Unusual octahedral Hg(II) dithiocarbamate: Synthesis, spectral and structural studies on Hg(II) complexes with pyrrole based dithiocarbamates and their utility for the preparation of α- and β-HgS

Article abstract of DOI:10.1016/j.poly.2016.08.001

Bis(N-(pyrrol-2-ylmethyl)-N-butyldithiocarbamato-S,S′)mercury(II) (1) and bis(N-(pyrrol-2-ylmethyl)-N-(2-phenylethyl)dithiocarbamato-S,S′)mercury(II) (2) were prepared and characterized by microanalysis, spectroscopy (IR,¹H and¹³C NM

Full text of DOI:10.1016/j.poly.2016.08.001

Accepted Manuscript
Unusual octahedral Hg(II) dithiocarbamate : Synthesis, spectral and structural
studies on Hg(II) complexes with pyrrole based dithiocarbamates and their util-
ity for the preparation of α- and β-HgS
Govindasamy Gurumoorthy, Subbiah Thirumaran, Samuele Ciattini
PII:
S0277-5387(16)30360-6
DOI:
http://dx.doi.org/10.1016/j.poly.2016.08.001
POLY 12138
Reference:
Polyhedron
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2 August 2016
Please cite this article as: G. Gurumoorthy, S. Thirumaran, S. Ciattini, Unusual octahedral Hg(II) dithiocarbamate :
Synthesis, spectral and structural studies on Hg(II) complexes with pyrrole based dithiocarbamates and their utility
for the preparation of α- and β-HgS, Polyhedron (2016), doi: http://dx.doi.org/10.1016/j.poly.2016.08.001
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Unusual octahedral Hg(II) dithiocarbamate : Synthesis, spectral and structural studies on
Hg(II) complexes with pyrrole based dithiocarbamates and their utility for the preparation
of α- and β-HgS
Govindasamy Gurumoorthya, Subbiah Thirumarana* and Samuele Ciattinib
aDepartment of Chemistry, Annamalai University, Annamalainagar- 608 002, India.
bCentro di Cristallografia Strutturale, Polo Scientifio di Sesto Fiorentino, Via della Lastruccia
No. 3, 50019 Sesto Fiorentino, Firenze, Italy
Correspondence e-mail: sthirumaran@yahoo.com
*Corresponding author
Dr. S. Thirumaran
Department of Chemistry
Annamalai University
Annamalainagar 608 002
Tamil Nadu, INDIA
Tel: +91 9842897597
E-mail: sthirumaran@yahoo.com

Unusual octahedral Hg(II) dithiocarbamate : Synthesis, spectral and structural studies on
Hg(II) complexes with pyrrole based dithiocarbamates and their utility for the preparation
of α- and β-HgS
Govindasamy Gurumoorthya, Subbiah Thirumarana* and Samuele Ciattinib
aDepartment of Chemistry, Annamalai University, Annamalainagar- 608 002, India.
bCentro di Cristallografia Strutturale, Polo Scientifio di Sesto Fiorentino, Via della Lastruccia
No. 3, 50019 Sesto Fiorentino, Firenze, Italy
Correspondence e-mail: sthirumaran@yahoo.com
Abstract
Bis(N-(pyrrol-2-ylmethyl)-N-butyldithiocarbamato-S,S′)mercury(II) (1) and bis(N-(pyrrol-
2-ylmethyl)-N-(2-phenylethyl)dithiocarbamato-S,S′)mercury(II)(2) were
prepared
and
1
characterized by microanalysis, spectroscopy (IR, H and 13C NMR) and their structures were
elucidated by X-ray crystallography. Complexes 1 and 2 exist as monomer and polymer,
respectively. The central mercury atom in 1 is asymmetrically chelated by two dithiocarbamate
ligands leading to a distorted tetrahedral geometry. In complex 2, the mercury is six coordinate
with distorted octahedral coordination geometry. In this case, both dithiocarbamate ligands
function as bridging triconnective ligand. This indicates that small changes in R groups of
dithiocarbamate ligand gave different structures. Complexes 1 and 2 were used as single source
precursors for the preparation of mercury sulfide nanoparticles. Mercury sulfides were
characterized by XRD, TEM, EDAX, IR, UV and fluorescence spectra. Solvothermal
decomposition of 1 yielded three different morphological (hexagonal, cube and spherical)
α- mercury sulfide nanoparticles and 2 gave only spherical β- mercury sulfide nanoparticles.

