Influence of functionalities over polymer, trimer, dimer formation and optical properties of cadmium dithiocarbamates

Article abstract of DOI:10.1016/j.poly.2016.06.047

Homoleptic cadmium(II) bis(dithiocarbamate) complexes having polymeric [Cd(L)₂]_∞(L?=?C₇H₅O₂CH₂NCS₂CH₂C₆H₅(L1), 1; C₆H₄NO₂CH₂NCS₂CH₂C₄H₃O (L2), 2; C₆H₄FCH₂NCS₂CH₂C₄H₃O (L3), 3), trinuclear [Cd(L4)₂]₃(L4?=?4-ClC₆H₄CH₂NCS₂CH₂C₄H₃O, 4) and dinuclear [Cd(L5)₂]₂, (L5?=?3-ClC₆H₄CH₂NCS₂CH₂C₆H₅, 5) structures have been synthesized and characterized by elemental analyses, spectroscopy (IR,¹H and¹³C {¹H} NMR and UV–Vis.) and their structures have been revealed by X-ray crystallography. In 1–3 the dithiocarbamate ligands are uniquely bonded to the Cd atoms in a μ₂,κ²S,S-chelating-bridging fashion, portraying 1D coordination polymeric structures in which the cadmium(II) ions adopt six coordinate distorted octahedral structures. In 4 the six dithiocarbamate ligands are spectacularly arranged about the Cd atoms resulting in a centrosymmetric trinuclear complex in which the central metal adopts an octahedral geometry and the terminal Cd atoms are in square pyramidal environments. Complex 5 has the well-established centrosymmetric dimeric structure in which the metal atoms have a five-coordinate trigonal bipyramidal geometry. Complexes 1–4 are rare examples of polymeric and trinuclear cadmium dithiocarbamate complexes. 1–5 show luminescent characteristics in solution and in the solid state arising from the metal perturbed intra-ligand charge transfer (ILCT) states. Their TG analyses show a single step decomposition with the formation of CdS nanoparticles, which have been examined by PXRD and HRTEM.

Full text of DOI:10.1016/j.poly.2016.06.047

Accepted Manuscript
Influence of functionalities over polymer, trimer, dimer formation and optical
properties of cadmium dithiocarbamates
Krishna K. Manar, Manoj K. Yadav, Anamika, Michael G.B. Drew, Nanhai
Singh
PII:
S0277-5387(16)30281-9
DOI:
http://dx.doi.org/10.1016/j.poly.2016.06.047
POLY 12088
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17 June 2016
Please cite this article as: K.K. Manar, M.K. Yadav, Anamika, M.G.B. Drew, N. Singh, Influence of functionalities
over polymer, trimer, dimer formation and optical properties of cadmium dithiocarbamates, Polyhedron (2016), doi:
http://dx.doi.org/10.1016/j.poly.2016.06.047
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Influence of functionalities over polymer, trimer, dimer formation and
optical properties of cadmium dithiocarbamates
Krishna K. Manar,a Manoj K. Yadav,a Anamika,a Michael G. B. Drewb and Nanhai Singh*a
aDepartment of Chemistry, Institute of Science, Banaras Hindu University, Varanasi 221005, India
Fax: +91-542-2386127, E-mail: nsingh@bhu.ac.in, nsinghbhu@gmail.com
bDepartment of Chemistry, University of Reading, Whiteknights, Reading, RG6 6AD (U.K.)

Abstract
Homoleptic cadmium(II) bis(dithiocarbamate) complexes having polymeric [Cd(L)2]∞ (L =
C7H5O2CH2NCS2CH2C6H5 (L1), 1;
C6H4NO2CH2NCS2CH2C4H3O (L2), 2;
C6H4FCH2NCS2CH2C4H3O
ClC6H4CH2NCS2CH2C4H3O,
(L3),
3),
trinuclear
dinuclear
[Cd(L4)2]3
[Cd(L5)2]2,
(L4
(L5
=
=
4-
3-
4)
and
ClC6H4CH2NCS2CH2C6H5, 5) structures have been synthesized and characterized by
1
elemental analyses, spectroscopy (IR, H and 13C {1H} NMR and UV-Vis.) and their
structures have been revealed by X-ray crystallography. In 1-3 the dithiocarbamate ligands
are uniquely bonded to the Cd atoms in a µ2,κ2 S,S-chelating-bridging fashion, portraying 1D
coordination polymeric structures in which the cadmium(II) ions adopt six coordinate
distorted octahedral structures. In 4 the six dithiocarbamate ligands are spectacularly arranged
about the Cd atoms resulting in a centrosymmetric trinuclear complex in which the central
metal adopts an octahedral geometry and the terminal Cd atoms are in square pyramidal
environments. Complex 5 has the well-established centrosymmetric dimeric structure in
which the metal atoms have a five-coordinate trigonal bipyramidal geometry. Complexes 1-4
are rare examples of polymeric and trinuclear cadmium dithiocarbamate complexes. 1-5 show
luminescent characteristics in solution and in the solid state arising from the metal perturbed
intra-ligand charge transfer (ILCT) states. Their TG analyses show a single step
decomposition with the formation of CdS nanoparticles, which have been examined by
PXRD and HRTEM.
1. Introduction
Growing interest in dithiocarbamate ligand chemistry is due to the functionalization of the
substituents on the N atom of the dithiocarbamate unit, which allows more complex
architectures via secondary interactions and the modification of their physical properties [1-
7]. Metal 1,1-dithiolates, including those of group 12 (Zn, Cd, Hg) metal dithiocarbamates,
are becoming increasingly important due to their rich variety of structures, optical properties
and molecular precursors for the formation of metal sulfide materials [4-6]. In contrast to a
plethora of examples of Zn(II) dithiocarbamates [2,3b] showing structural diversity, the
number and structural types of cadmium dithiocarbamate complexes reported to date are
extremely limited [1c,4,5]. Indeed the majority of known structures are centrosymmetric
dimers. In recent years some group 12 metal complexes with pyridyl functionalized
dithiocarbamate ligands involving distant hetero Py(N) and S,S-donor atoms displaying

