Synthesis, structure analysis, investigation of conductivity, thermal properties of polyphenol derivatives containing a rhodanine moiety and their Cu(II), VO(IV) complexes

Article abstract of DOI:10.1016/j.ica.2020.119642

In this study, 5-benzylidenerhodanine derivatives namely 5-(2-hydroxybenzylidene)-2-thioxothiazolidin-4-one (SAR) and 5-((2-hydroxynaphthalen-1-yl)methylene)-2-thioxothiazolidin-4-one (HNAR) used as monomer. The new polymers of SAR and HNAR (PSAR and PHNA

Full text of DOI:10.1016/j.ica.2020.119642

InorganicaChimicaActa508(2020)119642
Contents lists available at ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Research paper
Synthesis, structure analysis, investigation of conductivity, thermal
properties of polyphenol derivatives containing a rhodanine moiety and
their Cu(II), VO(IV) complexes
İsmet Kayaa,⁎, Ayşe Erçağb, Süleyman Çulhaoğlua,c
a Çanakkale Onsekiz Mart University, Faculty of Sciences and Arts, Department of Chemistry, Polymer Synthesis and Analysis Lab., 17020 Çanakkale, Turkey
b İstanbul University-Cerrahpaşa, Faculty of Engineering, Department of Chemistry, 34850 Avcılar, İstanbul, Turkey
c Varaka Kagit San. AŞ. Albayrak Holding Company, Altıeylül, Balıkesir, Turkey
A R T I C L E I N F O
A B S T R A C T
Keywords:
In this study, 5-benzylidenerhodanine derivatives namely 5-(2-hydroxybenzylidene)-2-thioxothiazolidin-4-one
(SAR) and 5-((2-hydroxynaphthalen-1-yl)methylene)-2-thioxothiazolidin-4-one (HNAR) used as monomer. The
new polymers of SAR and HNAR (PSAR and PHNAR respectively) were synthesized by oxidative poly-
condensation reaction. The polymers were characterized by elemental, FT-IR, UV–Vis, 1H NMR, 13C NMR, TG-
DTA analyses techniques. The molecular weight distribution values of the PSAR and PHNAR were determined by
size exclusion chromatography (SEC) analysis. According to the SEC analyses, the number average molecular
weight (Mn), weight average molecular weight (Mw) and polydispersity index (PDI) values of PSAR and PHNAR
were found to be 5300, 7250 g mol−1 and 1.368; 5750, 7350 g mol−1 and 1.278, respectively. The Cu (II), VO
(IV) complexes of PSAR and PHNAR (PSAR-Cu and PSAR-VO) were successfully prepared using Cu (AcO)2xH2O
and VOSO4x5H2O hydrate salts. The polymer-metal-complexes were characterized by FT-IR, elemental and TG-
DTA analysis techniques. The weight losses of PHNAR, PHNAR-Cu, PHNAR-VO, PSAR, PSAR-Cu and PSAR-VO
were found to be 69.50, 58.50, 62.25, 89.05, 74.55 and 61.75% at 1000 °C, respectively. TG analyses were
showed to be stable of synthesized polymers against thermal decomposition. Electrical properties of doped
polymers, undoped polymers and their complexes were determined. Also, the optical band gaps (Eg) of these
complexes were calculated from their absorption edges.
5-Benzylidene-rhodanine
Polymer-metal complex
Conductivity
Thermal analyses
Oxidative polycondensation
1. Introduction
in different oxidation states increases the application of these com-
pounds in a wide range. They also have higher sensitivity and se-
Rhodanines are five-membered heterocyclic compounds that have
range spectrum of biological activity (anticonvulsant, antibacterial,
antiviral, and antidiabetic) [1–6]. Many researchers reported rhodanine
derivatives as hepatitis C virus (HCV) protease inhibitor [7]. On the
other hand, they are known that rhodanine plays an important role in
biological reactions, i.e. in the inhibition of mycobacterium tubercu-
losis [8]. Condensation products of rhodanine with aldehyde and ke-
tones exhibit mildew proofing activity [9]. Mildew-proofing agents
containing –NCSS– in the structure are present in many plant fungi-
cides. Rhodanine derivatives have been used as acceptor moieties in a
variety of such push-pull compounds in fields such as nonlinear optics
and dye-sensitized solar cells [10].
lectivity for the analysis of certain noble metal ions [12]. The nucleo-
philic activity of the methylene carbon atom of the rhodanine ring at
position 5 allows reaction with electrophilic centers and the ready
formation of 5-substituted derivatives [13].
