Synthesis, spectral and structural characterization of Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) complexes with 2-mercapto-5-methyl-1,3,4-thiadiazole: A Zn(II) complex acting as a new sensitive and selective fluorescent probe for the detection of Hg2+ in H2O-MeOH medium

Article abstract of DOI:10.1016/j.poly.2013.07.027

Five new complexes, [Ni(mthd)₂(py)₂] (1), [Cu(en)₂](mthd)₂ (2), [H₂en][Hg(mthd) ₃]₂·2H₂O (3), [Cd (mthd) ₂(o-phen)₂]₂·H₂O (4) and [Zn(mthd)₂(bpy)] (5) (Hmthd = 2-mercapto-5-methyl-1,3,4-thiadiazole), have been synthesized. All the complexes have been fully characterized by various techniques: elemental analyses, IR, electronic and fluorescent spectral data. The ligand is present in the deprotonated thiol form in the complexes [Cu(en)₂](mthd)₂(2)and [Cd(mthd)₂(o-phen) ₂]₂·H₂O(4). In complex 2, the ligand isionically bonded, whereas it is covalently bonded through the sulfur in complex 4. In [Ni(mthd)₂(py)₂] (1) the ligand is N, S chelating bidentate bonded through the thiol sulfur and the thiadiazole ring nitrogen adjacent to it, forming a four membered chelate ring. The ligand is covalently bonded through the deprotonated thiadiazole ring nitrogen adjacent to the thiol sulfur in [Zn(mthd)₂(bpy)] (5). The complex anion in [H₂en][Hg(mthd)₃]₂·2H₂O (3) has a triangular planar geometry, with bonding through the deprotonated thiolato sulfur atoms from the three ligands. [Zn(mthd)₂(bpy)] (5) is highly fluorescent as compared to the other complexes and has been further used as a metal probe for sensing of Hg²⁺ in H₂O-MeOH solution. Complex 5, upon interaction with Hg²⁺, shows a hypochromic shift in the absorption spectra whereas the emission spectra exhibited 75% quenching fluorescence behavior. The electrochemical studies also suggest the interaction of Hg(II) with the Zn(II) complex, probably via the free thione sulfur.

Full text of DOI:10.1016/j.poly.2013.07.027

Accepted Manuscript
Synthesis, spectral and structural characterization of Ni(II), Cu(II), Zn(II),
Cd(II) and Hg(II) complexes with 2-mercapto-5-methyl-1,3,4-thiadiazole: A
Zn(II) complex acting as a new sensitive and selective fluorescent probe for the
detection of Hg2+ in H O-MeOH medium
2
Pooja Bharati, A. Bharti, M.K. Bharty, S. Kashyap, U.P. Singh, N.K. Singh
PII:
S0277-5387(13)00552-4
DOI:
http://dx.doi.org/10.1016/j.poly.2013.07.027
POLY 10258
Reference:
To appear in:
Polyhedron
Received Date:
Accepted Date:
17 May 2013
17 July 2013
Please cite this article as: P. Bharati, A. Bharti, M.K. Bharty, S. Kashyap, U.P. Singh, N.K. Singh, Synthesis, spectral
and structural characterization of Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) complexes with 2-mercapto-5-
methyl-1,3,4-thiadiazole: A Zn(II) complex acting as a new sensitive and selective fluorescent probe for the detection
of Hg2+ in H O-MeOH medium, Polyhedron (2013), doi: http://dx.doi.org/10.1016/j.poly.2013.07.027
2
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Synthesis, spectral and structural characterization of Ni(II), Cu(II), Zn(II),
Cd(II) and Hg(II) complexes with 2-mercapto-5-methyl-1,3,4-thiadiazole: A
Zn(II) complex acting as a new sensitive and selective fluorescent probe for
the detection of Hg2+ in H2O-MeOH medium
Pooja Bharati,a A. Bharti,a M.K. Bharty,a* S. Kashyap,b U.P. Singhb, N.K. Singha
a
Department of Chemistry, Banaras Hindu University, Varanasi- 221005, India
b Department of Chemistry, Indian Institute of Technology, Roorkee, Uttarakhand, India- 247667.
Abstract
.
Five new complexes, [Ni(mthd)2(py)2] (1), [Cu(en)2](mthd)2 (2), [H2en][Hg(mthd)3]2 2H2O (3),
[Cd(mthd)2(o-phen)2]2·H2O (4) and [Zn(mthd)2(bpy)] (5) (Hmthd = 2-mercapto-5-methyl-1,3,4-
thiadiazole), have been synthesized. All the complexes have been fully characterized by various
techniques: elemental analyses, IR, electronic and fluorescent spectral data. The ligand is present
in the deprotonated thiol form in the complexes [Cu(en)2](mthd)2 (2) and [Cd(mthd)2(o-
phen)2]2·H2O (4). In complex 2, the ligand is ionically bonded, whereas it is covalently bonded
through the sulfur in complex 4. In [Ni(mthd)2(py)2] (1) the ligand is N,S chelating bidentate
bonded through the thiol sulfur and the thiadiazole ring nitrogen adjacent to it, forming a four
membered chelate ring. The ligand is covalently bonded through the deprotonated thiadiazole
ring nitrogen adjacent to the thiol sulfur in [Zn(mthd)2(bpy)] (5). The complex anion in
[H2en][Hg(mthd)3]2·2H2O (3) has a triangular planar geometry, with bonding through the
deprotonated thiolato sulfur atoms from the three ligands. [Zn(mthd)2(bpy)] (5) is highly
fluorescent as compared to the other complexes and has been further used as a metal probe for
sensing of Hg2+ in H2O-MeOH solution. Complex 5, upon interaction with Hg2+, shows a
hypochromic shift in the absorption spectra whereas the emission spectra exhibited 75%
1