polymeric structures have been described [3b,7]. However, recently the time and solvent
dependent crystallization of cadmium bis(dithiocarbamate) produced the coordination
polymer [{Cd[S2CN(iPr)-CH2CH2OH]2}3·MeCN]∞ [5a].
The geometric constraints imposed by the substituents on the coordination spheres are
crucial in the stabilization of their overall structures. It is therefore critical to make changes to
the dithiocarbamate ligand environment in order to map out their fascinating structural
features and properties. Accordingly, on the 3- or 4- position of the benzene rings,
substituents with varying electronegativities, such as F, Cl, O and NO2, were incorporated in
the dithiocarbamate unit. The synthesis, crystal structures, photoluminescent characteristics
and thermal decomposition of the cadmium complexes 1-5 with new functionalized
dithiocarbamate ligands (Figure 1) have been undertaken. The polymeric (1-3), trimeric (4)
and dimeric (5) complexes thus formed and the supramolecular arrays sustained via
secondary interactions in these complexes are described in this contribution.
------------------------------------------------Figure 1 -------------------------------------------------
2. Experimental
2.1. Materials and general methods
The reagent grade chemicals Cd(OOCCH3)2·2H2O and 1,3-benzodioxole-5-carbaldehyde
(Aldrich), 4-fluorobenzaldehyde, 4-chlorobenzaldehyde, 3-chlorobenzaldehyde and 4-
nitrobenzaldehyde, (Avra), benzylamine, furfurylamine and carbon disulfide (S D Fine-
Chem) were used as received. The solvents were purified by standard procedures. All
reactions were carried out under ambient conditions.
The melting points were determined in open capillaries on a Gallenkamp’s apparatus and
are uncorrected. Elemental analysis (C, H, N) were performed on an Exeter CE-440 element
analyzer and sulfur was determined gravimetrically as BaSO4 [8]. IR (KBr discs) in the range
4000-400 cm-1 and 1H and 13C {1H} NMR spectra were recorded in CDCl3 solution on Perkin
Elmer IR and JEOL AL300 FT NMR spectrophotometers respectively. Chemical shifts are
quoted in parts per million (δ, ppm) with (CH3)4Si (TMS) as internal standard for 1H and 13C
{1H} NMR. The UV-Vis. absorption (200-800 nm) and photoluminescence spectral
measurements were carried out on Shimadzu UV-1800 and Horiba JobinYvon and Fluorolog-
3 spectrophotometers respectively. Thermogravimetric analysis (TGA) was performed on a
Perkin Elmer STA 6000 TG/DTA Thermogravimetric Analyzer with a heating rate of 10 °C
min-1 in a nitrogen atmosphere. Powder X-ray diffraction (PXRD) measurements were made

on a Brüker D8 diffractometer with Cu Kα radiation (λ =1.541836 Å) in the 2θ range 10-60°,
with a scan speed and a step size of 1° and 0.02° min-1 respectively. The transmission
electron microscopy measurements were conducted on a JEOL JEM-2100F field emission
transmission electron microscope operating at 200 kV. The samples were prepared by placing
1-3 µL of ethanol solutions of the complexes on copper grids and drying under a lamp.
2.2. Synthesis of the dithiocarbamate ligands (KL1-KL5) and complexes [Cd(L)2] (L = L1
(1), L2 (2), L3 (3), L4 (4), L5 (5)
The secondary amines required for the synthesis of dithiocarbamate ligands were
synthesized by the reaction of 1,3-benzodioxole-5-carbaldehyde (0.150 g, 1 mmol), 4-
nitrobenzaldehyde (0.151 g, 1 mmol), 4-fluorobenzaldehyde (0.124 g, 1 mmol), 3-
chlorobenzaldehyde (0.140 g, 1 mmol) or 4-chlorobenzaldehyde (0.140 g, 1 mmol) and
benzylamine (0.107 g, 1 mmol) or furfurylamine (0.097g, 1 mmol) dissolved in 15 mL
ethanol and refluxed for 8 h. The resulting reaction mixture was kept in an ice bath, stirred
and then NaBH4 and methanol were added to reduce the Schiff base to a secondary amine.
The product was extracted with dichloromethane (50 mL) and washed with distilled water (3
x 20 mL). The oily yellow to light pink product was collected on solvent removal. The
potassium salts of the dithiocarbamate ligands (KL1-KL6) were prepared by the reaction of
the secondary amines thus obtained. KL1-KL6 were dissolved in 10 mL THF, and KOH
(0.056 g, 1 mmol) was added followed by addition of carbon disulfide (0.076 g, 1 mmol)
under ice-cold conditions. The reaction mixture was stirred for 2-3 h and the solvent was
removed on a rotary evaporator. The product obtained was washed 2-3 times with diethyl
ether to yield a pale yellow solid product.
The complexes 1-5 were prepared according to the following general procedure. To a 20
mL stirred methanol solution of the ligand KL1 (0.35 g, 1 mmol), KL2 (0.34 g, 1 mmol),
KL3 (0.31 g, 1 mmol), KL4 (0.33 g, 1 mmol) or KL5 (0.34 g, 1 mmol)), was added gradually
a 20 mL methanol:water (80:20) solution of Cd(OOCCH3)2·2H2O (0.13 g, 0.5 mmol). In each
case the reaction mixture was stirred for 6 h, resulting in the formation of a light yellow
product. The precipitate thus formed was filtered off, washed with methanol followed by
diethylether. Light yellow crystals of 1-5 were obtained within three to four weeks by
dissolving the compounds in dichloromethane and layering with acetonitrile.
2.3. Characterisation data
2.3.1. Ligands (KL1-KL5)

