Synthesis, spectral properties of 1-substituted phenyl-3-(p- methoxycarbonyl)phenyl-5-phenylformazans

Article abstract of DOI:10.14233/ajchem.2013.13465

Formazans 1-14 were prepared by the coupling reaction of phenylhydrazones and diazonium salts of aniline or -NO2, -CH3, -OCH3, -I, substituted anilines. The phenylhydrazones were synthesized by condensation of benzaldehyde or methyl-4-formylbenzoate with phenylhydrazine. The structures of the compounds were confirmed by IR, 1H NMR and 13C NMR. The dependence of ?max upon the type of substituents and their positions on the phenyl ring was investigated using UV-visible spectra.

Full text of DOI:10.14233/ajchem.2013.13465

Asian Journal of Chemistry; Vol. 25, No. 6 (2013), 2989-2993
http://dx.doi.org/10.14233/ajchem.2013.13465
Synthesis and Spectral Properties of 1-Substituted
Phenyl-3-(p-methoxycarbonyl)phenyl-5-phenylformazans
1,*
1
2
HÜLYA SENÖZ , EBRU YILDIRIM and HABIBE TEZCAN
1Department of Chemistry, Faculty of Science, Hacettepe University, Beytepe 06800, Ankara, Turkey
2Department of Chemistry, Faculty of Gazi Education, Gazi University, Teknikokullar 06500, Ankara, Turkey
*Corresponding author: Tel: +90 31 22977960; E-mail: senoz@hacettepe.edu.tr
(Received: 18 January 2012;
Accepted: 5 December 2012)
AJC-12503
Formazans 1-14 were prepared by the coupling reaction of phenylhydrazones and diazonium salts of aniline or -NO2, -CH3, -OCH3, -I,
substituted anilines. The phenylhydrazones were synthesized by condensation of benzaldehyde or methyl-4-formylbenzoate with phenyl-
1
hydrazine. The structures of the compounds were confirmed by IR, H NMR and 13C NMR. The dependence of λmax upon the type of
substituents and their positions on the phenyl ring was investigated using UV-visible spectra.
Key Words: Formazan, Diazo coupling, Dyes, Spectroscopy.
visible spectrophotometer using 1 cm quartz cells in 10-4 mol
INTRODUCTION
L-1 CH3OH using 325 nm UV lamp in the range of 200-600
Since the first synthesis of formazan byVon Penchman1,2,
nm. The IR spectra were obtained on Thermo, Nicolet IS10-
FTIR spectrometer between 4000 and 400 cm-1. 1H NMR and
the investigation of formazans by chemists, biologists, techno-
logists and other specialists has been ongoing3. Because of
13C NMR spectral studies were performed on a Bruker 400
the presence of conjugate p-system in formazans, the redox
reactions of these compounds are typical. The main areas of
MHz spectrometer using CDCl3. All the elemental analysis
studies were carried out using a LECO-CHNS- 932 elemental
practical application are isomerization and tautomeric trans-
analyzer. Melting points were determined with an electrothermal
formations, and enhanced acidity and basicity4-7. Formazans
melting point apparatus and are uncorrected.
form tetrazolium salts when they are oxidized8. Tetrazolium
salts are reduced back to formazans by enzymes in the cell
and stain tissue. The tetrazolium-formazan system is classified
as a marker of vitality9 and this feature enables the determi-
nation of activity on tumor cells. This feature is the cause of
an increasing interest in the chemistry of formazans.
N
N
N
N
H
A
B
In this study, novel formazans with various substituents
attached to the 1-substituted phenyl-3-(p-metoxycarbonyl)
phenyl were synthesized (Fig. 1), their structures and spectral
behaviours were investigated by using elemental analysis, 1H
NMR, 13C NMR, IR, and UV-visible spectra. The aim of this
study is to clarify the spectral behaviour of novel formazans
in some application areas, such as medical, analytical, drug
applications, the dye industry and new organic synthesis. It is
also speculated that these compounds may be more suitable
for use in the fields than known substituted formazans.