1.Introduction
Mercury(II) dithocarbamate complexes have been extensively studied because of their
wide biological, industrial , agricultural and chemical applications [1-5]. Dithiocarbamate
ligands display a variety of coordination patterns such as monodentate, bidentate (isobidentate
or anisobidentate in chelating and bridging situations), triconnective etc., leading to a great
diversity of molecular and supramolecular structures [6]. Particularly, six different coordination
motifs have been observed for mercury(II) dithiocarbamates (scheme-1) [7]. There are two
mononuclear motifs (I and II). Motifs I and II feature a grossly distorted tetrahedral geometry [8]
and a square planar geometry [9], respectively about the central atom. Dimeric motifs fall in to
two distinct classes (motifs III and IV). These motifs are found that feature two chelating and
two bridging dithiocarbamate ligands. The only difference between the motifs III and IV relates
to the relative disposition of the bridging dithiocarbamate ligands ie., in motif III they lie to the
same side of the dimer[10] but for motif IV they lie in opposite sides[11]. The eight membered
ring in structural motifs III and IV can be described as a saddle and twisted chair conformations,
respectively. Trimeric motif (V) is found in [Hg3(thqdtc)6].py (thqdtc=1,2,3,4-
tetrahydroquinoline carbodithioate)[12]. In this motif the environments of two mercury atoms
are similar (five coordinated) but their environments are different from another mercury atom
(four coordinated). Finally there is one example of motif VI (layer structure) i.e. for
Hg(S2CNH2)2 [13]. In this case all dithiocarbamate ligands are bridging and each mercury atom
exists in a distorted tetrahedral geometry. Based on systematic studies of series of structures
where the only difference between them is in the nature of N-bound organic moiety, it has been
concluded that the actual structure adopted in Hg(II) dithiocarbamate complexes is dependant of
the N-bound organic moiety. This may be utilized as a design element in crystal engineering

especially in main group elements [6]. In addition to the structural properties, mercury(II)
dithiocarbamate complexes have been used as single source precursors for the preparation of
mercury sulfide nanoparticles [14-16]. Suitable changes in the organic moiety of dithiocarbamate
ligands can affect the phase and morphology of the metal sulfide nanoparticles [17]. Various size
and shape of mercury sulfide nanoparticles have a wide range of applications such as ultrasonic
transducers, image sensor, electrostatic image materials, flat-panel devices, photoelectric
conversion devices, non-linear optical material and solar cells [18-24]. Due to the interesting
structural variations of Hg(II) dithiocarbamate complexes and their utilization to prepare various
size and shape of mercury sulfide nanoparticles, herein we report synthesis, spectral and
structural studies on complexes 1 and 2 and preparation of mercury sulfide nanoparticles from
both the complexes.
2. Experimental
2.1 Materials and techniques
All chemicals were of analytical grade obtained from commercial sources and used
without further purification. IR spectra were recorded on a Thermo Nicolet Avatar 330 FT-IR
spectrophotometer (range: 4000–400 cm–1) as KBr pellets. The 1H and 13C NMR spectra were
recorded on BRUKER 400/100 MHz NMR spectrometer at room temperature in CDCl3 solvent.
PXRD and TEM images were performed using EQUINX 1000 and TECNAI T2 G2 make-FEI,
respectively. EDS were performed by SUPRA 55VP CARL. A Shimadzu UV-1650 PC double-
beam UV-vis spectrophotometer was used for recording the electronic spectra. Fluorescence
spectra were recorded using Perkin Elmer 1555 fluorescence spectrophotometer at room
temperature.

2.2. X-ray crystallography
Diffraction data were recorded on Xcalibur, Sapphire3 diffractometer using graphite-
monochromated MoKα radiation (λ= 0.71073 Å) at an ambient temperature. The structure was
solved by SHELXS 97 [25] and refined by full-matrix least square methods in SHELXL-97 [26].
All non-hydrogen atoms were refined anisotropically 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.
2.3. Computational study
The HOMO–LUMO energies was calculated with Gaussian 03 software package using
gradient-corrected DFT with the B3LYP functional, in which the LanL2DZ basis set was used
by including effective core potential functions [27].
2.4. Preparation of complexes
2.4.1.Preparation of amines
N-(pyrrol-2-ylmethyl)-N-butylamine and N-(pyrrol-2-ylmethyl)-N-(2-phenylethyl)
amine were prepared by general methods reported earlier [28].
Preparation of 1
N-(pyrrol-2-ylmethyl)-N-butylamine, (2.0 mmol) in ethanol was mixed with carbon
disulfide (2.0 mmol) under ice cold condition. To the resultant yellow dithiocarbamic acid
solution, aqueous solution of HgCl2 (1.0 mmol) was added with constant stirring. The solid which
precipitated was washed several times with cold water and then dried (scheme-2). Yield: 80%,
1
mp: 126°C. IR (KBr, cm–1): ν = 3389 (ν N-H), 1494 (νC–N), 1028 (νC–S): H NMR (400 MHz,
CDCl3): ꢀ 0.95 (6H, N-CH2-CH2-CH2-CH3); 1.36 (m, N-CH2-CH2CH2-CH3); 1.70 (m, N-CH2-

