A fluorescent dissymmetric thiosemicarbazone ligand containing a hydrazonequinoline arm and its complexes with cadmium and mercury

Article abstract of DOI:10.1002/ejic.201200815

A new dissymmetric thiosemicarbazone ligand containing a hydrazonequinoline arm, H₂AMeTsQ, and its chloride salt, [H₃AMeTsQ]Cl, were synthesized. Nine new complexes of cadmium and mercury with different structural characteristics were obtained under different reaction conditions as the ligand charge can be controlled by varying the amount of base. ¹¹³Cd and ¹⁹⁹Hg NMR spectroscopy together with X-ray diffraction indicated that the complexes form monomeric and dimeric structures and even a coordination polymer. Fluorescence spectroscopy showed that both protonated and neutral forms of the ligand were fluorescent as well as some of their cadmium and mercury derivatives. The fluorescence intensity decreased upon complexation and in some complexes a shift of the emission maximum was also observed.

Full text of DOI:10.1002/ejic.201200815

FULL PAPER
DOI:10.1002/ejic.201200815
A Fluorescent Dissymmetric Thiosemicarbazone Ligand
Containing a Hydrazonequinoline Arm and Its Complexes
with Cadmium and Mercury
David G. Calatayud,[a][‡] Elena López-Torres,[a] and
M. Antonia Mendiola*[a]
Keywords: Mercury / Cadmium / Chelates / S ligands / N ligands / Fluorescence
A new dissymmetric thiosemicarbazone ligand containing a
hydrazonequinoline arm, H2AMeTsQ, and its chloride salt,
[H3AMeTsQ]Cl, were synthesized. Nine new complexes of
cadmium and mercury with different structural characteris-
tics were obtained under different reaction conditions as the
ligand charge can be controlled by varying the amount of
base. 113Cd and 199Hg NMR spectroscopy together with X-
ray diffraction indicated that the complexes form monomeric
and dimeric structures and even a coordination polymer.
Fluorescence spectroscopy showed that both protonated and
neutral forms of the ligand were fluorescent as well as some
of their cadmium and mercury derivatives. The fluorescence
intensity decreased upon complexation and in some com-
plexes a shift of the emission maximum was also observed.
imaging agents in positron emission tomography (PET)
studies to identify hypoxic tissues.[17–20] Recently, a bis-
(thiosemicarbazonate)copper(II) complex has been pro-
posed to be of use as a copper-64 radiopharmaceutical to
assist in the diagnosis of Alzheimer’s disease,[21] and
fluorescent and biocompatible aromatic GaIII and InIII
bis(thiosemicarbazonato) complexes for dual mode optical
and PET or SPECT (single-photon emission computed
tomography) molecular imaging have been synthesized.[22]
In recent years, there has been growing interest in com-
pounds that can form selective and stable complexes with
cadmium and mercury to remove or to detect them.[23,24]
Some thiosemicarbazones show high selectivity for specific
metal ions,[25,26] so it could be expected that dissymmetric
ligands derived from thiosemicarbazides would be suitable
molecules for these purposes as they form stable tetraden-
tate chelates. The addition of a fluorophore allows the syn-
thesis of fluorescent molecules. The fluorescence can be in-
creased by the dissymmetry of the ligands, which makes
them suitable as precursors of luminescent or redox sen-
sors.[27–29]
On the other hand, the use of established fluorescence
tags as pendant fluorophores attached to some ZnII bis-
(thiosemicarbazonate) systems is likely to significantly per-
turb the distribution of the probe.[26,30] Therefore, there is
scope for designing small, intrinsically fluorescent mole-
cules that could act as versatile dual mode optical and PET
imaging probes. The higher intrinsic fluorescence coupled
with solubility and stability in a biologically compatible me-
dium should facilitate the monitoring of cell delivery and
biodistribution in cancer cells. In particular, the fluores-
cence emission of some zinc(II) bis(thiosemicarbazonato)
Introduction
The synthesis of organic compounds with a large number
of donor atoms has acquired special relevance in recent
years owing to their relationship with biological systems
and their ability to detect and remove metals harmful to
humans and the environment.[1–4] Within this group, the
thiosemicarbazones (TSCs) are ligands of great interest be-
cause of their versatility as donor systems, the variety of
chemical species that can result,[5] the wide and important
types of reaction they can undergo, and their biological,
structural and optical properties.[6–10] The design and syn-
thesis of dissymmetric double-Schiff-base ligands contain-
ing this TSC moiety started during the last decade, but only
few research groups have developed efficient strategies as
the accessibility of such dissymmetric ligands is often ham-
pered by several synthetic problems. The problems found in
the synthesis include ring-closure reactions or the obtain-
ment of the corresponding symmetric ligands, as well as
ligand mixtures that are very difficult to purify.[11–13] How-
ever, dissymmetric TSCs open the possibility of a greater
range of donor atoms and allow the properties of metal
complexes to be finely tuned for a variety of possible appli-
cations.[14–17] Complexes with copper have been explored as
[a] Departamento de Química Inorgánica, C/ Francisco Tomás y
Valiente 7, Universidad Autónoma de Madrid,
Cantoblanco, 28049 Madrid, Spain
Fax: +34-91-497-4833
E-mail: antonia.mendiola@uam.es
[‡] Present address: Departamento de Electrocerámica, Instituto
de Cerámica y Vidrio,
C/ Kelsen 5, CSIC, Cantoblanco, 28049 Madrid, Spain
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201200815
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complexes has previously been used to follow cellular up- tral ligand (1 and 9), except the polymeric mercury complex
take and intracellular localization in a range of different 4, in which the ligand was spontaneously singly deproton-
cancer cell phenotypes.[31–33]
ated. In most cases, the ligand charge could be controlled
To better understand the behaviour of this new family of by addition of the appropriate amount of base owing to
dissymmetric thiosemicarbazones, which match the require- the different acidity of the NH groups. In the reactions of
ments for cell labelling and/or chemical sensors for toxic H2AMeTsQ with one or two moles of base, it was possible
–
metals, we report herein the coordination chemistry of a to isolate complexes with one NO3 group and a negatively
–
new hybrid ligand derived from 2-hydrazinoquinoline and charged ligand (2 and 5) or without NO3 with the ligand
4-methyl-3-thiosemicarbazide (H2AMeTsQ) and its chlor- doubly deprotonated (3 and 6). In the reactions of
ide salt [H3AMeTsQ]Cl with cadmium and mercury ni- [H3AMeTsQ]Cl with one equivalent of base, 7 and 9, which
trates.
contain a neutral ligand, could be synthesized as the
The new complexes were fully characterized by elemental LiOH·H2O removed the proton on the quinoline ring.
