Binuclear isophthaloylbis(N,N-diphenylthioureate) transition metal complexes: Synthesis, spectroscopic, thermal and structural characterization

Article abstract of DOI:10.1016/j.molstruc.2020.127999

The isophthaloylbis(N,N-diphenylthiourea) molecule (H₂L ligand) reacts with Cu^I, Cu^II, Mn^III, Fe^II, Fe^III and Co^II ions to form binuclear complexes with formula [M₂(L-

Full text of DOI:10.1016/j.molstruc.2020.127999

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Binuclear isophthaloylbis(N,N-diphenylthioureate) transition metal complexes:
Synthesis, spectroscopic, thermal and structural characterization
Estefane Isis Teixeira, Cristiane Storck Schwalm, Gleison Antônio Casagrande,
Bárbara Tirloni, Vânia Denise Schwade
PII:
S0022-2860(20)30324-0
DOI:
https://doi.org/10.1016/j.molstruc.2020.127999
MOLSTR 127999
Reference:
To appear in: Journal of Molecular Structure
Received Date: 28 October 2019
Revised Date: 23 February 2020
Accepted Date: 3 March 2020
Please cite this article as: E.I. Teixeira, C.S. Schwalm, Gleison.Antô. Casagrande, Bá. Tirloni,
Vâ.Denise. Schwade, Binuclear isophthaloylbis(N,N-diphenylthioureate) transition metal complexes:
Synthesis, spectroscopic, thermal and structural characterization, Journal of Molecular Structure (2020),
doi: https://doi.org/10.1016/j.molstruc.2020.127999.
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Credit Author Statement
Binuclear isophthaloylbis(N,N-diphenylthioureate) transition metal
complexes: synthesis, spectroscopic, thermal and structural characterization
Estefane Isis Teixeira a, Cristiane Storck Schwalm a, Gleison Antônio Casagrande b,
Bárbara Tirloni c, Vânia Denise Schwade a, *
Estefane Isis Teixeira: Investigation, Visualization.
Cristiane Storck Schwalm: Investigation, Formal analysis (NMR) and discussion.
Gleison Antônio Casagrande: Formal analysis (solid state UV-Vis) and discussion.
Bárbara Tirloni: Formal analysis (single crystal X-ray diffraction, Raman), Resources.
Vânia Denise Schwade: Conceptualization, Methodology, Validation, Resources,
Writing - Review & Editing.

Binuclear isophthaloylbis(N,N-diphenylthioureate) transition metal complexes:
synthesis, spectroscopic, thermal and structural characterization
Estefane Isis Teixeira a, Cristiane Storck Schwalm a, Gleison Antônio Casagrande b, Bárbara
Tirloni c, Vânia Denise Schwade a, *
a Faculty of Exact Sciences and Technology, Federal University of Grande Dourados, Rod.
Dourados/Itahum, Km 12, 79804-970, Dourados/MS, Brazil
b Institute of Chemistry, Federal University of Mato Grosso do Sul, Av. Sen. Filinto Müller,
1555, 79074-460, Campo Grande/MS, Brazil
c Department of Chemistry, Natural and Exact Sciences Centre, Federal University of Santa
Maria, Av. Roraima, n.1000, 97105-900, Santa Maria/RS, Brazil
Corresponding author
* vaniaschwade@gmail.com and vaniaschwade@ufgd.edu.br
Highlights
The isophthaloylbis(N,N-diphenylthiourea) molecule reacts with metal ions which undergo, in
some cases, oxidation or reduction to form stable 2:2 or 2:3 metal to ligand stoichiometric
complexes. The transition metal complexes [M2(L-O,S)2] (M = CuII (1), NiII (2)), [M2(L-
O,S)3] (M = FeIII (4), CoIII (5)) and [Mn2(L-O,S)2(dmso)2] (3) were obtained. Complex 3
represents the first manganese complex with thiourea derivative ligand.
Abstract
The isophthaloylbis(N,N-diphenylthiourea) molecule (H2L ligand) reacts with CuI, CuII, MnIII,
FeII, FeIII and CoII ions to form binuclear complexes with formula [M2(L-O,S)2] (M = CuII (1),
NiII (2)) or [M2(L-O,S)3] (M = FeIII (4), CoIII (5)). In presence of dimethyl sulfoxide, [Mn2(L-
O,S)2(dmso)2] (3) was successfully obtained and represents the first manganese complex with
any thiourea derivative ligand. The ligand and the complexes were characterized by
spectroscopic techniques and elemental analysis. Complexes 1, 3, 4 and 5 were structurally
analyzed by single crystal X-ray diffraction data, confirming the O,S chelating coordination
mode. The stoichiometries were confirmed by thermal analysis with formation of the
corresponding metal oxides. The set of the performed analysis corroborated that some metal

ions undergo oxidation or reduction to form stable 2:2 or 2:3 metal to ligand stoichiometric
complexes with H2L.
Keywords: isophthaloylbis(N,N-diphenylthiourea), metal complexes, X-ray diffraction, UV-
Vis, NMR, Raman.
1. Introduction
Thiourea derivatives possess applications in the field of medicine, agriculture and analytical
chemistry. These compounds exhibit a range of biological activities and some of them have
shown, for example, good results as antitumor agents [1]. Thiourea based fluorescent
photoinduced electron transfer (PET) chemosensors containing neutral aromatic thiourea as
receptors have been studied [2], as well as colorimetric naked-eye chemosensors involving
proton transfer-based thiourea derivatives [3]. The thiourea groups of bis(thioureas) were used
as sites for anion receptor systems (such as F‒ and AcO‒) induced by hydrogen binding
interactions of host for high recognition selectivity for guest [4]. CuII and NiII compounds
with bis(thiourea) derivatives have been screened for their antioxidant and cytotoxic
inhibitions [5]. Additionally, thioureas and their metal complexes have been studied
concerning corrosion inhibitor potential and catalytic activities [6].
N-benzoylthioureas are versatile bidentate ligands in coordination chemistry, chelating metal
ions mainly in an O,S fashion. Symmetrical quadridentate bis(N-acyl/aroyl-thioureas) are able
to chelate two metal ions due to both N-acyl/aroylthioureas functions. These organic
molecules are known as bipodal derivatives and are also suitable for the synthesis of
multinuclear complexes with diverse architectures controlled by their design. Metal ions such
as CuII and NiII form stable complexes with bis(N-aroylthioureas) [7‒9], however, to the best
of our knowledge, there are no reports of MnII and CoIII complexes with isophthaloylbis(N,N-
dialkyl/aryl-thioureas) reported in the literature. In this way, this paper reports the structural
and additional characterization of a CuII complex (and the formation of an analogous NiII
compound), as well as the spectroscopic, thermal and structural characterization of MnII, FeIII
and CoIII binuclear complexes with isophthaloylbis(N,N-diphenylthiourea).
2. Materials and methods
2.1. Chemicals and apparatus

