Supramolecularly linked linear polymers of thallium(I) dithiocarbamates: Steric influence on the supramolecular interactions of methyl and ethylcyclohexyl dithiocarbamates of thallium(I)

Article abstract of DOI:10.1016/j.ica.2010.09.029

Spectral and single crystal X-ray structural studies on [Tl(mchdtc)] ₂ (1) and [Tl(echdtc)]₂ (2) (where mchdtc = methylcyclohexyldithiocarbamate and echdtc = ethylcyclohexyldithiocarbamate) were carried out. Both the synthesized comp

Full text of DOI:10.1016/j.ica.2010.09.029

Inorganica Chimica Acta 365 (2011) 480–483
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Note
Supramolecularly linked linear polymers of thallium(I) dithiocarbamates: Steric
influence on the supramolecular interactions of methyl and ethylcyclohexyl
dithiocarbamates of thallium(I)
Nagarajan Alexander a, Kuppukkannu Ramalingam a, , Corrado Rizzoli b
⇑
a Department of Chemistry, Annamalai University, Annamalainagar 608 002, Tamil Nadu, India
b Dipartimento di Chimica Generale ed Inorganica, Chimica Analitica, Chimica Fisica, Viale G.P. Usberti 17/A, Universita di Parma, I-43100 Parma, Italy
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 11 May 2010
Received in revised form 27 August 2010
Accepted 18 September 2010
Available online 29 September 2010
Spectral and single crystal X-ray structural studies on [Tl(mchdtc)]2 (1) and [Tl(echdtc)]2 (2) (where
mchdtc = methylcyclohexyldithiocarbamate and echdtc = ethylcyclohexyldithiocarbamate) were carried
out. Both the synthesized complexes were characterized by UV–Vis, fluorescence, IR, 1H and 13C NMR
spectra. IR spectra of the complexes show the contribution of the thioureide form to the structures. Both
compounds show weak fluorescence. The bond valence sums calculated for the complexes support the
highly covalent nature of the Tl–S interactions. A TlꢀꢀꢀꢀH short interaction observed in the methyl analogue
is totally absent in (2) because of the change in conformation of the cyclohexyl ring due to the introduc-
tion of ethyl group. Though the neighbouring non-bonded groups are flexible, thallium adjusts its thall-
ophilic contacts to retain a hemisphere free for its pair of ‘s’ electrons in the presence of a sterically
demanding ethyl group.
Keywords:
Thallium
Dithiocarbamates
Thioureide
Supramolecular
Single crystal X-ray structure
Ó 2010 Elsevier B.V. All rights reserved.
1. Introduction
films [7]. Chloro complex of thallium ions is largely related to the
application of triplet emitters in organic light emitting diode
Compounds of thallium show interesting structural and chemi-
cal properties. Thallium diethyldithiocarbamate is used for high-
resolution mapping of neuronal activity using noxious stimulation
in rats and acoustic stimulation, intracortical microstimulation and
pharmacological inhibition of neuronal activity with muscimol in
Mongolian gerbils [1]. TlAMG technique is used in activity-
dependent neuronal Tl+ uptake in the brain after intraperitoneal
injections of thallium(I) acetate [2]. The most dominant application
of Tl+ is the use of 201Tl for single photon emission computed
tomography (SPECT) imaging in humans, in particular for imaging
myocardial viability [3]. Thallium compounds find practical appli-
cation in the production of optical glass, lenses for IR equipment
and scintillation sensors, thallium containing complex oxides are
used in production of high-temperature superconductor [4]. Me-
tal–organic coordination polymers are attracting attention because
of their potential use as functional materials [5]. Tl(I) metalloor-
ganic compounds exhibit supramolecular interactions. The nature
of such supramolecular interactions is predicted by investigating
various ligand–thallium interactions [6]. Laser ablation is a well
known method of laser processing, laser ablation of thallium(III)
oxide is used for the production of related nanoparticles and thin
(OLED) technology [8]. From an inorganic chemist’s standpoint,
dithiocarbamates are highly versatile ligands towards main group
metals. They can stabilize a variety of oxidation states and coordi-
nation geometries and seemingly small modifications to the ligand
can lead to significant changes in the structural behaviour of the
complexes formed.