CH2-CH2-CH3); 3.67 (t, 4H, N-CH2-CH2-CH2-CH3); 4.94 (s, 4H, N-CH2 (pyrrole)); 6.10-6.13
13
(4H, H-3 and
H-4(pyrrole)); 6.80 (d, 2H, H-5(pyrrole)); 9.32 (2H, NH-pyrrole): C NMR
(100 MHz, CDCl3): ꢀ 13.7 (N-CH2-CH2-CH2-CH3); 20.0 (N-CH2-CH2-CH2-CH3); 28.5 (N-CH2-
CH2-CH2-CH3); 52.8 (N-CH2-CH2-CH2-CH3); 56.2 (N-CH2(pyrrole)); 107.8, 109.3, 119.1,
125.7 (pyrrole ring carbons); 203.6 (NCS2): Anal. Calcd. for C20H30HgN4S4 (%): C, 36.66; H,
4.61; N, 8.55; found (%): C, 36.51; H, 4.57; N, 8.48.
Preparation of 2
A method similar to that described for the synthesis of 1 was adopted; however, N-(pyrrol-2-
ylmethyl)-N-(2-phenylethyl)amine was used instead of N-(pyrrol-2-ylmethyl)-N-butylamine
(Scheme 2). Yield: 79%, mp: 130°C, IR (KBr, cm–1): ν = 3405 (ν N-H), 1481 (νC–N), 1029 (νC–S):
1H NMR (400 MHz, CDCl3): ꢀ 3.03 (t, 4H, CH2-CH2-C6H5); 3.89 (t, 4H, CH2-CH2-C6H5);
4.83 (s, 4H, CH2-(pyrrole)); 6.12-613 (4H, H-3 and H-4(pyrrole)); 6.80 (d,2H, H-5(pyrrole));
7.21-7.31(phenyl ring protons); 9.19 (2H, NH-pyrrole): 13C NMR (100 MHz, CDCl3): ꢀ
32.9 (N-CH2-CH2-C6H5); 54.0 (CH2-CH2-C6H5); 57.7 (CH2-pyrrole); 108.0, 109.5, 119.3, 125.5,126.9,
128.8, 137.8 (aromatic ring carbons); 204.1 (NCS2) Anal. Calcd. for : C28H30HgN4S4 (%):C, 44.76;
H, 4.02; N, 7.46; found (%): C,44.57; H, 4.03; N, 7.93.
2.4.2. Preparation of mercury sulfides
0.5 g of 1 was mixed with 15 ml triethylenetetraamine in a round bottom flask and then
the content of the flask was refluxed for 15 minutes. The dark red color precipitate was filtered
off and washed with methanol several times to remove the excess triethylenetetramine .
Similar procedure was adopted to prepare mercury sulfide from complex 2.

3. Result and discussion
3.1. Spectroscopic characterization
IR spectra of 1 and 2 are shown in Figures S1 and S2. Characteristic dithiocarbamate
vibrations for complexes 1 and 2 are found at 1494 and 1481cm-1 (v (thioureide)) and 1028
C-N
and 1029 cm-1 (v ), respectively. The presence of only one band in the region 1000 50 cm-1
C-S
supports the bidentate coordination of dithiocarbamate ligand, while the thioureide band near
1490 cm-1 indicates considerable double-bond character in the C–N bond. This behavior may
be attributed to the electron- releasing ability of amines, which forces high electron density
towards the sulfur atoms via the thioureide π-system, thus producing double bond character and
the v vibration is observed between single (v = 1350-1250 cm-1) and double (v = 1690-
C-N
C-N
C-N
1640 cm-1) bond energies.
13
1
1H NMR and C NMR spectra of 1 and 2 are given in Figures S3-S6. H and 13C NMR
spectra of both the complexes are typical of diamagnetic species and are consistent with their
1
chemical compositions. The H NMR spectra of both complexes 1 and 2 reveal the NH proton
signal at 9.32 and 9.19 ppm, respectively. This indicates that there is no direct metal ion
coordination to the deprotonated pyrrole nitrogen atoms. A typical singlet is found at 4.94 and
4.83 ppm for 1 and 2, respectively due to the methylene protons attached to pyrrole ring. The
characteristic resonances of the butyl and ethyl group of phenylethyl found in the aliphatic region
also support the proposed formulae of the dithocarbamate derivates. Aromatic proton signals due
to pyrrole and phenyl rings are appeared in the region 6.12-7.31 ppm.
In the 13C NMR spectra of 1 and 2, the 13NCS2 carbon signals are appeared at 203.6 and
204.1 ppm. An upfield shift was observed for both the complexes compared to the NCS2