Polymers are useful materials on account of their ease of fabrication,
flexibility, lightness of weight and chemical inertness. As such, elec-
trically conducting polymers are potential candidates for wide variety
of applications ranging from electrode materials, from organic batteries
to electrochromic display devices [14–16]. The polymers containing
phenol groups have excellent properties such as high thermal stability
[17], bonding ability to metals [18], electrochemical [19,20], anti-
microbial [21], semi conductive [19] and superior optical [19,22]
properties.
Rhodanine derivatives are a good series of ligands capable of
binding metal ions leading to metal complexes with increasing prop-
erties [11]. The high stable potential of rhodanine derivative complexes
Therefore, polychelates have also found wide spread applications in
nuclear chemistry, preconcentration and recovery of trace metal ions in
⁎ Corresponding author.
E-mail address: kayaismet@hotmail.com (İ. Kaya).
https://doi.org/10.1016/j.ica.2020.119642
Received 31 December 2019; Received in revised form 12 March 2020; Accepted 30 March 2020
Availableonline31March2020
0020-1693/©2020ElsevierB.V.Allrightsreserved.

İ. Kaya, et al.
InorganicaChimicaActa508(2020)119642
radioactive materials, control of pollution, hydrometallurgy, polymer
drug grafts and waste water treatment [23–25]. They can be used for
cleaning of poisonous heavy metals in the industrial waste waters. The
synthesis of polymer/oligomer-metal complexes is very important at
analytic and environmental chemistry. It seemes advantageous to at-
tempt for design and prepare a polymer-bound chelating ligand, which
would be able to form complexes with a variety of transition metals and
therefore have a large range of applications. It is, therefore interesting
to isolate and study Cu(II), VO(IV) complexes of new polyrhodanines.
In this study, we synthesized rhodanine based polymer compounds,
PSAR and PHNAR, from 5-(2-hydroxybenzylidene)-2-thioxothiazolidin-
4-one (SAR) and 5-((2-hydroxynaphthalen-1-yl)methylene)-2-thiox-
othiazolidin-4-one (HNAR). Then, the obtained polymers were con-
verted to their metal complexes by Cu(II) and VO(IV)) salts. Structures
of obtained polymer were confirmed by FT-IR, UV–Vis, 1H NMR, 13C
NMR, elemental analysis and TG-DTA techniques. The molecular
weight distribution values of the PSAR and PHNAR were determined by
size exclusion chromatography (SEC) analysis. The polymer-metal-
complexes were characterized by FT-IR, elemental and TG-DTA analysis
techniques. The thermal stabilities of the polymer and the polymer
complexes were thermogravimetrically studied. The optical band gaps
(Eg) of polymers and polymer-metal-complexes were calculated from
their absorption edges. Electrical properties of doped and undoped
polymer and polymer-metal-complexes were determined by four-point
probe technique at a room temperature and atmospheric pressure.
116.63 (C3-ipso), 133.27 (C4), 120.16 (C5-ipso), 127.73 (C6), 124.27
(C7), 129.72 (C8), 119.99 (C9), 158.00 (C10-ipso).