KL1, Yield: 0.26 g, 75%. IR (KBr, cm-1): 1330 ν(C=N), 1076 ν(C-S). 1H NMR (300.40 MHz,
CDCl3, δ, ppm): 7.18-7.10 (m, 5H, -C6H5), 6.91-6.60 (s, 3H, -C6H3CH2O2), 5.84 (s, 2H, -
CH2C6H3O2), 5.29-5.20 (s, 4H, -CH2C6H3CH2O2, -CH2C6H5), 13C {1H} NMR (75.45 MHz,
CDCl3, δ, ppm): 215.95 (CS2), 147.00, 146.27, 138.47, 132.44 (-C6H5), 128.42, 127.62,
126.91, 121.01 (-C6H3CH2O2), 108.30 (-CH2C6H3CH2O2), 53.94 (-CH2C6H5, -CH2C7H5O2).
1
KL2, Yield: 0.24 g, 73%. IR (KBr, cm-1): 1304 ν(C=N), 1016 ν(C–S). H NMR (300.40
MHz, CDCl3, δ, ppm): 8.10-7.39 (m, 4H, -C6H4), 6.28-6.22 (m, 3H, C4H3O), 5.55 (s, 2H, -
CH2C4H3O), 5.37 (s, 2H -CH2C6H5NO2). 13C {1H} NMR (75.45 MHz, CDCl3, δ, ppm):
216.69 (CS2), 152.12, 147.39, 146.08, 141.80, 128.10, 123.09 (-C6H5), 110.41-107.73 (-
C4H3O), 54.08 (-CH2C6H4NO2), 47.74 (-CH2C4H3O).
KL3, Yield: 0.21 g, 68%. IR (KBr, cm-1): 1271 ν(C=N), 1065 ν(C-S). 1H NMR (300.40 MHz,
CDCl3, δ, ppm): 7.48-7.07 (m, 4H, C6H4), 6.33-6.22 (m, 3H, -C4H3O), 5.38 (s, 2H, -
CH2C4H3O), 5.30 (s, 2H -CH2C6H4F). 13C {1H} NMR (75.45 MHz, CDCl3, δ, ppm): 216.20
(CS2), 152.08, 141.73, 134.73, 129.35, 129.26, 114.88 (C6H5), 110.44-107.93 (-C4H3O),
53.03 (-CH2C6H5F), 46.83 (-CH2C4H3O).
KL4, Yield: 0.23 g, 70%. IR (KBr, cm-1): 1285 ν(C=N), 1070 ν(C-S). 1H NMR (300.40 MHz,
CDCl3, δ, ppm): 7.48-7.23 (m, 4H, -C6H4), 6.33-6.22 (m, 3H, -C4H3O), 5.39 (s, 2H, -
13
CH2C4H3O), 5.29 (s, 2H -CH2C6H4Cl). C {1H} NMR (75.45 MHz, CDCl3, δ, ppm): 216.44
(CS2), 152.11, 141.65, 137.75, 130.82, 129.13, 127.89 (-C6H4), 110.35–110.83 (-C4H3O),
53.04 (-CH2C6H5Cl), 46.83 (-CH2C4H3O).
1
KL5, Yield: 0.34 g, 72%. IR (KBr, cm-1): 1300 ν(C=N), 1084 ν(C–S). H NMR (300.40
MHz, CDCl3, δ, ppm): 7.29-7.10 (m, 5H, -C6H5), 7.06-7.03 (m, 4H, -C6H4), 5.24 (s, 2H, -
CH2C6H5), 5.24 (s, 2H -CH2C6H4). 13C {1H} NMR (77.00 MHz, CDCl3, δ, ppm): 216.20
(CS2), 141.27, 138.32, 138.19, 130.71 (-C6H5),130.15, 129.90, 128.63, 127.15, 126.71,
122.20 (-C6H4), 54.65 (-CH2C6H5), 53.95 (-CH2C6H4Cl).
2.3.2. Complexes 1-5
1, Yield: 0.31 g, 83%. M.p.: 196-200 °C. Anal. calcd. for C32H28O4N2S4Cd: C 51.57, H 3.79,
N 3.76, S 17.17. Found: C 51.35, H 3.66, N 3.55, S 17.02. IR (KBr, cm-1): 1494 ν(C=N),
1
1040 ν(C-S). H NMR (300.40 MHz, CDCl3, δ, ppm): 7.33-7.25 (m, 10H, -C6H5), 6.92-6.74
(s, 6H, -C6H3CH2O2), 5.91 (s, 4H, -CH2C6H3O2), 5.16-5.05 (s, 4H, -CH2C6H3CH2O2, -