All the metal salts for the synthesis of the complexes were used as received from commercial
sources. N,N-diphenylamine and isophthaloyl chloride were purchased from Sigma-Aldrich.
KSCN was dried in an oven at 80 ºC for 2 hours. Acetone was dried with anhydrous CaSO4
and distilled prior to the use for the synthesis of H2L. Cu(PPh3)3Br was prepared according to
the literature [10]. The elemental analyses were performed on a Perkin Elmer 2400 series II
Elemental Analyzer. UV-Vis spectra were recorded at 1×10‒5 mol L-1 concentration in DMF
solution on a BEL photonics UV-M51 spectrophotometer. Solid UV-Vis spectra were
obtained on a Perkin-Elmer UV-Vis lambda 650S spectrophotometer. IR spectra (KBr pellets)
were recorded on a Jasco FT-IR-4100 spectrophotometer in the 4000‒400 cm-1 range (4 cm-1
of resolution). Raman spectra were measured on a Bruker SENTERRA Raman Microscope
from 3500 to 50 cm-1. NMR spectra were recorded on a Bruker DPX-NMR or Avance III
1
spectrometer, operating at 400 or 500 MHz for H nuclei, respectively, using THF-d8 or
CDCl3 as solvents. High-resolution mass spectra for H2L was obtained on a Micromass
Waters Q-Tof spectrometer (ESI positive mode) in acetonitrile. TG-DSC curves were
obtained on a NETZSCH STA 449 F3 thermal analyser using air atmosphere in the range of
30‒1000 ºC with heating rate of 10 ºC min-1 on an α-alumina crucible. The single crystal data
collection for the complexes was performed on a Bruker D8 Venture Photon 100
diffractometer with graphite monochromated Mo Kα radiation (λ = 0.71073 Å). The
structures were solved by direct methods, and least-squares refinement of the structures was
performed by the SHELXL-2018 program [11]. All the non-hydrogen atoms were refined
anisotropically. The hydrogen atoms were placed in calculated positions and refined
isotropically.
2.2. Synthesis
2.2.1. Synthesis of isophthaloylbis(N,N-diphenylthiourea), H2L
The synthesis of H2L was done under nitrogen atmosphere according to the literature [1, 12]
with some modifications. An acetone solution (30 mL) of isophthaloyl chloride (2.03 g, 0.01
mol) was added dropwise, by using an addition funnel, to an acetone solution (30 mL) of
potassium thiocyanate (1.94 g, 0.02 mol). The solution became turbid white. This mixture was
stirred for additional 1 h at room temperature. Then, a diphenylamine (3.38 g, 0.02 mol)
solution (in 25 mL of acetone) was slowly added using an addition funnel. The mixture turned
slightly orange with a clear solid. After heating under reflux and stirring for 30 min, the
mixture was cooled to room temperature and then poured on a beaker with cold water in an

ice bath. A gelatinous product formed and the supernatant was removed. To the gelatinous
product was added methanol, affording the H2L ligand as a yellow solid. In another
procedure, solid H2L was also obtained by storing the aqueous mixture in the refrigerator for
approximately 12 h.
Purification of the crude product was done in column chromatography using ethyl
acetate/hexane or chloroform/methanol mixtures as eluents.
2.2.2. Synthesis of the metal complexes
[Cu2(L-O,S)2] (1). CuCl2ꢀ2H2O (34 mg, 0.20 mmol) was dissolved in 3 mL of methanol and
added to a H2L (117 mg, 0.20 mmol) solution in 8 mL of dichloromethane in the presence of
0.30 mL of triethylamine. After 1.5 h under stirring at room temperature, the formed solid was
isolated by simple filtration, washed with methanol and dried.
The same product was obtained in a reaction using Cu(PPh3)3Br (0.20 mmol) instead of
CuCl2ꢀ2H2O. In this case, the copper(I) starting material was dissolved in 5 mL of an
acetonitrile/dichloromethane mixture (1:1). The clear solution was stored and needle shaped
brown crystals of [Cu2(L-O,S)2]ꢀ2CH2Cl2 were formed within one day.
[Ni2(L-O,S)2] (2). NiCl2ꢀ6H2O (47 mg, 0.20 mmol) was dissolved in 3 mL of methanol and
added to a H2L (117 mg, 0.20 mmol) solution in 8 mL of dichloromethane containing 0.30
mL of triethylamine. After 1.5 h under stirring at room temperature, the formed solid was
filtered, washed with methanol and dried.
[Mn2(L-O,S)2(dmso)2] (3). Mn(OAc)3ꢀ2H2O (80 mg, 0.30 mmol) was dissolved in 2 mL of
dimethyl sulfoxide and added to a H2L (176 mg, 0.30 mmol) solution in 3.5 mL of
dichloromethane with 0.30 mL of triethylamine. After 1.5 h under stirring at room
temperature, the solution was filtered and stored. Within 5 days the orange-red block shaped
crystals of [Mn2(L-O,S)2(dmso)2]ꢀ4DMSOꢀ0.5H2O were collected.
[Fe2(L-O,S)3] (4). FeSO4ꢀ7H2O (56 mg, 0.20 mmol) was dissolved in 3 mL of methanol and
added to a H2L (176 mg, 0.30 mmol) solution in 8 mL of dichloromethane in presence of 0.45
mL of triethylamine. The solution changed to turbid black. After 1.5 h under stirring at room
temperature, the formed solid was collected by filtration, washed with methanol and dried.