A= H, p-COOCH3;
B= (o,m,p)- NO2,-CH3,-OCH3, -I
Fig. 1. Structure of the studied formazan derivatives
General procedure:The synthesis of substituted formazans
were carried out using benzaldehyde (or substituted benzal-
dehydes), phenylhydrazine and aniline. Benzaldehyde (or
substituted benzaldehydes) were reacted with phenylhydrazine
at pH 5-6 to obtain benzaldehyde phenylhydrazone (or substi-
tuted benzaldehydephenylhydrazones). These hydrazones
were then coupled with the corresponding benzenediazonium
chloride at ca. -5 ºC10- 12
.
EXPERIMENTAL
Synthesis of 1,3,5-triphenylformazan (TPF) (1): Benzal-
dehyde (1.06 g, 0.01 mol) was dissolved in methanol (25 mL)
The UV-visible spectra of all the formazans synthesized
in this study were obtained with UNI CAM UV2-100 UV/

2990 Senöz et al.
Asian J. Chem.
and phenylhydrazine (1.08 g, 0.01 mol) was gradually added
with constant stirring at pH 5-6. The procedure was completed
in 0.5 h. The resulting yellow hydrazone was left on the bench
overnight and then was filtered and recrystallized from methanol.
The benzaldehyde phenylhydrazone (1.96 g, 0.01 mol) was
dissolved in methanol (35 mL) and (35 mL) buffer solution
[sodium hydroxide (2.50 g), sodium acetate (3.50 g) and
methanol (200 mL)] by constant stirring. In another flask
benzenediazonium chloride solution was prepared using aniline
(0.93 g, 0.01 mol) concentrated HCl (5 mL) and sodium nitrite
(0.75 g) at -5 ºC. This solution was added to the benzaldehyde
phenylhydrazone solution dropwise with constant stirring to
form formazan. The solution was stirred for 2 h at the same
temperature and stored for 2 days. Each compound was recrys-
tallized from methanol giving cherry red crystals. Yield 80 %,
m.p. 174 ºC (Lit11 172-174 ºC).
CH), 3025 (NH), 1609 (aromatic C=C), 1707 (C=O), 1515
(C=N), 1370 (N=N). H NMR (CDCl3) δ ppm: 2.50 (s, 3H,
1
CH3), 3.83 (s, 3H, OCH3), 7.26- 8.20 (m, 13H, Ar-H), 15.58
(s, 1H, NH). 13C NMR (CDCl3) δ ppm: 29.21 (CH3), 52.14
(OCH3), 112.98- 145.36 (Ar-C), 151.65 (C=N), 168.62 (C=O).
Anal. calcd. for C22H20N4O2: C, 70.94; H, 5.42; N, 15.04.
Found: C, 71.25; H, 6.01; N, 15.21.
1-(m-Tolyl-3-(p-methoxycarbonylphenyl)-5-phenyl
formazan (7): Bright brown crystals, yield 77 %, m.p. 158 ºC.
IR (λmax in cm-1): 3040 (aromatic CH), 2842-2940 (aliphatic
CH), 3019 (NH), 1609 (aromatic C=C), 1707 (C=O), 1506
1
(C=N), 1355 (N=N). H NMR (CDCl3) δ ppm: 2.49 (s, 3H,
CH3), 3.44 (s, 3H, OCH3), 7.32-8.26 (m, 13H, Ar-H), 15.69
(s, 1H, NH). 13C NMR (CDCl3) δ ppm: 29.47 (CH3), 52.37
(OCH3), 112.15-146.24 (Ar-C), 150.54 (C=N), 167.65 (C=O).
Anal. calcd. for C22H20N4O2: C, 70.94; H, 5.42; N, 15.04.
Found: C, 71.34; H, 5.69; N, 15.67.
Other compounds were prepared in similar manner and
characterization data of 2-14 were given.
1-(p-Tolyl-3-(p-methoxycarbonylphenyl)-5-phenyl
formazan (8): Rush brown crystals, yield 83 %, m.p. 175 ºC.
