Synthesis and spectral properties of some bis-substituted formazans

Article abstract of DOI:10.1016/j.saa.2007.05.061

Novel, 1,4-bis-[3,3′-phenyl-5,5′-(o-carboxyphenyl)-formaz-1-yl]-benzene-o-sulphonic acid and its derivatives contained {single bond}OH group at the o-, m-, p-positions of the 3-phenyl ring were synthesized. The structures of the formazans were confirmed by elemental analyses, GC-mass, IR, ¹H NMR, UV-vis spectra. Their absorption properties were investigated. It was seen that λ_max values shifted towards shorter wave lengths by 130 nm in CSPF relative to 1,3,5-triphenylformazan (TPF) due to the fact that the structure of CSPF contained electron withdrawing {single bond}COOH and {single bond}SO₃H groups (hypsochromic effect). With binding of {single bond}OH group to 3-phenyl ring of CSPF, it was observed a small bathochromic effect in accordance to the electron donating effect of {single bond}OH group.

Full text of DOI:10.1016/j.saa.2007.05.061

Available online at www.sciencedirect.com
Spectrochimica Acta Part A 69 (2008) 971–979
Synthesis and spectral properties of some bis-substituted formazans
Habibe Tezcan∗
Department of Chemistry, Gazi University, Faculty of Gazi Education, Teknikokullar, 06500 Ankara, Turkey
Received 8 February 2007; received in revised form 24 May 2007; accepted 26 May 2007
Abstract
Novel, 1,4-bis-[3,3ꢀ-phenyl-5,5ꢀ-(o-carboxyphenyl)-formaz-1-yl]-benzene-o-sulphonic acid and its derivatives contained OH group at the o-,
m-, p-positions of the 3-phenyl ring were synthesized. The structures of the formazans were confirmed by elemental analyses, GC-mass, IR, 1H
NMR, UV–vis spectra. Their absorption properties were investigated. It was seen that λmax values shifted towards shorter wave lengths by 130 nm
in CSPF relative to 1,3,5-triphenylformazan (TPF) due to the fact that the structure of CSPF contained electron withdrawing COOH and SO3H
groups (hypsochromic effect). With binding of OH group to 3-phenyl ring of CSPF, it was observed a small bathochromic effect in accordance
to the electron donating effect of OH group.
© 2007 Elsevier B.V. All rights reserved.
Keywords: Bis-substituted formazans dyes; Spectroscopy; IR spectroscopy; Mass spectra; Substituent effect
1. Introduction
tant [22]. Additional, substituents effects on formazans were
investigated [23–25].
There are numerous studies related to formazans such as their
synthesis, structural properties, photochromic transitions, tau-
tomer formation, redox potentials [1–6] and synthesis of crown
formazans [7,8]. Metal–formazan complexes were synthesized
and their thermogravimetric analyses, dissociation and stability
constants, formation constants and electrochemical behaviors
were examined [9–12].
The IR and Raman spectra were determined [5,13] and the
substituents effect upon complex forming, pKa values and the
dependence of their absorption properties upon pH were deter-
mined [14–16].
Formazansareeasilyoxidizedtogivetetrazoliumsalts. When
given to a living organism these salts are reduced back to for-
mazan depending upon the viability of the organism. These
enables the viability of the organism be tested by monitoring
formazan formation with spectroscopy. That is why the spectro-
scopic investigation of formazans is of importance.
The purpose of this study is to synthesize water-soluble
macromolecular bis-formazans with various structures and to
investigate their spectral properties. Also it is hoped that the for-
mazans synthesized in this study are less toxic and more suitable
for medical applications.
Formazan/tetrazolium system is described as the marker of
vitality [17]. These compounds are used in Brucella-ring test
in milk [18]. Blue tetrazolium/formazan systems are used to
demonstrate enzymes activity in normal and neoplastic tis-
sues but it was found to be 10 times more toxic in vivo
(mice) than mono tetrazolium/formazan system itself [19]. For-
mazan/tetrazolium system is quite useful in the determination of
the effect and the selection of anti-cancer drugs [20,21]. How-
ever, Kebler and Furusaki states that they cannot act as a marker
every time, since the age of the cell and medium are also impor-
Formazans are colored compound ranging from red to orange
or blue depending upon their structures. However, they did not
have their deserved place in dying industry as seen the applica-
tion of these compounds is based upon their color features. That
is why this study is mainly focused on λmax values of various
formazans and the substituents which effect the λmax values.