The same product was also obtained in reaction using FeCl3 (0.20 mmol) and N,N-
dimethylformamide as solvent.
Recrystallization was performed from dichloromethane solution with slow diffusion of diethyl
ether. Within 2 days black plate shaped crystals of [Fe2(L-O,S)3]ꢀ0.25CH2Cl2ꢀ0.35H2O were
obtained.
[Co2(L-O,S)3] (5). CoCl2ꢀ6H2O (48 mg, 0.20 mmol) was dissolved in 4 mL of acetonitrile
and added to a H2L (176 mg, 0.30 mmol) solution in 8 mL of dichloromethane. The solution
became green. Then 0.45 mL of triethylamine was added and some green solid started to
form. After 1.5 h under stirring at room temperature, the solid was isolated by simple
filtration and the solution was left to slow evaporation of the solvents. After 7 days, green
needle shaped crystals of [Co2(L-O,S)3]ꢀ6CH3CNꢀ0.5CH2Cl2ꢀ0.5H2O were observed.
When the same synthesis was carried out replacing acetonitrile by methanol, green plate
shaped crystals of [Co2(L-O,S)3]ꢀ4CH2Cl2ꢀCH3OHꢀ4H2O were formed in the mother solution.
If more methanol (8 mL) was added to the green solution after 1 h of reaction, precipitation of
a green solid is observed. The solid was isolated by filtration within 30 min of additional
stirring, washed with methanol and dried. In the next day, the additional green solid which
deposited in the mother solution was also isolated.
3. Results and discussion
3,3,3′,3′-tetraphenyl-1,1′-isophthaloylbis(thiourea), namely in this paper isophthaloylbis(N,N-
diphenylthiourea) – H2L, can be prepared, as other examples of bipodal 3,3,3′,3′-
tetraalkyl/aryl-1,1′-aroylbis(thioureas), through the reaction of isophthaloyl chloride and
potassium thiocyanate, followed by the addition of the corresponding secondary amine
(Scheme 1).

Scheme 1. Synthesis of the H2L bipodal ligand.
Isophthaloylbis(N,N-diphenylthiourea) can be used as a pre-designed chelating ligand to form
MII and MIII complexes via self-assembly. Metal to ligand stoichiometries of 2:2 and 2:3 can
be achieved, as it has been reported before for CuII, InIII, FeIII and some other metal complexes
with isophthaloylbis(N,N-diethylthiourea) [9, 13]. All the complexes (Scheme 2) were
obtained in moderate yields and characterized by analytical and spectral techniques. The X-
ray crystal structures of compounds [Cu2(L-O,S)2] (1), [Mn2(L-O,S)2(dmso)2] (3), [Fe2(L-
O,S)3] (4) and [Co2(L-O,S)3] (5) reveal binuclear arrangements. For the [Ni2(L-O,S)2] (2)
compound it is suggested to possess the same structure as 1, which is supported by analytical
and spectral data. Compound 2 presented poor solubility in most of the common organic
solvents, even in pyridine, when an adduct could be formed [14, 15]. No evidences of adduct
formation was observed since the solid maintained its color and did not dissolve even under
mild heating. In the literature, related NiII adducts have green color, being the crystals very
fragile, disintegrating rapidly on removal from the pyridine mother liquor [14]. Additionally,
due to the low solubility, it cannot be ruled out the possibility of a polymeric structure with
formula {Ni(L-O,S)}n.

Scheme 2. Synthesis of 2:2 and 2:3 self-assembled MII and MIII complexes. Conditions: r.t., 2
h, Et3N as base.
Reactions of isophthaloylbis(N,N-diphenylthiourea), H2L, with metal(II) ions in the presence
of triethylamine as base yielded binuclear complexes. Characterization and structure analysis
of the complexes were accomplished by elemental analysis, spectroscopic techniques such as
IR and Raman, as well as electronic absorption and thermal analysis. The prepared complexes
have shown characteristic colors, indicating oxidation of the metal ions in case of using CuI,
FeII and CoII salts as starting materials, and reduction in case of using MnIII salt. Oxidations
are attributed to the atmospheric oxygen present during the reaction synthesis. Reduction of
MnIII to MnII is probably related to the oxidation of some ligand during the reaction to
promote the reduction of MnIII. The consumption of part of the ligand in the redox reaction
led to a lower yield of complex 3. It is well known that thiourea oxidizes chemically and

electrochemically [16, 17]. In the oxidation, S‒S bonds are formed (Eq. 1) which, in this case,
can happen between two bis(thiourea) molecules or between distinct molecules (Figure 1).
Oxidation has been also observed with aroilselenoureas in the formation of
benzoylformamidine diselenide [18]. Additionally, manganese (III) acetate is used as an
oxidizing agent for many oxidations of organic compounds [19]. Finally, the reaction between
H2L bis(thiourea) and Mn(OAc)3 represents a clear redox process.
2C6H4[C(O)NHC(S)N(C6H5)2]2 → {C6H4[C(O)N=CN(C6H5)2]2S}2 + 4e‒ + 4H+
Eq. 1
Figure 1. Representation proposal of S‒S bonds formation in the oxidation of thiourea.
The complexes are stable at room temperature and have shown hygroscopicity, as can be seen
in the elemental analysis results. Table 1 summarizes the important analytical and physical
data of the ligand and complexes 1 − 5. The ligand to metal stoichiometries of the complexes
are 2:2 or 2:3. In case of complex 3, dimethyl sulfoxide is present as a ligand and as a
crystallization solvent in the complex since this compound was obtained only as a crystalline
product. In all other complexes, the solvents dichloromethane, acetonitrile or methanol
(present in the crystal structures in some cases) are presumably not present in the powder
samples due to their volatility.
Table 1. Analytical and physical data of H2L ligand and metal complexes.
Elemental analysis, %
Comp. Ligand/Complex
Yield
(%)
Found/(Calc.)
Color
Yellow
Brown
Nr.
M. Formula (F. Wt)
C
H
N
H2L
53
70.01
(69.60)
61.45
(61.29)
4.80
8.82
C34H26N4O2S2 (586.73)
[Cu2(L-O,S)2]·2H2O
C68H52N8O6S4Cu2 (1332.54)
(4.47) (9.55)
3.31 8.42
(3.93) (8.41)
82
1