IR (λmax in cm-1): 3050 (aromatic CH), 2995-2944 (aliphatic
CH), 3062 (NH), 1603 (aromatic C=C), 1717 (C=O), 1506
3-(p-Methoxycarbonylphenyl)-1,5-diphenylformazan
(2): Claret red crystals, yield 84 %, m.p. 172 ºC. IR (λmax in
cm-1): 3050-3000 (aromatic CH), 2943 (aliphatic CH), 3070
(NH), 1606 (aromatic C=C), 1715 (C=O), 1513 (C=N), 1350
(N=N). 1H NMR (CDCl3) δ ppm: 3.88 (s, 3H, OCH3), 7.32-
8.26 (m, 14H, Ar-H), 15.68 (s, 1H, NH). 13C NMR (CDCl3) δ
ppm: 52.09 (OCH3), 118.96-141.89 (Ar-C), 147.62 (C=N),
167.21 (C=O). Anal. calcd. for C21H18N4O2 : C, 70.36; H, 5.06;
N, 15.64. Found: C, 70.95; H, 5.09; N, 15.64.
1
(C=N), 1378 (N=N). H NMR (CDCl3) δ ppm: 2.46 (s, 3H,
CH3), 3.55 (s, 3H, OCH3), 7.32- 8.25 (m, 13H, Ar-H), 15.68
(s, 1H, NH). 13C NMR (CDCl3) δ ppm: 28.15 (CH3), 52.88
(OCH3), 115.34- 147.44 (Ar-C), 152.18 (C=N), 168.23 (C=O).
Anal. calcd. for C22H20N4O2: C, 70.94; H, 5.42; N, 15.04.
Found: C, 71.46; H, 5.55; N, 15.35.
1-(o-Nitrophenyl-3-(p-methoxycarbonylphenyl)-5-
phenyl formazan (3): Red brown crystals, yield 81 %, m.p.
194 ºC. IR (λmax in cm-1): 3050-3000 (aromatic CH), 2944
(aliphatic CH), 3062 (NH), 1609 (aromatic C=C), 1719 (C=O),
1-(o-Anisidyl-3-(p-methoxycarbonylphenyl)-5-phenyl
formazan (9): Purplish red crystals, yield 80 %, m.p. 163 ºC.
IR (λmax in cm-1): 3000 (aromatic CH), 2952 (aliphatic CH),
3020 (NH), 1589 (aromatic C=C), 1707 (C=O), 1509 (C=N),
1
1
1518 (C=N), 1324 (NO2), 1371 (N=N). H NMR (CDCl3) δ
1349 (N=N). H NMR (CDCl3) δ ppm: 3.85 (s, 3H, OCH3),
ppm: 3.04 (s, 3H, OCH3), 7.12- 8.48 (m, 13H, Ar-H), 15.65
(s, 1H, NH). 13C NMR (CDCl3) δ ppm: 52.24 (OCH3), 116.92-
142.87 (Ar-C), 152.83 (C=N), 166.98 (C=O). Anal. calcd. for
C21H17N5O4 : C, 62.50; H, 4.24; N, 17.36. Found: C, 62.95; H,
4.92; N, 17.55.
3.88 (s, 3H, OCH3), 6.96-8.15 (m, 13H, Ar-H), 15.38 (s, 1H,
NH). 13C NMR (CDCl3) δ ppm: 51.67 (OCH3), 52.84 (OCH3),
112.21- 148.45 (Ar-C), 151.85 (C=N), 167.58 (C=O). Anal.
calcd. for C22H20N4O3: C, 68.02; H, 5.19; N, 14.43. Found: C,
68.35; H, 5.40; N, 14.00.
1-(m-Nitrophenyl-3-(p-methoxycarbonylphenyl)-5-
phenyl formazan (4): Rusty brown crystals, yield 85 %, m.p.
191 ºC. IR (λmax in cm-1): 3040 (aromatic CH), 2951 (aliphatic
CH), 3090 (NH), 1616 (aromatic C=C), 1715 (C=O), 1513
1-(m-Anisidyl-3-(p-methoxycarbonylphenyl)-5-phenyl
formazan (10): Purplish red crystals, yield 80 %, mp 161 ºC.