Formazansarepolydentateligands withdonor atomsandthey
are used for analytical purposes for forming complexes with
trace metals. It also hoped that the formazans synthesized in this
study are suitable for these applications.
2. Results and discussion
∗
This study was carried out in three stages. The first step,
Fax: +90 312 2228483.
E-mail address: habibe@gazi.edu.tr.
TPF (1) (Scheme 1a) and new substituted bis-formazans (2–5)
1386-1425/$ – see front matter © 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2007.05.061

972
H. Tezcan / Spectrochimica Acta Part A 69 (2008) 971–979
2.1. Synthesis of formazans
There are three distinctive routes proposed for the synthesis
of formazans in literature [6]. The first one is the condensation
of aromatic and aliphatic aldehydes with phenyl hydrazine and
the coupling reaction of the resulting hydrazones with diazo-
nium salts [6]. Although this is highly cumbersome and resulting
products are difficult to purify, it has the advantage of be able to
synthesizing symmetrical and asymmetrical formazans [6,24].
The second way is the coupling of active methylene compounds
with two mols diazonium cations. This is highly practical and
easy but only gives symmetrical formazans [6,13]. The third way
is the phase transfer. However, it requires special regents such
as crown ethers and tetrabuthyl ammonium bromide, etc. [6].
The formazans in this study were synthesized by the first
way, coupling of hydrazones with diazonium cations in basic
media at −5 to 0 ◦C. The necessary hydrazones were obtained
by the condensation reaction of benzaldehyde (or substituted
benzaldehydes) and phenylhydrazine (or substituted phenylhy-
drazine) at pH 5–6. This is the most difficult and low yielding
route in the synthesis of formazans. The purification of the prod-
ucts is cumbersome and requires patience [6,25]. The reason for
the preference of this way in spite of all these setbacks is that the
starting material is easily available in every laboratory. We tried
to increase the yield in order to provide a cheap way to synthesize
formazans for medical, dying and analytic applications.
Scheme 1. The structure of the formazans synthesized.
Mechanism of TPF formation was traced with UV–vis spec-
tra. The fact that NH proton is more acidic than CH proton, the
first diazonium coupling was realized through NH proton, form-
ing orange colored 4-benzylidene-1,3-diphenyltetraz-1-en. This
is highly instable in basic media and gave an intermolecular rota-
tion turning into red colored formazans. This is in accordance
with previous study [25].
(Scheme 1b) were synthesized; in the second step, spectral prop-
erties of these formazans were determined. In the third stage
their structures and λmax values were elucidated. The shifts in
λmax values of 2–5 were evaluated in comparison to TPF (1) and
the shifts in λmax values of compounds (3–5) were evaluated in
comparison to CSPF (2).
Scheme 2. Synthesis of formazans.

H. Tezcan / Spectrochimica Acta Part A 69 (2008) 971–979
973
Table 1
Experimental data and elemental analysis of the formazans synthesized
Comp.
mp (◦C) (lit.)
Yield (%) (lit.)
Color
Elemental analysis
Calculated
Found
C
C
H
N
S
H
N
S
1
2
3
4
5
172–173(172–174)6
255–256
213
>300
207
75 (54)6,(63)24
Cherry red
Salmon
Cyclamen
Yellow-brown
Light brown
76.00
59.13
56.51
56.51
56.51
5.33
3.76
3.60
3.60
3.60
18.66
16.23
15.51
15.51
15.51
–
75.97
59.01
56.48
56.48
56.48
5.29
3.67
3.54
3.54
3.54
18.69
16.12
15.47
15.47
15.47
–
55
46
53
54
4.63
4.43
4.43
4.43
4.68
4.55
4.55
4.55
The basic buffer solutions employed were 0.1 M HClO4 +
0.05 M borax solution (pH 7.60–9.00) and 0.1 M NaOH +
0.05 M borax solution (pH 9.30–10.80). However, the best yield
was obtained with the NaOH + CH3COONa buffer solution (pH
10–12). The reaction scheme is provided in Scheme 2 and the
experimental data were tabulated in Table 1. The structures of
the formazans were elucidated by elemental analysis, Mass, IR,
1H NMR, UV–vis, spectral data.