chemical shift of bis (N-(pyrrol-2-ylmethyl)-N-butyldithiocarbamato-S,S′)nickel(II) (206.3 ppm)
and bis(N-(pyrrol-2-ylmethyl)-N-(2-phenylethyl)dithiocarbamato-S,S′)nickel(II) (206.9 ppm)
[28]. In general, the extent of deshielding is greater for the thioureide N13CS2 signal in main
group metal dithiocarbamates than those of normal valence state transition metal
dithiocarbamates [29]. Pyrrole and phenyl ring carbons are observed in the region 107.8-137.8
ppm.
3.2.Structural analysis of 1
The molecular structure of 1 is shown in Fig 1 and selected bond lengths and angles are
collected in Table 2. Single crystal X-ray structure indicates that complex 1 is a monomer. The
Hg(II) centre is coordinated by two anisobidentate dithiocarbamate ligands that define S4
coordination geometry. Two of the Hg–S bond distances, i.e. 2.4957(10) and 2.4771(10) Å are
significantly shorter than the Hg–S bond distances, i.e. 2.6327(11) and 2.6472(10) Å. There is a
large compression of the dithiocarbamate bite angles S1–Hg–S2 (71.10(3)⁰) and S3–Hg–S4
(71.02(3)⁰). These acute chelate angles introduce significant distortions in the coordination
geometry. These lead to enlargement of the other S–Hg–S angles with respect to the ideal
tetrahedral angle (109.5⁰). The configuration around the mercury atom is a strongly distorted
tetrahedral. The distorted tetrahedral coordination geometry (motif I) has been observed
previously in the structure of mercury(II) dithiocarbamates [30]. The four membered chelate
rings containing atoms Hg–S2–C10–S1 and Hg–S3–C20–S4 are coplanar within experimental
error. S4 sulfur atom forms intermolecular hydrogen bond with pyrrole NH proton H1 (Fig 2).
Two intermolecular C–H···π interactions between H5A and gravity centre of pyrrole ring [(C16-
C19,N4)], H14A and cg[(C6-C9,N4)] result in a dimer (Fig 3). There are also four

intramoleclular C-H···S interactions with distances in the range 2.516-2.724 Å (Fig. S7 and
Table-3 ).
3.3. Structural analysis of 2
Selected bond lengths and angles are listed in Table 4. Asymmetric unit of 2 is shown
in Fig 4a. Two dithiocarbamate ligands in bis(N-(pyrrol-2-ylmethyl)-N-(2-phenylethyl)
dithiocarbamato-S,S′)mercury(II) (2) are tridentate. In the asymmetric unit, Hg1 is coordinated
by S2 and S3. The S1 and S4 coordinated to Hg1i and Hg1ii, respectively. S2 and S4 are also
coordinated to Hg1i and Hg1ii, respectively (Fig. 4b). In the chain structure, each mercury atom
is coordinated to six sulfur atoms (S2, S3, S1i, S2i, S3ii, S4ii ) at distances of 2.501-2.939 Å . The
geometry of the coordination polyhedron [HgS6] is distorted octahedral geometry with a range
of angles from 66.02(4)⁰, i.e. the chelate angle to 163.38(4)⁰ for S2–Hg1–S3ii. The
dithiocarbamate ligands are coordinated to mercury atoms, forming two extended eight-
membered tricyclic moieties, [Hg1, Hg1i, S1, S2, C1, S1i, S2i and C1i] and [Hg1, Hg1ii,S3, S4,
C15, S3ii, S4ii and C15ii], whose geometry can be approximated by chair conformations. These
two moieties extended to form chain structure. There are four intramolecular C–H···S
interactions observed (Fig S8 and Table 5).
This structure is unique because of the following reasons: (i) This is the first example of
octahedral mercury(II) dithiocarbamate complex whereas the central metal atom in zinc trial
dithiocarbamate complexes is usually four or five coordinated [6]. (ii) In this complex, both
dithiocarbamate ligands are triconnective and bridging. (iii) The chain structure is different from
known structural motifs I–VI (see introduction).

