (kMo K = 0.71073 Å) operating at 50 kV at 40 mA at a
temperature of 100 K.
96.5%
semi-empirical from
equivalents
99.4%
none
The structures were solved by directed methods and refined by
2
Maximum and minimum
transmission
Refinement method
squares on F
Data/restraints/parameters 3892/0/244
Goodness-of-fit (GOF) on F
1.0000 and 0.6707
0.7075 and 0.6593
full matrix least squares based on F = 1.092 and 1.043, respec-
tively [18]. All calculations were carried out using SHELX-TL software
full-matrix least-
full matrix least-
2
squares on F2
package [19]. All non-hydrogen atoms were refined anisotropi-
cally. All hydrogen positions were initially located in the difference
map and for the final refinement; the hydrogen atoms were placed
geometrically and held in the riding mode. The last of the cycles of
refinement included atomic positions for all the atoms, and isotro-
pic thermal parameters for all the hydrogen atoms (see Table 1).
The structure of Compound 1 consists of a dimeric molecule
with a distorted tetrahedral geometry about each zinc atom as
shown in Fig. 1. Each zinc atom is coordinated to three dithiocarba-
mate ligands via the S atoms. While one dithiocarbamate atom is
chelating through its two S atoms, each of the other two uses
one sulfur atom to bond to a zinc atom and the other sulfur atom
is coordinated to the other zinc atom, thereby forming a bridge be-
tween the two zinc atoms. While the bridging dithiocarbamate li-
gand produces an eight-membered ring system, the chelation of a
3601/0/172
1.043
2
1.092
= 0.0412,
wR = 0.1019
= 0.0472,
wR = 0.1054
Final R indices [I > 2
r
(I)]
R
1
R
1
= 0.0305,
wR = 0.0694
= 0.0348,
wR = 0.0711
0.535 and ꢀ299
2
2
R indices (all data)
R
1
R
1
2
2
Largest diff. peak and hole
0.799 and ꢀ0.848
ꢀ
3
(
e Å )
the far IR region at 360–366 cm 1 is observed which correspond to
ꢀ
the
dithioligands.
The thermal properties of [Zn(pip-dtc)
were studied by DSC and TGA techniques in the temperature range
(Zn–S)
m . These bands are absent in the spectra of the
2
2
] and [Zn(thq-dtc) ]
Fig. 1. X-ray structure of [Zn(pip-dtc)2] (1).

1
32
L.D. Nyamen et al. / Polyhedron 67 (2014) 129–135
[
20,21]. The nearly constant values observed for the S–C bond
(
1
1.725(3)–1.732(3) Å) and for the C-N bond lengths (1.332(4)–
ꢀ
.478(4) Å) is an indication of the delocalization of the CS
2
elec-
trons. The bond distances and angles are given in Table 2.
4.1.2. Synthesis of HDA capped ZnS nanoparticles
The thermolysis of precursors in high boiling point solvents is a
well reported route to high quality nanoparticles. The size of the
nanoparticles depends on the reaction time and temperature, pre-
cursor/capping agent ratio, and alkyl groups. We have chosen cap-
ping groups HDA and TOPO which have been used successfully for
the passivation of cadmium chalcogenide nanoparticles [22,23].
The stability of the TOPO-capped particles is due to the it’s bulky
nature also provides increased steric hindrance [24,25]. In contrast
HDA a primary amine is a slightly weaker base than TOPO, with
less steric hindrance creating a larger capping density.
Fig. 2. X-ray structure of [Zn(thq-dtc)2] (2).
Table 2
Selected bond lengths (Å) and angles (°) for C20
20 2 4
H N S Zn.
The absorption spectrum of a HDA capped ZnS nanoparticles
synthesized from the [Zn(pip-dtc) ] complex at 180 °C is shown
2
in Fig. 3(a). The absorption spectrum is broad with the band edge
observed at 340 nm a slight blue shift in relation to bulk ZnS
345 nm). The absorption peak is sharp without any visible exci-
tonic features which is typical of ZnS nanoparticles [26].
C(2)–C(3)
C(2)–H(2A)
C(2)–H(2B)
C(12)–C(13)
1.521(4)
0.9900
0.9900
S(2)–Zn(1)–S(1)
S(3)–Zn(1)–S(4)
S(2)–Zn(1)–S(4)
S(1)–Zn(1)–S(4)
C(1)–S(1)–Zn(1)
C(1)–S(2)–Zn(1)
C(11)–S(3)–Zn(1)
C(11)–S(4)–Zn(1)
C(6)–C(5)–C(4)
C(5)–C(10)–N(1)
N(1)–C(2)–C(3)
N(1)–C(2)–H(2A)
C(3)–C(2)–H(2A)
C(7)–C(6)–C(5)
77.95(3)
78.54(3)
123.02(3)
128.94(3)
81.90(10)
82.35(10)
82.83(10)
81.30(10)
121.3(3)
116.4(3)
108.3(2)
110.0
0.9500
C(12)–H(12A)
C(12)–H(12A)
S(3)–Zn(1)–S(2)
S(3)–Zn(1)–S(1)
C(10)–C(5)–C(4)
C(9)–C(10)–N(1)
C(1)–N(1)–C(10)
C(1)–N(1)–C(2)
N(1)–C(1)–S(2)
N(1)–C(1)–S(1)
S(2)–C(1)–S(1)
1.514(4)
1.514(4)
128.66(3)
127.38(3)
120.7(3)
122.2(3)
123.9(2)
122.6(2)
121.3(2)
121.1(2)
117.56(17)
(
Semiconductor nanoparticles often exhibit narrow close-to-
band edge luminescence with lower energy emissions attributed
to trapping states and defects. The corresponding photolumines-
cence spectrum shows a narrow emission peak with the maximum
at 400 nm, a red shift in relation to the absorption peak (Fig. 3b).
The reaction temperature was increased to 270 °C as higher tem-
peratures produced more crystalline particles. The absorption
spectrum of the particles is sharper in relation to those synthesized
at 180 °C due to a narrower size distribution (Fig. 4a). The band gap
is observed at 338 nm. The corresponding photoluminescence
spectrum is narrow with the emission maximum at 390 nm
(Fig. 4b). The PL spectra for the reactions at both temperatures
showed some degree of tailing or deep trap emission which has
been observed previously for ZnS [5].
The TEM image of the HDA capped ZnS synthesized at 180 °C
shows close to spherical particles with an average diameter of
4.74 ± 0.64 nm (Fig. 5a). The TEM image of particles obtained at
the higher reaction temperature (270 °C) were also close to spher-
ical with an average diameter of 6.43 ± 0.60 nm (Fig. 5b). The pow-
der X-ray diffraction pattern of the ZnS nanoparticles prepared at
270 °C is shown in Fig. 6. The diffraction peaks at 2h = 28.5°,
47.7° and 56.6° are assigned to the (111), (220) and (311) planes
of zinc blende structure of ZnS.
110.0
120.7(3)
dithiocarbamate to each zinc centre produces a four-member ring
system.
The single crystal X-ray structure of Compound 2 illustrated in
Fig. 2 shows a monomeric molecule made up of a zinc atom at the
centre coordinated to two tetrahydroquinoline dithiocarbamate li-
gands. Each zinc atom is bonded to four sulfur atoms, two from
each tetrahydroquinoline dithiocarbamate ligand. The structure
therefore describes two four-member ring systems about the zinc
atom. The S atoms of the dithiocarbamate therefore defines a
distorted tetrahedral about the zinc centre. This distortion results
from the small bite angles (ca. 75°) of the dithiocarbamate chela-
tion. The Zn–S bond lengths are nearly identical (Zn–S range from
2
.3191(7) to 2.3595(9) Å) These Zn–S bond lengths have been
reported for similar zinc aliphatic dithiocarbamate complexes
0
.1
(
b)
0
0
0
0
0
0
0
0
0
.09
.08
.07
.06
.05
.04
.03
.02
.01
0
(
a)
3
35
385
435
485
535
585
635
685
Wavelength (nm)
2
Fig. 3. UV–Vis and photoluminescence (PL)spectra of HDA capped ZnS nanoparticles synthesized from [Zn(pip-dtc) ] at 180 °C.