HNAR: Dark orange solid; yield 88%. Mp: 190 °C. Found: C, 58.35;
H, 2.96; N, 4.88; S, 22.17%. Calcd. for C14H9NO2S2: C, 58.54; H, 3.14;
N, 4.88; S, 22.30%. For HNAR, 1H NMR (DMSO‑d6, δ, ppm): 12.90 (s,
eNH, 1H), 11.09 (s, eOH, 1H), 8.08 (s, C]CHexocyclic, 1H), 7.40–8.10
(m, Ar-CH, 6H). 13C NMR (DMSO‑d6, δ, ppm): 197.37 (C1-ipso), 169.94
(C2-ipso), 112.44 (C3-ipso), 133.72 (C4), 118.74 (C5-ipso), 155.02 (C6-
ipso), 123.33 (C7), 129.50 (C8), 129.18 (C9-ipso), 128.58 (C10),
128.43 (C11), 128.25 (C12), 124.33 (C13), 132.53 (C14-ipso).
2.3. Syntheses of the polymers
PSAR and PHNAR were synthesized by oxidative polycondensation
agent NaOCl in aqueous alkaline medium with SAR and HNAR, re-
spectively (Scheme 2). First, SAR or HNAR (1 mmol) was dissolved in
an aqueous solution of KOH (10%, aqueous solution). Then, 1 mmol
NaOCl was added to mixture drop by drop at 40 °C and the reaction
mixtures were heated to 80 °C under reflux, and reactions were main-
tained for another 12 h. At the end of reaction period, the poly-
merization solution was cooled to room temperature and precipitated
by neutralizing with HCl (37%). The product was filtered, washed with
hot water ethanol mixture, then dried in a vacuum oven at 60 °C [10].
Calcd. For PSAR: C, 51.06, H, 2.11; N, 5.91; S, 27.23. Found: C,
49.88; H, 2.00; N, 5.80; S, 27.00. For PSAR, FT-IR (cm−1): 3377 ν(OH/
H2O), 1694 ν(C]O), 1601, 1559 ν(C]C), 1071 ν(C]S), 1218 ν(CeO).
For PSAR, 1H NMR (DMSO‑d6, δ, ppm): 13.63 (s, eNH, 1H), 10.50 (s,
eOH, 1H), 8.15 (s, eC]CH exocyclic, 1H), 7.30–7.75 (m, Ar-CH, 2H).
13C NMR (DMSO‑d6, δ, ppm): 192.07 (C1-ipso), 159.21 (C2-ipso),
116.80 (C3-ipso), 138.07 (C4), 124.00 (C5-ipso), 128.67 (C6), 125.62
(C7), 132.34 (C8), 119.92 (C9), 152.64 (C10-ipso).
Calcd. For PHNAR: C, 58.95; H, 2.46; N, 4.91; S, 22.46. Found: C,
58.65; H, 2.30; N, 4.75; S, 22.20. For PHNAR, FT-IR (cm−1): 3337
ν(OH/H2O), 1696 ν(C]O), 1581, 1555 ν(C]C), 1070 ν(C]S), 1217
ν(CeO). For PHNAR, 1H NMR (DMSO‑d6, δ, ppm): 13.56 (s, eNH, 1H),
11.01 (s, eOH, 1H), 9.23 (s, eC]CHexocyclic, 1H), 7.20–8.08 (m, Ar-CH,
4H). 13C NMR (DMSO‑d6, δ, ppm): 197.38 (C1-ipso), 169.93 (C2-ipso),
112.41 (C3-ipso), 135.70 (C4), 118.76 (C5-ipso), 155.08 (C6-ipso),
124.31 (C7), 129.49 (C8), 129.12 (C9-ipso), 128.57 (C10), 128.42
(C11), 128.27 (C12), 123.31 (C13), 132.54 (C14-ipso).
2. Experimental
2.1. Materials and methods
All chemicals were used as analytical grade and of highest purity
available. Salicylaldehyde, 2-hydroxy-1-naphthaldehyde, rhodanine
were purchased from Aldrich. Acetic acid, sodium acetate, sodium hypo
chloride (NaOCl) (35% aqueous solution) and other solvents were
supplied from Merck Chemical Co. (Germany).