CH2C6H5), 13C {1H} NMR (75.45 MHz, CDCl3, δ, ppm): 206.53 (CS2), 148.00, 147.43 (-
C6H5), 134.84, 128.82, 128.59, 127.96, 121.76 (-C6H3CH2O2), 108.73 (-CH2C6H3CH2O2),
57.43 (-CH2C6H5, -CH2C7H5O2), UV-Vis. (nujol/CH2Cl2, λmax, nm, ε (M-1 cm-1)): 320, 370,
425/270 (1.38 x 104), 290 (8.76 x 103).
2, Yield: 0.29 g, 81%. M.p. 179-183 °C. Anal. calcd. for C26H22O6N4S4Cd: C 42.95, H 3.05,
N 7.71, S 17.60. Found: C 42.75, H 2.98, N 7.60, S 17.41. IR (KBr, cm−1): 1516 ν(C=N),
1
1014 ν(C–S). H NMR (300.40 MHz, CDCl3, δ, ppm): 8.14-7.25 (m, 4H, -C6H4), 6.39-6.31
(m, 3H, C4H3O), 5.29 (s, 4H, -CH2C4H3O), 5.15 (s, 4H -CH2C6H5NO2). 13C {1H} NMR
(75.45 MHz, CDCl3, δ, ppm): 206.69 (CS2), 148.26, 142.67, 133.76, 128.86 (-C6H5), 110.68-
110.46 (-C4H3O), 58.05 (-CH2C6H5), 50.84 (-CH2C4H3O), UV-Vis. (nujol/CH2Cl2, λmax, nm,
ε (M-1 cm-1)): 320, 370, 425/270 (1.50 x 104), 290 (8.42 x 103).
3, Yield: 0.27 g, 80%. M.p. 125-130 °C. Anal. calcd. for C26H22F2O2N2S4Cd: C 46.39, H
3.29, N 4.16, S 19.01. Found: C 46.22, H 3.35, N3.95, S 18.83. IR (KBr, cm-1): 1508 ν(C=N),
1015 ν(C-S). 1H NMR (300.40 MHz, CDCl3, δ, ppm): 7.59-7.13 (m, 4H, C6H4), 6.39 (m, 3H,
-C4H3O), 5.13 (s, 4H, -CH2C4H3O), 5.06 (s, 4H -CH2C6H4F). 13C {1H} NMR (75.45 MHz,
CDCl3, δ, ppm): 208.74 (CS2), 163.06, 159.84, 149.16, 142.84, 129.41, 129.30 (C6H5),
110.62-109.56 (-C4H3O), 56.75 (-CH2C6H5F), 50.55 (-CH2C4H3O), UV-Vis. (nujol/CH2Cl2,
λmax, nm, ε (M-1 cm-1)): 320, 370, 425/ 270 (1.92 x 104), 290 (8.29 x 103).
4, Yield: 0.29 g, 83%. M.p. 140-145 °C. Anal. calcd. For C78H66Cl6O6N6S12Cd3: C 44.23, H
3.14, N 3.97, S 18.13. Found: C 44.05, H 3.20, N 3.79, S 17.76. IR (KBr, cm-1): 1465
1
ν(C=N), 1012 ν(C-S). H NMR (300.40 MHz, CDCl3, δ, ppm): 7.35-7.25 (m, 4H, -C6H4),
6.39-6.32 (m, 3H, -C4H3O), 5.17 (s, 4H, -CH2C4H3O), 5.04 (s, 4H -CH2C6H4Cl). 13C {1H}
NMR (75.45 MHz, CDCl3, δ, ppm): 206.70 (CS2), 148.26, 142.67, 133.76, 128.86 (-C6H5),
110.68-110.46 (-C4H3O), 58.05 (-CH2C6H5Cl), 50.84 (-CH2C4H3O), UV-Vis. (nujol/CH2Cl2,
λmax, nm, ε (M-1 cm-1)): 320, 370, 425/270 (1.40 x 104), 290 (5.15 x 103).
5, Yield: 0.27 g, 76%. M.p. 148-152 °C. Anal. calcd. For C60H52Cl4N4S8Cd2: C 49.62, H
3.61, N 3.86, S 17.62. Found: C 49.45, H 3.71, N 3.65, S 17.43. IR (KBr, cm-1): 1475
1
ν(C=N), 988 ν(C–S). H NMR (300.40 MHz, CDCl3, δ, ppm): 7.28-7.16 (m, 5H, -C6H5),
7.02-7.16 (m, 4H, -C6H4), 5.02 (s, 4H, -CH2C6H5), 5.07 (s, 4H -CH2C6H4). 13C {1H} NMR
(77.00 MHz, CDCl3, δ, ppm): 207.31 (CS2), 137.13, 134.75, 134.55, 131.04, 130.81, 130.32