quenching fluorescence behaviour. The electrochemical studies also suggest the interaction of
Hg(II) with the Zn(II) complex, probably via the free thione sulfur.
Keywords: Thiadiazole complexes, N,S donor ligand, Fluorescent Zn(II) complex,
Electrochemical studies, Intermolecular interactions.
*Corresponding author Tel: +91 542 6702447; Fax: +91 542 2368127
*Email address:manoj_vns2005@yahoo.co.in, singhnk_bhu@yahoo.com
Introduction
The design and synthesis of fluorescent chemosensors for the selective detection of metal ions is
one of the most important research areas in chemistry due to the fundamental and necessary role
of these species in biological processes [1]. Search for reagents which can efficiently act as
fluorescence sensors for zinc(II) has been an active area of research [2]. An ideal small molecule
for a metal ion probe should possess high stability and the capability to quantitatively determine
the metal ion concentration with high selectivity and sensitivity toward the specified metal ion
when it is present in ion mixtures. If the sensor has a straightforward and high-yielding
preparative route, this is an additional practical advantage [3]. Hg2+ and Pb2+ have attracted the
attention of researchers due to their high toxicity and severe effects on living organisms [4].
Despite its high toxicity, mercury is extensively used in many industrial processes and in the
manufacture of important products [5]. It is distributed in the environment in various forms, like
elemental (Hg0), inorganic (Hg2+) and organic methyl mercury (CH3Hg+). Highly soluble and
reactive inorganic mercury (Hg2+) can bind to a variety of ligands and complexes present in
organisms, particularly those containing sulfur functionality [6].
One of the most interesting properties of mercapto-substituted thiadiazoles is the
existence of thiol-thione tautomerism which influences the reactivity of thiadiazoles in
2

polymerization processes, substitution reactions at the different moieties and for metal
complexation [7,8]. In a previous study, 2,5-dimercapto-1,3,4-thiadiazole and 2-mercapto-5-
methyl-1,3,4-thiadiazole have been shown to exhibit tautomeric equilibria, and the structures of
the compounds by ab initio and DFT computations support the thione form as being the most
stable [9]. There exists continuing interest in ambidentate nitrogen-sulfur heterocyclic thiolato
ligands on account of their presence in many molecules [10] containing both an endocyclic hard
N donor and an exocyclic soft S donor. Some work has been reported on the complexes of 1,3,4-
thiadiazole-2-thiones, but very little is known about mixed ligand complexes of these ligands.
In view of this, we have synthesized and characterized Ni(II), Cu(II), Hg(II), Cd(II) and
Zn(II) complexes of an ambidentate ligand, 2-mercapto-5-methyl-1,3,4-thiadiazole, containing
ethylenediamine/o-phen/bpy/py as a co-ligand. Among the complexes, we report the synthesis
and characterization of the fluorescent compound [Zn(mthd)2(bpy)] (5), which is engaged in
selective detection of Hg2+ over other metal ions (Pb2+, Cu2+, Ni2+, K+, Na+, Ag+, Zn2+ and Cr3+)
in water:MeOH (50:50 v/v) by additional bonding with the free donor site. This additional
bonding approach for metal ion sensing is very effective in that the organic ligand alone shows a
poor sensing ability to the metal ion. This fluorescent Zn2+ complex shows a highly effective “
turn off ” sensor for Hg2+; the free organic ligand moiety is a less effective sensor than the Zn2+
complex.
2. Experimental Section
2.1.Materials and characterization
Commercial reagents were used without further purification and all experiments were carried
out in the open atmosphere. 2-Mercapto-5-methyl-1,3,4-thiadiazole (Sigma-Aldrich) was used as
3

received. All solvents were purchased from Merck Chemicals, India, and were dried and distilled
before use by following standard procedures. Carbon, hydrogen, nitrogen and sulfur contents
were estimated on a CHN Model CE-440 Analyzer and on an Elementar Vario EL III Carlo Erba
1108. Magnetic susceptibility measurements were performed at room temperature on a Cahn
Faraday balance using Hg[Co(NCS)4] as the calibrant and electronic spectra were recorded on a
SIMADZU 1700 UV-Vis spectrophotometer in DMSO. IR spectra were recorded in the 4000-
1
400 cm-1 region as KBr pellets on a Varian Excalibur 3100 FT-IR spectrophotometer. H NMR
spectra were recorded in DMSO-d6 on a JEOL AL300 FT NMR spectrometer using TMS as an
internal reference. The electrochemical experiments were performed with a BAS CV-50W
voltammetric analyzer (Bioanalytical system, West Lafayette, USA), using a three-electrode
system with a Pyrolytic Glass electrode as the working electrode, a platinum wire as the counter
electrode and Ag/AgCl was used as the reference electrode.
2.2. Syntheses
2.2.1. Synthesis of [Ni(mthd)2(py)2] (1)
Ni(OAc)2∙4H2O (0.248 g, 1 mmol) and Hmthd (0.264 g, 2 mmol) were dissolved
separately in 20 ml methanol, mixed together and stirred for 1 h. The blue solid which separated
was filtered off, washed successively with an ethanol-water mixture (50:50) and air dried. The
precipitate was suspended in methanol to which pyridine (0.4 ml) was added and stirred for 2 h.
The resulting clear green solution was filtered and kept for crystallization. Green single crystals
of 1 suitable for X-ray analysis were obtained by slow evaporation of the solution over a period
of 15 days. Yield: 0.51 g, 48 %; m.p. 210 ºC; Anal. Found: C, 40.07; H, 3.31; N, 17.48; S, 26.74
%. Calc. for C16H16NiN6S4 (479.32): C, 40.06; H, 3.33; N, 17.52; S, 26.70 %. IR (KBr, cm-1):
4

ν(C=N) 1600, ν(N-N) 1040, ν(C=S) 939, ν(Ni-N) 634, ν(Ni-S) 432. UV-vis.[λmax, DMSO, cm-1]:
19010, 23810, 32363.
2.2.2. Synthesis of [Cu(en)2](mthd)2 (2)
Cu(OAc)2∙H2O (0.199 g, 1 mmol) and Hmthd (0.264 g, 2 mmol) were dissolved
separately in 15-20 ml methanol, mixed together and stirred for 1 h. The blue solid which
separated was filtered, washed with a methanol-water mixture (50:50 v/v) and finally with
methanol. A methanol solution (10 ml) of ethylenediamine (0.30 ml, 4 mmol) was added to the
methanol suspension of the above compound and stirred for 30 minutes. A clear dark blue
solution was obtained which was filtered off and kept for crystallization. Dark blue crystals of 2
suitable for X-ray analysis were obtained by slow evaporation of the above solution over a
period of 10 days. Yield: 0.64 g, 52 %; m.p. 130 ºC; Anal. Found: C, 26.78; H, 5.41; N, 24.94; S,
28.60 %. Calc. for C10H24CuN8S4 (448.20): C, 26.77; H, 5.35; N, 24.98; S, 28.55 %. IR (KBr,
cm-1): ν(NH) 3252, ν(C=N) 1599, ν(N-N) 1046, ν(C-S) 731, ν(Cu-N) 548, ν(Cu-S) 431. UV-vis.
[λmax, DMSO, cm-1]: 16400, 28410, 33558.
2.2.3. Synthesis of [H2en][Hg(mthd)3]2·2H2O (3)
A methanol solution (25 ml) of Hmthd (0.396 g, 3 mmol) was added slowly to a
methanol solution of HgCl2 (0.270 g, 1 mmol) and stirred for 2 h. A white precipitate was
obtained which was dissolved in a methanolic solution of en (1.2 ml). This clear solution was
filtered off and kept for crystallization. Colorless crystals of 3 suitable for X-ray analysis were
obtained by slow evaporation of the above solution over a period of 20 days. Yield: 0.77 g, 48
%; m.p. 160 ºC; Anal. Found: C, 18.62; H, 2.63; N, 15.20; S, 29.79 %. Calc. for
C20H34Hg2N14O2S12 (1288.63): C, 18.50; H, 2.70; N, 15.25; S, 29.95 %. IR (KBr, cm-1): ν(O-H)
5