IR (λmax in cm-1): 3000-3050 (aromatic CH), 2964 (aliphatic
CH), 3011 (NH), 1609 (aromatic C=C), 1709 (C=O), 1509
1
1
(C=N), 1340 (NO2), 1350 (N=N). H NMR (CDCl3) δ ppm:
(C=N), 1349 (N=N). H NMR (CDCl3) δ ppm: 3.94 (s, 3H,
4.48 (s, 3H, OCH3), 7.40- 8.46 (m, 13H, Ar-H), 15.29 (s, 1H,
NH). 13C NMR (CDCl3) δ ppm: 52.18 (OCH3), 111.63-149.29
(Ar-C), 149.77 (C=N), 167.01 (C=O). Anal. calcd for
C21H17N5O4: C, 62.50; H, 4.24; N, 17.36. Found: C, 62.91; H,
4.78; N, 17.65.
OCH3), 3.98 (s, 3H, OCH3), 6.86- 8.24 (m, 13H, Ar-H), 15.62
(s, 1H, NH). 13C NMR (CDCl3) δ ppm: 51.82 (OCH3), 52.56
(OCH3), 115.48-148.69 (Ar-C), 150.93 (C=N), 168.32 (C=O).
Anal. calcd. for C22H20N4O3: C, 68.02; H, 5.19; N, 14.43.
Found: C, 68.43; H, 5.56; N, 14.10.
1-(p-Nitrophenyl-3-(p-methoxycarbonylphenyl)-5-
phenyl formazan (5): Dark brown crystals, yield 77 %, m.p.
198 ºC. IR (λmax in cm-1): 3000 (aromatic CH), 2944 (aliphatic
CH), 3087 (NH), 1602 (aromatic C=C), 1719 (C=O), 1537
(C=N), 1320 (NO2), 1400 (N=N). 1H NMR (CDCl3) δ ppm: 3.47
(s, 3H, OCH3), 7.24- 8.40 (m, 13H, Ar-H), 15.36 (s, 1H, NH).
13C NMR (CDCl3) δ ppm: 52.20 (OCH3), 113.47- 146.82 (Ar-C),
150.43 (C=N), 166.76 (C=O). Anal. calcd. for C21H17N5O4: C,
62.50; H, 4.24; N, 17.36. Found: C, 62.80; H, 4.64; N, 17.73.
1-(o-Tolyl-3-(p-methoxycarbonylphenyl)-5-phenyl
formazan (6): Rusty brown crystals, yield 82 %, m.p. 207 ºC.
IR(λmax in cm-1): 3040-3000 (aromatic CH), 2952 (aliphatic
1-(p-Anisidyl-3-(p-methoxycarbonylphenyl)-5-phenyl
formazan (11): Rusty brown crystals, yield 77 %, m.p. 184
ºC. IR(λmax in cm-1): 3000 (aromatic CH), 2956 (aliphatic CH),
3025 (NH), 1604 (aromatic C=C), 1707 (C=O), 1504 (C=N),
1
1344 (N=N). H NMR (CDCl3) δ ppm: 3.88 (s, 3H, OCH3),
3.98 (s, 3H, OCH3), 6.90- 8.19 (m, 13H, Ar-H), 15.88 (s, 1H,
NH). 13C NMR (CDCl3) δ ppm: 51.26 (OCH3), 52.35 (OCH3),
113.62-147.71 (Ar-C), 150.24 (C=N), 166.92 (C=O). Anal.
calcd. for C22H20N4O3: C, 68.02; H, 5.19; N, 14.43. Found: C,
68.18; H, 5.28; N, 14.26.
1-(o-Iodophenyl-3-(p-methoxycarbonylphenyl)-5-
phenyl formazan (12): Brown crystals, yield 99 %, m.p.

Vol. 25, No. 6 (2013)
Synthesis of 1-Substituted Phenyl-3-(p-methoxycarbonyl)phenyl-5-phenylformazans 2991
205 ºC. IR(λmax in cm-1): 3040 (aromatic CH), 2940 (aliphatic
formazans (Scheme-II). The C=N stretching band at 1510-
CH), 3030 (NH), 1605 (aromatic C=C), 1703 (C=O), 1522
1500 cm-1 shows chelate structures. However, the C=N stretch-
1
(C=N), 1359 (N=N). H NMR (CDCl3) δ ppm: 3.88 (s, 3H,
ing band at 1561-1551 cm-1 shows non-chelate structures11,12
.