(-C6H5), 128.75-122.74 (-C6H4), 58.28 (-CH2C6H5), 57.90 (-CH2C6H4Cl), UV-Vis.
(nujol/CH2Cl2, λmax, nm, ε (M-1 cm-1)): 320, 370, 425/270 (2.31 x 104), 290 (7.81 x 103).
2.4. X-ray structure determinations
Single crystal X-ray diffraction data for the samples were measured on an Oxford
Diffraction X-calibur CCD diffractometer using Mo Kα radiation at 293 K for all samples,
except for 4 where the temperature was 150 K. Data reductions were carried out using the
CrysAlis program [9]. The structures were solved by direct methods using SHELXS-97 [10]
and refined on F2 by a full matrix least squares technique using SHELXL-97 [11]. Non-
hydrogen atoms were refined anisotropically and hydrogen atoms were geometrically fixed
with thermal parameters equivalent to 1.2 times the Ueq value of the appropriate carrier atom.
In 2 the five-membered rings are disordered with the oxygen atoms at two positions given
occupation factors of x and 1-x, with x refining to 0.55(2). In 4, a similar disorder was found
in the furan rings with the oxygen atoms at two positions. The disorder was treated similarly
with x refining to 0.52(4). In complex 5 the chlorine atom is disordered over two positions
and x refined to 0.613(9). Diagrams for all the complexes were drawn using the ORTEP,
Diamond and Mercury softwares [12].
2.5. Theoretical calculations
Single point calculations were carried out using the Gaussian 03 program [13]. Structures
were optimized using the B3LYP density functional together with basis sets LANL2DZ for
Cd, 6-31+G* for S and 6-31G for the remaining atoms. Input models were taken from the
crystal structures, but with hydrogen atoms given theoretical positions.
3. Results and discussion
The homoleptic complexes 1-5 were obtained in good yields by facile metathetical
reactions between Cd(OOCCH3)2·2H2O and the potassium salt of the ligands (KL1-KL6) in a
1:2 molar ratio, in 80:20 v/v methanol:water solution. The complexes are air-stable and melt
in the 125-200 °C temperature range. All the complexes have been characterised by
spectroscopy (IR, 1H and 13C NMR and UV-Vis.) and their solid phase luminescent behaviors
have been studied. Solid state structural determinations by X-ray crystallography revealed
polymeric (1-3), trinuclear (4) and dinuclear (5) structures. The justification for the formation
of rare polymeric (1-3) and trinuclear (4) structures and the involvement of remarkable C-
H…F, C-H…O and H...H interactions observed in some complexes, sustaining the

supramolecular structures, have been assessed by theoretical calculations. Their solution and
solid phase luminescence have been studied. The TGA decomposition products, yielding CdS
particles, have been examined by PXRD and HRTEM.
In the solid phase, when excited at 290-300 nm (Figure 2) complexes 1-5 show an emission
band near 400 nm with a Stokes shift of 80-100 nm, originating from the metal perturbed
ILCT states of the dithiocarbamate ligands. It is to be noted that despite conformational
rigidity upon coordination of the ligands to the metals and the extended structures, the
luminescent intensity of the polymeric complexes 1-3 are somewhat weaker due to the
presence of more the electronegative substituents F, N and O in the benzene ring of the
dithiocarbamate group acting as quencher than the tri- and dinuclear analogs (4 and 5) which
contain the relatively less electronegative chlorine atom. Upon excitation at 280 nm (Figure
S1) in CH2Cl2 solution, complex 5 show an emission band near 330 nm, whereas the polymer
2 and trimer 4 show emissions near 440 nm. This significant difference in emission spectra
between solid and solution may be attributed to the changes of the structures in solution.
------------------------------------------------Figure 2 -------------------------------------------------
3.1. Crystal Structures
Single crystals of complexes 1-5 were obtained within 3-4 weeks from a dichloromethane
solution layered by acetonitrile. Their molecular structures have been determined by X-ray
crystallography and are depicted in Figures S2-S4. Crystal data and refinement details are
listed (Table 1) and selected bond lengths and bond angles are given in Tables S1-S3
.
------------------------------------------------Table 1------------------------------------------------------
The Cd2+ ion, with a d10 configuration, shows no stereochemical preferences arising from
ligand field stabilization effects and therefore in principle it can display a variety of
coordination numbers, viz. 4, 5 and 6, and geometries. The crystallographic asymmetric unit
of 1-3 consists of one formula unit of the complexes [Cd(L)2]∞ (L = L1 1, L2 2, L3 3). These
complexes adopt similar structures in which the cadmium atom has a six coordinate distorted
octahedral environment and forms 1D coordination polymeric structures (Figure 3) based on
sequential edge-shared octahedra (Figure S5). In 1, 2 and 3 each dithiocarbamate group is
bonded to the cadmium atom in a µ2,κ2-S,S chelating-bridging fashion. In all three structures,
the metal atom occupies a 2-fold axis, being bonded to the ligand in a asymmetric bidentate
fashion with the Cd(1)-S(11) bond distance (range 2.541(1)-2.578(1) Å) being shorter than
the Cd(1)-S(13) bond distance (range 2.791(2)-2.822(1) Å). In addition, the Cd(1)-S(13i)

bond distances are in the range 2.749(1)-2.760(2) Å. These distances to S(13) and S(13i) are
somewhat longer than those observed for dimeric Cd(II) dithiocarbamate complexes (Table
2) [4a,5a] because of the higher coordination number of 6 about the metal center in the
polymeric structures. The justification for this polymeric structure has been investigated by
DFT calculations. First the energy of the monomeric 4-coordinate fragment was calculated
and compared to the structure containing a central 6-coordinate metal with 2 outer 5-
coordinate metals. The energy difference E(trimer)-3*E(monomer) is -42.55 kcal mol-1, thus
validating the formation of the trimer. However, it is clear that the structure of the 4-
coordinate fragment from the polymer, with a very distorted equatorial plane, is not what
would be found in such a moiety and therefore the structure was geometry optimized and
refined as expected to a tetrahedral structure in which the two chelate planes are
perpendicular. This trimeric fragment, taken from complex 1, was also geometry optimised
and the resulting energy difference of E(trimer)-3*E(monomer) reduced to -17.25 kcal mol-1.
------------------------------------------------Table 2------------------------------------------------------
The complexes 1-3 are rare examples of Cd(II) bis(dithiocarbamate) coordination polymers,
reported to date for the Py(N) [4a] or the S,S- donor [5a] atoms of the dithiocarbamate
ligands. They can be described as clathrates that contain channels in which the second
component can be trapped [14] (Figure S6).
------------------------------------------------Figure 3 -------------------------------------------------
A noteworthy feature of 1 is the formation of an unusual closed-shell hydrogen-hydrogen
(H-H = 2.34 Å) interaction (Figure 4) between the piperonyl hydrogen atoms of the
dithiocarbamate groups on neighboring molecules in the polymeric structure, which is
smaller than the sum of the van der Waals radii for the hydrogen atoms. This may be
attributed to the hydrogen atoms attached to the carbon atom bonded to oxygen atoms under
consideration that may induce partial positive and negative charges on the hydrogen atoms
involved in bonding [15]. Such a type of H-H interaction is rare and distinctly different from
the hydrogen, dihydrogen, agostic and anagostic bonding in the compounds [15a].
To test the significance of this interaction, we constructed a dimer containing two such
interactions (Figure 4) However single-point calculations show that the energy difference
E(dimer)-2*E(monomer) is +0.59 kcal mol-1 and therefore in this case these H…H
interactions are slightly repulsive.