[Ni2(L-O,S)2]·H2O
Light
70
62.72
3.62
(3.86) (8.59)
4.21 6.19
(4.88) (6.38)
3.64 8.84
(4.16) (8.67)
3.91 8.57
(4.01) (8.81)
8.46
2
3
4
5
C68H50N8O5S4Ni2 (1304.82)
brown
(62.59)
53.33
[Mn2(L-O,S)2(dmso)2]·4DMSO·0.5H2O Reddish 32
C80H85N8O10.5S10Mn2 (1757.10)
[Fe2(L-O,S)3]·4H2O
orange
Black
(54.68)
62.52
89
98
C102H80N12O10S6Fe2 (1937.88)
[Co2(L-O,S)3]·2H2O
(63.22)
64.89
Green
C102H76N12O8S6Co2 (1908.03)
(64.21)
The obtention of the H2L bipodal ligand was confirmed by mass spectrometry and by infrared,
1
Raman and H and 13C NMR spectroscopies. In the high resolution mass spectrum of the
ligand, the [M+H]+ peak was detected at m/z 587.1945 (calc. 587.1575). The peak at m/z
1173.3719 (calc. 1173.3073) refers to a protonated ion cluster, [M2+H]+, indicating that the
molecule might exist as a dimer under the ionization conditions. The spectra are given in the
Supporting Information (Figures S1‒S3). Possible α‒thioamide cleavage occurs under the
ionization condition since peaks at m/z 418.0981 (calc. 418.0678) and m/z 212.0777 (calc.
212.0528) are observed.
NMR spectroscopy
In the 1H NMR spectra of the ligand (in THF-d8), the NH protons are observed as a singlet at
10.19 ppm and the ortho-carbonyl hydrogens from the isophtalic spacer are observed as a
triplet at 7.93 ppm (1H, J = 1.5 Hz) and a doublet of doublets at 7.72 ppm (2H, J = 7.7 and
1.7 Hz). The signal from the remaining phenylene hydrogen most probably overlaps with the
two broad multiplets observed between 7.4‒7.1 ppm, which correspond to the remaining
twenty hydrogens from the two N-diphenyl terminal substituents. These data are presented in
Table 2.
1
The H NMR spectrum of the ligand was also recorded in CDCl3 in order to allow a straight
comparison with a CoIII complex analyzed in the same solvent. In this case, the NH protons
are observed as a broad singlet at 8.84 ppm, while the hydrogens from the spacer appear as
singlet at 7.87 ppm (1H), a doublet of doublets at 7.74 ppm (2H, J = 7.8 and 1.6 Hz) and a
triplet at 7.41 ppm (1H, J = 7.8 Hz). This latter signal partially overlaps with a multiplet (7.4-
7.3 ppm), corresponding to the remaining hydrogens from the two N-diphenyl terminal

substituents. The observed chemical shifts compare well with an analogous
isophthaloylbis(N,N-diethylthiourea) derivative [7].
13
In the C NMR spectra of the same compound (Figure 2), the signals at δ 185.4 and 163.2
ppm are attributed to the thiocarbonyl and carbonyl groups, respectively. Although there are
no 13C NMR data available in the literature for comparison, all the expected signals related to
the aromatic carbons of this ligand were also accounted for and their chemicals shifts are
consistent with the proposed structure. An attempted attribution is presented in Table 2.
Table 2. 1H and 13C NMR chemical shifts for H2L and tentative attributions. 1H NMR
chemical shifts for CoIII complex.
13C chemical shifts for H2L in THF-d8
C=S
(C6)
C=O
(C5)
Phenylene central ring
Phenyl rings
C1
C2
C3
C4
C7/C7’ C8/C8’ C9/C9’ C10/C10’
185.4 163.2 128.6
132.5
134.8
129.2
147.6
129.7 and 128.2
127.6
1H chemical shifts
Phenylene central ring
H1 H3 H4
Phenyl rings
N‒H
(H8-H10/H8’-H10’)
7.4 ‒ 7.1 (m)
10.19 (s) 7.93 (t) 7.72 (dd) 7.4 ‒ 7.1
H2L (THF-d8)
8.84 (s) 7.87 (s) 7.74 (dd) 7.41 (t)
7.4 ‒ 7.3 (m)
H2L (CDCl3)
‒
9.50 (t) 7.43 (dd) 6.89 (t)
7.4 ‒ 7.2 (m)
[Co2(L-O,S)3] (5) (CDCl3)

Figure 2. 13C NMR spectrum (100 MHz) of H2L in THF-d8.
The CoIII (d6) binuclear complex could also be analyzed by NMR spectroscopy due to its
diamagnetic low spin character (t2g eg configuration). Its 1H NMR spectrum was obtained in
CDCl3 as the solvent (Figure S6), and the absence of the NH resonance signal clearly
indicates a complexation reaction involving deprotonation of H2L. Further evidence of
complex formation are the shifts of the signals related to hydrogens on the isophtalic spacer of
the ligand, now observed at δ 9.50 (t, J = 1.6 Hz), 7.43 (dd, J = 7.7 Hz, J = 1.8 Hz) and 6.89
(t, J = 7.7 Hz) ppm. The upfield for the H4 signal shift (from 7.41 to 6.89 ppm), as well as the
remarkable downfield shift for H1 (from 7.87 to 9.50 ppm), follow the same pattern
previously described for a binuclear InIII complex formation with an analogous ligand [9]. The
chemical shifts are listed in Table 2.
6
0
Infrared and Raman spectroscopy
Tables 3 and 4 present the significant IR and Raman spectral data of isophthaloylbis(N,N-
diphenylthiourea), H2L ligand, and its metal complexes. Figure 3 shows the IR spectra of the
ligand and its complexes for comparison. It can be noted that the IR spectra present a small
broad band in 3360‒3440 cm‒1 region due to the absorbed water molecules (hygroscopic
solids). The Raman spectrum of H2L can be found in the supplementary material (Figure S4).