3409, ν(NH) 3316, ν(C=N) 1558, ν(N-N) 1077, ν(C-S) 768, ν(Hg-S) 427. 1H NMR (DMSO-d6, δ,
ppm): 2.93 (3H); 3.33 (2H, CH2); 6.64 (+NH3). UV-Vis. [λmax, DMSO, cm-1]: 33670, 37174.
2.2.4. Synthesis of [Cd(mthd)2(o-phen)2]2·H2O (4)
A solution of Hmthd (0.264 g, 2 mmol) in MeOH (10 ml) was added to a MeOH solution
(10 ml) of Cd(OAc)2·2H2O (0.266 g, 1 mmol). This mixture was stirred for 3 h at room
temperature. The resulting precipitate was filtered off and washed thoroughly with methanol. A
methanol solution of 1,10-phenanthroline (o-phen) (0.400 g, 2 mmol) was added to the methanol
suspension of the above compound and stirred for 1 h. A clear solution was obtained which was
filtered and kept for crystallization. Colorless crystals of 4 suitable for X-ray analysis were
obtained by slow evaporation of the above solution over a period of 20 days. Yield: 0.44 g, 40
%; m.p. 238 ºC; Anal. Found: C, 47.56; H, 3.07; N, 15.15; S, 17.05 %. Calc. for
C60H46Cd2ON16S8 (1488.49): C, 47.83; H, 3.20; N, 14.87; S, 17.03 %. IR (KBr, cm-1): ν(OH)
1
3435, ν(C=N) 1621, ν(N-N) 1019, ν(C-S) 728, ν(Cd-S) 427. H NMR (DMSO-d6, δ, ppm): 3.39
(3H, -CH3); 7.9-8.9 (8H, aromatic ring). UV-Vis.[λmax, DMSO, cm-1]: 34483.
2.2.5. Synthesis of [Zn(mthd)2(bpy)] (5)
A solution of Hmthd (0.234 g, 2 mmol) in MeOH (10 ml) was added to a MeOH solution
(10 ml) of Zn(OAc)2·2H2O (0.220 g, 1 mmol). This mixture was magnetically stirred for 2 h at
room temperature. The resulting white precipitate was filtered off, washed with methanol. A
methanol solution of 2,2'-bipyridyl (bpy) (0.156 g, 1 mmol) was added to the methanol
suspension of the above compound and stirred for 1 h. A clear solution was obtained which was
filtered and kept for crystallization. White crystals of 5 suitable for X-ray analysis were obtained
by slow evaporation of the above solution over a period of 15 days. Yield: 0.62 g, 54 %; m.p.
276 ºC; Anal. Found: C, 39.64; H, 2.91; N, 17.39; S, 26.42 %. Calc. for C16H14ZnN6S4 (484.00):
6

C, 39.66; H, 2.89; N, 17.35; S, 26.44 %. IR (KBr, cm-1): ν(C=N) 1600, ν(N-N) 1128, ν(C=S)
1
978, ν(Zn-N) 415. H NMR (DMSO-d6, δ, ppm): 3.05 (3H, -CH3); 7.6-8.9 (8H, aromatic ring).
UV-Vis. [λmax, DMSO, cm-1]: 35336, 32155.
Scheme 1. Preparation of complexes 1, 2, 3, 4 and 5.
3. Crystal structure determination
Data for complexes 1, 2 and 4 were recorded at 296(2) K on a Bruker three-circle
diffractometer and those of complexes 3 and 5 at 293(2) K on an Oxford Diffraction Gemini
diffractometer equipped with CrysAlis Pro./SMART 6000 CCD software using a graphite
monochromated MoKα (λ= 0.71073 Å) radiation source. The structures were solved by direct
methods (SHELXL-2008) and refined against all data by full matrix least-squares on F2 using
anisotropic displacement parameters for all non-hydrogen atoms. All the hydrogen atoms were
included in the refinement at geometrically ideal positions and refined with a riding model [11].
7

The MERCURY package and ORTEP-3 programs were used for generating the molecular
structures [12,13].
4. Results and Discussion
Salts of Ni(II), Cu(II), Cd(II) and Zn(II) react with Hmthd and then with a coligand to
yield complexes 1, 2, 4 and 5, respectively, whereas the reaction of HgCl2 with Hmthd in the
.
presence of ethylenediamine forms [H2en][Hg(mthd)3]2 2H2O (3). Scheme 1 depicts the
formation of the complexes which contain 2-mercapto-5-methyl-1,3,4-thiadiazole as a ligand and
py/en/o-phen/bpy as the coligand. The single crystal X-ray diffraction studies indicate that the
ligand (Hmthd) behaves as a uninegative monodentate ligand in complexes 2, 3, 4 and 5,
bonding either through the thiadiazole nitrogen adjacent to the thiol sulfur or the thiol sulfur, but
as uninegative chelating bidentate ligand in complex 1, bonding through the thiadiazole ring
nitrogen adjacent to the thiol sulfur. In [Ni(mthd))2(py)2] (1), both the nitrogen and sulfur sites of
the ligand are bonded to the nickel ion, forming a four membered chelate ring, having a distorted
octahedral geometry around the Ni(II) centre. All the complexes are air stable, non-hygroscopic
crystalline solids, which are partially soluble in common organic solvents but soluble in DMF
and DMSO, and they can be kept in desiccators over a prolonged period without any sign of
decomposition.
4.1. I.R. spectra
The ligand 2-mercapto-5-methyl-1,3,4-thiadiazole shows bands at 2868 and 1554 cm-1
due to ν(SH) and (C=N), respectively. The spectra of all the complexes show the absence of the
ν(SH) band, indicating bonding through the thiolato sulfur or thiadiazole nitrogen after
tautomerization and subsequent bonding through the thiadiazole nitrogen. The disappearance of
8

