Synthesis and characterization of gallium(III) dithiocarbamates as suitable nano-gallium(III) sulfide precursors

Article abstract of DOI:10.1515/mgmc-2015-0019

Gallium(III) complexes [Ga(chmdtc)₃] (1) and [Ga(chedtc)₃] (2) (where chmdtc=cyclohexylmethyldithiocarbamate and chedtc=cyclohexylethyldithiocarbamate) have been prepared and characterized by infrared, nuclear magnetic resonance (¹H and ¹³C) spectra, thermogravimetry, X-ray photoelectron spectroscopy, and single crystal X-ray diffraction (XRD). The thermogravimetric curves obtained for both complexes are almost similar. The final residue corresponded to gallium sulfide (Ga₂S₃) above 700°C for complexes (1) and (2). In the single crystal X-ray structure of [Ga(chedtc)₃] (2), Ga-S bonds, and the associated C-S bonds show asymmetry as a requirement of packing. The complex shows distorted octahedral geometry due to its bite angle variations. Nano-α-Ga₂S₃ was prepared from single source precursors [Ga(chmdtc)₃] (1) and [Ga(chedtc)₃] (2). Prepared nano-Ga₂S₃ have been characterized by powder XRD, energy-dispersive X-ray spectroscopy technique, and transmission electron microscopy (TEM)-selected area electron diffraction analysis showing the nano-sized nature of Ga₂S₃. TEM micrographs confirmed the size of the particles to be 50 nm.

Full text of DOI:10.1515/mgmc-2015-0019

Main Group Met. Chem. 2015; 38(3-4): 75–82
KSuyppnuktkhanenusRiasmaalinngadm*c, hG.Sa. rSaivacgutreunraitzhaantaniod Cnorroadfo gRizazollliium(III)
dithiocarbamates as suitable nano-gallium(III)
sulfide precursors
DOI 10.1515/mgmc-2015-0019
Received May 16, 2015; accepted July 10, 2015; previously published
online August 8, 2015
of their industrial applications (Shen et al., 2009; Li, et al.,
2011) and biological profiles (Bockman and Semin, 2003;
Gabriel et al., 2007). Gallium is the instant metal ion, later
than platinum, to be used in cancer dealing. Its activities
are numerous and different. It adapts a 3D structure of
DNA and inhibits its synthesis, modulates protein synthe-
sis, and inhibits the activity of a number of enzymes, such
as ATPases, DNA polymerases, ribonucleotide reductase,
and tyrosine-specific protein phosphatase. Gallium toxic-
ity is well documented in vitro and in vivo in animals. In
humans, the oral administration of gallium is less toxic.
Radioactive 67Ga and 68Ga show some promise in the
study of bone cancer, as compounds of these isotopes are
absorbed by the cancer deposits in the bone (Collery et al.,
2002; Ismail et al., 2013). Group 13 sulfides are an interest-
ing class of materials with promise in photovoltaic and
optoelectronic applications. The related ternary and qua-
ternary materials CuInxGaySe2 or CuInxGayS2 are of particu-
lar interest for solar cells (Nomura et al., 1992; Park et al.,
2001). Relatively, fewer reports of dithiocarbamate com-
pounds of gallium such as [Ga(S2CNEt2)]3, [Ga(S2CNCC4H4)3],
[R2Ga(S2CNEt2)], and [R2Ga[S2CN(Me)CH2CH2 CH2NMe2] and
the growth of gallium sulfide (Ga2S3) from dithiocarbamate
precursors have been reported in the recent past (Haggata
et al., 1995). In our continued interest in the production
of nano-Group 13 metal sulfides from the corresponding
dithiocarbamates, structural and chemical investigations
have been carried out (Sivagurunathan et al., 2013, 2014).