As seen from Table 1 that the yield of TPF is higher than that
reported in literature [6,24]. The lowest yield was obtained at the
o-position in 2–5 formazans. This can be attributed to the fact
that substituents are the closest to the reaction site in this posi-
tion, which sterically hinders the coupling reaction. The relative
increase in yield at both m- and p-positions verifies this hypothe-
sis. If an electronic effect (resonance and inductive effects) were
dominant, the best yield would be obtained at the o-position. The
biggest difficulty was encountered in the synthesis of m-OH
bis-formazan 4. The resulting product was resinous and non-
crystallizable. The synthesis was repeated several times using
dilute conditions and various pH values, to prevent this situation.
However, it was not possible to obtain perfect crystals.
towards the higher fields as a result of substituting OH groups
to the ring is lower compared with the shift towards the lower
fields as a result of substitution of COOH and SO3H. For
instance δ value makes a shift of 0.63 ppm higher field from
CSPF to o-HCSPF (8.55–7.92 ppm). This ꢀδ value is lower at
the m-position compared with o-position since there is no reso-
nance effect and only a weak inductive effect at the m-position.
This shift at the p-position is higher than m- and lower than
o-positions. Because at the p-position the inductive effect is
diminished but there is a resonance effect. That is why the δ
values of compounds 3–5 are at highly lower fields compared
with that of TPF but a little bit higher than CSPF. These peaks
are compatible with the structure depicted in Fig. 1 [26]. The
N H, Ar OH, COOH and SO3H groups were observed in
the expected regions (Table 2). Fig. 1 shows the 1H NMR spectra
of CSPF, o-HCSPF, p-HCSPF in CDCl3 at 25 ◦C.
2.3. IR spectra
TheIR datareportedin Table3 revealsthat forTPF, the C N
stretching band is located at 1500 cm−1. This shows the presence
of chelation through intramolecular hydrogen bonding in TPF.
The formation of a hydrogen bond between the electron pair on
N N and the hydrogen of NH turns the molecule into chelate
and causes intramolecular proton transfer [1,5,25]. There is an
element of symmetry in the molecule (Scheme 3).
2.2. 1H NMR spectra
As seen from Table 2 the 1H NMR data shows the δ values
of CSPF (2) shifted to lower field compared to those of TPF.
For instance δ a value for Ar H is 7.55 ppm in TPF (1) and
shifted to the lower field (8.55 ppm) in CSPF (2). This is per-
fectly justifiable since there are electron withdrawing groups
such as two COOH and one SO3H in the structure of CSPF
(2). In compounds 3–5 the substitution of OH group at the o-,
m-, p-positions resulted δ values to show a slight shift to higher
fields compared with compound 2. This is quite expectable from
the electron donating feature of OH group. However, the shift
The C N stretching peaks are observed at 1635–1520 cm−1
in compounds 2–5. This due to the fact that bis-formazans
are containing SO3H group and two COOH groups which
increase the steric hindrance and therefore decreasing chela-
tion strength. However, it is observed that although in a very
small extend there is the presence of chelate form in the equilib-
rium. If C N stretching band is located at 1565–1551 cm−1 or
higher, there is no chelation and the molecule is in the excited
Table 2
The 1H NMR data of formazans (1–5) (400 MHz, in CDCl3)
Comp.