OCH3), 6.92- 8.18 (m, 13H,Ar-H), 15.07 (s, 1H, NH). 13C NMR
(CDCl3) δ ppm: 52.77 (OCH3), 112.67- 148.91 (Ar-C), 152.45
(C=N), 167.45 (C=O). Anal. calcd. for C21H17N4O2I: C, 57.12;
H, 3.54; N, 11.59. Found: C, 57.85; H, 4.07; N, 11.87.
1-(m-Iodophenyl-3-(p-methoxycarbonylphenyl)-5-
phenyl formazan (13): Dark purplish crystals, yield 97 %,
mp 200 ºC. IR(λmax in cm-1): 3056 (aromatic CH), 2945
(aliphatic CH), 3087 (NH), 1602 (aromatic C=C), 1712 (C=O),
1539 (C=N), 1377 (N=N). 1H NMR (CDCl3) δ ppm: 3.88 (s,
3H, OCH3), 6.82- 8.13 (m, 13H,Ar-H), 15.39 (s, 1H, NH). 13C
NMR (CDCl3) δ ppm: 52.38 (OCH3), 113.81- 148.61 (Ar-C),
155.63 (C=N), 168.04 (C=O). Anal. calcd. for C21H17N4O2I:
C, 57.12; H, 3.54; N, 11.59. Found: C, 57.76; H, 3.39; N,
11.72.
For the studied formazans, 1-14, chelate structures (Scheme-
IIa) were found to be dominant while non-chelate structures
(Scheme-IIb) were few in equilibrium.
The lower values of the N=N stretching bands 1410-1350
cm-1 are probably due to the intramolecular hydrogen bond
and some chelate ring resonance. The N=N stretching band of
the chelate form of 1,3,5-triphenylformazan was located at
1357 cm-1 and the non-chelate form was located13 at 1461 cm-1.
In addition, the lower values of absorption bands N-H 3090-
3011 cm-1 show chelate structure4. Chelate structures have a
six-membered conjugated system in which p-electrons are
delocalized. Hence, the double bond characteristic decreases.
The stretching bands of C=N, N=N and N-H were observed at
lower frequencies. Other IR data can be evaluated in a similar
manner: aromatic CH, aliphatic CH, C=O, C=C stretching peaks
and NO2 vibration band were observed in the expected regions.
1-(p-Iodophenyl-3-(p-methoxycarbonylphenyl)-5-
phenyl formazan (14): Purplish red crystals, yield 69 %, m.p.
202 ºC. IR (λmax in cm-1): 3039 (aromatic CH), 2945 (aliphatic
CH), 3093 (NH), 1608 (aromatic C=C), 1714 (C=O), 1528
1
(C=N), 1397 (N=N). H NMR (CDCl3) δ ppm: 3.88 (s, 3H,
OCH3), 6.82-8.13 (m, 13H,Ar-H), 15.49 (s, 1H, NH). 13C NMR
(CDCl3) δ ppm: 52.81 (OCH3), 115.61-149.58 (Ar-C), 154.38
(C=N), 168.93 (C=O). Anal. calcd. for C21H17N4O2I: C, 57.12;
H, 3.54; N, 11.59. Found: C, 57.39; H, 3.96; N, 11.89.
N
N
N
N
N
N
N
N
H
H
R
R
(a)
(b)
RESULTS AND DISCUSSION
Scheme-II: Chelate and non-chelate structures
Synthesis and determination of structures of formazans:
In this study, 1,3,5-triphenylformazan (1) and new 1-substituted
phenyl-3-(p-methoxycarbonyl)phenyl-5-phenyl formazans
were synthesized (2-14). The formazans were prepared by the
coupling reactions of hydrazones with benzendiazonium
chlorides, in a basic medium under 0 ºC. The hydrazones were
obtained by the condensation reaction of phenyl hydrazine
with aldehyde (or substituted aldehydes). This route proved
to be time consuming and laborious. However, the advantage
of this route was that it is possible to synthesize both symmetric
and asymmetric formazans and could be conducted with common
chemicals present in all laboratories. Although purifying the
resultant product was difficult10, formazans were synthesized
in high yields. The reaction route is given in Scheme-I.