The structural parameters of the dithiocarbamate ligands them-
selves are not modified significantly on coordination to main group
elements [9]. Tl(I) and Tl(III) dithiocarbamates have been structur-
ally characterized [10–13]. The present work describes the synthe-
sis, spectroscopic, single crystal X-ray structural characterization
of [Tl(mchdtc)]2 (1) and [Tl(echdtc)]2 (2) [mchdtc = meth-
ylcyclohexyldithiocarbamate and echdtc = ethylcyclohexyldithioc-
arbamate]. Steric influence of the substituents on the
supramolecular interactions prevailing in the compounds is
analyzed.
2. Experimental
All the reagents and solvents employed were commercially avail-
able analytical grade materials and were used as supplied, without
further purification. IR spectra were recorded on ABB Bomen MB
104 spectrometer (range 4000–400 cmꢁ1) as KBr pellets. The elec-
tronic spectra were recorded in ethanol on a HITACHI U-2001
⇑
Corresponding author. Cell: +91 9443444154.
E-mail address: krauchem@yahoo.com (K. Ramalingam).
0020-1693/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2010.09.029

N. Alexander et al. / Inorganica Chimica Acta 365 (2011) 480–483
481
Table 1
Spectral data (NMR chemical shifts in ppm).
Complex
Uv–Vis nm
IR (cmꢁ1
)
NMR
a-CH
b-CH2
c
-CH2
d-CH2
a0-CH3/CH2
b0-CH3
N13CS2
(1)
434a
407b
434a
411b
1472*
1077**
1454*
1091**
1H
5.27(a)
61.67
5.23(a)
62.26
1.81–1.88(e)
30.34
1.81–1.91(e)
31.02
1.67–1.71(e)
3.43
35.05
3.90
–
–
–
13C
1H
25.63–25.48
25.79
202.4
–
202.0
(2)
1.70(e)
25.49
1.30–1.36
14.76
13C
42.98
*
**
a
mC–N
.
mC–S
.
CT.
b
Fluorescent bands excitation wavelength 350 nm.
Table 2
Crystal data, data collection and refinement parameters for [Tl(mchdtc)]2 and [Tl(echdtc)]2.
[Tl(mchdtc)]2 (1)
[Tl(echdtc)]2 (2)
Empirical formula
Formula weight
C
16H28N2S4Tl2
C18H32N2S4Tl2
813.4
785.4
Crystal dimension/mm
0.24 ꢂ 0.08 ꢂ 0.07
0.17 ꢂ 0.12 ꢂ 0.10
monoclinic
P21/n
6.6955(4)
15.4769(9)
12.3236(7)
105.2202(10)
1232.25(12)
2
Crystal system
Space group
a (Å)
b (Å)
c (Å)
monoclinic
P21/n
6.2451(4)
18.6625(12)
9.6616(7)
95.8057(12)
1120.28(13)
2
b (°)
U (Å3)
Z
Dcalc (g cmꢁ3
)
2.328
14.741
2.192
13.405
l
(cmꢁ1
)
F(0 0 0)
728
760
k (Å)
0.71073
0.71073
Index ranges
ꢁ7 6 h 6 7; ꢁ23 6 k 6 23; ꢁ11 6 l 6 11
ꢁ8 6 h 6 8; ꢁ18 6 k 6 18; ꢁ14 6 l 6 14
Reflections collected
Observed reflections
Rint
2214
1883
0.058
2224
1871
0.055
2
2
w ¼ 1=½r2ðF20Þ þ ð0:0447PÞ ꢃ where P ¼ ðF02 þ 2F2c Þ=3
W ¼ 1=½r2ðF20Þ þ ð0:0586Þ ꢃ where P ¼ ðF02 þ 2F2c Þ=3
Weighting scheme
Number of parameters refined
Final R1, wR2 (observed data)
Goodness-of-Fit(GOF)
110
0.0282, 0.0695
1.001
119
0.0397, 0.0894
1.059
spectrometer. Fluorescence spectra of the complexes were recorded
in ethanol. To prevent any non-linearity of the fluorescent intensity,
350 nm was chosen as the excitation wavelength. NMR spectra were
recorded on a Bruker 400 MHz spectrometer at room temperature
using CDCl3 as solvent.