------------------------------------------------Figure 4 -------------------------------------------------
The structures of complexes 2 and 3 are stabilized by non-covalent (C(37)-H...O(1/2-x,-
1/2+y, 3/2-z), 2.373, π···π, 4.352, 5.200; 2.654; C-H···S, 2.925 Å) and (C(31)-H···(F-C)(1-
x,1/2+y,3/2-z), 2.516,9 C(34)-H···(F-C)(3/2-x, -1/2+y, 3/2-z2.777 Å; C-H···π, 3.575 Å) [16]
interactions (Figures 5, 6, S7 and S8). The C-H···O interactions have been investigated by
DFT calculations. As shown in Figure 5, two molecules are connected across a centre of
symmetry by two C-H…O interactions. Single point energy calculations show E(dimer)-
2*E(monomer) to be -1.46 kcal mol-1, indicating a weak attractive interaction. There are two
C-H···F interactions of interest. One C-H···F interaction, shown in Figure 6, gave a value of -
1.74 kcal mol-1 for E(dimer)-2*E(monomer). In addition there are two C-H···F interactions
across a centre of symmetry, and here the E(dimer)-2*E(monomer) difference was calculated
as -2.49 kcal mol-1. In the crystal packing of 1-3, the central CdC2S4 core formed by the
surrounding molecules organize a ‘flower-like’ pattern along the ‘c’ axis (Figure S9).
------------------------------------------------Figure 5 -------------------------------------------------
------------------------------------------------Figure 6 -------------------------------------------------
Unlike the polymeric structures established for 1-3, complex 4 is a rare centrosymmetric
trinuclear molecule [4a] where six dithiocarbamate ligands are uniquely bonded to three
cadmium atoms in a κ2 S,S-chelating-bridging as well as S,S-chelating fashion. As shown in
Figures 7 and S3, the inner Cd(1) atom is situated on a centre of symmetry in a six-coordinate
octahedral environment, while the outer Cd(2) atoms occupy square pyramidal environments.
These terminal Cd(2) atoms are asymmetrically S,S-chelated by two dithiocarbamate ligands
with distances to the S(11) and S(13) atoms of 2.550(2) and 2.652(2) Å and to the S(41) and
S(43) atoms of 2.554(2) and 2.709(2) Å respectively. The longer bond formed to the S(43)
atom is no doubt due to the fact that it forms a bridge to the Cd(1) atom. The geometry
around the Cd(2) atom is best considered as a highly distorted square pyramid as the τ value
is 0.30 compared to 0.0 for an ideal square pyramid and 1.0 for a trigonal bipyramid. The
two chelating ligands around the Cd(2) atom intersect at an angle of 35.11(5)o and form a
distorted equatorial plane with an r.m.s. deviation of 0.186 Å. Thus the environment of the
Cd(2) atom is very different from that of the Cd(1) atom where the equatorial plane is
perforce planar. The metal atom Cd(2) is displaced by 0.577(1) Å from the equatorial plane
in the direction of the S(71) atom, bonded at a distance of 2.638(2) Å and which occupies an

axial position and also forms a bridge to the Cd(1) atom. Thus the dithiocarbamate groups are
bonded to the central Cd(1) and terminal Cd(2) atoms in a µ2,κ2 S,S-chelating-bridging
manner, thereby spectacularly forming a trinuclear structure. In this complex the central
Cd(1) atom lies at the center of symmetry and is bonded to two chelating dithiocarbamate
groups via the atoms S(71) and S(73) at distances of 2.707(2) and 2.585(2) Å, the longer
bond being found to the bridging sulfur atom S(71). Additionally, two S(43) atoms, which
are already bonded to the Cd(2) atom, occupy axial positions at the Cd(1) atom at 2.889(2) Å,
completing the distorted octahedral geometry about Cd(1) centre.
------------------------------------------------Figure 7------------------------------------------------------
The Cd(1)⋯Cd(2) distance of 3.851(1) Å within the molecule may indicate weak metal-
metal interactions. The supramolecular structure of this complex is stabilized by C-H···π, C-
H···S (Figure S10) and C-H···Cl interactions, as shown in Figure S11a. Notably the oxygen
atom on the furfuryl ring and sulfur atom in the dithiocarbamate unit form a seven-membered
ring tropolium-like structure, thereby stabilizing the supramolecular network in the crystal
structure of 4 (Figure S11b).
Single point DFT calculations were carried out on the trimer and the individual four-
coordinate monomers around the Cd(1) and Cd(2) atoms. The energy of the symmetric square
planar monomer around the Cd(1) atom was found to be more stable by -9.82 kcal mol-1 than
the distorted geometry around the Cd(2) atom. The trimer was found to be more stable by -
26.98 kcal mol-1 compared to the three distinct monomers, showing that the trimer is more
stable in the gas phase and that its formation in the crystal structure is not due to packing
effects.
Complex 5 forms a centrosymmetric dimeric structure (Figure S4), which is similar to the
few structurally characterized cadmium(II) dithiocarbamate complexes reported so far
[5,17,18]. The cadmium atom is bonded to two bidentate ligands at 2.545(3)-2.607(3) Å and
an additional sulfur atom S(41i) at a distance of 2.610(2) Å, which bridges to the other metal
atom. The two four-membered bidentate rings intersect at an angle of 49.4(1)o in 5. In the
dimeric structure the cadmium atoms are five-coordinate with a τ value of 0.618, thus
indicating that 5 has a distorted trigonal bipyramid geometry.
A comparison of the geometrical details of complexes 1-5 are given in Table 2. The closest
S···S contacts in the range 3.903-4.118 Å in complexes 1-5 do not account for the substantial