1
analysis, IR spectroscopy, H, 13C, 113Cd and 199Hg NMR Thus, with two equivalents of base a complex with one sin-
spectroscopy in solution and in the solid state, mass spec- gly deprotonated ligand is obtained (8), whereas with three
trometry, fluorescence spectroscopy and some of them by equivalents of base the ligand is doubly deprotonated to
single-crystal X-ray diffraction.
yield complexes 3 and 6.
Conductivity measurements of 3, 6 and 8 in N,N-dimeth-
ylformamide (DMF) showed that they are molecular spe-
cies, whereas the values observed for 1, 4, 7 and 9 corre-
sponded to 1:1 electrolytes and that for 2 was in the range
expected for 2:1 electrolytes.[34] The value for 5, which is
relatively high for a molecular species, could suggest partial
Results and Discussion
Synthesis
The absence or the presence of hydrochloric acid in the
reaction medium allowed the isolation of the neutral ligand
H2AMeTsQ or its chloride salt [H3AMeTsQ]Cl. The reac-
tivity of both ligands was explored in methanol and in the
presence of one or two equivalents of lithium hydroxide for
H2AMeTsQ and for [H3AMeTsQ]Cl, which has three acidic
hydrogen atoms, three equivalents of base were also used.
All the complexes showed a 1:1 ligand-to-metal stoichiome-
try, although their composition and structure depend on
the reaction conditions, in particular in the amount of base
used (Schemes 1 and 2), as the ligand can behave as a neu-
–
solvolysis of the coordinated NO3 group by DMF mole-
cules. The mass spectra of all the complexes showed peaks
corresponding to the ion [M(HAMeTsQ)]+. In addition, in
the spectrum of 2 the peak corresponding to the fragment
[Cd2(HAMeTsQ)2 + H]+ was observed, which suggests a
dimeric structure. In all the complexes, the calculated and
experimental isotopic splitting patterns were identical.
X-ray Analysis
The crystallographic and refinement data are summa-
tral, singly or doubly deprotonated donor. Thus, the synthe- rized in Table 1. In all the complexes, the ligand behaved at
sis without LiOH·H2O, or with one equivalent when least as a tetradentate N3S chelate, a coordination mode
[H3AMeTsQ]Cl was used, led to the formation of com- that leads to the formation of three five-membered chelate
plexes containing two nitrate groups, and therefore a neu- rings that confer high stability to the compounds. The Sup-
Scheme 1. Proposed structures of complexes obtained from H2AMeTsQ.
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Scheme 2. Proposed structures of complexes obtained from [H3AMeTsQ]Cl.
Table 1. Crystal data and structure refinement for 1, 2 and 4·DMSO.
1
2
4·DMSO
Formula
Formula weight
C15H24CdN8O9S
604.88
C16H23Cd N7O5S
537.87
C17H23HgN7O5S2
670.13
Crystal system
Space group
triclinic
P1
triclinic
P1
monoclinic
Cc
¯
¯
a [Å]
b [Å]
c [Å]
α [°]
9.5909(8)
11.4287(11)
11.8915(11)
113.464(4)
94.039(5)
106.783(5)
1118.93(18)
2
1.795
1.135
612
1.061
9.3384(2)
9.5141(3)
12.7202(5)
102.125(2)
95.684(2)
106.123(2)
1046.47(6)
2
1.707
9.681
544
1.057
15.460(2)
22.132(3)
7.5636(11)
90
117.775(7)
90
2289.8(5)
4
1.944
6.948
1304
1.021
32343
β [°]
γ [°]
U [Å3]
Z
Dc [Mgm–3]
Absorption coefficient [mm–1]
F(000)
Goodness of fit on F2
Reflections collected
Independent reflections
Final R1 and wR2[IϾ2σ(I)]
31148
4893 [R(int) = 0.0438]
0.0273, 0.0.0616
10626
3621 [R(int) = 0.0365]
0.0256, 0.0665
–0.719, 0.816
6495 [R(int) = 0.0573]
0.0277, 0.0630
–1.572, 1.162
Residual electron density (min./max.) [eÅ–3] –0.457, 1.048
porting Information contains a table with the full bond plane (Figure 1). The ligand skeleton can be considered
lengths and angles as well as the hydrogen bonding infor- planar with a maximum deviation from the least-squares
–
mation.
The crystal structure of
plane of 0.056 Å for C(2). The NO3 ion is coordinated in
an asymmetric mode, with one of the Cd–O bond lengths
1
is made up of
a
[Cd(H2AMeTsQ)(H2O)(NO3)]+ cation, a nitrate group and much longer than the other (Table 2). There is an extended
two water molecules. In the cation, the cadmium is coordi- network of hydrogen bonds between the NO3 groups and
–
–
nated to a neutral tetradentate ligand, a bidentate NO3
group and a molecule of water, which results in a capped
the water molecules, which leads to a 3D architecture.
Complex comprises the dimeric
2
unit
octahedral environment with the ligand in the equatorial [Cd(CH3OH)(HAMeTsQ)]22+, two nitrate groups and two
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Figure 1. Molecular structure of 1. The water molecules are omit-
ted for clarity. Thermal ellipsoids at 50% probability.
Figure 2. Molecular structure of 2. The water molecules are omit-
ted for clarity. Thermal ellipsoids at 50% probability.
Table 2. Selected M–L bond lengths in 1, 2 and 4·DMSO.
1
2
4·DMSO
M(1)–N(4)
M(1)–N(5)
M(1)–N(6)
M(1)–S(1)
M(1)–S(1)#1
M(1)–O(1)
M(1)–O(2)
M(1)–O(4)
2.385(2)
2.348(2)
2.2988(19)
2.5410(7)
–
2.406(2)
2.435(2)
2.636(2)
2.320(2)
2.335(2)
2.3044(19)
2.5411(6)
2.7356(6)
2.350(2)
–
2.440(11)
2.417(4)
2.278(4)
2.6458(11)
2.440(4)
–
–
–
–
water molecules (Figure 2). The cadmium ion is hexacoor-
dinated by one monodeprotonated tetradentate ligand, one
methanol molecule and the sulfur atom of a neighbouring
ligand that bridges to another Cd atom. The Cd–Sbridge
bond length is longer than the other Cd–S bond (Table 2).
Deprotonation takes place in the thiosemicarbazone
branch. The ligand is slightly buckled, and the sulfur atom
is 0.29 Å above the least-squares plane defined by C(1)–
N(2)–N(4)–C(2)–C(3)–N(5)–N(3)–C(4)–N(6). The cations,
the water molecules and the nitrates are bonded through
hydrogen bonds in the ac plane. These planes are linked by
CH···C–H interactions between the quinoline rings, which
gives rise to a 3D structure.
