Synthesis, spectroscopic studies and electrochemical properties of Schiff bases derived from 2-hydroxy aromatic aldehydes and phenazopyridine hydrochloride

Article abstract of DOI:10.2298/JSC120524151Y

Novel Schiff bases 1-4 were synthesized by the reaction of 2-hydroxybenzaldehyde, 2-hydroxy-5-methoxybenzaldehyde, 2-hydroxy-5- nitrobenzaldehyde and 2-hydroxy-1-naphthaldehyde with phenazopypridine hydrochloride (PAP), respectively, and their structures were elucidated by means of spectroscopic techniques. The electrochemical reduction of PAP and its Schiff bases (1-4) were realized on a glassy carbon electrode (GCE) in dimethyl sulfoxide (DMSO) using the cyclic voltammetric (CV) technique. The effect of functional groups on reduction potential of the Schiff bases was investigated. A general electrochemical reduction mechanism of the compounds is suggested.

Full text of DOI:10.2298/JSC120524151Y

J. Serb. Chem. Soc. 78 (6) 795–804 (2013)
JSCS–4458
UDC 542.9+547.571+547.551:547.864+
547.821+546.13:543.552:543.42
Original scientific paper
Synthesis, spectroscopic studies and electrochemical properties
of Schiff bases derived from 2-hydroxy aromatic aldehydes and
phenazopyridine hydrochloride
1
1
1
*
SULTAN YAGMUR , SELEHATTIN YILMAZ , GULSEN SAGLIKOGLU , MURAT
SADIKOGLU2, MUSTAFA YILDIZ1 and KAMRAN POLAT3
1Canakkale Onsekiz Mart University, Faculty of Science and Arts, Department of Chemistry,
17020, Canakkale, Turkey, 2Gaziosmanpasa University, Faculty of Education, Department of
Science Education, 60100, Tokat, Turkey and 3Ankara University, Faculty of Science,
Department of Chemistry, 06100, Ankara, Turkey
(Received 24 May, revised 13 December 2012)
Abstract: Novel Schiff bases 1–4 were synthesized by the reaction of 2-hyd-
roxybenzaldehyde, 2-hydroxy-5-methoxybenzaldehyde, 2-hydroxy-5-nitroben-
zaldehyde and 2-hydroxy-1-naphthaldehyde with phenazopypridine hydro-
chloride (PAP), respectively, and their structures were elucidated by means of
spectroscopic techniques. The electrochemical reduction of PAP and its Schiff
bases (1–4) were realized on a glassy carbon electrode (GCE) in dimethyl sulf-
oxide (DMSO) using the cyclic voltammetric (CV) technique. The effect of
functional groups on reduction potential of the Schiff bases was investigated. A
general electrochemical reduction mechanism of the compounds is suggested.
Keywords: phenazopyridine hydrochloride; Schiff base; spectroscopy; voltam-
metry.
INTRODUCTION
Phenazopyridine hydrochloride (PAP) is an analgesic drug used to provide
1–5
symptomatic pain relief in conditions such as cystitis and urethritis.
The elec-
trochemical reduction and determination of phenazopyridine hydrochloride were
5
realized on a carbon paste electrode by Osteryoung square wave voltammetry.
The electrochemical properties of PAP were also investigated by the adsorptive
6
stripping voltammetric technique. In addition, differential pulse polarography is
a convenient method for the analysis of nitrofurantoin and phenazopyridine in
7
tablet form.
8,9
Schiff bases are used extensively as ligands in coordination chemistry.
10
They have thermochromic and photochromic properties in their solid state.
*Corresponding author. E-mail: seletyilmaz@hotmail.com
doi: 10.2298/JSC120524151Y
795
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796
YAGMUR et al.
They are also used as model systems for biological macromolecules and catalytic
11,12
reactions.
There are relatively few studies on the electrochemical behavior of
13
imines or Schiff bases in aprotic media. A different mechanism was proposed
in non-aqueous media where hydrolysis does not pose problems.
In Schiff bases, the reduction potential is dependent on the size of the aro-
14–17
matic groups on either side of the –C=N– group,
attached to the aromatic ring
the types of substituent
15–19
20,21
and intra-molecular hydrogen bonds.
It
has also been claimed that the presence of electron withdrawing groups and hyd-
rogen bonding facilitate the reduction. Schiff base ligands consist of a variety of
substituents with different electron-donating and electron-withdrawing groups,
and therefore may have interesting electrochemical properties.