Table 3. Comparison between selected IR and Raman spectral data for H2L (cm‒1).
H2L
IR
Raman
ν(N‒H) ν(C‒H) ν(C=O)
ν(C=C)
*
ν(NCN) ν(C=S) δ(C‒H)
3166
3061
3063
1699
1703
1590, 1453
1591, 1453
1490
1491
1364
1365
1212
1163
1002
1004
‒
ν: stretching vibration; δ: bending vibration; * probably a combination of ν(C=C) and other vibrations.
Table 4. Selected IR and Raman spectral data of the metal complexes.
∙∙∙
∙∙∙
Nr. Complex
ν(C‒H)
ν(C‒O) ν(C=C) ν(NCO)
ν(NCN)
ν(NCS)
ν(C‒N) δ(C‒H)
∙∙∙
+ ν(C‒C)
3061
1505
1586,
1489
1587
1586,
1491
1587
1585,
1491
1588
1417
1374
1286
1243
1003
IR
[Cu2(L-O,S)2]
1
2
3072
3057
1505
1508
1446
1415
1382
1384
1299
1290
1268
1249
1002
1003
Raman
IR
[Ni2(L-O,S)2]
3055
3059,
2907
3084,
2887
3058
1521
1514
1460
1406
1387
1358
1293
1289
1272
1235
1001
1003
Raman
IR
[Mn2(L-
3
O,S)2(dmso)2]
1530
1506
1440
1422
1362
1381
1289
1285
1264
1244
1003
1003
Raman
IR
1589,
1489
1593
1588,
1490
1591
[Fe2(L-O,S)3]
[Co2(L-O,S)3]
4
5
3057
3060
1524
1517
1454
1410
1394
1370
1293
1284
1266
1246
1003
1003
Raman
IR
3047
1512
1447
1390
1292
1268
1002
Raman
ν: stretching vibration; δ: bending vibration.

Figure 3. IR spectra of H2L and metal complexes.
In the IR spectrum of H2L, the C=O and C=S stretching vibration band appear at 1699 and
1212 cm‒1, respectively. The N‒H stretching band is observed at 3166 cm‒1. These values are
close to those reported earlier for this molecule and analogues [1, 12]. On comparison of the
IR spectra of the ligand with its metal complexes, the N‒H stretching band disappears and the
C=O stretching band shifted from 1699 cm‒1 to around 1510 cm‒1. This shift of more than 150
cm‒1 to lower frequencies means that with the deprotonation on the –C(S)-NH-C(O)‒
fragments of the ligand a charge delocalization occurs between the isophthaloylbis(thioureate)
anions on coordinating with the metal ions, reflecting the formation of O,S chelates (Figure
4). The same trend of shifting would be expected for the thiocarbonyl stretching vibration
frequencies, however this vibration for the complexes could not be assigned unambiguously
since it is located in the fingerprint zone of the IR spectra.

Figure 4. Representation of the deprotonation process with charge delocalization in the chelating rings.
In the Raman spectra, the symmetric and antisymmetric M‒O and M‒S stretching modes are
probably located in the 420–260 cm-1 range (Figure 5). The exact attribution cannot be done
without support of computational studies.
Figure 5. Raman spectra of the complexes in the 900‒100 cm‒1 region. The ν(M‒O) and ν(M‒
S) bands are probably located in the window highlighted with the blue dashed lines.

UV-Vis spectroscopy
The electronic absorption spectra of H2L was investigated in solution and in solid state
(Figure 6). In solution, a thin band at 268 nm and another large band centered at
approximately 328 nm could be identified. The band at 268 nm is characteristic for π→π*
intraligand charge transition (ICT) and its intensity agrees with the presence of several
aromatic groups in H2L. The band at 328 nm can be attributed to n→π* ICT involving
electron pairs of carbonyl and thiocarbonyl groups. In the solid state, there are three bands in
the spectrum: at 250, 312 and 375 nm. The bands at 250 and 312 nm should be related to the
π→π* transitions of the phenyl and isophthalic rings, while the band at 375 nm is assigned to
n→π* transitions. For comparison, in solid state, absorption due to n→π* transitions has been
observed for terphenyl carboxylic acid derivative at 365 nm [20] and, in case of
bis(thiosemicarbazones), it has been observed at ca. 333 nm [21]. For the bis(thiourea) ligand
in this work, possible N‒HꢀꢀꢀS hydrogen bonds between bis(thiourea) molecules in the solid
state might be promoting UV-Vis absorptions at lower energies compared to absorption in
solution.
Figure 6. Solid state and DMF solution UV-Vis spectra of H2L.

The metal complexes formation was also confirmed by the UV-Vis spectra. In the solid state,
ligand to metal charge transitions (LMCT) and d‒d transitions are more easily observed than
in diluted solutions. These transitions appear as large bands in the range of 450 to 800 nm of
the spectra, as it can be seen in Figure 7. Complexes 1 and 2 have shown bands from 700 to
460 nm, related to d‒d electronic transitions, typical for ions in quadratic environment: (ν1 =
2Eg → 2T2g), for CuII (d9); and (ν2 = 3T1g(F) → 3T1g(P)), for NiII (d8) [22]. Complexes 4 and 5,
which are isostructural species due to their octahedral environments, have shown a broad
band centered at 570 nm (complex 4) or 650 nm (complex 5). For the CoIII (d6) complex, also
a slight shoulder at 480 nm can be observed, being these bands attributed to the electronic d‒d
1
1
1
1
transitions (ν1 = A1g → T1g and ν2 = A1g → T2g), typical for CoIII in octahedral
environment [23]; while for the FeIII (d5) complex, the (ν1 = 2T2g → 6A1g) electronic transition
appears. The same 2T2g → 6A1g electronic transition is observed for the isoelectronic MnII (d5)
complex (complex 3) throughout the band centered at approximately 525 nm. For all the
complexes, the highest energy bands (centered approximately at 380 and 250 nm) are related
to the LMCT and π‒π* electronic transitions (involving aromatic rings of the ligand in the
latter case), respectively.
Figure 7. Solid state UV-Vis spectra of the complexes.

In solution, the UV-Vis spectra of the complexes showed a hyperchromic effect when
compared with the free ligand. This effect is related to the appearance of new LMCT
electronic transitions, which take place after the complexation of the ligands to the metal
centers. These bands are centered at approximately 290 nm, except for complex 3, where this
band is not clearly observed, suggesting that de MnII ions hardly alter the electronic properties
of the ligand [20]. Indeed, the ICT (n→π*) and LMCT bands mask the absorptions due to d‒d
transitions in diluted solutions [24]. The π‒π* band remained unchanged at 267 nm (see
Figure S5 in the supplementary material).
Thermogravimetric analysis
The thermal stability of the complexes was assigned by thermogravimetric analysis. The
metal:ligand stoichiometry inspection was done for all the complexes. The TG data for the
investigations were collected in the temperature range of 30‒1000 ºC. Complex 3 was
thermally analyzed using the crystals of [Mn2(L-O,S)2(dmso)2]·4DMSO·0.5H2O. In the TG-
DSC curves of complex 3 (Figure 8) it can be noted that there is a significant mass loss below
200 ºC (104‒167 ºC), which can be explained by the loss of the solvate molecules as an
endothermic process. This mass loss corresponds to 18.12% (calc. 18.30%). The coordinated
dimethyl sulfoxide molecules are probably eliminated in the subsequent mass loss event when
the bis(thioureate) ligands decomposition starts. At 900 ºC, the complete ligands
decomposition under oxidative atmosphere (exothermic processes) leads to formation of
manganese oxide (MnO) with residue amount of 9.75% (calc. 8.07%).