The FT-IR spectra were recorded using PerkinElmer spectrum BX
FT-IR spectrometer between 4000 and 400 cm−1. UV–Vis spectra were
recorded with a PerkinElmer Lambda 25 in DMSO. C, H, N and S mi-
croanalyses were carried out using a LECO-CHNS-O-9320. The Cu and
VO percentages in the polymer-metal complexes were determined as
literature [26]. NMR spectra were obtained on a Varian AS 400 MHz
and Bruker 400 MHz Digital FT-NMR spectrometer with DMSO‑d6 as
solvent and TMS as internal reference. TG measurements were made
using a PerkinElmer Diamond Thermal Analysis system. Ten milligram
samples were heated between 25 and 1000 °C at a rate of 10 °C min−1 in
a dynamic nitrogen atmosphere. The number average molecular weight
(Mn), weight average molecular weight (Mw) and polydispersity index
(PDI) were determined by size exclusion chromatography (SEC) tech-
niques of Shimadzu Co. For SEC investigations were used a SGX (100 Å
and 7 nm diameter loading material) 3.3 mm i.d. × 300 mm columns;
eluent: DMF (0.4 mL min−1), polystyrene standards. A refractive index
detector was used to analyze the polymer at 25 °C oven temperature.
2.4. Synthesis of the polymer-metal complexes
A solution of Cu(AcO)2·H2O (1 mmol) in methanol (10 mL) was
added to warm solutions or suspensions of PSAR or PHNAR (2 mmol) in
tetrahydrofuran (20 mL). The mixtures were heated at 75 °C with con-
stant stirring for 3 h. The precipitated complexes were collected by
filtration, washed with a cold methanol/tetrahydrofuran (1:1) mixture
and then dried in vacuum oven. Vanadium complexes were prepared by
addition of vanadium sulfate (VOSO4·5H2O) to suspensions or solutions
of the polymer ligands at the similar procedure.
Metal complexes; PSAR-Cu: [(PSAR)2Cu·2H2O]·H2O. PHNAR-Cu:
[(PHNAR)2Cu 2H2O]·H2O
2.2. Syntheses of the monomers
PSAR-VO: [(PSAR)2VO H2O]·2H2O. PHNAR-VO: [(PHNAR)2VO
H2O]·2H2O.
Monomers containing 5-Benzylidenerhodanine namely 5-(2-hydro-
xybenzylidene)rhodanine, SAR and 5-(2-hydroxy- naphthylidene)rho-
danine, HNAR, were prepared by adding rhodanine to salicylaldehyde
or 2-hydroxy-1-naphthaldehyde in a solution of acetic acid and sodium
acetate. After stirring and refluxing for 2 h, the solid formed was filtered
out and vacuum dried (Scheme 1) [27,28].
SAR: Orange solid; yield 84%. Mp: 140 °C. Found: C, 50.49; H, 2.80;
N, 5.80; S 26.85%. Calcd. for C10H7NO2S2: C, 50.63; H, 2.95; N, 5.91; S,
27.00%. For SAR, 1H NMR (DMSO‑d6, δ, ppm): 13.73 (s, eNH, 1H),
10.65 (s, eOH, 1H), 7.85 (s, eC]CHexocyclic, 1H), 6.90–7.40 (m, Ar-CH,
4H). 13C NMR (DMSO‑d6, δ, ppm): 196.39 (C1-ipso), 170.03 (C2-ipso),
Calcd. for PHNAR-Cu: C, 41.74; H, 3.23; N, 3.48; S, 15.90; Copper,
15.78. Found: C, 41.25; H, 2.88; N, 3.20; S, 15.50; Copper, 15.35.
Calcd. for PHNAR-VO: C, 41.39; H, 3.20; N, 3.45; S, 15.77; Vanadium,
12.54. Found: C, 40.90; H, 2.85; N, 3.20; S, 15.55; Vanadium; 12.00.
Calcd. for PSAR-Cu: C, 34.04; H, 3.12; N, 3.97; S, 18.16; Copper, 18.01.