In both complexes, Hg–S distances are asymmetric. However, C–S distances are
symmetric and are shorter than the C–S single bond distance (1.81Å). Therefore all the C–S
bonds in both the structures are of partial double bond character as observed in most of the
dithiocarbamates [31]. The short thioureide C–N distances [1.330 (5) and 1.331(6) for 1 and 2,
respectively] in both the complexes indicate bonds have these double that these bonds have
strong double bond character and that the π-electron density is delocalized over the S2CN
moiety.
Single crystal X-ray structural analysis of 1 and 2 show that complexes 1 and 2 adopt
monomeric and polymeric chain structures, respectively. In complex 1, both dithiocarbamate
ligands function as anisobidentate and coordinated to the same mercury atom. The coordination
geometry around Hg atoms is distorted tetrahedral. In complex 2, both dithiocarbamate ligands
act as tridentate and coordinated to three mercury atoms. The geometry of the coordination
polyhedron is distorted octahedral. The structural difference between 1 and 2 are due to the size
and electronic effects of the N-bound organic moiety of the dithiocarbamate ligands and also
crystal packing effects.
3.4 Optimized structure
To compare the optimized structures and energy gap (HOMO ~ LUMO) of complexes 1
and 2 and to investigate reactive sites in 1 and 2, we tried to do DFT calculations for 1 and 2. But
we could not obtain the DFT calculation results for the chain structure of 2. Therefore, herein we
report the theoretical studies for 1. Selected bond distances and angles for 1 obtained by X-ray
diffraction analysis and also calculated by DFT are given in Table 6. In the optimized structure,
(Fig. S9) N-(pyrrol-2-ylmethyl)-N-butyldithiocarbamate ligand acts as bidentate. Two ligands

coordinate to mercury centre forming a tetrahedral geometry, similar to the structure obtained
from the single crystal X-ray structure determination. Comparison of bond lengths and angles
indicates a slight difference except S4–Hg–S1 angle. The observed slight differences could be
attributed to the fact that the geometric parameters from the DFT calculations were generated in
gaseous phase, while the experimental X-ray data were obtained in solid state. The large
difference between calculated and experimental S4–Hg–S1 angle (20.438 ⁰) may be due to the
intermolecular interaction of S4···H1observed in solid state. This interaction is absent in
optimized structure.
3.5 Frontier molecular orbitals
The two states of molecular orbitals, HOMO and LUMO give further understanding of the
electronic state and reactivity of molecules. Fig 5 exhibits the HOMO and LUMO of the
molecule. The mercury predominantly contributes to the HOMO, while the remaining are from
the four S atoms of the ligand. LUMO mainly located on pyrrole ring and a small contributions
from S, N of NCS2 moiety to LUMO. The HOMO (-2.0889 eV) and LUMO (-5.8958 eV) is
separated by an energy gap of 3.8070 eV. This gap is related to the stability and reactivity of the
complex.
3.6 Molecular electrostatic potential (MEP) surfaces
To investigate reactive sites for nucleophilic and electrophilic attack, the MEP surfaces
were plotted by DFT calculations. The plot of MEP surface of 1 is shown in Fig. S10.Different
values of electrostatic potential at the surfaces are represented by different colours. The
electrostatic potential increases in the order: red (most negative electrostatic potential) ˂ orange
˂ yellow ˂ green ˂ blue (most positive electrostatic potential) [32,33]. The negative electrostatic