Figure 3. Molecular structure of 4·DMSO. The water and DMSO
molecules are omitted for clarity. Thermal ellipsoids at 50% prob-
ability.
Spectroscopy
Complex 4 is made up of [Hg(HAMeTsQ)]+ units, one
The spectroscopic data of the organic molecules confirm
nitrate group, a water molecule and a dimethyl sulfoxide the formation of the new dissymmetric thiosemicarbazone
(DMSO) molecule (Figure 3). In the cation, the mercury is ligands. In the IR spectra of all the complexes, coordination
coordinated to a tetradentate ligand and to the sulfur atom of the thioamide group to the metal was indicated by the
of a neighbouring ligand that bridges two metal centres. shift of the ν(CS) band to lower frequencies compared to
The metal is in a distorted square-base pyramid (sbp), with that of the free ligand. In contrast, the ν(CN) bands were
τ = 0.054 (τ = 0 for sbp and τ = 1 for trigonal bipyramid, almost in the same position, but the crystal structure deter-
tbp).[35] The coordination mode of the ligand affords poly- minations of 1, 2 and 4 confirm coordination of a tetraden-
meric chains that run along the c axis. The nitrate group tate N3S ligand. This could be because thiosemicarbazones
and the water molecule are bonded to the cations through are extensively delocalized systems and the CN bond
hydrogen bonds with the NH groups. Although the hydro- lengths are relatively unaffected by metal coordination. The
gen atoms of the water molecules could not be located, they spectra of 1, 2, 4, 5, 7 and 9 also showed bands at ca.
–
clearly present short contacts with the DMSO molecule and 1385 cm–1 that confirmed the presence of NO3 groups.
with the NO3– ion, which suggests the presence of hydrogen
In the H NMR spectra of both forms (neutral and pro-
1
bonds that link the polymeric chains to form sheets in the tonated) of the ligand, it could be observed that the forma-
ac plane.
tion of the chloride salt caused a greater deshielding of the
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1
Table 3. Chemical shifts δ [ppm] and spin coupling constants J [Hz] observed in the H NMR spectra of the ligands and the complexes
in [D6]DMSO.
3-H
2-H
6-H,
6a-H[a]
1-H
9-H
5-H
11-H
12-H
10-H
15-H
13-H,
14-H
CH3OH
H2AMeTsQ
10.33,
1 H, s
10.14,
1 H, s
8.20,
1 H, d,
3J = 8.8
8.31,
1 H, q,
3J = 4.6
7.80,
1 H, d,
3J = 7.9
7.70–7.55,
3 H, m
7.31,
1 H, t,
3J = 7.3
3.04,
3 H, d,
3J = 4.6
2.26,
6 H, s
–
[H3AMeTsQ]Cl 12.28,
10.41,
1 H, s
8.55,
8.51,
1 H, q,
3J = 4.4
8.01,
1 H, d, 1 H,
3J = 7.7 br. s
8.11,
7.85,
1 H, t,
3J = 7.4
7.77,
1 H, d, 1 H, t,
3J = 9.4 3J = 7.5
7.57,
3.05,
3 H, d,
3J = 4.5
2.45,
3 H, s;
2.39,
–
–
0.8 H,
br. s
1 H, d,
3J = 9.4;
13.03,
3 H, s
0.3 H, br. s
1
2
11.59,
1 H, br. s 1 H, s
10.33,
8.60–8.33,
2 H, m
8.08–7.88,
2 H, m
7.78,
1 H, t,
3J = 7.5
7.57,
1 H, d, 1 H, t,
3J = 9.2 3J = 7.3
7.50,
3.05,
3 H, d,
3J = 4.5
2.37,
3 H, s;
2.35,
3 H, s
11.54,
1 H, s
–
–
8.34,
1 H, d,
3J = 9.0
7.54–7.43, 7.91,
1 H, m
7.29,
7.79,
7.54–7.43,
2 H, m
2.90,
3 H, d,
3J = 2.7
2.36,
3 H, s;
2.32,
4.08,
1 H, d, 1 H, d, 1 H, ddd,
3J = 7.6 3J = 9.0 4J = 1.3,
3J = 7.2,
1 H, q (OH),
3J = 5.2;
3.16,
3 H, d (CH3),
3J = 5.2
3 H, s
3J = 8.3
3
–
7.69,
1 H, d,
3J = 9.1
7.12–6.95, 7.52,
1 H, m
6.79,
7.43,
7.12–6.95,
2 H, m
2.85,
3 H, d,
3J = 4.7
2.24,
3 H, s;
2.23,
–
1 H, d, 1 H, d, 1 H, ddd,
3J = 7.3 3J = 9.1 4J = 1.2,
3J = 7.1,
3 H, s
3J = 8.5
4
5
6
12.12
1 H, s
–
–
–
8.46
1 H, d
3J = 8.4
8.10–7.95
2 H, m
7.43
1 H, d
3J = 8.9
7.93–7.45
2 H, m
7.54
1 H, t
3J = 6.9
2.95
3 H, s
2.38
3 H, s;
2.31
–
–
–
3 H, s
12.06,
1 H, s
8.43,
1 H, d,
3J = 9.0
7.91,
7.98,
7.42,
7.88–7.73,
2 H, m
7.52,
1 H, t,
3J = 7.4
2.93,
3 H, d,
3J = 4.5
2.37,
3 H, s;
2.31,
1 H, q,
3J = 4.5
1 H, d, 1 H, d,
3J = 7.8 3J = 8.9
3 H, s
–
7.59,
7.45–7.33, 7.51,
6.75,
7.45–7.33, 7.26,
7.03,
2.88,
2.24,
1 H, d,
3J = 10.5
1 H, m
1 H, d, 1 H, d, 1 H, m
3J = 6.7 3J = 9.8
1 H, d, 1 H, t,
3J = 9.5 3J = 6.5
3 H, d,
3J = 4.4
3 H, s;
2.20,
3 H, s
7
8
10.39,
1 H, s
10.16,
1 H, s
8.21,
1 H, d,
3J = 8.7
8.33,
1 H, q,
3J = 4.1
7.81,
1 H, d,
3J = 7.9
7.74–7.53,
3 H, m
7.33,
1 H, t,
3J = 7.4
3.03,
3 H, d,
3J = 4.5
2.27,
6 H, s
–
–
11.67,
1 H, br. s
–
8.26,
1 H, d,
3J = 9.0
7.49–7.36, 7.87,
1 H, m
7.25,
7.72,
7.49–7.36,
2 H, m
2.89,
3 H, d,
3J = 4.4
2.35,
3 H, s;
2.29,
1 H, d, 1 H, d, 1 H, t,
3J = 7.7 3J = 9.0 3J = 7.5
3 H, s
9
11.99,
1 H, s
10.68,
1 H, s
8.48,
1 H, s
8.88,
1 H, s
7.98,
1 H, d, 1 H, s
3J = 7.8
8.04,
7.82,
1 H, t,
3J = 7.2
7.65–7.36,
2 H, m
3.02,
3 H, d,
3J = 4.5
2.39,
6 H, s
–
[a] Only present in [H3AMeTsQ]Cl.