Found: C, 33.75; H, 2.80; N, 3.74; S, 17.86; Copper, 17.65. Calcd. for
PSAR-VO: C, 33.72; H, 3.09; N, 3.93; S, 17.98; Vanadium, 14.30.
Found: C, 33.27; H, 2.85; N, 3.79; S, 17.70; Vanadium, 13.75. For
PSAR-Cu, FT-IR (cm−1): 3406 ν(OH/H2O), 1685 ν(C]O), 1589, 1559
ν(C]C), 1070 ν(C]S), 1207 ν(CeO), 546 ν(MeO). For PSAR-VO, FT-IR
(cm−1): 3394 ν(OH/H2O), 1688 ν(C]O), 1602, 1556 ν(C]C), 1070
2

İ. Kaya, et al.
InorganicaChimicaActa508(2020)119642
Scheme 1. Syntheses of monomers.
Scheme 2. Synthesis of polymers.
complexes were obtained in DMSO using a digital conductivity meter
(WPA CMD 750). Solid state conductivities were measured on a
Keithley 2400 Electrometer. The pellets were prepared on hydraulic
press developing up to 1687.2 kg/cm2. Iodine doping was carried out
by exposure of the pellets to iodine vapor at atmospheric pressure and
room temperature in a desiccator. Ultraviolet–visible (UV–Vis) spectra
of polymer and polymer-metal complexes were measured by Perkin
Elmer Lambda 25 (Massachusetts, USA) by using DMSO at 25 °C. The
optical band gaps (Eg) of polymer and polymer-metal complexes were
calculated from their absorption edges.
Table 1
Solubility tests of the synthesized compounds.
Solvents
PSAR PSAR-VO PSAR-Cu PHNAR PHNAR-VO PHNAR-Cu
Methanol
THF
CH3CN
Toluene
Ethyl acetate
Chloroform
Hexane
Heptane
Acetone
DMF
⊥
+
–
–
⊥
–
+
+
⊥
–
+
+
+
–
+
+
+
–
–
–
⊥
–
–
–
–
–
–
–
–
–
–
–
–
⊥
+
–
+
+
–
–
–
–
–
–
–
–
–
–
–
+
+
–
+
+
⊥
+
+
+
+
+
+
+
+
⊥
+
+
3. Results and discussion
DMSO
3.1. Solubilities and structures of the compounds
+: Soluble, ⊥: partially soluble, –: insoluble.
PHNAR, PHNAR-Cu, PHNAR-VO, PSAR, PSAR-Cu and PSAR-VO
were dark brown at powder forms. The synthesized all compounds were
all stable in the solid state. The solubility test results are shown in
Table 1. According to Table 1, all synthesized polymers are soluble in
DMSO and DMF while insoluble in heptane, hexane, and toluene.
PHNAR and PHNAR-VO are soluble in chloroform, while others are
insoluble.
ν(C]S), 1205 ν(CeO), 900 ν(V]O), 435 ν(MeO). For PHNAR-Cu, FT-
IR (cm−1): 3387 ν(OH/H2O), 1683 ν(eC]O), 1561, 1512 ν(eC]C),
1071 ν(C]S), 1205 ν(CeO), 540 ν(MeO). For PHNAR-VO, FT-IR
(cm−1): 3385 ν(OH/H2O), 1684 ν(C]O), 15821, 1548 ν(C]C), 1071
ν(C]S), 1203 ν(CeO), 900 ν(V]O), 425 ν(MeO).
2.5. Solubility, electrical and optical properties
According to SEC chromatograms the calculated number-average
molecular weight (Mn), weight-average molecular weight (Mw) and
polydispersity index (PDI) values of PHNAR and PSAR measured using
UV detector were given in Table 2. As seen in Table 2, two separate
The solubility tests were done in different solvents by using 1 mg
sample and 1 mL solvent at 25 °C. The molar conductivity values of the
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İ. Kaya, et al.