the ν(SH) band in the spectrum of [Ni(mthd)2(py)2] (1) and the presence of bands at 1600 and
939 cm-1 due to ν(C=N) (thiadiazole ring) and ν(C=S), respectively, indicates that the nickel ion
is bonded through the thiadiazole nitrogen adjacent to the thiol sulfur and the thiadiazolato sulfur
after loss of a proton from the thiol sulfur. Further new bands appear at 634, 620 and 432 cm-1
due to ν(Ni-N) (py), ν(Ni-N) (thiadiazole) and ν(Ni-S), indicating the formation of a chelate ring
and bonding of pyridine to the nickel ion. The IR spectrum of complex 2 shows a band at 3210
cm-1 due to the NH stretching vibration of the en ligand. The disappearance of the ν(SH) band
shows the removal of the proton from the -SH group and the appearance of a new band at 548
cm-1 due to ν(Cu-N) (en) suggests the formation of a chelate with ethylenediamine [14]. The IR
.
spectrum of [H2en][Hg(mthd)3]2 2H2O (3) shows a band at 3410 cm-1 for ν(OH) of the water
molecules and a band at 3316 cm-1 for ν(NH) of the en molecule. The absence of a ν(SH) band
together with the appearance of a new band for ν(Hg-S) at 427 cm-1 suggests bonding of Hg(II)
with the thiolato sulfur after loss of a proton. The IR spectrum of complex 4 shows a band at
3456 cm-1 due to the OH stretching vibrations of the water molecule, and the absence of a ν(SH)
band due to the thiadiazole moiety of the ligand suggests the loss of the SH proton in the
complex. The appearance of two new bands at 580 and 427 cm-1 due to ν(Cd-N) and ν(Cd-S)
suggest bonding through the thiolato sulfur and o-phen nitrogen with the metal ion. The IR
spectrum of [Zn(mthd)2(bpy)] (5) shows a band at 1027 cm-1 due to ν(C=S), indicating that the
ligand is present in the thione form and is bonded through the thiadiazole nitrogen adjacent to the
thiol sulfur [15].
1
4.2. H and 13C NMR spectra
The 1H NMR spectrum of the ligand 2-mercapto-5-methyl-1,3,4-thiadiazole in DMSO d6
shows signals at 12.05, 3.32 and 2.49 ppm due to the thiadiazole NH, SH and methyl protons,
9

1
respectively, indicating the existence of the ligand in the thiol/thione tautomeric forms. The H
.
NMR spectrum of [H2en][Hg(mthd)3]2 2H2O (3) exhibits signals at δ 2.93 and 3.33 ppm for the
CH3 and CH2 (en) protons and a peak at δ 6.643 ppm for +NH3 of the protonated
ethylenediamine. The disappearance of the SH signal suggests bonding of the soft sulfur atom
with the soft Hg(II) in the complex. The 1H NMR spectrum of [Cd(mthd)2(o-phen)2]2·H2O (4) in
DMSO-d6 shows a signal at δ 3.39 ppm due to CH3 protons. The o-phen ring protons appear as a
1
multiplet between 7.9 and 8.9 (m, 8H) ppm. The H NMR spectrum of [Zn(mthd)2(bpy)] (5) in
DMSO-d6 shows a signal at δ 3.05 ppm due to CH3 protons. The bipyridyl ring protons appear
as a multiplet between δ 7.6 and 8.9 (m, 8H) ppm.
4.3. UV-Vis absorption, magnetic moments and photoluminescent studies.
A magnetic moment of 2.91 BM for [Ni(mthd))2(py)2] (1) and the presence of two bands
3
3
at 19010 and 23810 cm-1 (ε = 76 and 100 M-1 cm-1) assigned to the A2g→ A1g(F) (ν2) and
3T1g(P) (ν3) transitions, respectively, suggest a distorted octahedral geometry for the complex. A
high energy band observed at 32363 cm-1 (ε = 1.11 x 103 M-1 cm-1) may be assigned to an
intraligand/charge transfer transition. [Cu(en)2](mthd)2 (2) shows a magnetic moment of 1.72
BM, which indicates the presence of one unpaired electron. The presence of a broad band around
2
2
2
2
16400 cm-1 (ε = 120 M-1 cm-1) assigned to the envelope of the B1g→ A1g, B2g and Eg
transitions suggests a square planar geometry for the complex. Two other high energy bands,
observed at 28410 and 33558 cm-1 (ε = 4.50 x 103, 1.39 x 103 M-1 cm-1), may be assigned to
.
intraligand/charge transfer transitions. The [H2en][Hg(mthd)3]2 2H2O (3), [Cd(mthd)2(o-
phen)2]2·H2O (4) and [Zn(mthd)2(bpy)] (5) complexes are diamagnetic and show absorptions in
the region of 32150-37100 cm-1 (ε = 0.54 x 103 - 3.2 x 103 M-1 cm-1) due to intraligand/charge
10

transfer transitions [16]. The electronic absorption and emission spectra of complexes 1-5 are
depicted in Figures 1(a) and (b).
5. Metal ion sensing behavior of the Zn(II) complex
The sensing behavior of [Zn(mthd)2(bpy)] (5) with various metal cations (Pb2+, Cu2+,
Ni2+, K+, Na+, Hg2+, Ag+, Zn2+ and Cr3+) as their nitrate salts in H2O:MeOH (pH 7.4, 100 µM)
was investigated by UV-vis and fluorescence spectrophotometry. The absorption spectrum of
complex 5 (100 µM) in DMSO shows two bands at 285 and 311 nm (ε = 3.2 x 103, 1.79 x103 M-1
cm-1), due to intraligand/charge transfer transitions. Upon addition of 1.0 equivalent of Hg2+ ions
(100 μM), the absorbance decreased (~ 42 %) while λmax showed a slight blue-shift (~12 nm).
Under the same conditions, other metal ions, such as Ag+, Pb2+, Zn2+, Cr3+, Na2+, Ni2+, Cu2+ and
K+, showed a decrease in absorption with a red-shift in the UV-vis spectra. The fluorescence
spectra of [Zn(mthd)2(bpy)] (5) on addition of 1.0 and 2.0 equivalents of Hg2+ ions (100 μM)
showed 50 and 75 % quenching, but the other metal ions did not show such a quenching effect.
Fig. 2(a) and 2(b) show the fluorescence spectra and relative fluorescence of complex 5 in the
presence of solutions of different metal ions at 343 nm emission wavelength. Scheme 2 shows
the proposed mechanism for the interaction of [Zn(mthd)2(bpy)] (5) with Hg(NO3)2.
Scheme 2 Proposed mechanism for the formation of [Zn(mthd)2(bpy)] (5): 2Hg2+
5.1. Thermal gravimetric analysis
11