potential regions of the MEP surfaces are related to electrophilic reactivity and the positive
electrostatic potential regions to nucleophilic reactivity [34,35]. The most negative region of
the MEP surfaces is mainly localized over S atoms of NCS2 group and N atom of pyrrole
indicating that they are the most suitable atomic sites for elelctrophilic attack. The positive
region is localized on N atom of NCS2 group exhibiting that it is possible site for attack by
nucleophiles.
3.7 Characterization of metal sulfide nanoparticles
Mercury sulfide nanoparticles from complexes 1 and 2 are represented as samples 1 and
2, respectively. Powder X-ray diffraction patterns of the samples 1 and 2 displayed in Fig 6. All
the diffractions peaks in powder X-ray diffraction patterns of samples 1 and 2 could be indexed
to be hexagonal phase (α-HgS, cinnabar) and cubic phase (β-HgS, meta cinnabar). These are in
good agreement with standard data from the JCPDS card No. 89-7103 and 89-0432 for sample 1
and 2, respectively. In both the cases, no peaks due to any impurities were detected, revealing
the presence of single phase in the product.
TEM images of samples 1 and 2 are shown in Fig 7. TEM images of sample 1 (Fig.7(a)
and (b) ) reveal that most of the particles are spherical with diameter in the range 14-36 nm. A
few hexagonal and cubic particles are also present in the sample 1. In the case of sample 2, all
the particles are spherical with diameter in the range 20-30nm.
Powder X-ray diffraction and TEM studies support that the different phases, shape and
size of HgS nanoparticles can be prepared using mercury(II) dithiocarbamate complexes
containing various N-bound organic moiety of dithiocarbamate .

Energy dispersive X-ray spectra (Fig 8) of both the samples exhibit strong signals for
mercury and sulfur. This confirms that the solvothermal decomposition of both the complexes 1
and 2 yield mercury sulfide. Elemental analytical data obtained from EDS of sample 1 reveal
that the atomic percentage of Hg and S are 43.68 and 56.32 (ratio: 1:1.29), respectively. This
reveals that a higher number of sulfur atoms present in the products compared to mercury. This
may be due to the presence of some vacant sites of Hg 2+ or sulfur dangling bonds in the sample
1. In the case sample of 2, the atomic percentage of mercury and sulfur [53.15:46.85; ratio:
1:0.88] indicate the presence of excess Hg 2+ in the sample 2.
UV-vis absorption spectra of sample 1 and 2 are displayed in Fig 9(a) and (b),
respectively. An absorption maxima is appeared at 220 nm in the UV-Vis absorption spectra of
both the samples. A blue shift is observed in the absorption maxima relative to the bulk HgS
(620 nm) [36]. Generally, the absorption maxima (λ max) decreases with a decreasing size of the
nanoparticles as a consequences of quantum confinement of the photogenerated electron-hole
carriers [37].
Photoluminescence spectra of samples 1 and 2 are shown in Fig 10(a) and (b),
respectively. The spectra of samples 1 and 2 exhibit a broad emission peak at 364 and 340 nm,
respectively on excitation at 265 and 270 nm, respectively. These peaks are due to the core state
radioactive decay from CB to VB and the blue shift of the emission peak compared to those of
bulk HgS (588 nm) [38] is attributed to the quantum confinement effect.
Fig 11 shows the FTIR spectra of samples 1 and 2. In the spectra of both samples, a
broad band around 3400 cm-1 for samples 1 and 2 correspond to the stretching vibration of N–H
and the peaks in the region 2851-2959 cm-1 are assigned to the stretching vibrations of aliphatic

C–H. No peaks observed due to the stretching vibrations of C–N (thioureide), C–S and aromatic
C–H indicate the absence of dithiocarbamate ligands in the samples 1 and 2.
4. Conclusions
In this contribution, two Hg(II) dithiocarbamate complexes were prepared and fully
characterized. Crystal structure of 1 and 2 reveal that the complexes 1 and 2 are monomer and
polymer respectively, and the geometries around each mercury atom in 1 and 2 are distorted
tetrahedral and octahedral, respectively. This study suggests that the different structural motifs
can be obtained by changing the N-bound organic moiety of the dithiocarbamate ligands. Three
different morphological α-HgS and spherical β-HgS nanoparticles were obtained from 1 and 2,
respectively. This study also shows that various morphological and phase (α and β) HgS
nanoparticles can be prepared from different mercury (II) dithiocarbamate complexes.
5. Supplementary data
CCDC 1488853 and 1488854 contain the supplementary crystallographic data for
complexes
1
and 2. This data can be obtained free of charge via
http://www.ccdc.cam.ac.uk/conts/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.
Acknowledgements
Dr. S. Thirumaran is thankful to University Grants Commission (UGC), India (F. No. 42-
341/2013 (SR)) for providing fund for this research study. We are thankful to SAIF, Panjab
University, Chandigarh, India, for recording TEM images.