majority of the hydrogen atoms (Table 3). The additional of 2, 4, 5 and 8 showed only the loss of the acidic hydrogen
proton due to the protonation of the quinoline ring was atom from the thiosemicarbazone portion of the ligand,
not fully observed in [D6]DMSO, probably because of an which indicates that the ligand was singly deprotonated.
exchange with residual water molecules in the solvent. The The double deprotonation in 3 and 6 could be confirmed
1H NMR spectra of all the complexes confirmed the depro- by the lack of any signal above 10 ppm.
tonation state of the ligand as well as the loss of the hydro-
In the 13C NMR spectra of all the complexes, the signals
gen atom on the quinoline ring. The presence of two signals corresponding to the CS and CN groups and the quinoline
above 10 ppm, which correspond to the hydrogen atoms ring were shifted with respect to those of the free ligand,
from the acidic amine groups, in the spectra of compounds which indicates coordination through these groups. In the
1, 7 and 9 showed that the ligand was neutral. The spectra spectra of the mercury complexes, the shift of the CS signal
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to lower field was considerably larger than in the cadmium
derivatives, as could be expected, because the Hg–S bond is
stronger than the Cd–S bond.
It is known that the 113Cd chemical shift is very sensitive
to changes in the coordination number of cadmium as well
as to the nature of the bonding. Replacement of a sulfur
atom by a nitrogen or oxygen atom tends to give greater
shielding,[36–40] and a decrease in the coordination number
tends to give greater deshielding.[41,42] The presence of only
one signal in the spectra of all the complexes indicated only
one type of chemical environment for the cadmium ion. In
1, the signal was observed at δ = 122 ppm (–520 ppm vs.
CdMe2), which was in agreement with the N3SO3 environ-
ment found in the crystal structure. In 2, the value was
250 ppm (–392 ppm vs. CdMe2), which shows a lower coor-
dination number and an increase in the number of sulfur
atoms bound to the metal, as expected for the N3S2O envi-
ronment confirmed by X-ray analysis (Figure 4). In the
113Cd cross polarization magic angle spinning (CP/MAS)
NMR spectra of 3, 7 and 8, signals at 441, 418 and
440 ppm, respectively, could be observed (Figure 5), which
suggests that the cadmium ion in all three complexes has
the same coordination number and that it is lower than that
of 1 and 2. In view of the data from the other techniques,
a N3S2 coordination environment was proposed for 3 and
a N3SCl coordination environment for 7 and 8. The spec-
trum of 3 in DMSO showed a signal at δ = 307 ppm
(–335 ppm vs. CdMe2), which indicates coordination of the
solvent and therefore a higher coordination number.
Figure 5. 113Cd CP/MAS NMR spectra of 3, 7 and 8.
Figure 4. 113Cd NMR spectra ([D6]DMSO) of 1 and 2.
Figure 6. 199Hg NMR spectra of 4, 5, 6 ([D6]DMSO) and 9 (DMF
+ [D6]DMSO) ppm.
The 199Hg NMR is a useful tool for the determination
of the metal environment because the chemical shift is very
sensitive to its coordination sphere. According to the litera-
ture, a decrease in the coordination number tends to give –1124.1 ppm, respectively. The similarity of these shifts sug-
greater deshielding.[43–47] The spectra of 4, 5, 6 and 9 (Fig- gests that mercury had the same coordination number in all
ure 6) showed signals at –1133.8, –1111.2, –1042.3 and of the complexes and they are close to those found in other
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thiosemicarbazonate complexes in which the metal is penta- transfer mechanism, in which electron delocalization on the
coordinate.[44,48]
quinoline ring increases upon complexation and decreases
From the spectroscopic and analytical data, as well as the the fluorescence emission.[50,51] This charge delocalization
X-ray diffraction of 1, 2 and 4, we propose the structures increases when the ligand is deprotonated, so the fluores-
summarized in Schemes 1 and 2 for the rest of the com- cence intensity of the complexes with the neutral ligand is,
plexes.
in general, higher.
Fluorescence
The fluorescence emission spectra of H2AMeTsQ and its
chloride salt [H3AMeTsQ]Cl are shown in Figure 7. Both
forms of the ligand show fluorescence emission at similar
wavelengths, although for the neutral form it is more in-
tense. This difference can be justified by a quenching of the
fluorescence caused by the chloride ion. In fact, the de-
crease in the fluorescence intensity when the quinolinium
chloride is formed makes quinoline species suitable as fluo-
rescent sensors for the measurement of intracellular chlor-
ide ion levels.[49]
Figure 8. Emission spectra of H2AMeTsQ, 1, 4, 7, 8 and 9 (10–4 m)
in DMSO (λexc = 325 nm).
Conclusions
A new dissymmetric thiosemicarbazone ligand contain-
ing a hydrazonequinoline limb, H2AMeTsQ, was synthe-
sized as well as its chloride salt [H3AMeTsQ]Cl, and the
reactivity of both ligands with cadmium and mercury ni-
trate was explored. Owing to the different acidity of the NH
hydrogen atoms, the charge of the ligand could be con-
trolled by the use of stoichiometric amounts of lithium hy-
droxide, which led to the formation of complexes with dif-
ferent structural characteristics. In all of the complexes, the
ligand binds in a tetradentate N3S mode and in some com-
plexes also as a bridge through the sulfur atom to form
dimeric species and a coordination polymer. Both forms of
the ligand showed fluorescence emission, although the neu-
tral ligand was more fluorescent than the salt. Complex-
ation induced a quenching of the fluorescence emission, es-
pecially when the ligand was singly or doubly deprotonated.
Figure 7. Emission spectra of H2AMeTsQ and [H3AMeTsQ]Cl
(10–4 m) in DMSO (λexc = 325 nm).