Although the electrochemical reduction reactions of Schiff bases containing
22–25
–N=N– and –C=N– groups in aqueous medium
have been studied, insuffi-
cient studies have been directed to the electrochemical reduction of PAP and its
Schiff bases in aqueous and non-aqueous media. In the present study, the Schiff
bases 1–4 were synthesized and investigated by elemental analysis, FT-IR,
1
13
H-NMR, C-NMR, UV–Vis and MS spectroscopic techniques in order to study
their electrochemical properties in dimethyl sulfoxide (Scheme 1).
N
N
N
H
C
2 h
N
NH2
Ar
ArCHO
+
N
N
NH2
HCl
EtOH
N
(1-4)
H2N HCl
PAP
H3CO
O2N
Ar:
OH
OH
OH
OH
Compound :
1
2
3
4
Scheme 1. The synthesis of Schiff bases 1–4.
EXPERIMENTAL
Instrumentation
1
The H- and 13C-NMR spectra were recorded on a Bruker Avance DPX NMR spectro-
meter operating at 400 and 101.6 MHz, respectively. The infrared absorption spectra were
recorded on a Perkin Elmer BX II spectrometer in KBr discs and are reported in cm-1. The
UV–Vis spectra were measured using a Shimadzu 1208 series spectrometer. Carbon, nitrogen
and hydrogen analyses were performed with a Leco CHNS-932 analyzer. Melting points were
measured on an Electro Thermal IA 9100 apparatus using a capillary tube. LC mass spectra
were recorded on an Agilent 1100 MSD spectrometer with an ion source temperature of 240
°C. A Model Metrohm 757 VA trace analyzer (Herisau, Switzerland) was employed for the
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SYNTHESIS AND ELECTROCHEMICAL PROPERTIES OF PHENAZOPYRIDINE SCHIFF BASES
797
voltammetric measurements, with a three-electrode system consisting of a GCE (surface size,
ϕ = 7 mm, disc diameter, R = 2 mm Metrohm) working electrode, a platinum wire auxiliary
electrode and a Ag/Ag+ (0.01 M AgNO3/DMSO) reference electrode. Before each measure-
ment the working electrode was polished manually with polishing alumina (prepared from
0.01 μm aluminum oxide) on an alumina polish pad, then rinsed with ultra pure deionized
water and ethanol and DMSO. All measurements were performed after deoxygenating the
supporting electrolyte with argon gas for 5 min and 60 s for the sample prior to each measu-
rement.
Reagents
PAP was kindly supplied by Faco Inc. (Istanbul, Turkey). 2-Hydroxybenzaldehyde,
2-hydroxy-5-methoxybenzaldehyde, 2-hydroxy-5-nitrobenzaldehyde, 2-hydroxy-1-naphthal-
dehyde, EtOH, DMSO and tetrabutylammonium iodide (TBAI, 98 %) were obtained from
BDH Chemicals and alumina and silver nitrate were purchased from Merck (Germany).
Synthesis of the Schiff bases
2-({[6-Amino-5-(2-phenyldiazenyl)pyridin-2-yl]imino}methyl)phenol hydrochloride (1).
PAP (0.1 g; 4.0×10-4 mol) was added to a dry EtOH (100 mL) solution of 2-hydroxy-
benzaldehyde (0.049 g; 4.0×10-4 mol). The mixture was stirred and heated for 2 h. Compound
1 was obtained after EtOH evaporation and crystallization from chloroform/n-heptane.
2-({[6-Amino-5-(2-phenyldiazenyl)pyridin-2-yl]imino}methyl)-4-methoxyphenol hydro-
chloride (2). Compound 2 was obtained in a similar manner to 1 but using a dry EtOH (100
mL) solution of 2-hydroxy-5-methoxybenzaldehyde (0.0608 g; 4.0×10-4 mol).
2-({[6-Amino-5-(2-phenyldiazenyl)pyridin-2-yl]imino}methyl)-4-nitrophenol
hydrochloride (3). Compound 3 was obtained in a similar manner to 1 but using a dry EtOH
(100 mL) solution of 2-hydroxy-5-nitrobenzaldehyde (0.0668 g; 4.0×10-4 mol).
1-({[6-Amino-5-(2-phenyldiazenyl)pyridin-2-yl]imino}methyl)-2-naphthol hydrochloride
(4). Compound 4 was obtained in a similar manner to 1 but using a dry EtOH (100 mL)
solution of 2-hydroxy-1-naphthaldehyde (0.0688 g; 4.0×10-4 mol).