1
The H NMR data showed that the aromatic hydrogen
peaks of 1,3,5-triphenylformazan were observed between 7.22-
8.09 ppm. Each of the three phenyl rings of the formazan has
a different electron density, so the peaks of each aromatic H
showed a broad range14. The electron withdrawal effect of
substituent bonded phenyl rings and the double bond resonance
in the structure of 2-5 caused the aromatic hydrogen peaks to
shift towards lower fields, while the electron donating effect
of substituent bonded phenyl rings in the structure of 9-14
caused a shift in the aromatic hydrogen peaks towards higher
fields. Because of the weak electron donating effect of CH3,
in formazans 6-8, we observed that the values of chemical shifts
of aromatic-H were similar to that of 1,3,5-triphenylformazan.
1,3,5-Triphenylformazan and other formazans 2-14, exhi-
bited sharp NH signals in the downfield region between 15.29-
15.88 ppm (1H, s), indicative of an intramolecular hydrogen
bond, which decreases electron density around the proton and
thus moves the proton absorption to the lower field15,16. Fig. 2
gives the 1H NMR spectra of formazan 3 as an example.
O
N-NH-
Methanol
C
H2N-NH-
+
A
C
A
H
H
+
+
N
B
N
N
N
N
N
NaOH/ CH COONa
H
3
A
methanol
B
Scheme-I: The route followed in the synthesis of formazans
16 15 14 13 12 11 10
9
8
7
6
5
4
3
2
1
ppm
The IR data of formazans (1-14) reveal the C=N stretching
bands between 1539-1504 cm-1. C=N absorption values
determine either a chelate or non-chelate structure of the
Fig. 2. 1H NMR spectra of formazan 2

2992 Senöz et al.
Asian J. Chem.
13C NMR data revealed that 8 aromatic C signals were
The fact that the λmax1 of 3 and 5 showed a slight shift towards
a higher wavelength compared to 2 is not in accordance with
the electron withdrawing effect of the -NO2 group. This can
only be explained by the formation of an intramolecular H-
bond between the hydrogen atom of N-H and the oxygen atom
of the -NO2 group attached to the o-position of the 1-phenyl
ring for 3 (Scheme-IV) and that of the intermolecular H-bond
for 5. This diminishes the resonance effect of the o-NO2 group
and decreases its electron withdrawing effect. The significant
shift in the case of the m-NO2 (∆λmax = 7 nm, hypsochromic
effect) is due to the dominance of the withdrawing inductively.
observed in contrast to the expected 12 for 1 and 2. This proved
the presence of toutomerization and chelate formation for these
formazans12. For 3-14, p-substituted compounds gave 12
aromatic C signals and o- and m- substituted compounds gave
14 aromatic C signals. The C atoms of the imino-C (C=N),
-CH3, -OCH3, -C=O appeared in their expected chemical fields.
Structural analysis of the chelate form proved that this
was the EZ (trans-syn) isomer (Scheme-III). The majority of
formazans with this structure were characterized by the
presence of a low-field signal of NH in the 1H NMR spectra
and the lack of absorption bands in their IR spectra at 3500-
3100 cm-1 13. The chemical shift of the imino carbon atom of
these compounds in 13C NMR spectra was observed at δ 148-
151 ppm. The results of ab initio quantum-chemical calculations
of all possible conformations of these compounds suggest that
the EZ configuration was the most stable. To a large extent,
this structure was stabilized by a bridging N-H….N hydrogen
bond in the six-membered chelate ring where proton transfer
is possible.4,17 All the spectroscopic results support that the
studied formazans (1-14) have EZ configuration.
TABLE-1
UV-VISIBLE ABSORPTION MAXIMA* OF FORMAZANS (1-14)
Compound Substituents, B
λmax1 (nm) λmax2 (nm) λmax3 (nm)
H
H
480
477
480
470
480
485
477
480
475
480
495
485
475
490
320
319
310
310
315
325
325
320
340
320
320
320
365
360
240
241
230
235
235
230
240
240
245
240
245
220
245
245
1
2
o-NO2
m-NO2
p-NO2
o-CH3
m-CH3
p-CH3
o-OCH3
m-OCH3
p-OCH3
o-I
3
4
5
6
7
8
R5
9
10
11
12
13
14
N
N
N
N
R3
H
m-I
p-I
*UV spectra were recorded in CH3OH 10-4 mol/L
R
Scheme-III: EZ configuration of formazan
For compounds 6-8, the λmax1 values were shifted to 485,
477, 480 nm respectively. These values are in accordance with
the electron donating effects of the -CH3 group while shifting
to 475, 480, 495 were explained by the resonance electron
donating effect and inductive electron withdrawing effect of
the -OCH3 group for compounds 9-11.