Excitation of the complexes revealed a general quenching
of the fluorescence intensity. One maximum was observed
for 1, 4, 7 and 9, two were observed for 3 and 8, which were
considerably shifted with respect to that of H2AMeTsQ
(Figure 8), and complexes 2, 5 and 6 were not fluorescent;
in general, the cadmium derivatives were more fluorescent
than the mercury complexes. For the cadmium compounds
with a neutral ligand (1 and 7), the highest fluorescence
intensity was observed, followed by the mercury complex 9,
which also contains a neutral ligand. In 1 and 7, the maxi-
mum was not significantly shifted with respect to that of
the uncoordinated ligand, whereas in 9 it was shifted to
higher wavenumbers by 10 nm. The other complexes
showed significantly lower intensities. From these data, it
can be clearly concluded that deprotonation of the ligand
induces a decrease or a loss of the fluorescence emission
and reveals the importance of the electronic delocalization
in the quinoline ring, even when deprotonation takes place
in the thiosemicarbazone arm. The fluorescence quenching
Experimental Section
Materials and General Methods: All reagents were obtained from
standard commercial sources and were used as received.
Caution! Mercury and cadmium are highly toxic cumulative poisons,
and their compounds should be handled carefully.
Microanalyses were performed with a LECO CHNS-932 Elemental
Analyzer. IR spectra in the 4000–400 cm–1 range were recorded as
KBr pellets with a Jasco FT/IR-410 spectrophotometer. Fast atom
bombardment mass spectra were recorded with a VG Auto Spec
instrument using Cs as the fast atom and m-nitrobenzylalcohol (m-
NBA) as the matrix. Electrospray mass spectrometry experiments
were performed with an ion trap instrument LCQ Deca XP plus
might take place through a photoluminiscent electron (Thermo Instruments). An ESI source was used in positive ioniza-
Eur. J. Inorg. Chem. 2013, 80–90
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tion mode. Conductivity was measured using a freshly prepared
[H3AMeTsQ]Cl: This compound was prepared following the same
procedure described above, but in the presence of conc. HCl
(0.35 mL, 3.96 mmol). The suspension was stirred at room tem-
perature for 24 h. The yellow precipitate formed was collected by
filtration, washed with methanol and dried in vacuo; yield 91%
(0.92 g). If less hydrochloric acid than the stoichiometric amount
was added, a mixture of H2AMeTsQ and [H3AMeTsQ]Cl was ob-
tained. Both compounds can be easily isolated due to their different
solubilities; [H3AMeTsQ]Cl is less soluble. C15H19ClN6S (350.87):
calcd. C 51.35, H 5.46, N 23.95, S 9.14; found C 51.41, H 5.48, N
DMF solution (ca. 10–3 m) at 25 °C with a Crison EC-Meter BA-
1
SIC 30+ instrument. H, 13C, 113Cd and 199Hg NMR spectra were
recorded with a Bruker AMX-300 spectrometer using [D6]DMSO
or DMF/[D6]DMSO as solvents and using tetramethylsilane (TMS,
1H and 13C), CdMe2 and HgMe2 as internal references. 113Cd and
199Hg NMR experiments were recorded at 298 K using 10–1 m solu-
tions. 13C CP/MAS NMR spectra were recorded at 298 K with a
Bruker AV400WB spectrometer equipped with a 4 mm MAS NMR
probe and were obtained using a cross-polarization pulse sequence.
The external magnetic field was 9.4 T, the sample was spun at 10–
14 kHz and the spectrometer frequency was 100.61 MHz. For the
recorded spectra, a contact time of 4 ms and recycle delays of 4 s
were used. Chemical shifts are reported relative to TMS, using the
CH group of adamantane as a secondary reference (δ = 29.5 ppm).
113Cd CP/MAS NMR spectra were recorded with the same spec-
trometer, and the chemical shifts are reported relative to 0.1 m
Cd(ClO4)2 and with Cd(NO3)2·4H2O as secondary reference
(–100 ppm). Fluorescence emission spectra were recorded with a
Hitachi F-4500 fluorescence spectrophotometer using freshly pre-
pared DMSO solutions (ca. 10–4 m) at 25 °C.
24.09, S 9.10. IR (KBr): ν = 3377 (w), 3302 (m), 3279 (s), 3225 [s,
˜
ν(NH)], 1652 (vs), 1614 (m), 1606 (s), 1546 [s, ν(C=N) and thioam-
ide II], 822 (w, thioamide IV) cm–1. 1H NMR (300 MHz, [D6]-
DMSO): δ = 13.03 (br. s, 0.3 H, 6a-H), 12.28 (br. s, 0.8 H, 3-H),
3
3
10.41 (s, 1 H, 2-H), 8.55 (d, J = 9.4 Hz, 1 H, 6-H), 8.51 (q, J =
4.4 Hz, 1 H, 1-H), 8.11 (br. s, 1 H, 5-H), 8.01 (d, 3J = 7.7 Hz, 1 H,
9-H), 7.85 (t, J = 7.4 Hz, 1 H, 11-H), 7.77 (d, J = 9.4 Hz, 1 H,
3
3
3
3
12-H), 7.57 (t, J = 7.5 Hz, 1 H, 10-H), 3.05 (d, J = 4.5 Hz, 3 H,
15-H), 2.45 (s, 3 H, 13-H or 14-H), 2.39 (s, 3 H, 13-H or 14-H)
ppm. 13C CP/MAS NMR (400 MHz): δ = 178.2 (C-1), 152.8 (C-4,
C-2, C-3), 143.0 (C-8), 136.0 (C-6), 133.9 (C-11), 132.0 (C-9), 126.8
(C-12), 122.8 (C-10), 117.3 (C-7), 109.7 (C-5), 33.0 (C-15), 12.9 (C-
13, C-14) ppm. MS (ESI+): m/z = 315.1 [M]+.
2-Hydrazinoquinoline: A suspension of 2-chloroquinoline (1.50 g,
9.17 mmol) in hydrazine monohydrate (3 mL, 61.85 mmol) was
stirred under reflux for 2 h. The orange solid formed was collected
by filtration, washed with 100 mL of water and dried in vacuo;
yield 82% (1.20 g). C9H9N3 (159.19): calcd. C 67.90, H 5.70, N
[Cd(NO3)(H2AMeTsQ)(H2O)]NO3·2H2O (1): To a suspension of
H2AMeTsQ (100 mg, 0.32 mmol) in methanol (30 mL), a solution
of cadmium nitrate tetrahydrate (100 mg, 0.32 mmol) in methanol
(2 mL) was added. The solution was stirred under reflux for 8 h.