The thermal properties of [Zn(mthd)2(bpy)] (5) were studied by TG and DTA in the temperature
range 30-800 ºC under a nitrogen atmosphere. Thermogravimetric analysis of complex 5 showed
that the complex starts decomposing at 230 ºC and the thermogram exhibits four distinct
decompositions at 230, 290, 360 and 650 ºC. The weight loss (32.93 %) at 230 ºC could be
ascribed to the loss of the bipyridyl molecule with 2 % weight gain and the corresponding
endothermic peak at 267 ºC was obtained. The second decomposition at 290 ºC shows the weight
loss (32.04 %) for both ligands (mthd), whilst the third and fourth decompositions at 360 and 650
ºC show the degradation of the remaining organic moieties, and after 650 ºC the residue of 15.48
% left corresponds to zinc oxide. The corresponding endo and exothermic peaks in the DTA
were obtained at 327, 346 and 404 ºC (supple. Fig.1).
5.2. Electrochemical behaviour of [Ni(mthd)2(py2)] (1)
The cyclic voltammogram of [Ni(mthd)2(py2)] (1) (c = 100 μM, DMSO) obtained at a Pyrolytic
Graphite Electrode (PGE) in DMSO medium using 0.2 M TBAP as the supporting electrolyte in
the potential range -1.0 V to 0.8 V at a scan rate of 50 mV s-1 exhibits an anodic peak at -0.034 V
and an associated cathodic peak at -0.786 V with respect to the Ag/AgCl reference (supple. Fig.
2). The separation between the cathodic and anodic peak potentials (∆Ep = Epa - Epc) of 0.752
V and E1/2 [( Epa + Epc )/2] of 0.410 V indicates an irreversible redox process assignable to the
Ni(II)/Ni(III) couple [17].
5.3. Electrochemical studies of [Cu(en)2](mthd)2 (2)
The cyclic voltammogram of complex 2 (supple. Fig. 3a) obtained at a Pyrolytic Graphite
Electrode (PGE) in DMSO medium using 0.2 M KCl as the supporting electrolyte in the
potential range +1.0 V to -1.5 V with a scan rate 50 mV s-1 exhibits only an anodic peak at 0.
515 V with respect to the Ag/AgCl reference. The cyclic voltammogram of the complex
12

indicates an irreversible redox process assignable to the Cu(II)/Cu(III) couple. However, it is to
be noted that the peaks observed at 0.525 and 0.150 V are due to the ligand moiety in the
complex [18]. The anodic peak observed at 0.515 V without a corresponding cathodic peak can
be assigned to the tri-valent Cu(III), which after being oxidised from the complexing
environment could not be re-reduced [19,20].
5.4. ESR spectra
The frozen solution EPR spectrum of [Cu(en)2](mthd)2 (2) (supple. Fig. 3b) was recorded in
methanol at liquid nitrogen temperature. The EPR spectrum of the Cu(II) complex on the high
2
field side is more intense than the low field side, indicating a dx -y2 ground state for the copper(II)
ion. Analysis of the spectrum of complex 2 gives gII = 2.201 and g┴ = 2.014. The trend gII > g┴ >
2
ge (2.0023) observed for the complex under investigation also suggests a dx -y2 ground state for
the Cu(II) ion. Also, the observed gII value of less than 2.30 provides evidence for the
appreciable covalent character of the bonding between the Cu(II) ion and the attached ligand in
the complex [21].
5.5. Crystal structure description of [Ni(mthd)2(py)2] (1)
The ORTEP diagram of the complex [Ni(mthd)2(py)2] (1) (Fig. 3) contains a pair of
monodeprotonated ligands bonded to the Ni(II) ion via the thiadiazole nitrogen adjacent to the
thiol sulfur and the thione sulfur, forming two four membered chelate rings with a bite angle of
67.59(4) ° [N(1)-Ni-S(1)]; two pyridine molecules are also coordinated, completing the distorted
octahedral structure. The crystallographic data and structural refinement details of complex 1 are
given in Table 1 and selected bond lengths and angles are compiled in Table 2. The formation of
a four membered C2N2Ni chelate ring, with a bite angle of 67.59(4) °, represents a major
13

deviation from an octahedral geometry. The geometry and bonding parameters agree with those
of other pyridine containing complexes [Ni(NCS)2(4-methyl pyridine)/(4-ethyl pyridine)4]
[22,23]. The distances within the chelate rings are intermediate between single and double bond
lengths and the average bond lengths, C6-N1 = 1.315(2) and C6-S1 = 1.708(15) Å, suggest
considerable delocalization of charge [24]. In complex 1, the chelate rings and the thiadiazole
ring lie nearly in the same plane and make an extended coplanar system with both chelate rings.
The values of the dihedral angles suggest that the extended coplanar ring system of the two
ligands approach each other orthogonally and shows an unsymmetrical coordination of the two
ligands. Thus the two ligands bonded to Ni(II) are the mirror image of each other. Both pyridine
rings are symmetrically coordinated to the metal in a trans position. The pyridine rings of two
nearby molecules are tilted (ACB = 73.25 °) and displaced with respect to each other (supple.
Fig. 4). The displacement, as measured by the angle formed between the ring centroids AC and
the ring normal BC to the pyridine plane is found to be 0.178 Å with a displacement angle of
19.56 °, and the ring centroids contact (Cg···Cg) of 3.901 Å is well within the reported range
[25]. In the solid state the complex is stabilized via intermolecular C-H···N and C-H···S
interactions (supple. Table 1) between the thiol sulfur and thiadiazole nitrogen adjacent to the
thiol sulfur with the same hydrogen atom of the pyridine ring, leading to the formation of a
supramolecular linear chain structure.
5.6. Crystal structure description of [Cu(en)2](mthd)2 (2)
Fig. 4 shows molecular structure of [Cu(en)2](mthd)2 (2) with the atom labeling scheme,
showing a weak Cu···S interaction. The crystallographic data and structural refinement details of
complex 2 are given in Table 1 and selected bond lengths and angles are listed in Table 3. The
crystal structure of complex 2 consists of a complex cation, [Cu(en)2]2+, and the 2-mercapto-5-
14