Ar
H
N
H
Ar OH
COOH
SO3H
1
2
3
4
5
7.55–6.70(m,15H)
8.55–6.90(m,21H)
7.92–6.85(m,19H)
8.50–6.65(m,19H)
7.98–6.65(m,19H)
1.14 (s,1H)
–
–
–
–
2.50–2.25(s,2H)
2.75–2.60(s,2H)
2.55–2.20(s,2H)
2.05–1.70(s,2H)
10.90(s,2H)
10.80(s,2H)
10.85(s,2H)
10.85(s,2H)
11.28(s,1H)
11.27(s, 1H)
10.85(s,1H)
10.85(s,1H)
3.10(s,2H)
3.40(s,2H)
3.20(s,2H)

974
H. Tezcan / Spectrochimica Acta Part A 69 (2008) 971–979
expected at 1450–1400 cm−1. This decrease in wave number
stems from the resonance stabilization due to the formation
of chelation in the molecule. In substituted formazans (2–5),
N N stretching bands was observed between 1455 and
1330 cm−1. These values reveal that the excited state of the
molecule, distortion of the chelation and probable the pres-
ence of trans-formation (1455 cm−1). The values of 1420 cm−1
or higher is the indication of N N bands of the for-
mazans without chelation and the values of 1442 cm−1 or
higher is the verification of the trans conformation of the
molecule [6,27]. Also the very weak bands observed between
1360 and 1335 cm−1 is the proof of the presence of chelate
form in equilibrium with a very small extend. CNNC skele-
ton vibration peaks were observed in the fingerprint region as
expected from the structure of formazans. N H and Ar OH
stretching peaks appeared between 3600 and 3000 cm−1. Other
peaks were also in accordance with structure of formazans.
These results confirm the formula giving in Scheme 1. The
IR spectra of TPF, CSPF, o-, m-, p-HCSPF are shown in
Fig. 2(A–E).
2.4. Mass spectra
The mass spectra of formazans (1–5) were recorded and their
molecular ion peaks confirm the suggested formula Scheme 1.
The calculated and found values of the molecular weights of
some of the formazans are given in Section 3. Representa-
tive mass spectrum of the formazan (p-HCSPF, 5) is shown
in Fig. 3. The spectrum shows numerous peaks representing
successive degradation of the molecule. The observed peak at
m/z 722.01 (Calcd. 722.15) represents the molecular ion peak
of the complex with 3.27% abundance. Scheme 4 demonstrates
the proposed paths of the decomposition steps for the investi-
gated formazan (5). One of the strongest peaks (base peak) at
m/z 212.35 represents the stable species C6H4O3N4S. Elemen-
tal analysis and mass spectroscopic data also corroborated the
structures proposed in Scheme 1.
Fig. 1. 1H NMR spectra of CSPF, o-HCSPF, p-HCSPF measured in CDCl3 at
25 ◦C.
state. On the other hand, the location of the C N stretching
band between 1510 and 1500 cm−1 is the indication of chela-
tion [6,27]. Our upper limit for formazans (2–5) at 1635 cm−1
is the indication of the absence of chelation while the lower
limit of 1520 cm−1 verifies the presence of a very small chela-
tion. The fact that the peaks at 1530 cm−1 are very weak is
also another indication of the very small extent of the chelation
strength.
N N stretching bands in TPF was observed 1358 cm−1
.
This value shows chelating in the molecule since this band is
Table 3
The IR spectral data of formazans (1–5) (in KBr, cm−1
)
Comp.
C
N stretching
N
N stretching
Aromatic C
stretching
C
CNNC Skeletal
vibration
NH + Ar OH
stretching
COOH stretching
SO3H stretching
1
2
3
4
5
1500
1358
1600
1629
1620
1630
1622
800–600
930–600
850–620
920–610
850–620
3050–3000
3600
3480–3300
3600–3200
3400–3220
–
–
1540–1580
1590–1520
1635–1580
1600–1530
1455–1335
1418–1330
1450–1335
1420–1335
3400–3300
3390–3300
3420–3210
3395–3300
1420–1330
1385–1220
1410–1340
1380–1220
Scheme 3. Molecular chelating and symmetry.

H. Tezcan / Spectrochimica Acta Part A 69 (2008) 971–979
975
Fig. 2. IR spectra of: (A) TPF; (B) CSPF; (C) o-HCSPF; (D) m-HCSPF; (E) p-HCSPF.
*
2.5. Absorption spectra
observed at 270–300 nm originate from n → ␲ transitions of
C N groups in the molecule [3,24].