The yellow precipitate formed was collected by filtration, washed
with methanol and dried in vacuo; yield 75% (0.145 g). Yellow
crystals suitable for X-ray diffraction were obtained by slow evapo-
1
26.40; found C 67.50, H 5.64, N 26.30. H NMR (300 MHz, [D6]-
DMSO): δ = 8.04 (s, 1 H, NH), 7.86 (d, 3J = 9.0 Hz, 1 H, 6-H),
4
3
7.60 (dd, J = 1.1, J = 7.9 Hz, 1 H, 9-H), 7.56–7.44 (m, 2 H, 11-
4
3
3
H, 12-H), 7.15 (ddd, J = 1.4, J = 6.8, J = 8.0 Hz, 1 H, 10-H),
6.84 (d, 3J = 9.0 Hz, 1 H, 5-H), 4.30 (s, 2 H, NH2) ppm. 13C NMR
(300 MHz, [D6]DMSO): δ = 159.6 (C-4), 147.9 (C-6), 136.8 (C-8),
129.6 (C-11), 128.0 (C-9), 125.9 (C-12), 123.8 (C-10), 121.9 (C-7),
111.7 (C-5) ppm. MS (EI+): m/z = 159.1 (100) [M·]+.
ration of the mother liquor. M.p. 247 °C (decomposition). ΛM
=
69.5 Ω–1 cm2 mol–1. C15H24CdN8O9S (604.86): calcd. C 29.78, H
4.00, N 18.53, S 5.30; found C 30.02, H 3.88, N 18.62, S 5.36. IR
(KBr): ν = 3433 (m), 3234 (m), 3125 (w), 3225 [s, ν(OH), ν(NH)],
˜
1646 (s), 1621 (m), 1577 (s), 1505 [m, ν(C=N), thioamide II, +
δ(H2O)], 1384 [s, ν(NO)], 839 (w, thioamide IV) ppm. 13C NMR
(300 MHz, [D6]DMSO): δ = 179.1 (C-1), 157.1 (C-4), 150.7, 147.4
(C-2, C-3), 144.1 (C-8), 137.0 (C-6), 133.2 (C-11), 129.3 (C-9), 126.4
(C-12), 123.3 (C-10), 119.7 (C-7), 112.9 (C-5), 31.8 (C-15), 13.2,
12.4 (C-13, C-14) ppm. 13C CP/MAS NMR (400 MHz): δ = 173.6
(C-1), 155.0 (C-4), 151.6, 148.6 (C-2, C-3), 143.1 (C-8), 136.1 (C-
6), 132.2 (C-11), 128.6 (C-9), 125.4 (C-12), 122.4 (C-10, C-7), 112.7
(C-5), 32.8 (C-15), 12.5, 10.4 (C-13, C-14) ppm. 113Cd NMR
(300 MHz, [D6]DMSO): δ = 122.2 ppm. MS (ESI+): m/z = 427.0
[Cd(HAMeTsQ)]+. This complex can also be obtained from
[H3AMeTsQ]Cl.
Diacetyl-2-(4-methyl-3-thiosemicarbazone): This compound was
synthesized from 2,3-butanedione (diacetyl) and 4-methyl-3-thiose-
micarbazide, in water and in the presence of conc. HCl at 0 °C,
in accordance with a previously reported procedure.[52] 1H NMR
(300 MHz, [D6]DMSO): δ = 10.65 (s, 1 H, NH), 8.62 (m, 1 H,
NHCH3), 3.05 (d, 3 H, NHCH3), 2.42 (s, 3 H, CH3C=O), 1.96 (s, 3
H, CH3C=N) ppm. 13C NMR (300 MHz, [D6]DMSO): δ = 197.45
(C=O), 178.90 (C=S), 145.45 (C=N), 31.37 (NHCH3), 24.73
(CH3C=O), 9.99 (CH3C=N) ppm. MS (ESI+): m/z = 174.1 [M +
H]+.
H2AMeTsQ: To a suspension of HAMeTs (0.50 g, 2.89 mmol) in
dry methanol (15 mL), a solution of 2-hydrazinoquinoline (0.46 g,
2.89 mmol) in dry methanol (17 mL) was added. The mixture was
stirred at room temperature for 24 h. The pale-yellow solid formed
was collected by filtration, washed with methanol and dried in
vacuo; yield 68% (0.62 g). C15H18N6S (314.41): calcd. C 57.30, H
5.77, N 26.73, S 10.20; found C 57.20, H 5.60, N 26.65, S 10.10.
[Cd(HAMeTsQ)(CH3OH)]2(NO3)2·2H2O (2): A solution of cad-
mium nitrate tetrahydrate (69 mg, 0.22 mmol) in methanol (2 mL)
was added to a suspension of H2AMeTsQ (70 mg, 0.22 mmol) and
LiOH·H2O (9 mg, 0.22 mmol) in methanol (20 mL). The suspen-
sion was stirred under reflux for 5 h. The scarce amount of solid
formed was separated by filtration and discarded, and then the
IR (KBr): ν = 3343 (s), 3309 (s), 3229 [s, ν(NH)]; 1619 (m), 1606 solvent was partially evaporated and cooled to 4 °C until a yellow
˜
(s), 1575 (m), 1551 [s, ν(C=N) and thioamide II], 866 (w, thioamide
solid precipitated, which was collected by filtration, washed with
1
IV) cm–1. H NMR (300 MHz, [D6]DMSO): δ = 10.33 (s, 1 H, 3- cold methanol and dried in vacuo; yield 71% (0.084 g). Yellow crys-
3
3
H), 10.14 (s, 1 H, 2-H), 8.31 (q, J = 4.6 Hz, 1 H, 1-H), 8.20 (d, J
tals suitable for X-ray analysis were obtained by slow evaporation
3
= 8.8 Hz, 1 H, 6-H), 7.80 (d, J = 7.9 Hz, 1 H, 9-H), 7.70–7.55 (m,
of mother liquor. M.p. 262 °C (decomposition). ΛM
=
3
3 H, 5-H, 11-H, 12-H), 7.31 (t, J = 7.3 Hz, 1 H, 10-H), 3.04 (d,
185.5 Ω–1 cm2 mol–1. C32H46Cd2N14O10S2 (1075.72): calcd. C 35.73,
3J = 4.6 Hz, 3 H, 15-H), 2.26 (s, 6 H, 13-H, 14-H) ppm. 13C NMR
H 4.31, N 18.23, S 5.96; found C 35.69, H 4.23, N 18.14, S 5.85.
(300 MHz, [D6]DMSO): δ = 178.9 (C-1), 156.4 (C-4), 149.1, 147.4 IR (KBr): 3433 (m), 3276 (s), 3229 [s, ν(OH), ν(NH)], 1638 (w),
(C-2, C-3), 145.5 (C-8), 138.6 (C-6), 130.3 (C-11), 128.4 (C-9), 126.3 1615 (s), 1608 (s), 1588 (w), 1540 [s, ν(C=N), thioamide II, δ(H2O)],
(C-12), 125.0 (C-10), 123.5 (C-7), 110.3 (C-5), 31.7 (C-15), 12.0, 1385 [s, ν(NO)], 831(w, thioamide IV) cm–1. 13C NMR (300 MHz,
11.5 (C-13, C-14) ppm. MS (ESI+): m/z = 315.1 [M + H]+.