S···S intermolecular interactions in the solid state. Concomitant with the distances at 1.33(1)-
1.34(1) Å, the C-N bonds are intermediate between C-N single and double bond lengths in 1-
5, due to the dominant contribution of the canonical form. The C-S bond lengths in the range
1.695(5)-1.750(5) Å are shorter than the C-S single bond distance of 1.82 Å due to partial
conjugation over the N-C-S unit.
4. Thermal decomposition
The TGA plots are displayed (Figure S12) and the results are summarized in Table 3. The
TGA curves show a single step decomposition with the loss of organic fragments between
o
226 and 379 C, leaving residues consistent with the values calculated for the mass
percentage of bulk CdS. TG analyses reveal that complexes 1-5 may serve as potential single
source precursors for the formation of CdS materials.
------------------------------------------------Table 3------------------------------------------------------
The powder X-ray diffraction patterns (PXRD) for the TGA residues of 1-5 (Figure S13)
show broadened peaks indicating that the particles of CdS are of nanosize. The d-spacing
observed at (2θ) 26.5o corresponds to the [002] plane of hexagonal CdS [19a]. All
compounds show peaks at (110), (103) and (112) characteristic of wurtzite CdS [19b] in the
XRD patterns. A comparison of the diffraction peak positions of the TG decomposition
products with those of the standard (ICDD card no. 41-1049, 65-3414) reveals the hexagonal
phase of CdS.
The HRTEM images of CdS particles produced by the TGA decomposition of
representative complexes 1, 4 and 5 are displayed (Figure S14, a-f). The HRTEM results
show that the CdS nanoparticles [19] are approximately spherical in shape with a particle size
of 50 nm, shown in Figure S14 (a), (c) and (e). Further resolution at 5 nm shows rod-shaped
particles of for the decomposition product of 1, 4 and 5, Figure S14 (b, d and f).
4. Conclusions
New functionalized cadmium bis(dithiocarbamate) complexes having rare polymeric (1-
3), trinuclear (4) and dinuclear (5) structures have been synthesized and fully characterized.
In these complexes the supramolecular structures are shown to be sustained by attractive
H···H, C-H···F, C-H···O, C-H···Cl, C-H···S, C-H···π and π···π, interactions. The unusual
structures of 1-4 and the H···H, C-H···O, C-H···F-C interactions have been supported by
theoretical calculations. Complexes 1-5 show luminescent characteristics in solution and in

the solid phase. A study of their TG decomposition products reveals that they could serve as
single source molecular precursors for the preparation of CdS nanoparticles.
Acknowledgements
We gratefully acknowledge the Science and Engineering Research Board (SERB) for
financial support through Project: SB/SI/IC-15/2014 (NS), the University Grants
Commission (UGC), New Delhi for SRF (KKM) and the Department of Chemistry, CAS-
UGC-I, Banaras Hindu University for the X-ray and infrastructural facilities. We also thank
the University of Reading and EPSRC for funds for the diffractometer used for determination
of the structure of 4.
Appendix A. Supplementary data
CCDC 1400102-1400105 and 1400107 contains the supplementary crystallographic data for
1-4
and
5.
These
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 email:
deposit@ccdc.cam.ac.uk. Supplementary data associated with this article can be found, in the
online version, at http://dx.doi.org.
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Table 1. Crystallographic data and refinement parameters for complexes 1-5
Compound
1
2
3
4
5
Chemical formula C32H28Cd1N2O4S4 C26H22Cd1N4O6S4 C26H22Cd1F2N2O2S4 C78H66Cd3 Cl6 N6 O6 S12 C60H52Cd2Cl4N4S8
Formula weight
Crystal system
Space group
a(Å)
745.20
monoclinic
C2/c
727.12
monoclinic
C2/c
673.10
monoclinic
I2/a
2118.00
triclinic
P1
1452.14
triclinic
P1
29.600(11)
12.999(5)
8.137(4)
90
32.563(3)
11.0399(9)
8.0979(6)
9990
8.1055(4)
11.0157(5)
29.7296(15)
90
12.480(5)
13.775(5)
14.028(5)
109.396(5)
103.317(5)
97.946(5)
2152.1(14)
1
10.9841(18)
12.627(2)
12.6482(17)
110.124(14)
107.153(13)
95.680(14)
1534.1(4)
1
b (Å)
c (Å)
α (ᵒ)
β (ᵒ)
94.250(5)
90
99.808(7)
90
92.814(5)
90
γ (ᵒ)
V (Å3)
3122(2)
4
2868.6(4)
4
2651.3(2)
4
Z
ρcalc (g cm-3)
1.585
1.684
1.686
1.634
1.572
T (K)
293(2)
1.007
293(2)
1.101
150(2)
1.181
293(2)
293(2)
µ (Mo Kα) (mm-1)
F(000)
1.266
1.182
1512
1464
1352
1062
732
Reflections
collected
12147
3514
6280
3179
9124
3852
17581
9480
11579
6752
Independent
reflections
Reflections with I
2555
2379
3354
5269
3005
> 2σ(I)
Final indices [I
>2σ(I) ]R1 , wR2
0.0601,0.1578
0.0500, 0.1297,
0.0295, 0.0653
0.0630, 0.1486
0.0952, 0.2551
a
b
R1[a],wR2[b] [all
data]
0.0838, 0.1816
0.979
0.0715, 0.1437
1.088
0.0368, 0.0682
1.054
0.1259, 0.1805
0.959
0.1865, 0.3086
0.925
GOF c
Residual
electronDensity,
e/Å3
1.855, -1.597
0.845, -0.648
0.430, -0.739
1.289,0.742
1.888, -0.737
b
aR1 = Σ ║Fo│-│Fc║/ Σ │Fo│, wR2 = {[Σ w (Fo2– Fc2)/ Σ w (Fo2)2]}1/2 , cGOF= S= { Σ [w(Fo2-Fc2)2]/(n-p)}1/2,
where n is the number of reflections, and p is the number of the refined parameters.