InorganicaChimicaActa508(2020)119642
Table 2
The number average molecular weight (Mn), weight average molecular weight (Mw), polydispersity index (PDI), and % values of the synthesized polymers.
Molecular weight distribution parameters
Compounds
Total
Mn
Fraction I
Mn
Fraction II
Mn
Mw
PDI
Mw
PDI
%
Mw
PDI
%
PHNAR
PSAR
5750
5300
7350
7250
1.278
1.368
4200
4450
6750
8300
1.458
1.586
60
70
22,400
25,200
26,600
29,000
1.188
1.151
40
30
Fig. 1. 1H NMR (a) and 13C NMR (b) spectra of SAR.
fractions for all polymers were obtained. Total values of number-
average molecular weight (Mn), weight-average molecular weight (Mw)
and polydispersity index (PDI) values of PHNAR and PSAR were found
to be 5750, 7350 g mol−1 and 1.278; 5300, 7250 g mol−1 and 1.368,
respectively. According to these results, PHNAR and PSAR contain
approximately 24–30 and 26–35 repeated units, respectively. The ob-
tained results confirm the polymeric structures. The synthesized
Table 3
The optical band gaps (Eg) and λmax (nm) values of compounds.
PHNAR
PHNAR-Cu
PHNAR-VO
PSAR
PSAR-Cu
PSAR-VO
λmax (nm)
Eg (eV)
389
2.64
460
2.51
429
2.55
327
3.32
395
2.85
382
2.98
4

İ. Kaya, et al.
InorganicaChimicaActa508(2020)119642
Table 4
Thermal decomposition values compounds.
Compound
TGA
DTA
endo
aTon bTmax
cT20 dT50 % Char at
1000 °C
PHNAR
218 272
269 359 30.50
295 595 41.50
318 635 34.75
216
–
209, 410
PHNAR-Cu 210 217, 274, 335
PHNAR-VO 200 206, 275, 405,
850
PSAR
PSAR-Cu
243 276, 362
210 342, 415, 525,
825
273 330 10.95
301 395 25.45
236
–
PSAR-VO
208 282, 324, 523,
834
296 618 38.25
218
a
Fig. 2. Absorption spectra of PHNAR, its Cu (II) and VO (IV) complexes.
The onset temperature.
b
c
Temperature of the maxima of the peak.
Temperature corresponding to 20%.
Temperature corresponding to 50%.
d
polymers have low molecular weights.
The observation and changes of the ligands in the FT-IR spectrum
during coordination were investigated. According to elemental analysis
(1:2, metal: ligand stoichiometry), the IR spectra of the complexes show
that the ligands behaves as a bidentate and monobasic. The polymer
ligands gave two bands at ∼3200–3040 cm−1 due to asymmetric and
symmetric stretching vibrations of NeH group. The broad absorption of
a band located at ∼3377–3337 cm−1 is assigned to □OH. In addition,
furthermore, ligands exhibit
1696 cm−1, a medium-strong C]C band around 1601 and 1555 cm−1
and a medium-intensity C]S band around 1070 cm−1. The spectra of
all studied complexes showed broad band in the range
a very strong C]O band around
,
a
3157–3450 cm−1 assigned to υ(OH), suggesting the presence of water
molecules. NH bands observed in the ligands in the 3060–3159 cm−1
range and OH bands were masked due to the presence of coordinated
and hydrated water in the complexes. All complexes show significant
shifts to lower frequencies for υ(C]O) band, suggesting coordination of
the metal ion through the carbonyl oxygen atom [29]. The strong
phenolic υ(CeO) bands [30] at ∼1217 cm−1 in the free ligands are
shifted towards lower wave numbers in their complexes, consistent
with coordination via the deprotonated phenolic oxygen [31]. Some
new medium or weak bands are observed in the range 546–425 cm−1
and are tentatively assigned to the ν(MeO)/ν(MeN) modes [23]. In
addition, the vanadium complexes exhibit a strong band in the
955–965 cm−1 range due to the terminal ν(V]O) stretching [32].