methyl-1,3,4-thiadiazole thiolate (mthd) anions. The complex cation consists of two
ethylenediamine molecules which chelate Cu(II) in equatorial positions and two ionic bonds with
1,3,4-thiadiazole-2-thiadiazolato anions. The Cu-N distances are found to be in the range 2.016-
2.022 Å (Table 4), which is normal for Cu-N (en) coordination. The bite angle for the CuC2N4
five membered ring is 84.10(10) °, indicating a substantial distortion in the complex cation.
Similar geometrical parameters for the coordination sphere have been reported for other diaqua
bis-ethylenediamine Cu(II) complexes [26,27]. Each [Cu(en)2]+2 cation forms a pair of
intermolecular Cu···S interactions with a distance of 2.975 Å, which is well within the distance of
3.2 Å for the sum of Van der Waals' radii of Cu and S, but greater than a Cu-S covalent bond
[28,29]. The Cu(II) in D2h symmetry is bonded to four nitrogen atoms of two en groups, which
offer interesting hydrogen bonding packing. In the solid state, the complex is stabilized via
intermolecular N-H···N interactions (supple. Table 2) between both thiadiazole nitrogens and the
NH2 hydrogen atoms of ethylenediamine, which produce a ladder-like arrangement (supple. Fig.
5).
5.7. Crystal structure description of [H2en][Hg(mthd)3]2·2H2O (3)
The crystallographic asymmetric unit of complex 3, consists of an H2en2+ cation, two complex
[Hg(mthd)3]- anions and two water molecules. The crystallographic data and structural
refinement details of complex 3 are given in Table 1 and selected bond lengths and angles are
listed in Table 4. There are two complex anions present in the asymmetric unit of complex 3,
both are structurally identical except for a slight variation in bond lengths and angles. The
coordination number of three around each Hg(II) centre in the complex anion is completed by
sulfur atoms from three 1,3,4-thiadiazole-2-thiolate anions bonded through Hg-S1, Hg-S3, Hg-
S5 and Hg-S7, Hg-S9, Hg-S11 at the distances of 2.443(6), 2.477(7), 2.447(6) and 2.478(7),
15

2.448(6), 2.462(6) Å, respectively. One H2en2+ cation is present between two units of complex
[Hg(mthd)3]- anions (Fig. 5). The two thiadiazole rings in each complex unit are almost planar,
making a dihedral angle ACB of 71.66° in units containing Hg1 and Hg2. The thiadiazole rings
of both complex anion units are almost parallel, but displaced with respect to each other (supple.
Fig. 6). The displacement, as measured by the angle formed between the ring centroids AB and
the ring normal BC to the thiadiazole plane, is found to be 1.194 Å with a displacement angle of
17.44°, and the ring centroids contact (Cg···Cg) of 3.782 Å is well within the reported range. In
the solid state the complex is stabilized via intermolecular N-H···O, C-H···N, O-H···N, N-H···S,
N-H···N and C-H···S interactions (supple. Table 3) between the thiadiazole nitrogen adjacent to
the thiol sulfur and hydrogen atoms of the water molecules. In addition there are Hg···S and S···S
interactions between the sulfur of the thiadiazole ring and the thiol group, leading to a stacked
linear type arrangement of molecules (supple. Fig. 7).
5.8. Crystal structure description of [Cd(mthd)2(o-phen)2]2·H2O (4)
The ORTEP diagram of complex 4 shows that in the centrosymmetric unit of [Cd(mthd)2
(o-phen)2]2·H2O the metal ion is six coordinate octahedral, bonded to two thiol sulfur atoms and
four nitrogen atoms of the o-phen ligands (Fig. 6). The crystallographic data and structural
refinement details of complex 4 are given in Table 1 and selected bond lengths and angles are
listed in Table 5. The two o-phen ligands bond to cadmium via Cd1-N1, Cd1-N2, Cd1-N3 and
Cd1-N4 at distances of 2.422(2), 2.409(2), 2.447(2) and 2.391(2) Å respectively (Table 5), and
these and the Cd-S (2.623 Å) distances are in the normal ranges reported for Cd-N and Cd-S
bond lengths [30,31]. The C-N and C-S bond lengths indicate their double bond and single bond
character, respectively, thereby suggesting that the ligand is present in the thiol form in complex
4. The bond lengths and angles of the heterocyclic ligand moiety (mthd) are comparable to those
16

found in other monodentate thiadiazole ligands. The elements of the structure are joined to each
other in the crystal packing by means of an extended system of H-bonds where a hydrogen atom
belonging to the o-phen ligand participates in the structure. The complex is stabilized via
intermolecular C-H···O and C-H···S interactions (supple. Table 4) occurring between the oxygen
atoms of the water molecule and the thiol sulfur and CH hydrogens of a phenyl ring, leading to a
scorpion-like architecture. In addition, there are weak O-H···N interactions between the
thiadiazole nitrogen atoms and hydrogen of water molecules, forming a single helix-like
structure in complex 4. The thiadiazole ring and one o-phen ring are almost parallel (ACB =
77.85 °), but they aredisplaced with respect to each other. The displacement, as measured by the
angle formed between the ring centroids AB and the ring normal BC to the thiadiazole plane,
was found to be 0.057 Å with a displacement angle of 18.99 °, and the ring centroids contact
(Cg···Cg) of 3.662 Å is well within the reported range [32]. The crystal structure of complex 4 is
stabilized via π∙∙∙π interactions between the thiadiazole ring and one o-phen ring. In addition,
there are weak intermolecular π∙∙∙π interactions between two o-phen rings which are almost
parallel [ACB = 90.34°, displacement = 0.248 Å, displacement angle = 20.94°, Cg···Cg = 3.901
Å]. The values of the π∙∙∙π distances suggest stronger interactions between the o-phen and
thiadiazole rings as compared to o-phen-o-phen ring interactions (supple. Fig. 8).
5.9. Crystal structure description of [Zn(mthd)2(bpy)] (5)
Fig. 7 shows an ORTEP diagram of [Zn(mthd)2(bpy)] (5) with the atom numbering scheme. The
four coordination number of complex 5 is fulfilled by two nitrogen (adjacent to the thiol sulfur)
atoms from two thiadiazole ligands and two nitrogen atoms from one bpy ligand. The
crystallographic data and structural refinement details of complex 5 are given in Table 1. The
average bond lengths C3-S1 = 1.701(16), C6-S3 = 1.692(16), C2-S2 = 1.680(19) and C5-S4 =
17