RESULTS AND DISCUSSION
Schiff bases are important in diverse fields of chemistry due to their biolo-
gical activities. In addition to their biological activities, their photochromic cha-
racteristics have led to their usage in various areas, such as the control and
measurement of radiation intensity, display systems and optical computers. In the
field of coordination chemistry, the ortho hydroxylated type of Schiff bases has
received overwhelming attention, particularly in the study of complex formation.
Recently, it was found that the introduction of lateral polar hydroxyl groups
enhanced the molecular polarizability and stabilized the liquid crystalline com-
pounds. These compounds also contain interesting groups, such as (–N=N– and
–C=N–), for electrochemical studies.
Analytic and spectral data of the synthesized Schiff bases
2-({[6-Amino-5-(2-phenyldiazenyl)pyridin-2-yl]imino}methyl)phenol hydro-
chloride (1). Brown crystals; yield: 0.12 g, 86 %; m.p.: 227 °C; Anal. Calcd. for
C H ClN O: C, 61.10; H, 4.53; N, 19.80 %. Found: C, 61.10; H, 4.56; N,
18 16
5
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YAGMUR et al.
–1
19.79 %; IR (KBr, cm ): 3306 (m, O–H); 3071 (m, Ar–H); 1631 (m, C=N);
1
1450 (s, C=C); 1264 (m, C–O); H-NMR (400 MHz, DMSO, δ / ppm): 14.86
(1H, s, Ar–OH); 8.59 (1H, s, Ar–CH=N–); 6.29 (2H, s, Ar–NH –); 6.61–7.90
2
13
(11H, m, Ar-H); C-NMR (100.6 MHz, DMSO, δ / ppm): 192.0, 162.3, 155.2,
146.8, 139.1, 137.5, 136.8, 129.9, 129.6, 128.3, 119.9, 118.9, 117.7, 117.1,
117.1, 116.2.
2-({[6-Amino-5-(2-phenyldiazenyl)pyridin-2-yl]imino}methyl)-4-methoxy-
phenol hydrochloride (2). Brown crystals; yield: 0.130 g, 85 %; m.p.: 195 °C;
Anal. Calcd. for C H ClN O : C, 59.45; H, 4.69; N, 18.25 %. Found: C, 59.45;
19 18
5 2
–1
H, 4.73; N, 18.25 %; IR (KBr, cm ): 3298 (m, O–H); 3079 (m, Ar-H); 1623 (m,
C=N); 1451 (s, C=C); 1266 (m, C–O); H-NMR (400 Hz, DMSO, δ / ppm):
1
15.85 (1H, s, Ar–OH); 8.63 (1H, s, Ar–CH=N–); 6.32 (2H, s, Ar–NH –); 6.64–
2
13
–7.92 (10H, m, Ar-H); 3.79 (3H, s, Ar–OCH ); C-NMR (101.6 MHz, DMSO,
3
δ / ppm): 191.2, 155.9, 152.6, 150.1, 142.3, 130.1, 129.7, 126.6, 126.5, 122.5,
119.2, 118.8, 117.8, 116.8, 114.5, 110.3, 55.92.
2-({[6-Amino-5-(2-phenyldiazenyl)pyridin-2-yl]imino}methyl)-4-nitrophenol
hydrochloride (3). Brown crystals; yield: 0.136 g, 86 %; m.p.: 167 °C; Anal.
Calcd. for C H ClN O : C, 54.20; H, 3.79; N, 21.08 %. Found: C, 54.21; H,
18 15
6 3
–1
3.79; N, 21.07 %; IR (KBr, cm ): 3306 (m, O–H); 3063 (m, Ar-H); 1619 (m,
C=N); 1451 (s, C=C); 1336 (m, C–O); H-NMR (400 MHz, DMSO, δ / ppm):
1
12.21 (1H, s, Ar–OH); 8.90 (1H, s, Ar–CH=N–); 8.44 (2H, s, Ar–NH –); 6.21–
2
13
8.51 (10H, m, Ar-H); C-NMR (101.6 MHz, DMSO, δ / ppm): 192.2, 166.1,
142.3, 139.3, 130.1, 129.2, 128.8, 127.3, 125.2, 124.3, 123.1, 121.1, 119.3,
118.2, 116.4, 115.2.