L.D. Nyamen et al. / Polyhedron 67 (2014) 129–135
133
(
b)
(
a)
Wavelength (nm)
Fig. 4. (a) UV–Vis and (b) photoluminescence spectra of ZnS nanoparticles synthesized from [Zn(pip-dtc)
2
] at 270 °C.
a
b
Fig. 5. TEM image of HDA capped ZnS nanoparticles synthesized at (a) 180 °C and (b) 270 °C.
500
400
300
200
100
0
(
111)
(
220)
(
311)
25
35
45
55
65
2
Ɵ
(degree)
2
Fig. 6. Powder X-ray diffractogram of ZnS nanoparticles synthesized from [Zn(pip-dtc) ] in HDA at 270 °C.

1
34
L.D. Nyamen et al. / Polyhedron 67 (2014) 129–135
a
b
2
Fig. 7. (a)TEM image of HDA capped ZnS nanoparticles synthesized from [Zn(thq-dtc) ] at 270 °C and (b) corresponding HRTEM image.
(
b)
0
0
0
.25
0
.2
(a)
.15
0
.1
.05
0
2
85
335
385
435
485
535
585
635
685
Fig. 8. (a) UV–Vis and (b) photoluminescence spectra of ZnS nanoparticles synthesized from [Zn(thq-dtc)
2
] in 6 g of HDA at 270 °C.
0
0
0
0
0
0
0
.7
.6
.5
.4
.3
.2
.1
0
(a)
(b)
(ii)
(i)
2
85
335
385
435
485
535
585
635
685
Fig. 9. (a) TEM images of ZnS nanoparticles from [Zn(thq-dtc)
2
] synthesized in TOPO at 240 °C and corresponding (b) (i) UV–Vis spectrum (ii) PL spectrum.
The reaction at 270 °C was repeated using the [Zn(thq-dtc)
2
]
displays an absorption band edge at band at 351 nm (Fig. 8a). The
emission spectrum is narrow with the emission maximum at
394 nm (Fig. 8b). The [Zn(thq-dtc) ] complex was also thermolysed
2
in TOPO at a temperature of 240 °C (Fig. 9a). The TEM image of the
TOPO capped ZnS shows spherical particles with an average diam-
eter of 3.82 ± 0.40 nm. The particles are evenly spread across on
complex. Well defined spherical particles with an average particle
size of 5.94 ± 0.25 nm were observed as shown in Fig. 7a. The cor-
responding HRTEM image (Fig. 7b) shows particles with distinct
lattice fringes. The lattice spacing of 2.9 nm was indexed to the
(
111) plane of cubic ZnS. The absorption spectrum of the particles

L.D. Nyamen et al. / Polyhedron 67 (2014) 129–135
135
the grid appearing monodispersed. The absorption spectrum
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Acknowledgements
This work was supported by the Department of Science and
Technology (DST) and National Research Foundation (NRF) of
South Africa through DST/NRF South African Research Chairs Initia-
tive for Professor of Nanotechnology. Ms. L.D. Nyamen also
acknowledges the Organization for Women Scientists for the
Developing World (OWSDW) formerly TWOWS for a Sandwich
Postgraduate Fellowship. The authors also acknowledge the Centre
for Electron Microscopy, University of Kwa-Zulu Natal for the TEM
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