Figure 8. TG-DSC curves of complex 3 in air atmosphere.
The thermogravimetric analysis for complexes 1, 2, 4 and 5 was performed using the powder
samples isolated at the end of the reaction synthesis. By analysis of the TG curves (Figure S7)
it can be noted that for the [M2(L-O,S)2] (M = Cu, Ni) and [M2(L-O,S)3] (M = Fe, Co)
complexes the decomposition begins up to 150 ºC. Mass loss events due to the decomposition
of the bis(thioureate) ligands were observed under the oxidative atmosphere. A single
decomposition step has been observed for complex 2. At 900 ºC, the formation of metal
oxides MO (M = Cu, Ni) or M2O3 (M = Fe, Co) as residues were evaluated. The residues
amounts for MO are 8.54% (calc. 11.61% for 2) and 11.68% (calc. 12.27% for 1) while for
M2O3 the amounts are 9.61% (calc. 8.56% for 4) and 11.14% (calc. 8.86% for 5).
Complex 2 showed the highest stability (up to 350 ºC). This observation probably reflects the
strong interaction of NiII ions and the deprotonated thiourea ligands which does not allowed
us to proceed recrystallization for its structural analysis since there was no solubility.
Crystal structures
Compounds 1, 3, 4 and 5 were structurally analyzed by single crystal X-ray diffraction. Table
5 presents the relevant crystallographic data. All complexes have shown binuclear
compositions. The structure of 2 is expected to be isostructural to complex 1. The
crystallographic data for compound 1 confirms the proposed structure given earlier in the

literature for CuII complex with isophthaloylbis(N,N-diphenylthiourea) [25]. The ellipsoids
plots of the structures are available in the supporting information (Figures S8‒S12). The X-
ray diffraction data for complex 4 were collected at 296 K and the solvents could not be
solved in a better way, however it does not gives doubt about the structure of the complex.

Table 5. Crystal and structure refinement data for compounds 1, 3, 4 and 5. Crystals of 5 were obtained with different solvate molecules.
Compound
[Cu2(L-O,S)2]ꢀ2CH2Cl2,
1
[Mn2(L-O,S)2(dmso)2]
ꢀ4DMSOꢀ0.5H2O, 3
[Fe2(L-O,S)3]
ꢀ0.25CH2Cl2ꢀ0.35H2O, 4
[Co2(L-O,S)3]
[Co2(L-O,S)3]
ꢀ6CH3CNꢀ0.5CH2Cl2ꢀ0.5H2O ꢀ4CH2Cl2ꢀCH3OHꢀ4H2O, 5’
, 5
Molecular formula
Formula weight
Temperature (K)
Crystal system
C70H52Cl4Cu2N8O4S4
1466.31
100(2)
Triclinic
P‒1
C80H85Mn2N8O10.5S10
1757.03
120(2)
Triclinic
P‒1
C102.25H73.20Cl0.50Fe2N12O6.35S6 C114.5H92ClCo2N18O6.5S6
C107H92Cl8Co2N12O11S6
2315.74
100(2)
Triclinic
P‒1
1893.31
2169.73
296(2)
100(2)
Monoclinic
P21/n
Triclinic
P‒1
Space group
Unit cell dimensions
a = 9.9410(13) Å
b = 13.548(3) Å
c = 13.973(2) Å
α = 118.607(5)°
β = 98.742(4)°
γ = 94.507(5)°
1607.9(4)
a = 11.8863(5) Å
b = 13.0807(5) Å
c = 15.1958(6) Å
α = 78.8780(10)°
β = 74.0000(10)°
γ = 66.5560(10)°
2074.35(14)
1
a = 15.8208(7) Å
b = 19.9111(10) Å
c = 33.1344(17) Å
α = 90°
β = 97.701(2)°
γ = 90°
a = 15.4752(8) Å
b = 17.7934(8) Å
c = 21.8201(11) Å
α = 87.184(2)°
β = 85.367(2)°
γ = 65.716(2)°
5457.9(5)
a = 15.9503(7) Å
b = 18.1067(9) Å
c = 21.7058(10) Å
α = 87.422(2)°
β = 84.309(2)°
γ = 64.2730(10)°
5619.5(5)
Volume (Å3)
Z
10343.5(9)
4
1
2
2
Absorption coefficient
1.015
0.619
0.471
0.507
0.659
(mm‒1)
F(000)
750
915
3912
2248
2384
Reflections collected /
independent
Data / restraints /
parameters
48927 / 9784 [R(int) =
0.1237]
9784 / 0 / 415
66817 / 12692 [R(int) = 616811 / 32157 [R(int) =
72632 / 33253 [R(int) =
0.0770]
33253 / 1 / 1345
84132 / 18547 [R(int) =
0.0669]
18547 / 0 / 1276
0.0422]
0.1736]
12692 / 9 / 530
32157 / 1074 / 1149
2
1.032
1.032
1.051
1.042
1.029
Goodness-of-fit on F
Final R indices
[I>2sigma(I)]
R1 = 0.0700, wR2 =
0.1418
R1 = 0.0523, wR2 =
0.1253
R1 = 0.0994, wR2 = 0.2371
R1 = 0.0836, wR2 = 0.1860
R1 = 0.1032, wR2 = 0.2794
R indices (all data)
R1 = 0.1409, wR2 =
0.1611
R1 = 0.0749, wR2 =
0.1349
R1 = 0.1905, wR2 = 0.2826
R1 = 0.1825, wR2 = 0.2197
R1 = 0.1371, wR2 = 0.3060

The coordination by the O,S donor atoms is expected in complexes containing deprotonated
bis(thioureas) working as anionic ligands. The binuclear crystal structures of the CuII (1), MnII
(3) and CoIII (5) complexes are shown in Figures 9–11. For the FeIII complex (4), the structure
is virtually identical to the CoIII complex (5) and, for this reason, no additional figures are
given for it. Selected bond lengths and angles of complexes 1, 3, 4 and 5 are summarized in
Table 6. The corresponding labeling scheme for complex 4 has been adopted from Figure 10a.
(a)
(b)
Figure 9. (a) Molecular structure of [Cu2(L-O,S)2]ꢀ2CH2Cl2, 1. (b) View along the planar
center of the molecule. Hydrogen atoms and solvent molecules were omitted for clarity.
Symmetry operator: ‘ ‒x+1, ‒y+1, ‒z+2.