1-({[6-Amino-5-(2-phenyldiazenyl)pyridin-2-yl]imino}methyl)-2-naphthol hyd-
rochloride (4). Brown crystals; Yield: 0.133 g, 83 %; m.p.: 237 °C; Anal. Calcd.
for C H ClN O: C, 65.43; H, 4.46; N, 17.35 %. Found: C, 65.43; H, 4.49; N,
22 18
5
–1
17.34 %; IR (KBr, cm ): 3282 (m, O–H); 3062 (m, Ar-H); 1633 (m, C=N); 1455
(s, C=C); 1365 (m, C–O); H-NMR (400 MHz, DMSO, δ / ppm): 15.34 (1H, s,
1
Ar–OH); 8.61 (1H, s, Ar–CH=N–); 6.60 (2H, s, Ar–NH –); 7.58–
2
13
–8.96 (13H, m, Ar-H); C-NMR (101.6 MHz, DMSO, δ / ppm): 193.2, 164.5,
155.1, 138.8, 130.5, 130.1, 129.8, 129.7, 129.6, 128.2, 128.0, 124.6, 122.8,
121.7, 119.7, 112.9, 109.9, 108.9, 108.3, 106.4.
1
13
FT-IR, H-NMR, C-NMR and UV spectroscopy
–1
The vibration bands with the wave numbers 3306, 3298, 3306 and 3282 cm
–1
(O–H); 3071, 3079, 3063 and 3062 cm (C–H, Ar–H); 1450, 1451, 1451 and
1455 cm (C=C) and 1264, 1266, 1336 and 1365 cm (C–O, Ar–O) were
–1
–1
observed for compounds 1–4, respectively. The C=N bond was observed at 1631,
–1
1623, 1619 and 1633 cm for 1–4, respectively. The stretching frequency
–1
observed at 2875–2745 cm in compounds 1–4 showed the presence of O–H···N
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SYNTHESIS AND ELECTROCHEMICAL PROPERTIES OF PHENAZOPYRIDINE SCHIFF BASES
799
26,27
intramolecular hydrogen bonds.
The C=N bond, which is partially account-
able for the existence of enol–imine form, can also be inferred from the IR
spectra of compounds 1–4. Compounds 1–4 with strong bands at 1278, 1280,
–1
1282 and 1284 cm , respectively, possessed high percentages of the enol–imine
28
tautomer due to stabilization of the phenolic C–O bond.
1
The H-NMR data for compounds 1–4 show that the tautomeric equilibrium
favors the enol–imine in DMSO. The OH protons were observed as singlets at
14.86, 15.85, 12.21 and 15.34 ppm for compounds 1–4, respectively. The azome-
thine protons were observed as singlets at 8.59, 8.63, 8.90 and 8.61 ppm for com-
pounds 1–4, respectively. The amine protons were found as singlets at 6.29, 6.32,
8.44 and 6.60 ppm for compounds 1–4. The phenyl protons resonated as multi-
plets at 6.61–7.90, 6.64–7.92, 6.21–8.51 and 7.58–8.96 ppm for compounds 1–4,
respectively. The singlet of the Ar–OCH protons was observed at 3.79 ppm for
3
13
compound 2. The C-NMR spectra of compounds 1–4 have 16, 17, 16 and 20
signals, respectively.
The UV–Vis spectra of the compounds were studied in DMSO. The Schiff
bases exhibited absorptions in the range greater than 400 nm in polar and non-
26,27
polar solvents.
The UV–Vis spectrum of ortho hydroxylated Schiff-bases
that exist mainly as the enol–imine structure is indicated by the presence of a
band at <400 nm, while compounds existing either as keto–amine or as mixture
of enol–imine/keto–amine forms show a new band, especially in polar and non-
26–29
polar solvents in both acidic and basic media, at >400 nm.
Compounds 1–4
showed absorption above 400 nm in DMSO. The enol–imineketo–amine tauto-
merisms of the compounds 1–4 are found to be 40, 38, 48 and 49 % in DMSO,
respectively.
1
13
In conclusion, UV–Vis, H-NMR and C-NMR results showed that the
compounds existed in the enol–imine form in DMSO.
Electrochemical studies
The reduction properties of PAP and its Schiff bases were investigated using
a GCE by cyclic voltammetry in the potential range 0 to –3 V. The cyclic vol-
tammetry (CV) curves of these compounds are given in Fig. 1. The curves were
recorded in DMSO solution containing 0.1 M tetrabutylammonium iodide
–1
(TBAI) as a supporting electrolyte at a scan rate of 3 V s . Three cathodic peaks
were observed for PAP and compounds 1, 2 and 4 and four peaks for compound
3. A new reduction peak, which was thought to belong to the reduction of the
NO group, appeared at –2.7 V on the CV curve for compound 3.