In this paper, we report the synthesis, nuclear magnetic
resonance (NMR) and infrared (IR) spectroscopic, thermo-
gravimetric, and X-ray photoelectron spectroscopy (XPS)
studies of [Ga(chmdtc)3] (1) and [Ga(chedtc)3] (2). The
molecular structure of compound (2) was determined by
Abstract: Gallium(III) complexes [Ga(chmdtc)3] (1) and
[Ga(chedtc)3] (2) (where chmdtcꢀ=ꢀcyclohexylmethyldithio-
carbamate and chedtcꢀ=ꢀcyclohexylethyldithiocarbamate)
have been prepared and characterized by infrared,
nuclear magnetic resonance (1H and 13C) spectra, thermo-
gravimetry, X-ray photoelectron spectroscopy, and single
crystal X-ray diffraction (XRD). The thermogravimetric
curves obtained for both complexes are almost similar.
The final residue corresponded to gallium sulfide (Ga2S3)
above 700°C for complexes (1) and (2). In the single crystal
X-ray structure of [Ga(chedtc)3] (2), Ga-S bonds, and the
associated C-S bonds show asymmetry as a requirement of
packing. The complex shows distorted octahedral geom-
etry due to its bite angle variations. Nano-α-Ga2S3 was pre-
pared from single source precursors [Ga(chmdtc)3] (1) and
[Ga(chedtc)3] (2). Prepared nano-Ga2S3 have been charac-
terized by powder XRD, energy-dispersive X-ray spectros-
copy technique, and transmission electron microscopy
(TEM)-selected area electron diffraction analysis showing
the nano-sized nature of Ga2S3. TEM micrographs con-
firmed the size of the particles to be 50 nm.
Keywords: continuous shape measure; crystal structure;
dithiocarbamate; gallium(III); nano-gallium(III) sulfide.
Introduction
Dithiocarbamates of gallium, indium, and thallium have single crystal X-ray diffraction (XRD) analysis. The dithi-
continued to attract attention in recent years on the account ocarbamates are shown in Scheme 1.
*Corresponding author: Kuppukkannu Ramalingam, Department of
Chemistry, Annamalai University, Annamalainagar 608 002,
Tamil Nadu, India, e-mail: krauchem@yahoo.com
Results and discussion
The synthesis of tris(cyclohexylmethyldithiocarbamato)
gallium(III) and its ethyl analogue has been accomplished
G.S. Sivagurunathan: Knowledge Institute of Technology,
Department of Chemistry, Salem 637 504, Tamil Nadu, India
Corrado Rizzoli: Department of General and Inorganic Chemistry,
University of Parma, 43100 Parma, Italy
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76ꢀ ꢀK. Ramalingam et al.: Nano-gallium sulfide precursor dithiocrbamates
1
S
C
S
C
carbon (Van Gaal et al., 1979). In the case of (2), the H
NMR of α-CH proton of the cyclohexyl ring appeared at
4.56 ppm and α′-CH2 protons at 3.73 ppm correspond-
ing to two protons. The β′-CH3 protons of the ethyl group
appeared as a well-resolved triplet at 1.31–1.38 ppm. The
proton signals in (2) appeared without much change as
observed in (1) with slight deshielding. The 13C NMR of (2)
showed the characteristic thioureide signal at 201.09 ppm.
β′(H3)C appeared at 13.99 ppm as a much shielded signal
and the α′-CH2 appeared highly deshielded at 44.15 ppm
compared to complex (1). The 13C chemical shifts of the
cyclic ring appeared similar in (1) and (2).
S
S
N
N
Me
Et
chedtc
chmdtc
Scheme 1:ꢀSchematic drawing of the dithiocarbamates and their
abbreviations.
MeOH
GaCl3
Ga(OMe)3 (in situ)
3 cyclo-C6H11(Et)NC(S)SH
-3 HCl
3 cyclo-C6H11(Me)NC(S)SH
-3 MeOH
-3 MeOH
[Ga(chedtc)3]
[Ga(chmdtc)3]
1
2
Scheme 2:ꢀSynthesis of gallium dithiocarbamates (1) and (2).