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Table.1.Crystal data, data collection and refinement parameters for complexes 1 and 2
Parameters
1
2
C28 H30 Hg N4 S4
751.39
Empirical formula
C20 H30 Hg N4 S4
Formula weight
655.31
Crystal system
triclinic
P ī
monoclinic
P 21 /c
Space group
a/Å
8.3997(5)
9.8463(5)
15.2994(8)
103.904(4)
95.242(5)
93.949(5)
1217.73(12)
2
8.5939(2)
29.6100(7)
11.0514(5)
90
b/Å
c/Å
α/⁰
91.928(3)
90
β/⁰
γ/⁰
V/Å3
2810.61(16)
4
Z
Dcalc/gcm-3
µ/cm-1
F(000)
λ/Å
1.685
1.613
0.136
0.142
644
1480
MoKα (0.71073)
MoKα (0.71073)
−11 ≤ h ≤ 11, −12 ≤ k ≤ 13, −20 ≤ −11 ≤ h ≤ 11, −27 ≤ k ≤ 37, −13
Index ranges
l ≤ 20
5601
4710
≤ l ≤ 14
6481
Reflections collected
Observed reflections
[I > 2σ(I)]
4902
w=1/[σ2(Fo )+(0.0152P)2+0.3842 w=1/ [σ2 (Fo )+(0.0241P)2]
P] where P=(Fo +2Fc2) /3
2
2
Weighting scheme
where P=(Fo +2Fc2) / 3
2
2
262
334
Parameters refined
R[F2 > 2σ(F2)], wR(F2)
GOOF
0.0361, 0.0686
1.082
0.0452, 0.0847
1.064

Table .2. Selected bond lengths (Å) and bond angles (°) of complex 1
Bond distances (Å)
Bond angles (°)
Hg1 S3 2.4771(10)
S3 Hg1 S2 137.98(4)
Hg1 S2 2.4957(10)
Hg1 S1 2.6327(11)
Hg1 S4 2.6472(10)
S4 C20 1.720(4)
S3 C20 1.741(4)
S1 C10 1.728(4)
S2 C10 1.745(4)
N2 C10 1.330(5)
N4 C19 1.364(5)
N4 C16 1.372(5)
N3 C20 1.329(5)
N3 C14 1.481(5)
N3 C15 1.490(5)
N1 C9 1.361(5)
N1 C6 1.367(5
S3 Hg1 S1 137.14(3)
S2 Hg1 S1 71.10(3)
S3 Hg1 S4 71.02(3)
S2 Hg1 S4 132.62(3)
S1 Hg1 S4 115.62(3)
S1 C10 S2
118.5(2)
C20 N3 C14 122.0(3)
C20 N3 C15 122.8(3)
S4 C20 S3
118.8(2)
C14 N3 C15 115.2(3)
C10 N2 C4 122.0(4)
C10 N2 C5 122.2(3)
N3 C20 S3 119.4(3)
N2 C10 S1 121.8(3)
N2 C10 S2 119.8(3)
N3 C20 S4 121.7(3)

Table.3. Geometric details of hydrogen bonding (Å,º) in 1
Interactions
D–H
0.97
0.97
0.97
0.97
0.86
0.97
0.97
H···A
2.619
2.568
2.516
2.627
2.971
2.938
3.104
D···A
D–H···A
105.47
107.15
111.32
105.17
112.29
130.99
147.06
C4 ―H4A···S1a
3.026 (4)
3.001 (4)
3.007 (4)
3.029 (4)
3.392 (4)
3.649
C5―H5B···S2a
C15―H15B···S3a
C14―H14A···S4a
N1―H1···S4b
C14―H14A···Cg(C6-C9,N4)c
C5―H5A···Cg (C16-C19,N4)c
3.912
a-intramolecular C–H···S hydrogen bonding
b-Intermolecular N–H···S interactions
c-intermolecular C–H···ꢁ (chelate) interaction