[D6]DMSO): δ = 175.0 (C-1), 152.5 (C-4), 145.8 (C-2, C-3), 143.7
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(C-8), 140.6 (C-6), 131.8 (C-11), 129.0 (C-9), 125.8 (C-12), 125.1
(C-10), 125.0 (C-7), 113.3 (C-5), 30.0 (C-15), 15.0, 14.8 (C-13, C- by filtration, washed with methanol and dried in vacuo; yield 95%
14) ppm. 113Cd NMR (300 MHz, [D6]DMSO): δ = 249.7 ppm. MS (0.116 g). M.p. 180 °C (decomposition). ΛM = 2.8 Ω–1 cm2 mol–1.
at room temperature for 24 h. The red solid formed was collected
(FAB+): m/z (%) = 851.0 (7) [Cd2(HAMeTsQ)2 + H]+, 427.0 (70) C15H18HgN6OS (531.00): calcd. C 33.92, H 3.42, N 15.83, S 6.02;
[Cd(HAMeTsQ)]+.
found C 34.01, H 3.50, N 15.73, S 5.98. IR (KBr): ν = 3428 (m),
˜
3332 [s, ν(OH), ν(NH)], 1617 (s), 1548 (s), 1532 [s, ν(C=N), thioam-
ide II, δ(H2O)], 811 (w, thioamide IV) cm–1. 13C NMR (300 MHz,
[D6]DMSO): δ = 160.9 (C-1), 148.8 (C-4), 145.5 (C-2, C-3), 144.8
(C-8), 135.9 (C-6), 130.2 (C-11), 128.2 (C-9), 124.2 (C-12), 123.4
(C-10), 121.9 (C-7), 121.4 (C-5), 29.8 (C-15), 14.9, 14.1 (C-13, C-
14) ppm. 199Hg NMR (300 MHz, [D6]DMSO): δ = –1042.3 ppm.
MS (ESI+): m/z = 515.1 [Hg(HAMeTsQ)]+. This complex is also
formed with [H3AMeTsQ]Cl in the presence of two or three mol
of lithium hydroxide.
[Cd(AMeTsQ)]2·H2O (3): A solution of cadmium nitrate tetrahy-
drate (71 mg, 0.23 mmol) in methanol (2 mL) was added to a sus-
pension of H2AMeTsQ (70 mg, 0.22 mmol) and LiOH·H2O
(19 mg, 0.44 mmol) in the same solvent (20 mL). The suspension
was stirred for 24 h at room temperature. The red precipitated
formed was collected by filtration, washed with methanol and dried
in vacuo; yield 87% (0.085 g). M.p. 150 °C (decomposition). ΛM
=
2.7 Ω–1 cm2 mol–1. C30H34Cd2N12OS2 (867.60): calcd. C 40.68, H
4.10, N 18.98, S 7.24; found C 40.94, H 4.16, N 19.15, S 7.36. IR
Complexes from [H3AMeTsQ]Cl: The reactions were carried out
in the same conditions described for the complexes obtained from
H2AMeTs: metal to ligand ratio 1:1, in methanol as solvent and
also in the absence or in the presence of 1, 2 or 3 equiv. of
LiOH·H2O.
(KBr): ν = 3430 (s), 3322 (s), 3203 [m, ν(OH), ν(NH)], 1617 (s),
˜
1546 (s), 1529 [s, ν(C=N), thioamide II, δ(H2O)], 822 (w, thioamide
IV) cm–1. 13C NMR (300 MHz, [D6]DMSO): δ = 173.8 (C-1), 161.5
(C-4), 147.5, 146.4 (C-2, C-3), 142.5 (C-8), 136.3 (C-6), 130.0 (C-
11), 128.0 (C-9), 124.2 (C-12), 123.2 (C-10), 121.3 (C-7), 121.0 (C-
5), 29.9 (C-15), 14.8, 13.8 (C-13, C-14) ppm. 113Cd NMR
(300 MHz, [D6]DMSO): δ = 307.2 ppm. 113Cd CP/MAS NMR
[Cd(Cl)(H2AMeTsQ)]NO3·H2O (7): This yellow compound was
obtained in the presence of 1 mol of LiOH·H2O; yield 79%
(0.056 g). M.p. 258 °C (decomposition). ΛM = 69.3 Ω–1 cm2 mol–1.
CdC15H20N7SO4 (506.84): calcd. C 35.55, H 3.98, N 19.34, S 6.33;
(400 MHz):
δ = 441.4 ppm. MS (ESI+): m/z = 427.0
[Cd(HAMeTsQ)]+. This complex can also be synthesized from
[H3AMeTsQ]Cl in the presence of three mol of lithium hydroxide.
found C 40.94, H 4.16, N 19.15, S 7.36. IR (KBr): ν = 3447 (m),
˜
3188 (m), 3157 [m, ν(OH), ν(NH)], 1647 (m), 1615 (s), 1604 (s),
1583 (s), 1528 [s, ν(C=N), thioamide II, δ(H2O)], 1385 [s, ν(NO)],
835 (w, thioamide IV) cm–1. 13C NMR (300 MHz, [D6]DMSO): δ
= 178.6 (C-1), 155.1 (C-4), 149.7, 147.9 (C-2, C-3), 143.5 (C-8),
139.6 (C-6), 130.9 (C-11), 128.6 (C-9), 124.6 (C-12), 124.1 (C-10),
113.2 (C-7), 111.1 (C-5), 31.7 (C-15), 12.2, 11.9 (C-13, C-14) ppm.
113Cd CP/MAS NMR (400 MHz): δ = 418.1 ppm. MS (ESI+): m/z
= 427.0 [Cd(HAMeTsQ)]+.
[[Hg(HAMeTsQ)]NO3·H2O]n (4): To a suspension of H2AMeTsQ
(75 mg, 0.24 mmol) in methanol (20 mL), a suspension of mercury
nitrate monohydrate (82 mg, 0.24 mmol) in methanol (2 mL) was
added. The mixture was stirred at room temperature for 3 d. The
yellow solid formed was collected by filtration, washed with meth-
anol and dried in vacuo; yield 78% (0.111 g). Suitable crystals for
X-ray diffraction were obtained by slow evaporation of a solution
in DMSO. M.p. 135 °C (decomposition). ΛM = 78.4 Ω–1 cm2 mol–1.