There are three distinctive peaks in the UV–vis spectra of
formazans. The λmax1 values are specific to formazans skele-
ton. This is why that this study is concerned with λmax1
values. Formazan peaks λmax1 values are generally observed at
410–500 nm and may be shifted to 350–600 nm depending upon
the structure. These peaks are due to ␲ → ␲ and n → ␲ elec-
tronic transitions in formazan skeleton. λmax2 Values generally
appeared at 300–350 nm, corresponding to electronic transitions
of N N group in the molecule. λmax3 Values sometimes
Theelectronicabsorptionspectraofformazanswererecorded
in methanol, DMSO, DMF, 1,4-Dioxane, CH2Cl2. As a sample
UV–vis value of in methanol was interpreted and tabulated in
Table 4. The λmax1 values are observed for TPF (1) and bis-
formazan CSPF (2) at 483 and 352 nm, respectively. There is
a shift of ꢀλmax1 = 131 nm towards shorter wavelengths (hyp-
sochromic effect). This is in accordance with the fact that CSPF
contains compared with TPF electron withdrawing groups such
as COOH and SO3H in its structure (Scheme 1b). In com-
*
*

976
H. Tezcan / Spectrochimica Acta Part A 69 (2008) 971–979
pounds 3–5 there are OH groups attached to 3,3-phenyl rings in
addition to electron withdrawing, such as COOH and SO3H
groups in compound 2. The λmax1 values were observed at 356,
353 and 354 nm as a result of the attachment of OH groups to o-,
m-, p-positions of 3,3ꢀ-phenyl rings (compounds 3–5). This is
explained by the electron donating nature of OH group. The most
distinctive shift was observed at the o-position (ꢀλmax1 = 4).
There is resonance effect as dominate. That is because OH group
attached at the o-position is the closest to the reaction site. There
is no resonance effect at the m-position and the inductive effect
is highly diminished. That was why there was a small shift such
as ꢀλmax1 = 1 nm in this position. At the p-position the inductive
effect vanishes and OH acts as an only electron donating group
with resonance effect. Since it is far away from the reaction site
compared with o-position, the shift of p-position is lower than o-
position but higher than m-position where there is no resonance
effect (ꢀλmax1 = 2 nm).
Fig. 3. Mass spectrum of the formazan (p-HCSPF, 5).
Scheme 4. Proposed fragmentation pattern of p-HCSPF (5).

H. Tezcan / Spectrochimica Acta Part A 69 (2008) 971–979
977
Table 4
UV–vis absorption λmax values of formazans (1–5) (CH3OH, 10−4 mol l−1
)
Comp.
λmax1 (nm) (Abs)
λmax2 (nm) (Abs)
ꢀλmax1 according to TPF (nm)
ꢀλmax1 according to CSPF (nm)
1
2
3
4
5
483 (0.370)
352 (0.912)
356 (1.590)
353 (0.912)
354 (1.222)
335 (0.614)
233 (0.565)
218 (1.714)
218 (1.714)
219 (1.282)
–
131
127
130
129
–
–
4
1
2
Column 4: ꢀλmax1 = λmax1 (TPF) − λmax1 (substituted formazans). Column 5: ꢀλmax1 = λmax1 (CSPF) − λmax1
(HCSPF).
chemicals and solvents used in the syntheses were of reagent
grade and were used without further purification.
3.1. Synthesis of 1,3,5-triphenylformazan (TPF, 1)
1,3,5-Triphenylformazan was synthesized by the reaction
of benzaldehyde (1.06 g, 0.01 mol), phenylhydrazine (1.08 g,
0.01 mol), aniline (0.93 g, 0.01 mol), concentrated HCl (5 ml)
and sodium nitrite (0.75 g) in a methanol, at 0–5 ◦C described
in literature [24,25].
3.2. Synthesis of 1,4-bis-[3,3ꢀ-phenyl-5,5ꢀ-(o-
carboxyphenyl)-formaz-1-yl]-benzen-2-sulphonic acid
(CSPF, 2) and;1,4-bis-[3,3ꢀ-(o-, m-, p-hydroxyphenyl)-5,5ꢀ-
(o-carboxyphenyl)-formaz-1-yl]-benzen-2-sulphonic acid
(o-, m-, p- HCSPF, 3–5)
Fig. 4. The electronic absorption of formazans in CH3OH, 10−4 mol/l.
Another important point was the λmax1 values of bis-
formazans (2–5) relative to TPF (1). λmax1 Values of compounds
2–5 were observed at 352, 356, 353, 354 nm, respectively. There
was a shift towards a relatively short wavelength (hypsochromic
effect) due to the fact that bis-formazans contain highly electron
withdrawing groups. The fact that there were shifts of 131,127,
130, 129 nm for substituted bis-formazans 2–5 relative to TPF
is in good accordance with the structure of these compounds
(Scheme 1). These shifts changed slightly to the opposite direc-
tion upon attachment of OH groups to the molecule. Fig. 4
shows the electronic absorption spectra of formazans in CH3OH.