Thermogravimetric analysis
Thermograms of [Ga(chmdtc)3] (1) and [Ga(chedtc)3] (2)
by the reaction of a methanolic solution of GaCl3 and the are shown in Figure 1A and B, respectively. Both com-
corresponding freshly prepared dithiocarbamic acid in a plexes showed single-stage decompositions, and the ther-
1:3 stoichiometric ratio (Scheme 2).
mogravimetric curves obtained for both complexes were
almost similar. The percentages within the brackets refer
to the moiety lost/residue left behind. The thermal decom-
position of [Ga(chmdtc)3] (1) started by losing the solvent
toluene (0.5C7H8;% calcd.: 6.8, found: 6.5) in the first stage
IR spectroscopic studies
For complexes (1) and (2), the νC-N (thioureide) bands followed by the loss of chmdtc. The total mass loss corre-
were observed at 1478 and 1474 cm-1, respectively. The sponded to 78% and the final product of thermal decompo-
ν(C-S) stretching bands were observed at approximately sition was Ga2S3 (% calcd.: 17.5, found: 17.4). In the second
1000 cm-1, supporting the bidentate coordination mode stage, decomposition occurred from 280°C to 320°C due
(Baskaran et al., 2008; Arul Prakasam et al., 2009; to the loss of the chmdtc ligand. Compound (2) started
Marimuthu et al., 2012) of the dithiocarbamate to the decomposing by losing toluene (% calcd.: 6.3, found: 5.8)
metal center, and the νC-H bands were observed in the up to 290°C. Considerable mass loss was observed from
range of 2852–2929 cm-1.
290°C to 320°C. The final residue corresponded to Ga2S3
(% calcd.: 16.3, found: 16.1). The differential thermal
analysis (DTA) curves of complex (1) showed exothermic
signals at 290°C and 340°C. The exothermic signal indi-
cates the decay of dithiocarbamates. Thermal analysis
NMR spectroscopic studies
NMR spectra were recorded at room temperature with confirmed the proposed formulas of the compounds.
tetramethylsilane as an internal reference and CDCl3 as
the solvent. The chemical shifts reported in the Spectral
Data Base for Organic Compounds (SDBS) for the parent XPS analysis
1
amines are shown in brackets for comparison. The H
NMR of complex (1) showed an intense signal at 4.57(m) The survey scan of [Ga(chmdtc)3] (1) and [Ga(chedtc)3] (2)
ppm corresponding to a single proton integration due (Figure2AandB)confirmedthepresenceofgallium,sulfur,
to α-CH of the cyclohexyl ring, and CH3 protons (α-CH3) nitrogen, and carbon in the samples. Gallium showed
attached to the nitrogen appeared at 3.22(s) ppm with two signals corresponding to 2p electrons at 1120.0(2p3/2
)
proton integration corresponding to three. The α-CH and 1146.0(2p1/2) eV in (1) and (2) (Figure 2C and D). The
and α′-CH3 protons were affected to a maximum extent gallium atom showed the binding energy at 1116.7(2 p3/2) eV
on complexation. In the cyclohexyl ring, all equatorial (Ghosh et al., 2007; Budz et al., 2009). The experimen-
protons were deshielded to a large extent compared to the tally observed binding energies were significantly higher
axial protons. The 13C NMR spectrum of (1) showed a weak than those reported for the elemental gallium, indicat-
signal at 201.1(3) ppm due to the characteristic thioureide ing the increased positive nature of the metal ion in the
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K. Ramalingam et al.: Nano-gallium sulfide precursor dithiocrbamatesꢂ
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[1]krsg-21.ngb-ds3
TG
at 287.5 eV for both compounds. The similarity in binding
energies indicated similarity in the electronic environ-
ments of carbon atoms in both compounds.
exo
[1]
A
7
6
5
4
3
2
1
0
DTA
100
90
80
70
60
50
40
30
20
Structural analysis
Crystal data, data collection, and refinement parameters of
complex (2) are given in Table 1. Selected bond parameters
are given in Table 2. The ORTEP diagram of complex (2)
is shown in Figure 3. In complex (2), the gallium center is
coordinated by six sulfur atoms of three dithiocarbamate
ligands. Four formula units are present in a unit cell. The
compound is monomeric. Compound (2) crystallized with
a toluene moiety, which was used for crystallization. A
significant short contact of 2.855 Å was observed between
H15B (cyclohexyl ring) and the S1 atom. Ga-S bonds and the
associated C-S bonds showed asymmetry [Ga-S: 2.4164(12)–
2.4481(12) Å and C-S: 1.714(4)–1.731(4) Å] as a requirement
of packing. The mean Ga-S bond distance in the compound
is 2.4362(13) Å. The complex shows distorted octahedral
geometry due to its bite angle variations. The mean S-Ga-S
and S-C-S angles are 73.64(2)° and 115.8(2)°, respectively.