C15H19HgN7O4S (594.01): calcd. C 30.32, H 3.23, N 16.51, S 5.39;
[Cd(Cl)(HAMeTsQ)] (8): This complex was formed in the presence
of 2 mol of LiOH·H2O; yield 88% (0.063 g). M.p. 288 °C (decom-
position). ΛM = 6.5 Ω–1 cm2 mol–1. CdC15H17N6SCl (461.27): calcd.
C 39.06, H 3.71, N 18.22, S 6.95; found C 38.74, H 3.62, N 18.10,
found C 30.05, H 3.38, N 16.70, S 5.47. IR (KBr): ν = 3334 (m),
˜
3222 (m), 3191 (m), 3146 [m, ν(OH) + ν(NH)], 1648 (m), 1617 (s),
1606 (s), 1540 [m, ν(C=N), thioamide II, δ(H2O)], 1385 [s, ν(NO)],
835 (w, thioamide IV) cm–1. 13C NMR (300 MHz, [D6]DMSO): δ
= 167.7 (C-1), 151.8 (C-4), 146.2, 144.8 (C-2, C-3), 142.6 (C-8),
141.9 (C-6), 132.6 (C-11), 129.4 (C-9), 125.8 (C-12), 125.4 (C-10),
125.0 (C-7), 114.1 (C-5), 29.9 (C-15), 14.0, 13.0 (C-13, C-14) ppm.
199Hg NMR (300 MHz, [D6]DMSO): δ = 1133.8 ppm. MS (ESI+):
m/z = 515.1 [Hg(HAMeTsQ)]+.
S 6.93. IR (KBr): ν = 3320 (s), 3195 (m), 3153 [w, ν(NH)], 1617
˜
(s), 1608 (s), 1581 (m), 1531 [s, ν(C=N), thioamide II], 828 (w,
thioamide IV). 13C CP/MAS NMR (400 MHz): δ = 172.5 (C-1),
153.5 (C-4), 147.2 (C-2, C-3), 144.4 (C-8), 140.6 (C-6), 131.4 (C-
11), 129.0 (C-9), 125.9 (C-12, C-10, C-7), 111.7 (C-5), 28.8 (C-15),
16.5 (C-13, C-14) ppm. 113Cd CP/MAS NMR (400 MHz): δ =
439.7 ppm. MS (ESI+): m/z = 427.0 [Cd(HAMeTsQ)]+.
[Hg(NO3)(HAMeTsQ)] (5): A suspension of mercury nitrate mono-
hydrate (76 mg, 0.22 mmol) in methanol (2 mL) was added to a
suspension of H2AMeTsQ (70 mg, 0.22 mmol) and LiOH·H2O
(9 mg, 0.22 mmol) in methanol (20 mL). The suspension was
stirred at room temperature for 48 h. The orange solid was col-
lected by filtration, washed with methanol and dried in vacuo;
[Hg(NO3)(H2AMeTsQ)]NO3 (9): This complex was obtained in the
absence or in the presence of 1 mol of LiOH·H2O; yield 73%
(0.065 g). M.p. 202 °C (decomposition). ΛM = 67.0 Ω–1 cm2 mol–1.
HgC15H18N8SO6 (639.01): calcd. C 28.19, H 2.84, N 17.54, S 5.02;
found C 28.24, H 2.99, N 17.60, S 5.84. IR (KBr): ν = 3353 (s),
˜
yield 77% (0.098 g). M.p. 174 °C (decomposition). ΛM
=
3295 (s), 3194 (m), 3104 [w, ν(NH)], 1650 (s), 1617 (m), 1532 [w,
ν(C=N), thioamide II], 1385 [s, ν(NO)], 828 (w, thioamide IV)
cm–1. 13C CP/MAS NMR (400 MHz): δ = 170.4 (C-1), 152.4 (C-
4), 148.7, 145.3 (C-2, C-3), 141.1 (C-8, C-6), 135.0 (C-11), 129.7
(C-9), 126.6 (C-12), 122.2 (C-10), 119.8 (C-7), 112.6 (C-5), 29.2 (C-
15), 17.5, 15.5 (C-13, C-14) ppm. 199Hg NMR (300 MHz,
47.0 Ω–1 cm2 mol–1. C15H17HgN7O3S (575.99): calcd. C 31.27, H
2.98, N 17.03, S 5.55; found C 31.40, H 3.12, N 17.19, S 5.54. IR
(KBr): ν = 3352 [m, ν(NH)], 1616 (m), 1544 (m), 1536 [m, ν(C=N),
˜
thioamide II], 1385 [s, ν(NO)], 827 (w, thioamide IV) cm–1. 13C
NMR (300 MHz, [D6]DMSO): δ = 168.1 (C-1), 151.9 (C-4), 146.2
(C-2, C-3), 142.9 (C-8), 141.6 (C-6), 132.4 (C-11), 129.3 (C-9), 125.6
(C-12), 125.4 (C-10), 125.0 (C-7), 114.1 (C-5), 29.7 (C-15), 15.1,
14.9 (C-13, C-14) ppm. 199Hg NMR (300 MHz, [D6]DMSO): δ =
–1111.2 ppm. MS (ESI+): m/z = 515.1 [Hg(HAMeTsQ)]+.
[D6]DMSO):
δ = –1124.1 ppm. MS (ESI+): m/z = 515.0
[Hg(HAMeTsQ)]+.
X-ray Crystallography: The data for 1, 2 and 4 were acquired with
a Bruker AXS Kappa Apex-II diffractometer equipped with an
Apex-II CCD area detector with a graphite monochromator (Mo-
Kα radiation, λ = 0.71073 Å). The substantial redundancy in data
allowed empirical absorption corrections (SADABS)[53] to be ap-
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0.23 mmol) and LiOH·H2O (20 mg, 0.48 mmol) in methanol
(20 mL), a suspension of mercury nitrate monohydrate (79 mg,
0.23 mmol) in methanol (2 mL) was added. The mixture was stirred
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SAINT program, which also applied corrections for Lorentz and
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CCDC numbers 883498 (for 1), -883499 (for 4) and -883500 (for 2)
contain the supplementary crystallographic data for this paper.
These data can be obtained free of charge from the Cam-
bridge Crystallographic Data Centre via www.cdcc.cam.ac.uk/
data_request/cif.
Supporting Information (see footnote on the first page of this arti-
cle): Table with the full bond lengths and angles as well as the
hydrogen bonding information.
Acknowledgments
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We thank César J. Pastor from “Servicio Interdepartamental de
Investigación” (SidI) of the Universidad Autónoma de Madrid
(Spain) for the crystal measurements. We also thank the Ministerio
de Economía y Competitividad, Instituto de Salud Carlos III for
funding (project number PS09/00963).
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Received: July 17, 2012
Published Online: November 7, 2012
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