In -I substituted compounds 12-14, the λmax1 values were
shifted to 485, 475, 490 nm, while in compound 2, the λmax1
value was 477 nm.As it is known, iodine is affected by inductive
electron withdrawing and resonance electron donating effects
which have an opposing effect on each other. Since iodine has
lower electronegativity, the inductively electron withdrawing
effect is less than the electron donating effect by resonance.
Hence, iodine showed the ∆λa = + 8 nm bathocromic effect at
the o-position. However, at the m-position, the resonance effect
was very weak and there was only a decreased inductive effect.
For this reason the hypsochromic effect was observed to be as
little as ∆λa= -2 nm. For the case of p-position the resonance
Table-1 lists all the peaks observed in the UV-visible
region for the studied compounds, 1-14. The spectra exhibited
three main absorption peaks3,18. The first broad peak λmax1 is
characteristics of the formazan skeleton due to π-π* and n-π*
electronic transitions in the skeleton. This peak is generally
observed at 410-500 nm and shifted to 600 nm depending on
the structure19,20. The λmax2 and λmax3 peaks are sharp and
appeared at around the 300-350 nm and 270-300 nm corres-
ponding hydrazone skeleton and originated from the π-π* and
n-π* electronic transitions in the -N=N- and -C=N- groups.
The λmax1 value of 1,3,5-triphenylformazan (1) at 480 nm
shifted to lower wavelength (hypsochromic effect) 477 nm
when the 3-phenyl ring was substituted with the -COOCH3
group at p-position (2). This is in good accordance with the
-COOCH3 withdrawing effect of the ester group. The λmax1
values were observed at 480, 470 and 480 nm compounds 3-5.
N
N
N
N
N N
H
A
C
A
C
H
A
C
N N
-
N N
H
N N
N
N
O
N
O
-
O
O
O
O
Scheme-IV: Hydrogen bond formation between the -NO2 and N-H groups

Vol. 25, No. 6 (2013)
Synthesis of 1-Substituted Phenyl-3-(p-methoxycarbonyl)phenyl-5-phenylformazans 2993
effect of iodine is dominating. That is why λmax1 shifted
towards as high a wavelength as ∆λa = +13 nm (bathocromic
effect).
These results are shown in Fig. 3-a to compare
unsubstituted 1 and monosubstituted formazan 2 and in
Fig. 3-b to compare monosubstituted 2 with disubstituted
formazans 9-11.
Conclusion
We have synthesized 13 new formazans and elucidated
their structures by elemental and spectral analysis. The spectral
behaviours of all the formazans via 1H NMR, 13C NMR, IR,
and UV-visible spectra. IR and NMR spectra showed that the
studied formazans 1-14 may be extensively in the chelate and
a little in the non-chelate structures in equilibrium. The forma-
tion of an intramolecular hydrogen bond between the lone pair
of nitrogen with the hydrogen of NH into chelate structure
decreases electron density around the proton and thus moves
the proton absorption to a lower field. In the evaluation of UV
spectra, it was seen that they were in accordance with the charac-
teristic peaks of formazans and the effects of substituents on
absorption lmax were observed in the expected regions.
2
(a)
TPF
Formazan 2
1,5
1
0,5
0
ACKNOWLEDGEMENTS
This work was supported financially by Hacettepe Uni-
versity (Research Center Office/Projects No: 09D12601001).
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2,5
2
(b)
Formazan 2
Formazan 9
Formazan 10
Formazan 11
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Fig. 3. UV-visible spectra of: (a) compound 2 compared with 1,3,5-
triphenylformazan; (b) compounds 9-11 compared to 2 (in CH3OH
10-4 mol/L)