decomposition temperature and compositions for the two com-
plexes are as follows: [Tl(mchdtc)]2 (Yield: 65%; dec. 224 °C). Anal.
Calc. for C16H28N2S4Tl2 (785.38); C, 24.47; H, 3.60; N, 3.57. Found:
C, 24.34; H, 3.20; N, 3.27%. And [Tl(echdtc)]2 (Yield: 67%; dec.
194 °C). Anal. Calc. for C18H32N2S4Tl2 (813.44); C, 26.58; H, 3.40;
N, 3.44. Found: C, 26.27; H, 3.26; N, 3.21%.
2.1. X-ray crystallography
3. Results and discussion
Intensity data were collected at ambient temperature (295 K)
on a Bruker SMART 1000 CCD diffractometer using graphite mono-
3.1. Infrared, electronic, fluorescence and NMR spectral studies
chromated Mo K
a radiation (k = 0.71073 Å) [14]. All the non-
hydrogen atoms were refined anisotropically and the hydrogen
atoms were fixed geometrically. Details of crystal data, data collec-
tion and refinement parameters for (1) and (2) are summarized in
Table 2.
Spectral data for the compounds are shown in Table 1. The a-CH
and a0-CH3 protons are affected by the complexation to a maxi-
mum extent as a result of deshielding. In the cyclohexyl ring all
the equatorial protons are deshielded to a large extent compared
to the axial protons. Thioureide carbon shows the signal at
202.4 ppm in compound (1) and at 202.0 ppm in (2).
2.2. Preparation of (disubstituted dithiocarbamato)thallium(I);
[Tl(R1R2dtc)]2
3.2. BVS calculation
N-Methyl N-cyclohexylamine (2 mmol, 0.26 mL) in ethanol and
carbon disulphide (2 mmol; 0.12 mL) in ethanol were mixed under
ice-cold condition (5 °C) to obtain yellow dithiocarbamic acid solu-
tion. To the freshly prepared dithiocarbamic acid solution, an aque-
ous solution of TlF (2 mmol, 0.446 g) was added with constant
stirring. A pale yellow solid separated from the solution, which
was filtered, washed with alcohol and was dried in air. A similar
procedure was employed for the preparation of the N-ethyl N-
cyclohexylamine (2 mmol, 0.29 mL) analogue. Percentage of yield,
For both the complexes, bond valence sums were calculated by
summing up the bond valence contributions from five Tl–S and one
TlꢀꢀꢀꢀC interactions [15]. The values are 1.2689 and 1.2897 for com-
plexes (1) and (2) respectively. In the above complexes, the values
are higher than the expected formal oxidation state of +1. The
higher values observed in the present set of compounds support
the fact that the Tl–S bonds are more covalent and the back bond-
ing effects are very highly pronounced [16].

482
N. Alexander et al. / Inorganica Chimica Acta 365 (2011) 480–483
Table 3
Selected bond distances (Å) and bond angles (°) for compounds (1) and (2).