UV–vis absorption λmax1 values of formazans were tabulated
in Table 5 and given in Fig. 5A–D. As seen λmax1 values were
changed with solvent species.
Benzaldehydeando-, m-, p-hydroxybenzaldehyde(0.02 mol)
were dissolved with methanol (40 ml). o-Hydrazynobenzoic
acid (0.02 mol) was dissolved in methanol (80 ml) and water
(20 ml). o-Hydrazynobenzoic acid solution was added to the
benzaldehyde and o-, m-, p-hydroxybenzaldehyde solutions
with constant stirring in dropwise fashion adjusting the pH 5–6.
Yellow colored hydrazone of 2, light yellow colored hydra-
zoneof3, yellowcoloredhydrazoneof4anddarkyellowcolored
hydrazone of 5 compounds were precipitated out. The products
are recrystallized from methanol–water mixture. Hydrazones
were dissolved in methanol (75 ml) and water (25 ml) under
reflux. The basic buffer solution was prepared by adding NaOH
(2.50 g) and sodium acetate (3.50 g) to 200 ml methanol under
reflux and added to hydrazone solutions as prepared above. The
mixture was cooled down to 0 ◦C and kept ready for the coupling
reaction (stock solution).
3. Experimental
At the other side a o-sulphobenzen-1,4-di-diazonium chlo-
ride solutions were prepared with 2,5-diaminobenzen sulphonic
acid (1.88 g, 0.01 mol) concentrated HCl (5 ml), NaNO2
All chemicals were obtained from Merck and Fluka expect
sodium hydroxide that was purchased from Sigma–Aldrich. All
Table 5
UV-vis absorption ␭
values of formazans at different solvents (1–3, 5)
max
Solvents
Comp.
CH3OH λmax1 (nm) (Abs)
DMSO λmax1 (nm) (Abs)
DMF λmax1 (nm) (Abs)
1,4-Dioxane λmax1 (nm) (Abs)
CH2Cl2 λmax1 (nm) (Abs)
1
2
3
5
483 (0.370)
352 (0.912)
356 (1.590)
354 (1.222)
487 (0.522)
364 (0.673)
359 (1.111)
362 (1.878)
484 (0.757)
363 (1.292)
356 (0.494)
362 (1.849)
486 (0.276)
358 (1.562)
364 (0.912)
363 (0.532)
484 (0.853)
357 (0.789)
367 (0.524)
367 (1.749)

978
H. Tezcan / Spectrochimica Acta Part A 69 (2008) 971–979
Fig. 5. The electronic absorption in CH3OH, DMSO, DMF, 1,4-Dioxane, CH2Cl2·10−4 mol/l: (A) compound 1; (B) 2; (C) 3; (D) 5.
(1.40 g,0.02 mol) in usual way at −5 to 0 ◦C. This diazonium
solution was added in dropwise manner to basic buffer hydra-
zone solutions as prepared above and cooled down to 0 ◦C, in
ice bath at constant stirring for the coupling reaction. Care was
taken for the temperature not exceeds −5 to 0 ◦C. The reaction
was completed in about 120–150 min. The mixture was stirred
for 2–3 more hours at the same temperature. The mixture was
kept in the fridge at the same temperature for 3–5 days. The
salmon colored (2), cyclamen colored (3), brown colored (4)
red-brown colored (5) formazans precipitated out. The product
was recrystallized from methanol + water + dioxan mixture.
Mass analysis for C34H26O7N8S, M: 690.30. Mass m/z (eV):
690.12 (M+, 0.51%), 658 (2.21%), 599 (5.27%), 520 (11.48%),
300 (47.25%), 255 (78.89%), 240 (67.33%), 188 (22.46%).
Mass analysis for C34H26O9N8S, M: 722.15. Mass: m/z (eV):
722.01 (M+, 3.27%), 256.11 (7.62%), 212.35 (96.94%), 150.98
(24.74%), 105.74 (44.39%), 76.11 (80.10%), 45.24 (23.60%).