2
Since the –N=N– group (all compounds) is more susceptible to reduction
than the –C=N– (compound 1–4) and NO (compound 3), the –N=N– group is
2
22–25
reduced at less negative potential than the other groups.
As could be seen
from Fig. 1, the first peak (about –1.0 V) can, therefore, be attributed to the
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YAGMUR et al.
reduction of the –N=N– (azo) group. The second peak (about –1.5 V) may most
probably be due to the reduction of –C=N– (azomethine) group of the adsorbed
molecule and the third peak (about –2.0 V) was thought to be due to the reduc-
30
tion of –C=N– group of the molecule in solution. The NO group is reduced at
2
a more negative potential than the others. The fourth peak (about –2.7 V) can
conveniently be attributed to reduction of the NO group. Electrochemical data of
2
these compounds are given in Table I.
Fig. 1. The cyclic voltammograms of 2×10-3 M PAP and its Schiff bases in 0.1 M
TBAI/DMSO at a GCE. Scan rate = 3.0 V s-1.
TABLE I. Peak potential and peak current values of 2×10-3 M PAP and its novel Schiff bases
in 0.1 M TBAI/DMSO at a GCE from CV. Scan rate = 3 V s-1
Peak 1
Peak 2
Peak 3
Peak 4
Compound
Ep1 / V Ip1 / μA Ep2 / V Ip2 / μA Ep3 / V Ip3 / μA Ep4 / V Ip4 / μA
PAP
–0.73
–0.78
–0.79
–0.61
–0.76
20.70
22.50
23.70
13.60
23.90
–1.68
–1.76
–1.77
–1.26
–1.71
31.00
33.50
34.90
14.30
35.30
–2.22
–2.30
–2.33
–1.69
–2.26
12.80
20.30
20.60
–
–
–
–
–
–
1
2
3
4
26.60 –2.77 14.50
24.50
–
–
As can be seen from Table I, the current values of the two –C=N– groups of
the Schiff bases were found to be nearly twice that of the single –C=N– group of
PAP. The reduction potentials depend on the electronegativity of the groups in
14–21
Schiff bases.
While the reduction potential had a negative value for com-
pound 3, it was observed that compound 2 had a more negative potential value.
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SYNTHESIS AND ELECTROCHEMICAL PROPERTIES OF PHENAZOPYRIDINE SCHIFF BASES
801
The observed reduction potentials of the Schiff bases were –0.78, –0.79, –0.61
and –0.76 V (–N=N–), –1.76, –1.77, –1.26 and –1.71 V (–C=N–) and –2.30,
ads
–2.33, –1.69, –2.26 V (–C=N–) for compounds 1–4, respectively. The effects of
–1
various scan rates between 0.1–10 V s on the peak potential and the peak
–3
current of 2×10 M PAP and its Schiff bases were evaluated. Scan rate studies
were performed to assess whether the processes on the GCE were under diffu-
31–40
sion- or adsorption control.
–3
The cyclic voltammograms of 2×10 M PAP and its Schiff bases were
obtained in 0.1 M TBAI/DMSO on a GCE. A linear relationship existed between
–1
the peak current and square root of the scan rate between 0.1–10 V s (corre-
lation coefficient about 0.99), which showed that the reduction process was
predominantly under diffusion-control over the complete scan rate range studied.
In addition, a plot of the logarithm of the peak current vs. the logarithm of the
scan rate gave a straight line (correlation coefficient about 0.99) with a slope of
33–43
about 0.5, which is the expected value for an ideal reaction of solution species.
Therefore, a diffusion component must be taken into account. Other studies were
conducted in line with this phenomenon.
Mechanism of the electrochemical reduction of the compounds
When describing electrochemical reactions, an “E” and “C” formalism is
32,33
often employed.
E represents an electron transfer; sometimes E and E are
O R
used to represent oxidations and reductions, respectively. C represents a chemical
reaction, which can be any elementary reaction step, and is often called a “fol-
lowing” reaction.
The electrochemical reduction mechanisms are given in Scheme 2 for PAP
1–4. The electrochemical reduction occurred in three steps. The –N=N– and the
–C=N– groups were reduced in the first and the second step in compounds PAP
and compounds 1–4 and in the last step, the –NO group was reduced in com-
2
pound 3. Both the –C=N– groups in PAP and the Schiff bases were reduced at
the same potential.