Table .4. Selected bond lengths (Å) and bond angles (°) of complex 2
S1 Hg1i S3ii
S4 Hg1ii S3ii
S2 Hg1ii S3
S1 Hg1 S3
S4 Hg1i S2i
S2 Hg1 S2
S3 Hg1i S2
S3 Hg1 S2
C1 S2 Hg1
C1 S2 Hg1
Hg1 S2 Hg1
C15 S3 Hg1
C15 S3 Hg1
N1 C2 C3
99.57(4)
67.02(4)
163.38(4)
99.80(4)
103.71(4)
83.74(4)
111.54(4)
161.83(4)
99.18(16)
79.97(18)
96.26(4)
80.60(18)
99.82(19)
112.5(4)
109.1
Bond distances (Å)
Hg1 S1i
2.5011(13)
2.5016(13)
2.7927(14)
2.8747(14)
2.8823(15)
2.9391(14)
1.726(5)
Hg1 S4ii
Hg1 S2
Hg1 S3ii
Hg1 S3
Hg1 S2i
S2 C1
S3 C15
N3 C15
N3 C16
N3 C24
N1 C1
1.716(5)
1.337(6)
1.469(5)
1.473(6)
1.325(6)
N1 C2
1.478(5)
N1 C10
N4 C28
1.478(6)
N1 C2 H2A
N1 C10 H10A
N1 C10 H10B
N1 C1 S2
1.359(7)
108.7
108.7
120.5(4)
119.7(4)
119.7(3)
Bond angles (°)
S1 Hg1i S4ii
S1 Hg1i S2
S4 Hg1ii S2
159.76(5)
92.54(4)
103.94(4)
N1 C1 S1
S2 C1 S1
Symmetry code: i = 1-x, 2-y, -z;
ii= -x, 2-y, -z

Table.5. Geometric details of hydrogen bonding (Å,º) in 2
Interactions
D–H
0.97
0.97
0.97
0.97
H···A
2.574
2.602
2.536
2.616
D···A
D–H···A
107.73
105.69
108.04
105.17
C2 ―H2A···S1a
C10―H10B···S2a
C24―H24A···S3a
C16―H16A···S4a
3.014 (5)
3.013 (5)
2.983 (5)
3.018 (5)
a-intramolecular C–H···S hydrogen bonding

Table. 6. Theoretical and experimental of selected bond distances(Å) and bond angles(˚)
for complex 1
Bond distances
(Å)
XRD
DFT/LanL2D
Z
Hg1-S1
Hg1-S2
Hg1-S3
Hg1-S4
S1-C10
S2-C10
S3-C20
S4-C20
N2-C10
N3-C20
N2-C4
2.633(1) 2.7274
2.496(1) 2.7685
2.477(1) 2.7661
2.647(1) 2.7288
1.728(4) 1.7994
1.745(4) 1.8073
1.740(5) 1.8078
1.721(4) 1.7988
1.329(5) 1.3462
1.329(5) 1.3463
1.467(5) 1.4914
1.486(6) 1.5064
1.481(5) 1.4913
1.490(5) 1.5065
N2-C5
N3-C14
N3-C15
Bond angles (˚) XRD
DFT/LanL2D
Z
S4-Hg1-S3
S4-Hg1-S1
S4-Hg1-S2
S3-Hg1-S1
S3-Hg1-S2
S1-Hg1-S2
S1-C10-S2
S1-C10-N2
S2-C10-N2
S4-C20-S3
S4-C20-N3
S3-C20-N3
C10-N2-C5
C10-N2-C4
C5-N2-C4
71.02(3) 69.033
115.62(3) 136.058
132.62(3) 132.807
137.14(3) 133.162
137.97(4) 128.693
71.10(3) 69.029
118.4(2) 119.414
121.8(3) 120.205
119.8(3) 120.379
118.8(2) 119.387
121.7(3) 120.288
119.5(3) 120.322
122.2(3) 122.431
122.0(3) 122.896
115.8(3) 114.664
115.2(3) 114.663
122.7(3) 122.375
122.0(3) 122.951
C15-N3-C14
C15-N3-C20
C14-N3-C20

Schemes and Figure captions
Scheme 1. Structural variations in mercury(II) dithiocarbamates
Scheme 2. Preparation of complexes 1 and 2.
Figure 1. ORTEP of complex 1.
Figure 2. Intermolecular C-H···S interaction in complex 1.
Figure 3. Intermolecular C–H···π (chelate) interaction in complex 1.
Figure 4. (a) Asymmetric unit and (b) ORTEP of complex 2 (Symmetry code: i = 1-x, 2-y, -z;
ii= -x, 2-y, -z)
Figure 5. Graphical images of the HOMO and LUMO of complex 1
Figure 6. Powder X-ray diffraction patterns of (a) α-HgS and (b) β-HgS
Figure 7. TEM images of (a) α-HgS and ) (b) β-HgS
Figure 8. Energy dispersive spectra of (a) α-HgS and (b) β-HgS
Figure 9. UV-Vis spectra of (a) α-HgS and (b) β-HgS.
Figure 10. PL spectra of (a) α-HgS and (b) β-HgS.
Figure 11. IR Spectra of (a) α-HgS and (b) β-HgS.

Scheme-1

Scheme-2

Figure 1.

Figure 2.

Figure 3.