DMSO, DMF, 1,4-DioxaneandCH2Cl2 using325 nmlamp. The
elemental analysis studies were carried out by LECO-CHNS-
932 elemental analyzer. Mass spectra were recorded on a micro
mass UK Platform-II device at 70 eV electron impact modes.
Acknowledgement
We are very grateful to the Gazi University Research Fund for
providing financial support for this project (Project No: 04/97-09
Ankara-Turkey).
References
[1] L. Hunter, C.B. Roberts, J. Chem. Soc. 9 (1941) 820.
[2] A.M. Mattson, C.O. Jensen, R.A. Dutcher, J. Am. Chem. Soc. 70 (1948)
1284.
[3] G. Arnold, V.C. Schiele, Spectrochim. Acta 25 (1966) 685.
[4] V.C. Schiele, Chemische Berichte 30 (1964) 308.
[5] J.W. Lewis, C. Sandorfy, Can. J. Chem. 61 (1983) 809.
[6] A.R. Katritzky, S.A. Belyakov, D. Cheng, H.D. Durst, Synthesis 5 (1995)
577.
[7] Y.A. Ibrahim, A.H.M. Elwahy, A.H.M. Abbas, Tetrahedron 50 (1994)
11489.
[8] A.A. Abbas, Tetrahedron 54 (1998) 12421.
[9] O.E. Sherif, Y.M. Issa, M.E.M. Hassouna, S.M. Abbas, Monatshefte fu¨r
Chemie 124 (1993) 627.
3.3. Physical measurements
1H NMR spectra were recorded on a BRUKER 400 MHz
spectrophotometer using CDCl3, in 10−4 M. The IR spectra
were recorded on a MATTSON 100-FT-IR spectrophotometer
between 4000 and 400 cm−1 using KBr pellets. The UV–vis
spectra were obtained with UNICAM UV2-100 UV–vis spec-
trophotometer using 1 cm quartz cell, in 10−4 M CH3OH,
[10] A. Uchiumi, A. Takatsu, H. Tanaka, Anal. Sci. 7 (1991) 459.

H. Tezcan / Spectrochimica Acta Part A 69 (2008) 971–979
979
[11] S.S. Badawy, Y.M. Issa, H.M. Abdel Fattah, Transition Met. Chem. 14
(1989) 401.
[21] H. Wan, R. Williams, P. Doherty, D.F. Williams, J. Mater. Sci.: Mater. Med.
5 (1994) 154.
[12] G.M. Abou-Elenien, J. Electroanal. Chem. 375 (1994) 301.
[13] U. Yuksel, Post Doctoral Thesis, Turkish Aegean University, 1981.
[14] M. Grote, U. Hu¨ppe, A. Kettrup, Hydrometallurgy 19 (1987) 51.
[15] A. Uchiumi, A. Kawase, Anal. Sci. 7 (1991) 119.
[16] Y.M. Issa, N.T. Abdel Ghani, O.E. Sherif, Bull. Soc. Chim. Fr. 128 (1991)
627.
[17] A.M. Mattson, C.O. Jensen, R.A. Dutcher, Science 5 (1947) 294.
[18] R.M. Wood, Science 112 (1950) 86.
[19] A.M. Rutenberg, R. Gofstein, A.M. Seligman, Cancer Res. 10 (1950)
113.
[22] M. Kebler, S. Furusaki, J. Chem. Eng. Jpn. 30 (1997) 718.
[23] H. Tezcan, T. Uyar, R. Tezcan, Turk. J. Spectrosc. Aegean Univ. 9 (1988)
8;
H. Tezcan, T. Uyar, R. Tezcan, Turk. J. Spectrosc. Aegean Univ. 10 (1989)
82.
[24] H. Tezcan, S. Can, R. Tezcan, Dyes Pigments 52 (2002) 121.
[25] H. Tezcan, N. Ozkan, Dyes Pigments 56 (2003) 159.
[26] F. Schiman, Nuclear Magnetic Resonance of Complex Molecules, vol. 1,
Vieweg and Sohn GmbH, Braunschweig, 1970.
[27] L.J. Bellamy, The Infrared Spectra of Complex Molecules, Methuen, Lon-
don, 1962.
[20] J.A. Plumb, R. Milroy, S.B. Kaye, Cancer Res. 49 (1989) 4435.