(a)
(b)
Figure 10. Molecular structure of [Mn2(L-O,S)2(dmso)2]ꢀ4DMSOꢀ0.5H2O, 3. (b) View along
the planar center of the molecule. Hydrogen atoms and solvent molecules were omitted for
clarity. Symmetry operator: ’ ‒x+1, ‒y+1, ‒z+1.

(a)
(b)
Figure 11. (a) Molecular structure of [Co2(L-O,S)3]ꢀ4CH2Cl2ꢀCH3OHꢀ4H2O, 5’; (b) View
along the Co‒Co connecting direction. Hydrogen atoms and solvent molecules were omitted
for clarity.

Table 6. Selected bond lengths (Å) in compounds 1, 3, 4 and 5.
Bond
(M = Cu or Mn)
M(1)-S(1)
[Cu2(L-O,S)2]
ꢀ2CH2Cl2, 1
2.2414(10)
2.2513(10)
[Mn2(L-O,S)2(dmso)2]
ꢀ4DMSOꢀ0.5H2O, 3
2.5243(6)
Bond
(M = Fe or Co)
M(1)-S(1)
M(1)-S(3)
M(1)-S(5)
M(2)-S(2)
M(2)-S(4)
M(2)-S(6)
[Fe2(L-O,S)3]
ꢀ0.25CH2Cl2ꢀ0.35H2O, 4
2.4042(13)
[Co2(L-O,S)3]
ꢀ6CH3CNꢀ0.5CH2Cl2ꢀ0.5H2O, 5
2.2150(10)
[Co2(L-O,S)3]
ꢀ4CH2Cl2ꢀCH3OHꢀ4H2O, 5’
2.2196(19)
M(1)-S(2)’
2.4924(6)
2.4371(12)
2.4229(13)
2.4655(12)
2.4347(13)
2.2315(12)
2.2500(11)
2.2205(10)
2.2041(10)
2.2185(19)
2.208(2)
2.214(2)
2.247(2)
2.4093(12)
2.2153(10)
2.221(2)
M(1)-O(1)
M(1)-O(2)’
M(1)-O(3)
1.937(2)
1.944(2)
---
2.0804(14)
2.0758(15)
2.0694(16)
M(1)-O(1)
M(1)-O(3)
M(1)-O(5)
M(2)-O(2)
M(2)-O(4)
M(2)-O(6)
2.004(3)
2.006(3)
1.978(3)
2.038(3)
1.993(3)
1.993(3)
1.931(3)
1.939(2)
1.913(2)
1.935(2)
1.942(2)
1.906(2)
1.932(5)
1.914(5)
1.942(5)
1.922(5)
1.913(5)
1.930(5)
S(1)-C(13A)
S(2)-C(14A)
1.728(4)
1.725(4)
1.712(2)
1.714(2)
S(1)-C(13A)
S(2)-C(14A)
S(3)-C(23A)
S(4)-C(24A)
S(5)-C(33A)
S(6)-C(34A)
1.720(4)
1.723(4)
1.727(5)
1.701(5)
1.737(5)
1.731(5)
1.727(4)
1.733(4)
1.732(4)
1.728(4)
1.740(4)
1.721(4)
1.735(7)
1.726(8)
1.732(7)
1.755(9)
1.729(7)
1.723(8)
O(1)-C(11A)
O(2)-C(12A)
1.267(4)
1.267(4)
1.261(2)
1.259(2)
O(1)-C(11A)
O(2)-C(12A)
O(3)-C(21A)
O(4)-C(22A)
O(5)-C(31A)
O(6)-C(32A)
1.257(5)
1.253(5)
1.252(5)
1.258(5)
1.254(5)
1.264(5)
1.257(4)
1.254(4)
1.259(5)
1.258(4)
1.263(4)
1.267(4)
1.273(8)
1.247(9)
1.252(9)
1.256(9)
1.274(8)
1.268(8)
Symmetry operation used to generate equivalent atoms: ‘ [‒x+1, ‒y+1, ‒z+2, for 1]; [‒x+1, ‒y+1, ‒z+1, for 3].