The thioureide bond shows a mean value of 1.332(4) Å and
indicates a partial double-bonded nature of the C-N bond.
The nature of the substituents associated with the dithi-
ocarbamates does not alter the coordination environment
around the gallium center to a large extent because of its
relatively big ionic radius (76 nm; Andrews et al., 2000;
Dutta et al., 2002; Goshal and Jain, 2007).
[1]
100
200
300
400
500
600
700
[1]krsg-22.ngb-ds3
TG
exo
[1]
DTA
B
100
90
80
70
60
50
40
30
20
6
5
4
3
2
1
0
[1]
100
200
300
400
500
600
700
Continuous shape measure (CShM)
Figure 1:ꢀThermogravimetry-DTA: (A) [Ga(chmdtc)3] and
(B) [Ga(chedtc)3].
CShM reckons the distance of a given structure from
the desired ideal symmetry or from a reference shape
compounds. Elemental sulfur showed a binding energy (Zabrodsky et al., 1992; Keinan and Avnir, 2000; Alvarez
corresponding to the removal of S2p electron at 164.0 eV. et al., 2002; Ok et al., 2006). The descriptions of geometries
In compounds (1) and (2), the signals were observed such as ‘slightly distorted’ or ‘severely distorted’ relative
at 166.5 eV for both compounds (Figure 2E and F). The to the reference polyhedron is qualitative in nature. The
increase in binding energy is an indication of the loss of extent of distortion of a particular molecular structure
electron density from the sulfur atoms to the coordinated from an ideal polyhedron can be quantified by symmetry
gallium. A very highly significant increase in binding measures. The CShM approach has been successful in such
energy was observed in the removal of N1s electrons viz., quantification in dealing with transition metal complexes
403.0 and 403.5 eV in (1) and (2), respectively, compared and metal oxides. The ideal geometries associated with
to the corresponding binding energy of the elemental N1s hexacoordinated atoms are ideal octahedron (iOh) or ideal
electron (398.4 eV). The observation signifies the delocali- trigonal prism (itp). In the present investigation, the coor-
zation of the lone pair of electrons on the nitrogen leading dination around gallium has been found to be distorted
to the thioureide from of the structure. The binding energy octahedron (dOh) in (2). In the present case, the CShM of
of C1s electron in elemental carbon was 285.0 eV. In the GaS6 core is 2.513. The observed CShM value clearly indi-
present investigation, corresponding electrons were lost cates the closeness of (2) to octahedral geometry.
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ꢀK. Ramalingam et al.: Nano-gallium sulfide precursor dithiocrbamates
A 18000
D
3000
16000
14000
12000
10000
8000
6000
4000
2000
0
2800
2600
2400
2200
2000
-600
-400
-200
0
200
400
600
1110
1120
1130
1140
1150
1160
eV
eV
1600
1500
1400
1300
1200
1100
1000
900
25000
B
E
20000
15000
10000
5000
0
800
-600
-400
-200
0
200
400
600
155
160
165
eV
170
175
eV
1600
1500
1400
1300
1200
1100
1000
900
F
2800
C
2700
2600
2500
2400
2300
2200
2100
2000
1900
155
160
165
170
175
1110
1120
1130
1140
1150
1160
eV
eV
Figure 2:ꢀXPS: (A and B) survey scans of [Ga(chmdtc)3] and [Ga(chedtc)3], (C and D) 2p3/2 electrons at 1120.0 eV and 2p1/2 electrons at
1146.0 eV, and (E and F) S2p electron at 166.5 eV in (1) and (2).
the bond parameters. The method depends on the Rij
Bond valence sum (BVS) calculation
value for an i-j bond in a compound that is principally
BVS calculations proffer a reliable method of assigning ionic (Brown and Altermatt, 1985; Bresse and O’Keefe,
formal oxidation states of an atom in a compound from 1991; Brown, 2002, 2009). In a compound, the oxidation
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ꢂ79
Table 1:ꢀCrystal data, data collection, and refinement parameters
for [Ga(chedtc)3] (2).