The 1H NMR spectra were recorded in DMSO‑d6 in order to identify
the structures of monomers and polymers. 1H–13C NMR spectra of SAR
are given in Fig. 1. According to 1H NMR spectra of HNAR, SAR,
PHNAR and PSAR, the proton signals of eNH and eOH groups were
observed in 12.90, 11.09; 13.73; 10.65; 13.56, 11.01 and 13.63,
10.50 ppm, respectively. Aromatic eCH peaks are observed between
7.20 and 8.08 ppm. Additionally, 13C NMR spectra of compounds were
confirmed [33,34]. According to 13C NMR spectra, the carbon atom
signals of –CH] and ipso carbon of eOH group of HNAR, SAR, PHNAR
and PSAR were observed in 133.72, 155.02; 133.27, 158.00; 135.70,
158.08 and 138.07, 152.64 ppm, respectively.
Fig. 3. Absorption spectra of PSAR, its Cu (II) and VO (IV) complexes.
Fig. 4. Electrical conductivities changes of I2-doped PHNAR, PSAR and their Cu
(II) and VO (IV) complexes.
3.2. Optical and electrical properties
The absorption spectra of polymer and polymer-metal complexes
were recorded by using DMSO, respectively, at 25 °C and are given in
Table 3 and Figs. 2 and 3. The optical band gap (Eg) values of PHNAR,
PHNAR-Cu, PHNAR-VO, PSAR, PSAR-Cu and PSAR-VO were found to
be 2.64, 2.51, 2.55, 3.32, 2.85 and 2.98, respectively. According to
these results, Eg value of PSAR-VO was higher than other polymer-metal
complexes.
Scheme 3. Coordination of iodine during polymers doping.
5

İ. Kaya, et al.
InorganicaChimicaActa508(2020)119642
Fig. 5. TGA curves of PHNAR, PSAR and their Cu (II) and VO (IV) complexes.
Fig. 6. DTG curves of PHNAR, PSAR and their Cu (II) and VO (IV) complexes.
PSAR, PSAR-VO, PSAR-Cu, PHNAR, PHNAR-VO and PHNAR-Cu
had been suggested the conductivity mechanisms of polymers for
doping with iodine [35]. Nitrogen is a very electronegative element and
it is capable of coordinating an iodine molecule. Coordination of iodine
during doping period of PHNAR and PSAR is as follows (Scheme 3).
Coordination of iodine with polymers and pyridine solutions had been
suggested at the literatures as follows [25,27].
As seen from these results, the conductivity of the polymer-metal
complexes were found as higher than the polymers. These reasons are
from the metal atoms in the structure of the polymer-metal complexes.
This may be described by the length of conjugation and the existence of
metal atoms in complexes arising from delocalization of π-electrons in
the chelate ring. The increasing conjugation length in complexes may
lead to higher conductivity [15]. The curves are mostly indistinguish-
able. It can be noticed that the introduction of the metal ions into or-
ganic polymer increased its electrical conductivity.
have conductivities of 2.110 × 10−12, 2.250 × 10−12, 2.340 × 10−12
,
2.640 × 10−12, 2.710 × 10−12 and 2.845 × 10−12 S cm−1, respec-
tively, before doping. When doped with iodine, their conductivities
could be increased by about three orders of magnitude (up to 10−3
S
cm−1). Fig. 4 shows the doping results for PSAR and PHNAR and their
Cu(II) and VO (IV) complexes with iodine for the various times at 25 °C.
In the doping of polymers and their metal complexes with iodine, the
conductivities first increases greatly with doping time, but then tends to
level-off. The maximal (or saturated) conductivity of PSAR, PSAR-VO,
PSAR-Cu, PHNAR, PHNAR-VO and PHNAR-Cu was found to be
1.015 × 10−8
2.163 × 10−8
1.565 × 10−8
,
1.565 × 10−8
and
1.701 × 10−8
,
1.701 × 10−8
,
1.763 × 10−8
1.015 × 10−9
,
,
2.214 × 10−8
S
cm−1
,
,
,
1.763 × 10−8
,
2.163 × 10−7 and
2.214 × 10−7 S cm−1, respectively. According to these values, the
highest conductivity was observed in PHNAR-Cu compound. Diaz et al.