The analysis of the crystal structures shows that the isophthaloylbis(N,N-diphenylthioreate) anions
coordinate to a two distinct metal ions since the molecule possesses two arms with oxygen and
sulfur donor atoms. The structures of complexes [Cu2(L-O,S)2] (1) and [Mn2(L-O,S)2(dmso)2] (3)
represent the stable planar arrangement due to the coordination of the bis(thiourea) ligands to the
MII metal ions. In the other hand, by having a look to the structures of complexes [Fe2(L-O,S)3] (4)
and [Co2(L-O,S)3] (5) it can be noted that there is also possible to accommodate three bis(thiourea)
ligands in the formation of binuclear complexes, which reflects the flexibility of the chelate system
to provide stable coordination environment for MIII ions.
By means of the C‒O distances (that are in the range of 1.25‒1.27 Å) and C‒S distances (in the
range of 1.70‒1.75 Å) it is clear that for all the complexes a charge delocalization occurs due to the
deprotonation with elongation of the C‒O and C‒S bonds. For comparison, in free
isophthaloylbis(thioureas), these distances are in the range of 1.21‒1.23 Å and 1.66‒1.68 Å,
respectively [12, 14, 15, 26, 27]. The charge delocalization in the –S-C-N-C-O– fragments
consequently causes the shortening of the N‒C bond lengths in the chelating rings (Figure 4).
The M‒O and M‒S bond lengths in complexes [Cu2(L-O,S)2] (1) and [Fe2(L-O,S)3] (4) are in
accordance with other reported binuclear CuII and FeIII complexes with isophthaloylbis(thioureates).
In complex 1 the Cu‒O and Cu‒S distances are 1.937(2)‒1.944(2) and 2.2414(10)‒2.2513(10) Å,
respectively. These distances in CuII complexes in the literature are in the range of 1.93‒1.97 Å
(Cu‒O) and 2.23‒2.27 Å (Cu‒S) [8, 9, 12]. The geometry of the four-coordinated copper centers is
distorted quadratic (Figure 9). In complex 4 the Fe‒O and Fe‒S distances are in the range of
1.978(3)‒2.038(3) and 2.4042(13)‒2.4655(12) Å, respectively. The distances in a FeIII complex in
the literature are in the range of 1.98‒2.01 Å (Fe‒O) and 2.42‒2.46 Å (Fe‒S) [13]. The geometry of
the six-coordinated iron centers is octahedral.
In complex [Co2(L-O,S)3] (5) the Co‒O and Co‒S distances are in the range of 1.91‒1.94 and 2.20‒
2.25 Å, respectively. As expected, these distances are shorter than the distances reported for a
binuclear CoII complex with isophthaloylbis(N,N-diisobutylthioureate) (which distances are in the
range of 2.00‒2.08 Å and 2.30‒2.42 Å, respectively) [27]. CoIII is a smaller ion compared to CoII
ion having shorter bond lengths with the ligands. This fact is related to the larger attraction of the
electrons from the donor atoms of the ligands with the increase of the oxidation state [28]. The
geometry of the six-coordinated cobalt centers is octahedral (Figure 11).
The MnII complex, [Mn2(L-O,S)2(dmso)2] (3), is the first manganese complex with
isophthaloilbis(thioureas). It can be found only a trinuclear polymeric compound of MnIIBaIIMnII
composition with 2,6-dipicolinoylbis(N,N-morpholinoylthiourea) [29]. In this trinuclear compound
(Figure 12), MnII occupies the ‘side positions’, coordinating each one by three sets of O,S donor

atoms in an octahedral environment. The BaII ions adopt a methanol ligand and each second of them
establishes two additional bonds to the adjacent sub-units via a morpholinyl residue, resulting in an
infinite zigzag chain. In complex 3 obtained in this work (Figure 10), chelating coordinating mode
by O,S donor atoms was also observed with MnII ions. However, the Mn‒O and Mn‒S distances in
complex 3 (2.0758(15)‒2.0804(14) and 2.4924(6)‒2.5243(6) Å, respectively) are shorter than those
in the trinuclear bimetallic complex (average of 2.17 and 2.57 Å for Mn‒O and Mn‒S,
respectively). This observation can be rationalized by the absence of a big metal ion in the central
cavity of the molecule that does not causes elongation especially of the Mn‒O bond. The geometry
of the five-coordinated MnII ions in complex 3 is pyramidal quadratic (Figure 10). The τ5 parameter
[30] is equal to 0.19. The apical position is occupied by the oxygen atom of the dimethyl sulfoxide
molecule with a bond length of 2.0694(16) Å.
Figure 12. Chain-structure of [BaMn2(L)3(MeOH)]n [28].
In the crystal structure of complex 3 hydrogen bonds are observed between the water and dimethyl
sulfoxide solvate molecules. The distances between the donor and acceptor atoms of the O‒H···O
hydrogen bonds are 2.800(11) and 2.761(16) Å (Table 7). Hydrogen bonds are also observed
between the solvate molecules in the crystal structure of complex 5 which crystallized in a
dichloromethane/methanol/water mixture. Details of the O‒H···O and O‒H···Cl hydrogen bonds
are listed in Table 7. Figures S12 and S13 depict those hydrogen bonds.
Table 7. Hydrogen bonds for complexes 3 and 5’ [Å and °].
D-H...A
d(D-H)
d(H...A)
d(D...A)
<(DHA)
[Mn2(L-O,S)2(dmso)2]·4DMSO·0.5H2O (3)

O(3S)-H(1S)...O(2S^a)’’
O(3S)-H(1S)...O(2B^b)’’
0.85(2)
0.85(2)
2.33(14)
2.14(12)
2.800(11)
2.761(16)
115(12)
130(13)
[Co2(L-O,S)3]·4CH2Cl2·CH3OH·4H2O (5’)
O(1S)-H(1SA)...O(2S)
O(2S)-H(1S)...O(1S)
0.84
0.88
0.94
0.85
0.85
1.87
1.95
1.92
2.84
2.38
2.67(2)
2.67(2)
160.2
139.0
166.9
153.5
153.8
O(2S)-H(2S)...Cl(6A^a)
O(5S^b)-H(7S^b)...Cl(8)’
O(6S)-H(9S)...O(5S^b)
2.846(19)
3.62(4)
3.16(5)
Symmetry transformations used to generate equivalent atoms:
For (3): ‘’ ‒x+1, ‒y+2, ‒z+2; for (5’): ‘ x‒1, y+1, z.
4. Conclusion
In this work we demonstrated that isophthaloylbis(N,N-diphenylthiourea) reacts with first row
transition metal ions in the presence of triethylamine as base to generate binuclear complexes with
formula [M2(L-O,S)2] (M = CuII (1), NiII (2)) or [M2(L-O,S)3] (M = FeIII (4), CoIII (5)). Oxidation of
CuI, FeII and CoII ions was observed in reaction with isophthaloylbis(N,N-diphenylthiourea), as well
as reduction of MnIII ions in the formation of [Mn2(L-O,S)2(dmso)2] (3). The complexes were
successfully characterized by spectroscopic techniques (IR, Raman, UV-Vis), elemental and
thermogravimetric analysis. CoIII complex (5) was also analyzed by 1H NMR spectroscopy. Single
crystal X ray diffraction data confirmed that the ligand coordinates by the O,S donor atoms under
deprotonation and, more significantly, that it is possible to obtain MnII complexes with thiourea
ligands, being complex 3 the first reported example of a non-bimetallic compound.
Acknowledgements
This work was supported by CAPES - Brazilian Federal Agency for Support and Evaluation of
Graduate Education. The authors gratefully acknowledge the financial support provided by the
Brazilian funding agency FINEP (Contract: 04.13.0448.00/2013).
Appendix A. Supplementary data
Supplementary data to this article can be found online at https://doi.org/xxx. CCDC 1961619,
1961620, 1961621, 1961622 and 1961623 contain the supplementary crystallographic data for this