1
2
Tl(1)-S(1)
Tl(1)-S(1)i
Tl(1)-S(2)
Tl(1)-S(2)i
S(1)-C(1)
S(2)-C(1)
N(1)-C(1)
2.975(1)
3.086(1)
3.162(1)
3.165(2)
1.722(5)
1.729(5)
1.340(6)
Tl(1)-S(1)
Tl(1)-S(1)ii
Tl(1)-S(2)
Tl(1)-S(2)ii
S(1)-C(1)
S(2)-C(1)
N(1)-C(1)
3.078(2)
3.063(2)
2.982(2)
3.164(2)
1.720(6)
1.730(6)
1.340(7)
S(1)-Tl(1)-S(1)i
S(1)-Tl(1)-S(2)
S(1)i -Tl(1)-S(2)
S(1)-Tl(1)-S(2)i
S(2)-Tl(1)-S(2)i
C(1)-S(1)-Tl(1)i
Tl(1)-S(1)-Tl(1)i
C(1)-N(1)-C(8)
C(1)-N(1)-C(2)
106.52(3)
57.59(3)
81.00(3)
82.69(4)
110.05(3)
86.20(15)
73.48(3)
120.6(4)
122.7(4)
S(1)-Tl(1)-S(1)ii
S(1)-Tl(1)-S(2)
S(1)ii -Tl(1)-S(2)
S(1)-Tl(1)-S(2)ii
S(2)-Tl(1)-S(2)ii
C(1)-S(1)-Tl(1)ii
Tl(1)-S(1)-Tl(1)ii
C(1)-N(1)-C(8)
C(1)-N(1)-C(2)
106.89(4)
58.38(4)
81.70(5)
78.61(4)
107.02(4)
87.1(2)
73.11(4)
120.7(5)
121.9(4)
Fig. 3. Stacking of [Tl(mchdtc)]2 in the unit cell.
Symmetry codes: (i) 1-x, 1-y, -z; (ii) 2-x, 1-y, 1-z.
Fig. 1. ORTEP diagram of [Tl(mchdtc)]2 (30% probability level; i = 1 ꢁ x, 1 ꢁ y, ꢁz).
Fig. 4. ORTEP diagram of [Tl(echdtc)]2 (30% probability level: i = 2 ꢁ x, 1 ꢁ y, 1 ꢁ z).
Fig. 2. Linear polymeric chains of [Tl(mchdtc)]2.
Fig. 5. Linear polymeric chains of [Tl(echdtc)]2.
3.3. Structural analysis
of 3.428(4) Å. (the sum of the van der Waals radii for Tl and C is
3.73 Å) [16]. Interestingly, the TlꢀꢀꢀꢀTl distance in the complex with-
in a dimer is 3.626(5) Å, which is shorter than sum of the van der
Waals radii (3.92 Å), suggesting the presence of a TlꢀꢀꢀꢀTl interac-
tion. Coordination of a bulky Tl(I) ion, results in the widening of
the S–C–S angle to 118.2(3)° (normal angle ꢄ109°). The widening
of the angles enhances a stronger interaction between thallium
and carbon atom in addition to the sulphurs. In the crystal packing,
a long range interaction of 3.347(1) Å connects each thallium atom
Selected bond lengths and bond angles for (1) and (2) are given
in Table 3. The ORTEP diagram of [Tl(mchdtc)]2 is shown in Fig. 1.
Tl(I) is bound to a single molecule of mchdtc by a short and a rel-
atively long sulphur interaction measuring 2.9747(14) and
3.1621(14) Å. In addition, in the dimeric unit, it is also bound to
the sulphurs of a centrosymmetrically-related mchdtc molecule
at 3.086(1) and 3.165(2) Å. A weak interaction prevails between
the Tl and C(l) atoms of the dithiocarbamate moiety at a distance
with
a sulphur atom of an adjacent dimeric unit, forming

N. Alexander et al. / Inorganica Chimica Acta 365 (2011) 480–483
483
one-dimensional polymeric chains along the crystallographic a
axis involving supramolecular interactions (Fig. 2). The Tl–S–Tl an-
gle within the chain is 152.21°. Stacking of the chains along the c
axis reveals the presence of TlꢀꢀꢀꢀH contacts (2.96 Å; Fig. 3), which
are among the shortest reported so far [17].
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.ica.2010.09.029.