Empirical formula
Formula weight
Crystal dimensions (mm)
Crystal system
Color
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
C30.50H52GaN3S6
722.83
0.12ꢃ×ꢃ0.09ꢃ×ꢃ0.06
Monoclinic
Colorless
Space group
a (Å)
P21/n
9.826(3)
b (Å)
21.166(6)
c (Å)
18.236(5)
α (°)
90
β (°)
97.518(5)
γ (°)
90
U (Å3)
3760.1(19)
Z
4
Dc (g cm-3)
μ (cm-1)
1.277
Figure 3:ꢀORTEP of [Ga(chedtc)3] (2).
40% probability ellipsoids were used for the presentation.
4.573
F(000)
θ (°)
1532
7.36–19.44
Diffractometer
Scan type
Index ranges
Reflections collected
Unique reflections
Observed reflections
Foꢃ>ꢃ4σ (Fo)
Bruker APEX-II CCD
ω scans
is used as reported (Brown and Altermatt, 1985) and Rij
is the experimentally determined bond distance. The
constant b is assumed to be 0.37. For compound (2), BVS
was calculated by summing up the bond valence contri-
butions from six Ga-S interactions. The BVS value was
found to be 2.987. In the present case, the BVS value
clearly establishes the formal oxidation state of gallium
as +3.0; therefore, a considerable ionic character to the
predominantly covalent bonding in the compound is
clear (Summers et al., 1994).
-11ꢃꢃ≤ꢃꢃhꢀꢀ≤ꢀꢀ11; -25ꢃꢃ≤ꢃꢃkꢃꢃ≤ꢃꢃ25; -21ꢃꢃ≤ꢃꢃlꢃꢃ≤ꢃꢃ21
38537
3820
6810
Weighting scheme
ꢃ
ꢃ
wꢃ=ꢃ1/[σ2(Fo2)+(0.0365P)2+2.8992P],
where Pꢃ=ꢃ(Fo2+2Fc2)/3
433
Number of parameters
refined
Final R, Rw (observed data) ꢃ
Goodness-of-fit
0.0456, 0.0835
0.997
ꢃ
Table 2:ꢀSelected bond distances (Å) and bond angles (°).
Bond distances (Å)ꢁ Bond angles (°)
Preparation of Ga2S3 by nonconventional
solvothermal decomposition of
[Ga(chmdtc)3]·0.5C7H8 (1)/
Ga(1)-S(1) ꢃ
2.4203(13)ꢃ
2.4481(12)ꢃ
2.4529(13)ꢃ
2.4164(12)ꢃ
2.4262(13)ꢃ
2.4353(12)ꢃ
1.328(4)ꢃ
S(1)-Ga(1)-S(2)
S(3)-Ga(1)-S(4)
S(5)-Ga(1)-S(6)
S(1)-C(1)-S(2)
S(3)-C(10)-S(4)
S(5)-C(19)-S(6)
C(1)-N(1)-C(2)
C(10)-N(2)-C(17)ꢃ
C(19)-N(3)-C(20)ꢃ
C(1)-S(1)-Ga(1)
C(1)-S(2)-Ga(1)
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
73.63(4)
73.52(4)
73.77(3)
115.6(2)
115.8(2)
116.1(2)
121.0(3)
119.8(3)
[Ga(chedtc)3]·0.5C7H8 (2)
Ga(1)-S(2) ꢃ
Ga(1)-S(3) ꢃ
Ga(1)-S(4) ꢃ
Ga(1)-S(5) ꢃ
Ga(1)-S(6) ꢃ
Aꢁmixtureꢁofꢁtris(cyclohexylmethyldithiocarbamato)
gallium(III)ꢁorꢁtris(cyclohexylethyldithiocarbamato)
gallium(III) (1 g) as a clear solution in chloroform (100 mL)
was heated with diethylenetriamine (2 mL) at 60°C for
C(1)-N(1)
ꢃ
C(10)-N(2) ꢃ
C(19)-N(3) ꢃ
1.335(4)ꢃ
1.334(4)ꢃ
122.0(3) 45 min (Scheme 3). The solid black crystalline Ga2S3
S(1)-C(1)
S(2)-C(1)
ꢃ
ꢃ
1.717(4)ꢃ
ꢃ
ꢃ
85.84(13)
obtained was separated from chloroform, washed with
1.731(4)ꢃ
84.68(14)
ether and chloroform in a drop of dodecylamine, and
S(3)-C(10) ꢃ
S(4)-C(10) ꢃ
S(5)-C(19) ꢃ
S(6)-C(19) ꢃ
1.714(4)ꢃ
C(10)-S(3)-Ga(1) ꢃ
C(10)-S(4)-Ga(1) ꢃ
C(19)-S(5)-Ga(1) ꢃ
C(19)-S(6)-Ga(1) ꢃ
84.76(13)
dried in air. The ease of formation of the nanosulfide
1.725(4)ꢃ
85.67(14)
from (1) was greater than (2).