The molar conductivity values of the complexes were obtained in
6

İ. Kaya, et al.
InorganicaChimicaActa508(2020)119642
Fig. 7. DTA curves of PHNAR, PSAR and their Cu (II) and VO (IV) complexes.
DMSO. All complexes have conductivity in the range 8.7–20.3 Ω−1 cm2
(II) and VO(IV) complexes. The obtained polymers and complexes were
characterized by elemental, FT-IR, UV–Vis, 1H- 13C NMR, TG-DTA
analyses techniques. Also, the synthesized compounds were character-
ized by solubility tests, conductivity and SEC techniques.
Electrochemical and optical properties of the synthesized compounds
were also investigated and it was found that the synthesized polymer-
metal complexes have quite lower band gaps than the polymers due to
their high conjugated structures. Electrical conductivity measurements
show that the synthesized polymers and polymer-metal complexes are
semi-conductors and they can be used as semi-conductive polymer in
electronic, opto-electronic and photovoltaic applications. Thermal de-
gradation characteristics were also determined. According to the ob-
tained results the synthesized polymer-metal complexes have higher
stabilities than polymers. Consequently, because of the fine thermal
stabilities the synthesized compounds can be used to produce tem-
perature-stable materials. The presence of coordinated and hydrated
water molecules in Copper(II) and Oxo vanadium(IV) complexes is
confirmed by thermal analyses.
mol−1, thus showing a nonelectrolyte nature [36].
3.3. Thermal studies
The thermal stability and decomposition of PHNAR, PSAR and
polymer-metal complex were studied by TGA-DTG-DTA analyses at N2
medium and thermal analysis results and the curves of these analyses
were given in Table 4 and Figs. 5–7, respectively. The carbines residues
of PHNAR and PSAR were formed at low amount such as 30.50 and
10.95%. The final decomposition steps of the complexes are attributed
to complete decomposition of the complexes leaving M residues
(M = Cu and V). PHNAR-Cu, PHNAR-VO, PSAR-Cu and PSAR-VO were
formed metal oxide residues (CuO or V2O5); 41.50, 34.75, 25.45 and
38.25% at 1000 °C, respectively. According to TGA curves of PHNAR-
Cu, PHNAR-VO, PSAR-Cu and PSAR-VO, to be high of thermal stability
of polymer-metal complexes may be indicate the formation of metal-
oxygen valance and metal-nitrogen coordination bond between
polymer-metal ions [36]. The presence of coordinated and hydrated
water molecules in Copper(II) and Oxo vanadium(IV) complexes were
confirmed by thermal analyses.
The thermal behavior of these complexes showed that the hydrated
complexes lost water molecules of hydration and coordination in the
first step followed immediately by decomposition of the ligand mole-
cules in the subsequent steps. The final decomposition steps of the
complexes are attributed to complete decomposition of the complexes
leaving M residues (M = Cu and V). This confirms the results of ele-
mental analysis.
Declaration of Competing Interest
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influ-
ence the work reported in this paper.
Appendix A. Supplementary data
Supplementary data to this article can be found online at https://
doi.org/10.1016/j.ica.2020.119642.
The thermograms of possess one main stage of decomposition cor-
responding to loss of both hydration and coordination water molecules
in the same stage (Fig. 4) with a mass losses of PHNAR-Cu, PHNAR-VO,
PSAR-Cu and PSAR-VO were found to be 7.20, 12.00, 9.20 and 10.00,
respectively, within temperature range 50–210 °C. Theoretical values of
PHNAR-Cu, PHNAR-VO, PSAR-Cu and PSAR-VO were found to be 7.77,
7.84, 9.12 and 10.00, respectively.
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