As can be seen from the mechanism given in Scheme 2, the first step is the
2e reduction of the diazenyl group of PAP, in which the –N=N– bond opens
2–
+
resulting –N–N – dianion. Then, the hydrazine anion binds 2H , resulting in the
formation of a hydrazine compound (–NH–NH–). In the second step, the imine
–
groups of PAP and its Schiff bases form a radical anion (C–N ) with a 1e elec-
tron transfer. Then, the negatively charged nitrogen atom binds to a proton result-
ing in C–NH. This radical carbon atom takes one more electron giving a carb-
–
anion C –NH. Finally, the carbanion reacts with a proton from the solution,
resulting in an amine (CHNH). In the third stage, the NO group in compound 3
2
is reduced. According to these data, it can conveniently be claimed that the reac-
32
tions occur according to an EC mechanism.
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YAGMUR et al.
H2N HCl
HCl
H2N
2-
N
N
1. Step
+2e-
N
N
N
N
C
Ar
H
N
N
C
Ar
H
+
+2H
H N
HCl
2
NH
N
HN
N
C
Ar
H
H2N HCl
2-
HCl
H2N
2. Step
NH
HN
N
+2e-
.
H
NH
HN
N
Ar
N
C
H
.
N
Ar
C
+
+2H
HCl
H2N
.
NH
HN
NH
H
.
NH
Ar
C
+2e-
HCl
H2N
2-
HCl
H2N
NH
HN
H
NH
+
+2H
..
H
C
NH
HN
NH
NH
Ar
H
..
NH
Ar
H
C
Scheme 2. Electrochemical reduction mechanism of PAP and the Schiff bases 1–4.
CONCLUSIONS
In the present work, the Schiff bases 1–4 were synthesized and characte-
rized, and the electrochemical properties of PAP and its Schiff bases were inves-
tigated by cyclic voltammetry. A simple, sensitive and selective CV technique
was developed for the examination of the electrochemical reduction behavior of
PAP and its Schiff bases 1–4 on a GCE. While the electrochemical reduction
occurred over three steps for PAP and compounds 1, 2 and 4, compound 3 had a
fourth step. As could be seen from the cyclic voltammograms, the first, second
and third peaks belong to the –N=N–, –C=N– and –C=N–(ads) groups, respecti-
vely, and the fourth peak belongs to the NO group.
2
It could also be concluded that the reduction potentials and currents depended
on the electron withdrawing groups and hydrogen bonding on either side of the
14–17
–N=N– and –C=N– groups.
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SYNTHESIS AND ELECTROCHEMICAL PROPERTIES OF PHENAZOPYRIDINE SCHIFF BASES
803
И З В О Д
СИНТЕЗА, СПЕКТРОСКОПСКО ИСПИТИВАЊЕ И ЕЛЕКТРОХЕМИЈСКЕ ОСОБИНЕ
ШИФОВИХ БАЗА ДОБИЈЕНИХ ОД 2-ХИДРОКСИ АРОМАТИЧНИХ АЛДЕХИДА И
ФЕНАЗОПИРИДИН-ХИДРОХЛОРИДА
SULTAN YAGMUR1, SELEHATTIN YILMAZ1, GULSEN SAGLIKOGLU1, MURAT SADIKOGLU2, MUSTAFA YILDIZ1
и KAMRAN POLAT3
1
Canakkale Onsekiz Mart University, Faculty of Science and Arts, Department of Chemistry, 17020,
2
Canakkale, Turkey, Gaziosmanpasa University, Faculty of Education, Department of Science
3
Education, 60100, Tokat, Turkey и Ankara University, Faculty of Science,
Department of Chemistry, 06100, Ankara, Turkey
У реакцијама између 2-хидроксибензалдехида, 2-хидрокси-5-метоксибензалдехида,
2-хидрокси-5-нитробензалдехида, 2-хидрокси-1-нафталдехида и феназопиридин-хидро-
хлорида (PAP) синтетизоване су нове Шифове базе (1–4), које су окарактерисане при-
меном спектроскопских метода. Електрохемијска редукција феназопиридин-хидрохло-
рида (PAP) и одговарајућих Шифових база (1–4) је извођена на електроди од стакластог
угљеника (GCE) у диметил-сулфоксиду (DMSO) применом цикличне волтаметрије (CV).
Испитиван је утицај функционалних група на потенцијал редукције Шифових база.
Поред тога, предложен је механизам електрохемијске редукције испитиваних једињења.
(Примљено 24. маја, ревидирано 13. децембра 2012)
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