1.721(4)ꢃ
1.718(4)ꢃ
85.16(13)
84.93(12)
60°C
CHCl3,
HN(CH2CH2NH2)2
state of a central atom i bonded to j matches the bond
valence, Sij, and the total valence of the central atom,
nano-sized Ga2S3
[Ga(chmdtc)3]
which is its oxidation state, ∑Sijꢀ=ꢀexp[(Ro-Rij)/b], and Ro Scheme 3:ꢀSynthesis of nano-Ga2S3.
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80ꢀ ꢀK. Ramalingam et al.: Nano-gallium sulfide precursor dithiocrbamates
Powder XRD analysis
The powder XRD pattern of the nano-Ga2S3 corresponded
to the hexagonal Ga2S3 nanocrystals with lattice constants
of aꢀ=ꢀ11.120 Å, bꢀ=ꢀ 6.395 Å, and cꢀ=ꢀ7.002 Å, consistent with
the JCPDS 16-0500. The signals from (110), (-311), (020),
(-112), (310), and (221) planes are characteristic signals of
α-Ga2S3, which are clearly distinguishable in the wurtz-
ite form of Ga2S3. Solvothermally prepared Ga2S3 showed
sharp intense signals in its powder XRD, which indicates
good crystalline nature of the material.
High-resolution transmission electron
microscopy (HRTEM) and energy-dispersive
X-ray spectroscopy (EDX) analysis
The HRTEM and selected area electron diffraction (SAED)
of the nano-α-Ga2S3 are shown in Figure 4. The partly
spherical nature of the particles was confirmed by the
TEM micrographs, and the particles are in the range of
50 nm. SAED confirmed the crystalline nature of the
nano-sized α-Ga2S3. The SAED pattern can be indexed to
the (110) and (-311) planes, confirming the wurtzite phase
of α-Ga2S3 nanoparticles. The HRTEM images of α-Ga2S3
display fringes with interlayer spacing in the order of
0.50 0.01 nm, equal to the lattice spacing of the (110)
planes of hexagonal α-Ga2S3 nanocrystals. The corre-
sponding EDX (Figure 5) indicates that the nanoparticles
consisted of Ga and S in the ratio of 2:3.
Figure 4:ꢀTEM-SAED patterns of nano-α-Ga2S3 (100 and 10 nm).
c:\edax32\genesis\genspc.spc 08-Jan-2013 12:46:30
LSecs: 86
1.9
Conclusions
S
The gallium dithiocarbamates [Ga(chmdtc)3] (1) and
[Ga(chedtc)3] (2) were prepared in good yields, charac-
terized by IR, NMR, and XPS techniques, and used as
Ga2S3 precursor. Thermal analysis confirmed the pro-
posed formulas of the compounds, and compound (1) is
slightly thermally more stable than (2). In the XPS study,
experimentally observed binding energies of gallium are
significantly higher than those reported for the element,
indicating the increased positive nature of the metal ion
in the compounds. A similar increase in binding energy of
sulfur is an indication of the loss of electron density from
the sulfur atoms to the coordinated gallium. The molecu-
lar structure in the solid state of compound (2) was estab-
lished by single crystal XRD analysis. Ga-S bonds and
the associated C-S bonds showed significant asymmetry
1.5
Ga
1.1
0.7
Ga
0.4
0
Ga
2
4
6
8
10 12 14 16 18 20 22 24
Energy-keV
[Ga-S: 2.4164(12)–2.4481(12) Å and C-S: 1.714(4)–1.731(4) Å]. Figure 5:ꢀEDX of α-Ga2S3.