1.722 (17) Å, are normal for thiadiazole complexes. The Zn-N bond distances of 1.942(14),
2.010(13), 2.062(14) and 2.074(13) Å, (Table 6) are comparable to the bond lengths reported for
other complexes of Zn(II) containing bpy [33,34]. The shorter Zn-N (thiadiazole) bond length, as
compared to Zn-N (bpy), indicates that the thiadiazole nitrogen bonds more strongly than the bpy
nitrogen. In the solid state, the complex is stabilized via intermolecular C-H···S interactions
occurring between the thione sulfur and the CH hydrogen of the bpy ring, forming a one
dimensional linear arrangement of molecules. A two dimensional rectangular arrangement of
metal atoms is obtained by C-H···S and N-H···S interactions between the molecules (supple.
Table 5, Fig. 9).
6. Conclusion
The new complexes [Ni(mthd)2(py)2] (1), [Cu(en)2](mthd)2 (2), [H2en][Hg(mthd)3]2·2H2O (3),
[Cd(mthd)2(o-phen)2]2·H2O (4) and [Zn(mthd)2(bpy)] (5), derived from 2-mercapto-5-methyl-
1,3,4-thiadiazole, have been synthesized and well characterized by various spectroscopic
techniques, including their crystal structure determination. In addition to hydrogen bonding, the
complexes [Ni(mthd)2(py)2] (1), [H2en][Hg(mthd)3]2·2H2O (3) and [Cd(mthd)2(o-phen)2]2·H2O
(4) contain π∙∙∙π interactions which stabilize their structures. The free 2-mercapto-5-methyl-
1,3,4-thiadiazole is a less effective sensor, but is a “turn-on” sensor upon complexation with
Zn(II), showing high sensitivity and being a selective “turn-off ” sensor for the Hg2+ metal ion.
Photoluminescence studies indicate that the [Zn(mthd)2(bpy)] complex (5) is a fluorescent
material with a maximum emission at 375 nm at an excitation wavelength of 311 nm. The UV-
vis spectra of the Zn(II) complex with the Hg2+ metal ion (in a 1:2 ratio) also indicates the “turn-
off” sensing behavior of the complex. Thermogravimetric analysis reveals that the complex
18

[Zn(mthd)2(bpy)] (5) has high thermal stability due to the high dimensionality of the molecule,
which encourages its fluorescence behaviour.
7. Acknowledgement
Dr.M.K. Bharty is thankful to the Department of Science and Technology, New Delhi, India for
the award of a Young Scientist Project (No. SR/FT/CS-63/2011). Ms. Pooja Bharati thanks
CSIR, New Delhi for the award of a SRF.
8. Supporting Information
CCDC 864050, 864048, 909609, 864047 and 888324 contain the supplementary
.
crystallographic data for [Ni(mthd)2(py)2] (1), [Cu(en)2](mthd)2 (2), [H2en][Hg(mthd)3]2 2H2O
(3), [Cd(mthd)2(o-phen)2]2·H2O (4) and [Zn(mthd)2(bpy)] (5), respectively. These data can be
obtained free of charge via http://www.ccdc.cam. ac.uk/ conts/retrieving.html, or from the
Cambridge Crystallographic Data Center, 12 Union Road, Cambridge CB2 1EZ, UK; fax:
(+44)1223-336-033; or e-mail: deposit@ccdc. cam. ac. uk.
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23

Fig. 1 (a) Absorption spectra (b) Photoluminescent spectra of Hmthd and complexes 1-5 (c = 100 μM)
Fig. 2 (a) Photoluminescent spectra of complex 5 (c = 100 μM); (b) Relative fluorescence of complex 5 (light grey
bar) at 343 nm emission intensity in the presence of different metal ion solutions (black bar).
Fig. 3 Ortep diagram of [Ni(mthd)2(py)2] (1)
1

Fig. 4 Molecular structure of [Cu(en)2](mthd)2 (2)
.
Fig. 5 Ortep diagram of [H2en][Hg(mthd)3]2 2H2O (3)
2

Fig. 6 Ortep diagram of [Cd(mthd)2(phen)2]2·H2O (4)
Fig. 7 Ortep diagram of [Zn(mthd)2(bpy)] (5) ‘
3

.
Table 1. Crystallographic data for [Ni(mthd)2(py)2] (1), [Cu(en)2](mthd)2 (2), [H2en][Hg(mthd)3]2 2H2O (3),
[Cd(mthd)2(o-phen)2]2·H2O (4) and [Zn(mthd)2(bpy)] (5)
Compound
1
2
3
4
5
Empirical formula
C16H16N6NiS4
C10H24CuN8S4
C20H34Hg2N14O2S12 C60H44Cd2N16OS8 C16H14N6S4Zn
Formula weight
T (K)
479.32
296(2)
448.20
296(2)
1288.63
293(2)
1486.49
296(2)
483.90
293(2)
0.71073
Monoclinic
P 21/c
0.71073
Monoclinic
P 21/c
0.71073
Triclinic
P 1
0.71073
Monoclinic
C 2/c
0.71073
Monoclinic
C 2/c
λ (Mo K) (Å)
Crystal system
Space group
a (Å)
8.696(3)
9.212(3)
12.702(4)
90.00
6.536(4)
21.046(12)
7.252(4)
90.00
8.434(7)
9.482(7)
13.363(7)
79.981(5)
80.979(6)
74.875(7)
1009.11(13)
1
20.383(6)
25.541(6)
14.404(3)
90.00
8.607(2)
14.114(15)
33.874(5)
90.00
b (Å)
c (Å)
 (º)
β (º)
91.8680(10)
90.00
110.396(3)
90.00
125.613(10).00
90.00
91.13(2)
90.00
 (º)
V (Å3)
1017.11(6)
2
935.15(9)
2
6096.5(3)
4
4114.2(12)
8
Z
Dcalc (Mg m-3)
μ (mm-1)
F(000)
1.565
1.592
2.121
1.620
1.563
1.378
1.624
8.262
1.029
1.614
492.0
466.0
620.0
2992.0
1968
Crystal size (mm3)
θ range (º)
Index ranges
0.25x0.23x0.21 0.23x0.19x0.17
0.30x0.27x0.25
2.93-29.08
-11≤ h ≤11
-12≤ k ≤12
-13≤ l ≤18
5434
0.25x0.21x0.19
1.46-28.04
-26≤ h ≤26
-33≤ k ≤33
-17≤ l ≤19
51280
0.25x0.23x0.21
1.5-23.79
-11≤ h ≤11
-19≤ k ≤10
-43≤ l ≤46
8523
2.34 - 25.00
-10≤ h ≤ 9
-10≤ k ≤10
-13≤ l ≤15
14561
1.94- 28.38
-8 ≤ h ≤ 8
-27 ≤ k ≤28
-9 ≤ l ≤ 9
16951
Reflections
collected
Independent
reflections
1789
2344
4692
7394
5737
Data/restraints/
parameters
1789/0/125
0.831
2344/0/107
0.807
5434/9/397
1.023
7394/0/395
1.001
5737/0/245
1.567
Goodness-of-fit on
F2
Final R indices
wR2 [I>2σ(I)](Rint)
Final R indices (all
data)
0.0205, 0.0859
0.0224, 0.0907
0.217, -0.198
0.0367, 0.1062
0.0682, 0.1340
0.324, -0.322
0.0395, 0.0505
0.0852, 0.0926
1.249, -1.018
0.0340, 0.1123
0.0484, 0.1349
1.514, -0.667
0.0442, 0.1031
0.0670, 0.1132
2.300, -2.302
Largest diff.
peak/hole (e Å-3)
a R1 = Σ||Fo| – |Fc||Σ|Fo|.
b R2 = [Σw(|F2 | – |F2 |)2/Σw|F2 |2]1/2.
o
c
o
1