The ORTEP diagram of [Tl(echdtc)]2 is shown in Fig. 4. The coor-
dination geometry of the metal is very similar to that observed in
(1), with the thallium atom bound to two sulphur atoms of the
same echdtc molecule at 2.982(2) and 3.078(2) Å and to two other
sulphurs of a centrosymmetrically-related dithiocarbamate moiety
at 3.063(2) and 3.164(2) Å. A relatively weak TlꢀꢀꢀꢀS interaction of
3.640(2) Å is observed. The TlꢀꢀꢀꢀC(1) and TlꢀꢀꢀꢀTl separations within
a dimer are 3.362(6) and 3.658(1) Å, respectively. The S–C–S angle
of the dithiocarbamate is 118.0(3)°. As observed in (1), adjacent di-
meric units are linked along the a axis into a one dimensional poly-
meric chain by TlꢀꢀꢀꢀS contacts (Fig. 5), where. Tl–S–Tl angle
(159.46°) shows a slight increase with respect to the methyl ana-
logue. In contrast with (1), no TlꢀꢀꢀꢀH short contacts are present
among the chains because of the change in conformation of the
cyclohexyl ring due to the introduction of ethyl group. Though
the neighbouring non-bonded groups are flexible, thallium adjusts
its contacts to retain a hemisphere free for its pair of s electrons in
the presence of a sterically demanding ethyl group [18].
References
[1] J. Goldschmidt, T. Wanger, A. Engelhorn, H. Friedrich, M. Happel, A. Ilango,
M. Engelmann, I.W. Stuermer, F.W. Ohl, H. Scheich, NeuroImage 49 (2010)
303.
[2] J. Goldschmidt, W. Zuschratter, H. Scheich, NeuroImage 23 (2004) 638.
[3] R.A. Patel, G.A. Beller, Curr. Opin. Cardiol. 5 (2006) 457.
[4] N.S. Zefrov (Ed.), Khimicheskaya entsiklopediya, Chemical Encyclopedia, vol. 4,
Bol’shaya Ros, Entsiklepediya, Moscow, 1995, p. 492.
[5] C. Janiak, J. Chem. Soc. (2003) 2781.
[6] R.P. Feazell, C.E. Carson, K.K. Klausmeyer, Inorg. Chem. 45 (2006) 935.
[7] P.R. Willmott, J.R. Huber, Rev. Mod. Phys. 72 (2000) 315.
[8] M.A. Baldo, M.E. Thompson, S.R. Forrest, Pure Appl. Chem. 71 (1999) 2095.
[9] P.J. Heard, K.D. Karlin (Eds.), Prog. Inorg. Chem. 53 (2005) 1.
[10] A.V. Ivanov, O.A. Bredynk, A.V. Gerasimenko, O.N. Antzutkin, W. Forsling, Russ.
J. Coord. Chem. 32 (2006) 339.
[11] H. Pritzkow, P. Jennische, Acta Chem. Scand., Ser. A 29 (1975) 60.
[12] E. Elfwing, H. Anacker-Eickhoff, R. Hesse, Acta Chem. Scand. 30 (1976)
335.
[13] C. Rizzoli, K. Ramalingam, N. Alexander, Acta Crystallogr., Sect. E 64 (2008)
1020.
[14] Bruker, SMART, SAINT and SADABS, Bruker AXS Inc., Madison, Wisconsin, USA, 1998.
[15] M. O’Keefe, N.E. Brese, J. Am. Chem. Soc. 113 (1991) 3226.
[16] S.P. Summers, K.A. Abboud, S.R. Farrah, G.J. Palenik, Inorg. Chem. 33 (1994)
88.
Appendix A. Supplementary material
[17] A.V. Ivanov, O.A. Bredynk, A.V. Gerasimenko, O.N. Antzutkin, Doklady Phys.
Chem. 420 (2008) 130.
[18] F. Wiesbrock, H. Schmidbaur, J. Am. Chem. Soc. 125 (2003) 3622.
CCDC 747993 and 747992 contain the supplementary crystallo-
graphic data for (1) and (2). These data can be obtained free of