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K. Ramalingam et al.: Nano-gallium sulfide precursor dithiocrbamatesꢂ
ꢂ81
yellow dithiocarbamic acid solution. To the freshly prepared dithi-
ocarbamic acid solution, GaCl3 (10 mmol, 1.8 g in methanol) was
added dropwise with constant stirring for approximately 3 h. A white
precipitate separated from the mixture was filtered, washed with
methanol, and dried in air. The solid was then recrystallized from
dichloromethane/toluene (1:1, v/v) mixture. Yield 72%; dec. 232°C
[anal. calcd. for C2 7. 5 H46N3S6Ga (680.79)% C, 48.51; H, 6.81; N, 6.17.
Found C, 48.47; H, 6.78; N, 6.13].
The mean Ga-S bond distance is 2.4362(13) Å. The complex
showed distorted octahedral geometry due to the bite
angle variations. The thioureide bond showed a mean
value of 1.332(4) Å distance. The CShM of GaS6 core is 2.513,
which clearly indicates the closeness of (2) to octahedral
geometry. BVS calculations proffer a value of 2.987, which
clearly established the oxidation state of gallium as +3;
therefore, the ionic interactions prevail in the compound.
Nano-α-Ga2S3 particles were found to be of 50 nm size.
Synthesisꢂofꢂtris(cyclohexylethyldithiocarbamato)gallium(III);
[Ga(chedtc)3]·0.5C7H8 (2):ꢂCyclohexylethyl amine (30 mmol, 1.3 mL
in 25 mL methanol), carbon disulfide (30 mmol, 2.3 mL), and GaCl3
(10 mmol, 1.8 g) were used and a procedure as described above was
followed. Yield 80%; dec. 220°C [anal. calcd. for C30.50H52GaN3S6
(722.83)% C, 50.68; H, 7.25; N, 5.81. Found C, 50.63; H, 7.21; N,
5.76]. GaCl3 in methanol will undergo extensive methanolysis and
Ga(OCH3)3 will be the true species reacting with the dithiocarbamate.
Experimental
Reagents and equipment
Gallium(III) chloride (Sigma-Aldrich, India; assay: 99.99%) and the
cyclohexylmethyl amine and cyclohexylethyl amine (Sigma-Aldrich;
assay: 98%) were used as supplied without further purification. IR
spectra were recorded on an Avatar Nicolet Fourier transform IR
spectrometer (range, 4000–400 cm-1; USA) as KBr pellets of the com-
pounds. Electronic spectra were recorded in CCl4 on a Hitachi U-2001
double-beam spectrometer (Tokyo, Japan). Thermal analysis was
carried out with NETZSCH STA 449F3 (Germany) instrument under
nitrogen atmosphere with a heating rate of 20 K min-1. 1H (400 MHz;
CDCl3; Me4Si) and 13C NMR (100.6 MHz; CDCl3) spectra were recorded
on a Bruker AMX-400 spectrometer (USA) at room temperature using
CDCl3 as a solvent. The powder diffraction data were collected in the
2θ rangeꢀ=ꢀ2–80° using Bruker D8 X-ray diffractometer (USA) equipped
with CuKα radiation at fixed current and potential. The scan speed
and step sizes were 0.05° min-1 and 0.00657, respectively. The scan-
ning electron micrographs of the samples were recorded with JEOL
JSM-5610Lv microscope (Tokyo, Japan). The HRTEM measurements
were carried out on JEOL 2100 (field emission) with an accelerating
voltage of 200 kV (Tokyo, Japan).
Supplementary material
CCDC 1025449 contains the supplementary crystallographic data for
(2). The data can be obtained free of charge at http://www.ccdc.cam.
ac.uk/con-ts/retrieving.html or from the Cambridge Crystallographic
Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223
336 033; or e-mail: deposit@ccdc.cam.ac.uk.
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