Table 2. Selected bond lengths (Å) and bond angles (o) for [Ni(mthd)2(py)2] (1)
Bond lengths (Å)
Ni(1)-N(1)
Bond angles (°)
2.074(12)
2.083(12)
2.567(4)
1.708(15)
1.315(2)
1.334(2)
1.337(2)
1.378(19)
N(1)-Ni(1)-N(1)
N(1)-Ni(1)-N(3)
N(1)-Ni(1)-S(1)
N(1)-Ni(1)-S(1)
S(1)-Ni(1)-S(1)
C(6)-S(1)-Ni(1)
C(6)-N(1)-Ni(1)
C(1)-N(3)-Ni(1)
180.0(10)
89.0(5)
112.4(4)
67.5(4)
180.0(3)
73.1(5)
99.8(9)
Ni(1)-N(3)
Ni(1)-S(1)
S(1)-C(6)
N(1)-C(6)
N(3)-C(1)
N(3)-C(5)
N(1)-N(2)
121.9(11)
Table 3. Selected bond lengths (Å) and bond angles (o) for [Cu(en)2](mthd)2 (2)
Bond lengths (Å) Bond angles (°)
Cu(1)-N(4)
Cu(1)-N(3)
S(1)-C(3)
N(1)-N(2)
N(2)-C(3)
C(3)-S(2)
2.016(3)
2.022(2)
1.748(3)
1.388(4)
1.318(4)
1.700(3)
N(4)-Cu(1)-N(4)
N(4)-Cu(1)-N(3)
N(3)-Cu(1)-N(3)
C(4)-N(3)-Cu(1)
C(5)-N(4)-Cu(1)
180.0(1)
84.1(10)
180.0(1)
108.4(18)
108.7(18)
.
Table 4. Selected bond lengths (Å) and bond angles (o) for [H2en][Hg(mthd)3]2 2H2O (3)
Bond lengths (Å)
Hg(1)-S(1)
Hg(1)-S(3)
Hg(1)-S(5)
S(1)-C(1)
Bond angles (°)
S(1)-Hg(1)-S(3)
2.443(6)
2.477(7)
2.447(6)
1.65(2)
1.79(2)
1.42(3)
1.33(3)
1.54(2)
1.42(2)
119.3(2)
S(1)-Hg(1)-S(5)
S(3)-Hg(1)-S(5)
C(1)-S(1)-Hg(1)
C(1)-S(2)-C(2)
N(1)-C(1)-S(2)
N(1)-C(1)-S(1)
C(1)-N(1)-N(2)
N(14)-C(20)-C(19)
121.5(2)
118.7(2)
105.2(9)
91.3(10)
108.9(16)
129.2(17)
114.7(17)
109.4(10)
S(2)-C(1)
N(1)-N(2)
C(1)-N(1)
C(20)-N(14)
N(13)-C(19)
Table 5. Selected bond lengths (Å) and bond angles (o) for [Cd(mthd)2(o-phen)2]2·H2O (4)
Bond lengths (Å)
Cd(1)-N(1)
Bond angles (°)
N(4)-Cd(1)-N(2)
2.422(2)
2.409(2)
2.623(9)
1.721(3)
1.727(3)
1.357(3)
1.363(4)
1.318(5)
90.6(8)
153.9(8)
69.1(8)
107.3(7)
156.7(6)
89.1(6)
Cd(1)-N(2)
Cd(1)-S(1)
S(1)-C(25)
S(2)-C(25)
N(1)-C(5)
N(2)-C(9)
N(5)-N(6)
N(4)-Cd(1)-N(1)
N(2)-Cd(1)-N(1)
N(4)-Cd(1)-S(1)
N(2)-Cd(1)-S(1)
N(1)-Cd(1)-S(1)
C(25)-S(1)-Cd(1)
C(5)-N(1)-Cd(1)
105.8(11)
115.7(17)
2

Table 6. Selected bond lengths (Å) and bond angles (o) for [Zn(mthd)2(bpy)] (5)
Bond lengths (Å)
Zn(1)-N(1)
Zn(1)-N(3)
Zn(1)-N(6)
Bond angles (°)
1.942(14)
2.010(13)
2.062(14)
N(1)-Zn(1)-N(3)
N(1)-Zn(1)-N(6)
N(3)-Zn(1)-N(6)
118.4(6)
130.3(6)
101.0(5)
Zn(1)-N(5)
S(1)-C(3)
2.074(13)
1.701(16)
1.355(17)
1.42(2)
1.407(15)
1.354(16)
1.34(2)
N(3)-Zn(1)-N(5)
N(1)-Zn(1)-N(5)
N(6)-Zn(1)-N(5)
C(3)-N(1)-N(2)
C(3)-N(1)-Zn(1)
N(2)-N(1)-Zn(1)
C(11)-N(5)-Zn(1)
N(1)-C(3)-S(1)
121.9(6)
101.2(5)
79.6(5)
108.2(14)
118.3(10)
133.2(13)
114.0(10)
118.0(12)
C(16)-N(6)
N(1)-C(3)
N(1)-N(2)
C(7)-N(5)
N(5)-C(11)
N(6)-C(12)
1.35(2)
3