Table 2. A comparison of selected geometrical details of complexes 1-5 with previously reported analogous
dithio complexes
Complex
Cd-S (Å)
Geometry
OCT
OCT
OCT
OCT
OCT
OCT
OCT
SP, OCT
SP, OCT
TBP
Structure
1-D polymer
1-D polymer
1-D polymer
1-D polymer
2-D polymer
2-D polymer
2-D polymer
Trinuclear
Ref
a
[Cd(CS2C7H5O2CH2NCH2C6H5)2]∞ (1)
[Cd(CS2C6H4NO2CH2NCH2C4H3)2]∞ (2)
[Cd(CS2C6H4FCH2NCH2C4H3O)2]∞ (3)
[{Cd[S2CN(iPr)CH2CH2OH]2}3·MeCN]∞
[Cd(S2CC5H4NCH2NCH2C6H5)2]∞
[Cd((S2CC5H4NCH2)2N)2]∞
2.5781(14)- 2.7914(17)
2.5744(11-2.7719(11)
2.5413(5)- 2.8219(5)
2.580-2.774
a
a
5a
4a
4a
4a
a
2.6521(10)-2.6874(9)
2.6629(9)-2.6800(9)
2.6251(9)-2.6773(9)
2.5499(18)-2.8885(17)
2.5384(17)-2.9143(13)
2.540(3)- 2.842(3)
2.579-2.742
[Cd(S2CC5H4NCH2NCH2C4H3O)2]∞
[Cd3(S2CClC6H4CH2NCH2C4H3O)6] (4)
[Cd3(S2CCH3C6H4CH2NCH2C4H3O)6]
[Cd2[S2C 3-ClC6H4CH2NCS2CH2C6H5] (5)
[Cd2[S2CN(iPr)CH2CH2OH]4·2H2O·2MeCN]
[Cd2(S2CC8H6NCH2NCH2NC5H4)4]
[Cd(S2CNC4H10)2]2
Trinuclear
4a
a
Dinuclear
SP
Dinuclear
5a
4a
5b
5c
2.5701(14)- 2.6895(14)
2.5359(5)- 2.8123(5)
2.513(5)- 2.888(5)
SP
Dinuclear
SP
Dinuclear
Cd[S2CN( n -C4H9)2] 2
TBP
Dinuclear
aThis work. OCT = octahedral, SP = square pyramid , TBP = trigonal bipyramidal.
Table 3. TGA results for complexes 1-5
Residue wt.
T in TGA
Expected product
observed (calcd.)
(°C)
of decomposition
%
1
2
3
4
5
260-332
240-379
238-307
226-308
260-355
38.9(35.39)
CdS
CdS
CdS
CdS
CdS
59.5(61.64)
64.1(64.66)
40.9(40.25)
39.8(40.76)

Figures with captions
Figure 1. Potassium salts (KL1-KL5) of the dithiocarbamate ligands used in this work.
Figure 2. Photoluminescence spectra of complexes 1-5 in the solid phase.

Figure 3. Polymeric structure of 1.
Figure 4. The C–H⋯H-C interactions in complex 1 involved in the supramolecular network organization
(hydrogen atoms, except those involved in the interactions, are omitted for clarity).

Figure 5. Supramolecular structure of 2 stabilized by C–H⋯O interactions (hydrogen atoms, except those
involved
in
the
interactions, are omitted for clarity).

Figure 6. Supramolecular structure of 3 sustained by C–H⋯F-C interactions (hydrogen atoms, except those
involved in the interactions, are omitted for clarity).
Figure 7. Coordination environment about the Cd atoms in 4 (with hydrogen atoms omitted for clarity).

Justification
•
Five Cd(II) complexes of new functionalized dithiocarbamate ligands have been
synthesized and characterized.
•
•
X-ray crystallography has revealed rare polymeric and trimeric structures.
The supramolecular structures have been sustained by C-H....F-C, C-H...O and H...H
non-covalent interactions, which have been corroborated by theoretical calculations.
•
•
All the complexes showed luminescent characteristics.
TG analysis and decomposition products have been examined.

Graphical Abstract
Homoleptic cadmium(II) bis(dithiocarbamate) complexes displaying 1D coordination
polymeric (1-3), trimeric (4) and dimeric (5) structures have been synthesized and fully
characterized. Their luminescent properties have been studied.